How to Test for a Stuck Open Fuel Pressure Regulator! [A ScannerDanner Premium Lecture]

what we were going over today is fuel pressure too low issues we are going over fuel pressure or fuel rest pressure testing and I have a couple of hyperlinks for videos we actually watched those this morning this is actually a shot of a fuel pressure regulator that's leaking this would be section 16 we're going to be going over Page 6 7even and 8 something like that page six is our fuel pressure too low page and this is on a return type system mechanical return type system so there's some other background info this would be I believe section 14 that I have in my book which is types of fuel injection system so there's a lot of information that really we haven't covered yet as a class but the nice thing about what we do here is we have a live vehicle it has a problem and it's directly related to what we're talking about so the rest of this video we're going to do this as a class we're going to figure out what's going on with this car as far as fuel pressure it does have a fuel pressure problem so let's go to the car and and see what we got okay one more time cycle that [Music] key all you see we had 30 PSI on the prime and then immediately dropped to zero so we have a few problems one was cranking when we initially did this we had around 20 psi the car would not start two with it running the pressure was lower than normal and three as soon as you shut the key off pressure bleeds down now so multiple issues I I think what we'll do next is let's get this running again and I'll show you the regulator vacuum hose test next so go ahead and start the car back up okay what we want to see for this part when I take this vacuum hose off the regulator which is right here we want to see roughly a 6 to1 PSI pressure rise that's pretty standard and you see we really had no change there at all that is a problem so we're around 32 33 PSI take that off really no change at all and when you see that most of the time when we see this condition that is from a weak pump shut that back off and really the way to explain that would be the pump is never reaching the pressure that the regulator would normally open and so you're really looking at pump maximum pressure right now that's what this looks like looks like a faulty fuel pump a little bit of history in this car I think would be helpful this fuel pressure regulator was replaced was actually uh a month or so ago it was actually leaking and we replaced this for him fixed the bleed down problem a month or so ago and now it's back with a long crank time and he's got a misfire too that that needs to be addressed but separate problem so it had the regulator replaced our fuel pressure is low what I'd like to do in this case would be to check my pump powers and grounds next or check pump maximum pressure and the thing about checking pump maximum pressure on this design is this uses plastic fuel lines so this is your pressure line coming in right here this is your return line and when you study return type systems what you'll what you'll learn is that if you block the return line off you can force the fuel pump to put out its Max maum pressure as far as a spec for pump maximum pressure something that I use is it should be roughly two times the system pressure the spec listed on the ver says 50 to 52 PSI key on engine off let's talk about that measurement for a second 50 to 52 PSI so call it 50 psi key on engine off would be basically your wide openen throttle pressure and the reason we say the Keyon engine off is wide open throttle is there is no vacuum on this hose for this regulator right now at all so what we can assume safely is that our running idle presser will be roughly 10 psi less than that and I said 6 to 10 8 to 10 somewhere in that range we can call it 10 so let's say 40 at idle 50 wide open throttle is where we should be on this vehicle you saw what we had at idle which was around 32 we are too low we take the vacuum hose off we should get roughly a 10 psi rise that's not happening our fuel pressure is bleeding down immediately it looks like a faulty fuel pump what we like to do again is pinch the return line check our maximum pressure problem is it's plastic fuel line so we don't want to do that one just yet if our pump is faulty which is where we're at right now most likely a faulty fuel pump we also want to check pump powers and grounds what I'll do for this is I'll put two hyperlinks in to two videos we just watched you guys remember the Ford Ranger with the bad ground under the driver's door and then there was a GM with a bad block ground both of those with fuel pressure problems we just watch those in class together I'll hyperlink those in here for you guys too when you watch this video later you'll be able to click on that and watch it um it very important is the point that we check pump powers and grounds now the problem is you guys saw the classroom right we don't have a lift in this classroom so we really don't want to crawl underneath the car we don't want to jack it up and get underneath to check pump powers and grounds we are trying to avoid that step so there's another check that I've shown before and I I want to show my students here too and actually again we've done this but this will be a good review and that is to check the pump current flow from under the hood can we do that and the answer is yes