- This is my RB25 Swapped S14. And it's gonna make a
bunch of power, I swear, once I figure out what's wrong with it. So what do you do when all of a sudden your project car runs low on power? Or even worse, won't start at all? Well, maybe you consider
pushing it into the ocean, or even worse, pushing
it to a mechanic shop and paying them to tell
you what's wrong with it. Or that just won't do. So, where do you start,
when your car won't? (car engine revving) So today, we're gonna give
you a proper introduction to my S14, and then, we're gonna use it to show you guys how to diagnose a car that's running poorly
or just won't run at all. I'm Zach, and this is
another one of my money pits. (upbeat music) If you've been watching this show, you've probably seen this
little Nissan in the background staring at me, grin with envy
while I spent countless hours, working on the Miata. Well today, that all changes. So, this is a car I've always wanted. It's a 1997 Nissan 240SX, which means it's a cocky
or a facelift front end, which means it's the
best looking front end of all the 240s we got here in the States. But where I'm from, you really don't come
across these that often, so I never had one. But, as soon as I moved out here, I knew, it was only a matter of time before I got sucked into one. And I sure did get sucked into one. First off, the body is a huge
positive, it's super clean, and you really don't find these in this good a shape,
that often and if you do, people are asking way
too much money for them. But the other biggest
positive, is under the hood. It's got an RB25. It's a straight six
turbo, and it is awesome. It makes all the noises you
could ever want it to make. But when I bought the car, the
positives really ended there. It was a clean body and it had an RB25. But it needed a lot of
work, to get it roadworthy. We've done a lot of
stuff since I bought it. I've replaced the turbo, I've done the whole emission system, I've done the whole fuel system, I did a new throttle body, I did a new catch can, I did a new wastegate. So much stuff has been done, and we are so close, to
getting this thing on the dyno and actually making power. But then the other day,
it fell on its face, and has been having issues running at all. (car engine revving) Now I've got a pretty good
hunch of what is going on, but I thought this would
be the perfect opportunity, to show you guys how to do some diagnosis, on a car that's running poorly. So, to just jump right into
it in terms of diagnosis, the first thing we need to understand, is what an engine needs to
run, it's pretty simple. It needs air, it needs fuel, it needs spark, and it needs compression. So, we'll take a look at
those four overall systems, and then we'll figure out which system the issue lies within, and then we'll take a
deeper look at that system, and pinpoint the issue. It's gonna be a day of
doctoring, call me Dr. House. First let's talk about air. I'd say usually, in my
experience, it's not air. But let's talk about a few issues you could have with the air system. Especially on a turbo car, your boost couplers can come loose, and you can have a boost
leak, which is not good, then you're not getting all
the air into your engine that you're supposed to be. If you've got any sort of a leak after the thing that meters your air, like if you've got a mass
airflow sensor on your car, like the Miata does, if there's a leak after
the mass airflow sensor, that can confuse the ECU, if the mass airflow sensor is dirty, or maybe the wires are worn through, that can also confuse the ECU, so that it doesn't know
how much air it's getting. So it could be air in those senses. This car doesn't have
a mass airflow sensor, it runs on manifold absolute pressure, and I just installed that
as part of a new ECU. So I know that's not the problem, I know my boost couplers are tight, I know that air is not the
issue in this situation. Okay, next, spark. Spark is
maybe the simplest because, all you need is a spark, and it's pretty easy to check for it. I'll show you a couple
of really simple ways. The first, is with this
tool, this is a spark tester. And you can get these
at any auto parts store, Harbor Freight, they
only cost a couple bucks. So, real quick, I'm gonna
pop off on my coil packs, then this is gonna go in line, in between the coil
pack and the spark plug, and we should see if it's sparking by this lighting up in here. - [Eddie] We got it. - Okay, so that's one way, to test whether or not you have spark, and it's pretty easy
