Chevrolet C4 Corvette - No Start Diagnosis

there are viewers and welcome back to the self-made Auto Channel so we've got this 89 Chevrolet Corvette here it's got the big five seven in it and a six-speed yeehaw and it's been sitting in storage for four years not running at all so the guy finally decided to get it out and ditch the car you know get something that you can actually drive that he wants to drive so what happened is he started it up it ran really poorly you know kind of skipping bucking it's kind of what he'd expect with you know 4-year old gas so then he went borrowed a dealer plate from somebody cuz the things not in the road he went out just you know just pissed pounded this thing all over town I said it started running really good he was like happy with it thinking about not getting rid of that blah blah blah and he went to somewheres and shut the key off and the rest is history she came out on a flatbed well this sounds all too familiar with anybody who watches the SMA videos back in the archive we did another shitty Corvette with the same engine and I believe the same year except that had the you know weaksauce automatic in it it was that white one I think that was an 89 or maybe hear something 87 I don't know it was a c4 body style but you remember right that car ran fine cold it would start cold and the guy had the same exact symptom you know he went to the Walmart or wherever shut it off and no beans baby she was done running that car had shorted out fuel injectors so same symptoms same car same engine we're gonna cut right to the chase we're gonna do some current ramping right at the fuse box the car has set up here all day I did start it up it runs like crap it's kept sandbox and you know it's like it would barely start so I hope it starts again so we can do this but it's a group fired injection system so you've got four injectors on each side they all fire at the same time you know per Bank you know when the cult group group fired that's not individual sequential fuel injection and just sprays the gas and hopes for the best you know that type the system so a pretty old school but these injectors are notorious for for going bad I want to call them the bull Tech injectors or whatever they come and I'll keep track a little bit particular it's but like I say we've seen this before so we're gonna skip right to it and see what we see all right so we right here in the passenger side where the these panel is should be a couple of pieces in here hopefully for injection according to the liner diagram so here they are we got injector number two we got this 10 and I've got these little jumper leads so we're gonna take our fuse plug it into our jumper lead then we're gonna plug this into the fuse box and then this will give us a loop to stick our ant plant on okay so we're gonna take shove this rate the female terminals on the fuse box that's objection number two Wow serious objection number one thunder was that Hanna oh sweet this huge number - and we'll make the same loop with this we'll shove this in so we've got pretty much Bank 1 and bank 2 so now we've got essentially two loops that will throw our current our current clamp on to get our current ramping for the injectors now instead of going into the whole in-depth on this I'll put links to the other video that we did showing you know some current ramp testing and stuff like that the only difference in the first video we never tested it at the fuse box so what we'd expect to see here because they're all fired at the same time essentially we're gonna have four times the amperage of a single injector now if one injector is shorted this whole you know this whole waveform is gonna be you know shorted so we expect to see this nice steady build up you know until it Peaks and then you know when the injector fires or when the injectors turned off rather you know goes back to zero zero amps and then just you know a nice steady ramp with a little dip in it you know where the pintle actually opens you can actually see that event on a good injector waveform I think we really demonstrated that good in the other Corvette video that we did so I grabbed our scope we'll hook onto this we'll see what we see and then we'll take our diagnosis from there okay so I've got our current plant all set up here and it's sitting in the driver's seat we're gonna see if it starts I don't know if it will because there was running really really poorly in either case we should be able to grab some current rantings information the guy did confirm that it was a fuel delivery issue they actually told me it needed a fuel pump he's got this this little guy here this is a fuel pump cover or something for the match that's here he's already got taken off so it would be easier for us to change the dew point and I guess if you gave her a little spritz of the good stuff it would start so but I'm not expecting any problems with the fuel pump because I could hear it when it turns on but I am suspecting some big-time injector problems so let's see hopefully we got this going the right way all right go ahead and crank it and see if it starts we're trying to get in okay go ahead it's like I'm not getting any that's because we got our scope on stop instead of record rookie mistake common rookie mistake alright hand let's try this again got my current plan backwards doesn't act like a once it's dirt though okay try it again oh wait a minute let's see here I want to capture wave for him okay go ahead well show's over folks look at that that Bank has at least one short of the injector so it's pulling about five amps we're just zoom in on this this is that's above the most terrible injector waveform you can get you can see there is no current build-up when that curtain when an injector driver is turned on and immediately you know spikes right out so that's that Bank I can smell a little bit of gas or something here don't you smell some funk in it so it probably has like one silver so spray it okay so that's one bank what we've got this facing so that should be the same on this one all right let's crank it over look at this Bank and see what happens yeah that's good that same exact thing so this could bogna if you didn't really know what you're looking for because you know these these waveforms look identical you know so if you're just doing a comparison you know if we didn't know better you could really get slit I think a mop before with it but that's that is a bad injector waveform unfortunately I think when we did the other Corvette video I did a my my all tell so I don't have the saved injector waveforms here but what we can do for sake of demonstration just really quick we'll go in here to the component tester we'll see if it has which mean this is okay let's see fuel systems injector current ramp there it is let's see just all that stuff I want to see if it shows us a picture it does show us a picture so this is what we'd expect to see regardless of its you don't amplitude you know that's what we'd expect to see let's see and then they show examples here you know if an injector has high current flow suspect short or low resistance the injector if injector peak is lower missing expect open or high resistance and injector wiring or driver you know also shown an open there but this is showing the pattern essentially that we're getting you know absolutely rubbish but that is what we'd expect to see just a nice steady buildup usually I have like a little little dip in them right here where the Pennell opens so that's it folks what you could do at this point or what we could do what we could elect to do is go through and check each individual injector and see which one is shorted which one isn't because it's not likely that all eight of them are shorted there's at least one on each bank more than likely more click and say when this thing ran it ran terrible like maybe four five cylinders something like that just barely runs with these you tear them apart you just get all new injectors it's just all there is to it they're paying the neck to put injectors in I do have a video on that and I'll link to that but there's nothing more here to show this obviously has shorted injectors I'm gonna take because I know a short video I'm gonna throw a couple of links to other videos where the current ramp is used to diagnose I think I even has some of those I may have some of those so make sure you look in the description below a super handy tool to have whether using it on you know just a regular graphing meter you don't need you know super fancy scope we could have used our alter I'll tell we could use our Vantage you know anything like that and you know this works out pretty good because we don't have to really unhook anything other than taking out a fuse that's it we've diagnosed this this vehicle at the very least needs all the injectors and being that it's got four year old gas and I'm gonna highly recommend you know fuel filter and the fact that we completely drained the tank and fill it up with some ethanol free gas so this could go back in somebody's barn and sit for another four years without as big of casualties here so that's a Google+ Facebook check us out around those subscribe to our channel if you want I wish that you would you know you want to so click the button if you haven't done that yet and remember viewers if I can do it you can do it thanks for watching

Channel: South Main Auto Repair LLC

Views: 70,746

Rating: 4.9353576 out of 5

Keywords: chevy corvette, 5.7 tpi, multec injectors, fuel pump, no gas, no start, fuel injectors, current ramping, injector current, shorted fuel injector, fuel injection, no fuel, no spark, sma, avoca ny, eric o, MULTEC FUEL INJECTOR FAILURE, Multec II, problem injectors, wont crank, wont start, stalls when hot, starts hard

Id: cdG0MaKc36M

Length: 11min 34sec (694 seconds)

Published: Sat May 14 2016