on this vehicle we can our fuel pump we've already identified it and what we want to do carefully is we want to jump the relay and use our amp prob around the jumper wire now now the thing about this there's a major safety issue issue here so for all of you guys watching this if we if we end up jumping the wrong pins let's see if I can get you a shot of the pins on this pins 30 you see is this top left and 87 are my load side of the fuel pump nice thing about GMS is they give you pictures so that's cool 30 and 87 that's our load side of the pump 87a is not used in this application 85 and 86 would be the control coil and what we want to do is we want to run a jumper between 30 and 87 and put our an probe around it so we can measure current flow from under the hood of what our fuel pump is now the thing is guys if you make a mistake and jump 86 and 85 what will happen is you will fry the transistor in the engine computer for the fuel pump relay it is super critical that you jump the right pins a lot of guys love to jump relays this is why I don't like to jump a relay like this I would prefer in most applications to jump the relay on the control side with a test light harness plugged in I've shown this before but that's not what we're trying to do here we need to have a spot to put our an probe and we're going to put a jumper in there carefully and then we're going to put our amp probe around that so I know they do sell relay adapters that have a loop in it in fact AES wave is the one that has them you plug this adapter in plug it in the box and then the adapter has a loop for current flow and that really takes that safety issue out out of the equation um the issue of course would be space in this power distribution box but anyway we're going to use a jumper wire so go ahead and install that and wait before you do that it is top bottom left yeah hold on but it's top just so everybody's aware it's top left and bottom right but remember when we flip this around it's backward so it's going to be top right and bottom left okay don't forget that top right and bottom left and the adapter we're using something else while Brandon's hooking that up for me the adapter we're using is the exact same pin diameter as this relay now I've had guys that use T pins and will stuff them in there and then what they end up doing is spreading the female terminals wider than they should be and then the relay has a loose contact just want to show you guys where I got these from for any of you guys that have an old snapon Mt 2500 laying around and has the multi1 adapter in it and the multi1 adapter has all these leads you know it's that one that we never use so what I ended up doing because I have like 10 of them so I destroyed one I cut the ends off and the nice thing about that is the pins are the exact size that I need for this application and so that's what we did we just took a uh the old multi1 adapter and cut it apart and now that's my dumper wire right there you can hear the fuel running through the fuel rail right now there's something else we could have done too which was we could have commanded the fuel pump to turn on with with the with the scant to Carl I'm going to make you famous okay Carl there's Carl say hi Carl hi um Carl could have done a uh bir directional control and turned the fuel pump on with a scano but the problem with that would be we would not have a spot to put our amp probe you know that would energize the relay that would make the pump run but our goal here was to connect our amp probe to this jumper and get an amperage reading of our fuel pump we're on the 20 amp setting for this low amp probe so what we're going to do is we're going to uh go right to the scope multimeter and then we're going to go to our lap scope and you know there's a couple different ways to do this but for now low amp 20 is perfect and turn those cursor off for right now so click the cursor tab hide them good and uh what we want to see is a a line across the screen and you see this line is not here right now and I see a trigger setting and most likely what this means is our amp probe is upside down right now so there's a couple ways we can do this we can actually invert the signal or I can flip my amp clamp do you remember how to invert it very good okay now with the Varys which is a little bit different than the the Pico which we've been playing around with and I've had some questions on this too is is how do you zoom in on a picture on the on the Varys and the thing about the Varys when it's frozen is you can't so you just have to realize that and take your pictures differently if this was the Pico I would take a very very long time base and zoom in if it's the Varys we take a short time base and zoom out so we have the best of both worlds what I would suggest we do for this too is we will Pete detect this and uh that'll just give me a little bit more that's basically my my sampling that'll give me a little bit more detail with this and we're going to do two things with this we're going to measure RPM and we're going to look at current flow so let let me talk about the current flow first before we go any further you guys can see actually this one right here will give me the live measurement we are at 7 1/2 amps on average on this fuel pump and what we are addressing with a low pressure problem see if this makes sense to you guys you have low fuel pressure we