if you have that tool. But, I'll show you an even easier way, with just a spark plug. Okay. So the idea here
is just to insert a plug in your coil pack, or into your plug wire, and then the only thing we need to do is make sure that somehow we ground, the ground side of the plug, which is the threads
up to the ground strap. So, easy enough, actually I guess here we'll just sit it on the turbo. And now, I'm gonna go crank the ignition, and we should see spark here
at the plug, if we have Spark. Alright, so that is how you
test spark, and we've got spark. So, that was pretty easy, right? Now, let's move on to compression. So, doing a compression
test can test your valves, your piston rings, your head gasket, all sorts of things
internally in your engine. So, we're gonna do a
quick compression test. I've got my tester here, I think I bought this at Harbor Freight, it's probably 40 or 50 bucks. It's pretty simple, we just
got to remove a spark plug to test the cylinder. We'll take this hose, and it goes right down
in to the plug threads. And now we've got a hose
attached to our cylinder. So, we'll put our pressure
gauge on it, nice and easy. Cumbersome steel, don't fail me now. Okay, so now we don't have any sparks, so we're good to do our compression test, the engine is not gonna start. Generally in any gasoline engine, you're gonna want over 100
psi and all of your cylinders, and you're gonna want them all to be within about 10% of each other. So, without further ado,
I'm gonna go crank it, you're gonna keep an eye on it, right? Okay, how do we do? - [Eddie] About 120. - 120, that's a little
lower than I was expecting. But, I know that compression
isn't the issue on this, so we're gonna move to the fourth thing, that an engine needs to run in that fuel. (upbeat music) The first thing that we wanna do in terms of checking our fuel system, is to check and make sure
that there's fuel pressure. I bought this kit from Harbor Freight, I think it was about 40 bucks, or you can rent this from
any auto parts store. It's a fuel pressure gauge, and you can put this right
in line of your fuel line, with some supplied hose. Or, it comes with a bunch of fittings, that will screw into a
receptacle or a Schrader valve on your fuel rail. But, if you're like me, and you're fiddling with stuff a lot, and you wanna be able to keep an eye on your fuel pressure pretty regularly, you've got a fuel pressure gauge on your fuel pressure
regulator in your engine bay. An engine usually wants about 43.5 pounds of fuel pressure at idle,
really at all times. So, when I turn the key on, I should See this come
up to about 43.5 psi. That's what I have it set to. Okay, so what happened? - [Eddie] We got about 20. - 20?
That's low. Our fuel pressure is only at 20 psi, when it should be at about 43.5. So, that means we've got an
issue with our fuel system. And there's only a handful
of things in our fuel system that it can be. So let's work our way
through the fuel system, and check them off. So, the first thing we're gonna do, is actually visually
inspect the fuel system, from front to back to make sure that we don't have any
just straight up leaks. And also use your nose,
'cause, you know, gas stinks. So, okay, no fuel leaks. I've actually been through
the fuel system front to back, I've had the gas tank out, because that's the whole thing on these. I know there are no fuel leaks, in the external sense. But, now it does kind of sound like we've got maybe an internal leak. Then next thing we've got, is
this fuel pressure regulator. All right, so I guess
there are kind of two ways, that our fuel pressure
regulator could be the problem. For one, the diaphragm
inside of the regulator could be torn, which would
let it leak up into this top, which would mean that this
hose would be full of fuel, and it isn't. Doesn't even really smell like fuel. So, that's fine, not the diaphragm there. So the other thing that could happen, is that the fuel pressure regulator could be stuck open inside, and just bleeding pressure
back to the tank constantly. So, what I'll do is pop the return line off the bottom of the regulator here, and then I'll go cycle the key, and if it basically just
dumps fuel out the return, then we know that our
fuel pressure regulator, is just letting pressure off. - You good?
- Yep - [Zach] Just carry on. - [Eddie] So you want
gas coming out right? - No.
- I'm just kidding. - [Zach] I know!