could have a bad power bad ground right and we're going to hyperlink those videos in here that had bad grounds do you have here's your question to you guys do you have a bad pump power or ground when you have over seven amps of current flow going to the fuel pump now your question to me would be what's normal amp flow well there isn't really a spec for that we have a range we use you know 4 to 6 amps for a regular PFI system right 30 to 40 PSI maybe 8 to 10 amps for a GM CPI vortek that's you know 50 to 60 PSI this one's in the 40 to 50 range so I think our amperage is right where it needs to be and so question again do we have a bad power or ground causing our low fuel pressure problem when we have normal current flow no we don't so here do we need to go under the car or do we need to take the car out of the classroom put it on the rack and check our pump powers and graphs i' say no no we don't so how much of an advantage is that if you're laying in the driveway at home or if you're at one of the shops I've taken you guys on a field trip with me that one shop we were at the P gravel driveway or it's not P gravel that would be easier to lay on it's like the real chunky heavy gravel I don't want to lay in that driveway to check the pump powers and grounds this test is telling me I don't need to so this looks like a bad pump let's show you one more measurement just because we can not because we have to we have the ability to look at pump RPM so I'm going to let you work it Carl first thing we want to do again for you guys we're on a 10 millisecond screen and we can zoom out we can zoom in but we have to save our pixel right so let's change our time base to 5 milliseconds first that's going to be click that button right there that one right there and then yep there you go he and then back so we're looking at detail we'll let it roll for a little bit fill the buffer up and then go ahead and hit the yellow Square which will stop the picture right there and then what we'll do now is hit the zoom right here and what that will do is take that collected data in the buffer and zoom out now we have the best of both worlds we can zoom in and out this line right here wherever you move it to and then you have a zoom level so go to times one and everyone can see where we were that's where we were that's where we saved it go to x 2 Time 4 I believe is the next one that one looks good maybe even times what's that eight yeah go times eight okay cool that one's perfect all right then hit the check mark get that box out of there all right here's what we want to do guys we want to measure pump RPM and to measure pump RPM what we do is we find unique characteristics within this so what we look for is really one rotation of this and I'm going to let you do that Carl all right pull your cursors in and then I'm going to let you pick the unique characteristic you like and then find it again okay if you are correct uh a nice guide for us is that these systems GMS usually run an eight bar pump so we should have eight bars or eight humps in between our two cursors if you did that right it looks like we have more than that why don't use this low point for me that low one and then use use that low one again that looks like a pretty pretty good pattern right we see that and then I see it again and again count the starting there count that as one for me you don't have to count out loud but just give me a number looks like 10 is that 10 that's 10 you count 10 I'm surprised this would be the first 10 bar pump that I've seen a domestic car the all of our domestics for GM chry they're all eight bar all the ones that I've used but hey maybe this is a heavier Duty pump that looks like 10 bars and that means one rotation is what we have right there between our cursors that's one rotation hit this button again and that gives us our time difference so we want our Delta time which is that number what's that say 9. 9.8 milliseconds all right so the way that we do the math for that is you know this one's actually pretty easy cuz it's almost 10 milliseconds but what you need to know is you have 1,000 millisecs in a second and 60,000 milliseconds in a minute and so what we do is we take 60,000 and we divide it by the number we have which is 9.8 was 9.08 yeah 60,000 ided by 9.08 is there's your number 6,67 so this pump is running at 6,67 RPM and and the nice thing about that is we can well number one we can do it uh but number two is we can also use this as a guide to helping us too and I have to be honest with you guys I really haven't used the pump RPM to help me all that much the wave form of course the amperage of course the RPM I've just seen it be so variable car to car the number we use a number that I have in my book 4 to 6,000 RPMs or typical range so our pump ampage looks good our pump RPM looks good but our pressure is low here's what we know for sure PES and grounds not a problem this looks like a bad fuel pump we have to address one more thing okay the last step for this and this is the same information I have in my book so you guys that are following alone this would be section 16 I believe it's page8 where I talk about pin off the return lot perform the following engine running return type system if possible pinch or block off the return lot now I said engine running in my book right now the fuel pump is running would be the equivalent of the engine running okay so we modified it a little bit we want to pinch the return line and check our pump maximum pressure because we could have potentially a fuel pressure regulator that's stuck open that's causing low pressure this is not common guys I I could probably count on on maybe both hands over the past 20 years how many times I've seen a fuel pressure regulator caus too low of pressure this is not common but it's still worth doing return type system if we pinch the return line essentially what we're doing would be this and we would be restricting the return line so it would not matter what the regulator's doing and we are able to check the pump's maximum pressure doing that the problem though is these are plastic fuel lines we don't want to pinch off plastic fuel lines so what we're going to do now we're going to take this jumper out Dan can you do that for me can I get you on camera can I can I mention where you're from from Russia Dan is from Russia we need to hear your accent a little bit Dan hello from Russia nice nice That's cool Dan is here from Russia in in this class of course he flew all the way here just to be with me right no no that's not why but we could say that cuz it makes me feel better all right so you can say it okay so thank you Dan um I lost my train of thought what were we going to do now take the jumper okay yes thank you no problem um took the jumper out we disabled the pump and you see our our rest pressure is pretty much gone down to zero what we're going to do is we're we're going to take the return line off of the rail and we're going to install a rubber line so we can pinch it off so I'm going to have my friend uh Phil can I can I get you on camera too all right we'll get over there by that return line and take that off for me and I'll film you doing it thank you Phillip I'll make you a star I'm already a star you're already a star yeah all right he's using a uh disconnect tool and he has uh of course some glasses on we're being safe safety is important now this is one of those quick disconnects and they're not fun to do I'm not going to get you zoomed in on what he's doing so you're okay no pressure there there Philip we won't uh hey nice job did that very quick so what we've done is we've taken the the return line off of the rail we are going to install a rubber line with a clamp that we are able to block off and check our pump maximum pressure yeah unfortunately we don't have any we don't have any uh needl nose vice grips right now we're using what we have that will work fine let me get a shot of what that looks like okay so what we've done we've taken this this fuel line off here we've installed a rubber tube with a clamp and then we've blocked it off with a pair of ice grips doesn't have to to be anything special I'd prefer needle nose vice grips in this application but uh we'll jump it real quick make sure we don't have any fuel coming out of there remember top right bottom left do not jump the wrong pins all right stop we got to leak around the clamp stop stop you need to tighten that clamp up a little bit more we always want to be safe about what we're doing guys is very important problem problem here too is I believe our diameter line that we chose is a little bit uh thicker than the one we used last time isn't it philli yes so I don't know if you can't get that tighter then we'll change the line got that pretty much all right now shine that light light so I don't have any Shadows good right there all right now go ahead and and uh jump that [Music] again okay good all right take it off whoa all right a few things when you do this check you do not want to run the pump for any long period of time and by long period of time I'm saying like 15 seconds Max we can easily burn out a fuel pump by doing what's called a dead head test this is a pump maximum pressure test and and so let me get back over in the front on the pressure gauge now that our leak is good and and we'll get a shot of what that looks like okay so we have the return line removed and blocked go ahead and jump that nice okay good we jumped it and then let off run it for a few more seconds so I can get get that number I can't see is that 80 that hit 80 85 okay good take um wait jump one more time why did that drop down that fast cuz we got leak right there off are we leaking again probably cuz I could he it no leak one more time we hit 90 and then it dropped I don't want to run this long but what happened I don't know how much of that showed up in the last segment but I saw 90 PSI on the camera I want to talk about that 90 PSI number for a second 90 lb of fuel pressure with the return line pinched 32 lb of pressure under normal system right with it closed within its Loop in other words the return lines connected pumps running Regulators involved what we have is not a bad fuel pump does that make sense guys yeah this this condition absolutely no question about it is a stuck open fuel pressure regulator now I mentioned earlier that we had changed this for him what I didn't tell you purposefully on the camera at least I didn't want you guys jumping the gun on me too soon he called me a few weeks later and said his regulator was leaking again and so he changed it on his own that's twice the original one was leaking the the new one was leaking and so he put a second new one on it this is that second new one well guess what this one is also bad so wherever he's getting this part from he needs to go somewhere else we're getting some dunk Parts here no question about it all right so I want to before we J this again I want to address what happened we were at 90 lb of pressure and then all of a sudden it dropped off again what happened is fuel started coming up out of the top of the regulator so that's really just another warning with this maximum pressure test on how short of a period of time you want to do this now this regulator was already damaged it was already open too soon we didn't have fuel running out of the top now we have major fuel running out of the top we pulled the line off and it sprayed everywhere good thing we had our safety glasses on um so we kind of rigged it I'm hoping we can see this event again this really isn't the best idea uh I have a a line on there and a pair of vice grips and a a zip tie holding this line on and we're going to be under a lot of pressure um so just do this briefly I want to I want to make sure that we didn't do anything else and rupture another line okay good let it off that's fine that's all I that's all I wanted to see this 90 lbs of pressor tells us is that this had a stuck open fuel pressure regulator it was not a bad fuel pump and this is the step you need to do to confirm that when you have low fuel pressure pinch the return line momentarily check your max pressure If system pressure pretty much doubles that tells you your pump is good we had about 90 lbs of pressure on a 40 to 50 psi system I am totally fine with this fuel pump again briefly jump that for me and hopefully what I can show you guys on camera all right that's good and I really can't right now because this clamp that we have holding on here really is nothing more than two zip ties and it's really not stealing it all the way I'm getting gasoline leaking out of here so this bleed down issue you're still looking at when we originally did this it held fuel pressure so not only did we have a fuel pressure problem from this opening too soon it was also the cause of our immediate bleed down issue too so what we'll do at this point we'll put the new regulator in this and then we'll refilm our pressors and make sure that it's holding rest pressure we're not going to redo the dead head test you guys saw briefly on the camera 90 lbs of pressure that was perfectly fine I'm not going to redo that especially in light of this diaphragm rupturing when I did it I've never seen that before but hey this is a warning to you guys doing the dead head test don't do it for a long period of time if this was a well made regulator it wouldn't have happened okay first time I've ever seen this again I'm not throwing the part supply company under the bus here uh but we are going to change this regulator and then I'll get you a shot when we're done okay I have the old regulator pulled apart I wanted to show you guys where the failure occurred in this and also talk about really the the sealing of these so I think the first thing would be let's talk about the failure and this regulator would sit sit like this there's a spring that sits over top and and then this upper chamber would hold the spring and then what they do is they you know pretty much squeeze this together and and uh it's kind of a pinch seal between this housing I had to pull all this apart used a pair of side Cutters and just kind of Twisted it apart to get this apart so it's a pinched seal for this so the gasket the diaphragm serves two purposes one it seals the fuel from leaking out and then also uh it is sealing from entering the upper upper chamber but look at the the damage in this diaphragm right here and we didn't cause that if you look at this carefully I mean it looks like that was part of the manufacturing process when they stake this together when they crimped it that this wasn't really crimped very well in this area there's two layers for this this for this diaphragm there's a a bottom and a top the other evidence here is look at the spring the spring is actually this spring is actually bent I don't know if I can really show that on the camera maybe get a side view that kind of shows it look how cockeyed the spring is and so what we believe was going on is this diaphragm was actually sitting crooked and with it sitting crooked because of a bent spring and a poor crimp connection here that was causing this ball and seat area to not line up like it should have and that was causing a major dump of fuel back to the tank so this is the area here this ball a little kind of springloaded ball and then there's the seat those two should line up and that's what SEALs the return so with that Clos pressure is going to rise and with that open pressure is going to drop and again we believe this was not lined up properly so what happened was when we pinched the return line and did the dead head test that's Max fuel pressure and we hit 90 lbs of pressure this area here that had a weakness ruptured or moved out of the way and allowed all that fuel to come out of the top and that's what happened if you watch that segment of the video we were at 90 lbs of pressure and then it dropped back back down to 32 or so and then when we pinched the return line again it would not go any higher and what had happened is we pretty much uh killed this thing the rest of the way but we believe again this problem was there like I said before I have never seen a dead head test rupture a regulator diaphragm but we believe it's because of poor manufacturing that this was like this and so good lesson though as far as doing a dead head test and the usefulness of it so again two places that these Regulators can leak one would be the ball and seat area and what that would cause when they leak there generally is fuel pressure would be normal but what you'd have is a long crank time and then the second one where a diaphragm will leak is the the diaphragm actually ruptures fuel comes through the diaphragm into the upper chamber into the vacuum area and then it gets pulled into the engine this will also give you a long crank time but it will be accompanied by a rich condition negative fuel trim numbers and things like that so I think the manufacturing process on these aftermarket diaphragms it's completely different from the factory what I will do is try to put a still picture in here from one of my other videos it was a GM CPI where we changed the regulator and it was a a fiber material coated with rubber from the factory very very heavy heav Duty compared to this very thin two pieces of rubber diaphragm that's being used in this part so I guess you get what you pay for all right let's go check out the car and see what the new regulator does okay go ahead and shut that off what we want to see now is this thing should hold pressure on shut down it's holding better than what it was before but it is still not holding holding properly guys we've already gone through the steps on this and the procedure would be pinch the pressure line if it holds it's pump check valve pinch the return line if it holds it is the regulator and it holds when we pinch the return line so we put in piece of rubber tube again pinch the return line it holds that means our new fuel pressure regulator the ball and seat area is still leaking on on this brand new part so you know I'm not the one responsible for getting parts for these people I I told him to get me a part from somewhere else I'm not sure where he got this the running of the car the performance of the car will be okay you know we're holding around 20 psi now you know is that enough I'm not sure you know the idea of this rest pressure would be when the engine is hot especially hot when everything is baking under the hood and you shut the car off that rest pressure keeps the fuel from boiling in the fuel rail and so what will happen is when the pressure drops the boiling point also drops it boils sooner and you come out from the store say 15 minutes later you will now have a long crank time this car will probably still have that symptom unless he gets me a good pressure regulator I think this is good enough though for this video would you guys agree that we were able to properly identify a bad regulator it was not a bad fuel pump but I think the procedures we went through are very valuable car comes in you got low fuel pressure don't be in a hurry to put a fuel pump in it even though nine times out of 10 when you have low fuel pressure you need a pump we've all done it we've all seen it do your checks you know it will save you that you know 10% that one time out of 10 it'll save you from making a Miss call and and really for this car it was as simple as pinching off the return line a little bit difficult with the plastic lines but it's still worth doing the other checks that we showed I think were valuable we go to the fuse box we dump the relay we measure the current flow of our jumper wire what that saved us from having to do is go under the car and check our pump powers and grounds because we want to do that too checking pump powers and grounds when you have low fuel pressure is critical so that was a valuable test that test showed us good current flow we also measured the pump RPM which was just another uh another trick that you can use as far as checking how that pump operation is amperage looked good so we said we didn't have a power and ground problem low fuel pressure we were ready to call the pump we did the dead head test dead head test said no not the pump bad regulator and I think that's what we just saw very very valuable we talk about it a lot now we're able to show it we still don't like this rest pressure can you cycle that key for me one more time let's watch it one more time and again I'm not going to take this fuel line back off for you guys you're just going to have to trust me that this new regulator is leaking on the return line and that shouldn't happen you should not be able to watch a gauge drop in some of the other videos I've done I'll throw a hyperlink into one I had on a GM CPI injection system where we did the regulator it held for an hour and a half and only Dro maybe 7even PSI in an hour and a half that's more like what you want to see we don't want to be able to see a fuel pressure gauge drop like that ever so it is what it is I think we'll wrap this one up and then we'll attack this misfire this car has next

Channel: ScannerDanner

Views: 49,531

Keywords: engine performance diagnostics, technician training, auto technician training, rosedale tech, auto repair, ASE L1, how-to, DIY auto repair, ScannerDanner Premium, automotive electrical systems, check engine light, diagnostic training, troubleshooting electrical faults, auto mechanics, auto mechanic training, online auto mechanics

Id: ZG8rMJwILxA

Length: 35min 8sec (2108 seconds)

Published: Thu Jan 18 2024