(laughing loudly) - Okay, so that rules out
our fuel pressure regulator, which is to be expected. I mean, it's a new regulator, and they don't really
go bad that frequently. So, this moves us further
along in our fuel system. We've ruled out leaks, we've
ruled out our injectors, and we've ruled out
our pressure regulator. So now it's time to go back to the tank, and look at the thing
that makes the pressure in the first place, the
fuel pump and its circuit. Alright, so now we're
back here at the trunk, we've worked our way down the fuel system, and we've gotten back to
where the gas tank is, and in the gas tank, lives the fuel pump. So we're gonna test the
fuel pump and it's circuit. Which should be pretty easy,
the set up is pretty good. My battery is right here, my
fuel pump relay is right here, and my fuel pump itself,
is right in there. So the first thing I'm gonna
do, is pop out this relay, and I'm gonna use this jumper I made, just a little piece of
wire with two connectors. So I'm gonna jumper
the power on the relay, to the fuel pump, so I can power up the
fuel pump constantly. And then I'm gonna
check and just make sure that the fuel pump is
getting battery voltage. I'm gonna do that, with my multimeter. So, to check voltage, in this case, we're gonna be checking
voltage on automotive system, which works on a 12 volt battery. So, this is not an
auto-ranging multimeter, like some of them are. You have to select the range which you're gonna be measuring in. So, since this is a 12 volt system, we know it's gonna be less than 20 volts. So, I've got selected the 20
volt range on my voltmeter. So, we're good to measure
anything below 20 volts. Let's go ahead and check battery voltage. So the battery's got about 12.75 volts, nice and charged, that's sweet. So now we're gonna power up the fuel pump, and see how much voltage it's getting. (upbeat music) Now we can see the fuel pump is getting about our battery
voltage, it's getting 12 volts, so that seems pretty normal. So, that is just kind of
another thing checked off. The pump is getting voltage, so why is it not making pressure? Let's get down to the pump, get it out of the tank
and take a closer look. Alright, so, it seems that
our fuel pump has voltage, so that sounds good. It sounds like the problem
must lie with our fuel pump. But before we go pulling
it out and replacing it, we need to do one more test, and it's a really important test. It's called a voltage drop test. And basically what this is gonna do, is allow me to measure the
circuit the fuel pump is in, in terms of wiring, and make sure that the problem
doesn't lie within the wire. And basically what we're
doing, is looking to make sure that there's no large use of voltage, anywhere in that circuit. We're gonna wanna see about
a half a volt at most, in terms of voltage drop on this circuit. So, let's go ahead and do it. Positive on the positive terminal, and negative on the positive
terminal of the fuel pump, and again, we're looking
for half a volt or less. Oh baby! So we've got .49, so it should be okay. It is a little bit high though. Now let's do the same thing
with the ground circuit. Remember, the fuel pump is still running. Negative onto the negative
terminal of the battery, positive to the negative
terminal on the fuel pump. And we're getting about
half a volt here too, just a touch over, actually .53, which is on the upper end, of how much voltage drop
I'm okay with seeing, but it should be okay for a fuel pump. So, now we know that we don't have a huge resistance in our wiring, and everything else seems to be okay, now it's time to pull the fuel pump out, and see what's going on. - [Eddie] Oh, what do we got? - See that hose, that
should be all the way down on this little outlet here. Instead, it's blown off, aka, not gonna make much fuel
pressure, aka our problem. This is a kind of inconvenient spot. All right, so, that is everything. Now, basically all we need to do, is jumper our relay to
turn the fuel pump on, go to the front, and see
if we've got fuel pressure. I think we're gonna. Hey, 44 psi, that's what you wanna see. We've got fuel pressure, which means this thing
should start pretty easily. (Eddie screaming) What was that?
Was it a spider? - [Eddie] Yeah - Okay.
- Bro, I felt that crawling on me, that was a genuine scream. - I know, it was great.
Was it black widow? Just tell me Yes.
- Oh, yes. - Okay, cool. All right, let's see what we got. (car engine revving) - [Eddie] Yeah (mumbles). There we go. - Just been a minute she's
since she's been alive. Alright, she's running,
let's let her warm up. Hey, it's finally not lean at idle. So this is an untuned car,
I've gotten it on a base tune, I've got it tuned to the point that I'm able to drive
it around the block, but it's not quite tuned. So, we're gonna let her warm up, and then we'll see if she
goes around the block. Alright, so we're just taking her for a quick spin around the block, to make sure that things
are running right. I'm feeling pretty good,
and starting to think that it's time to go get this thing tuned. I need a diff! Well, sweet. That's a productive day in my book. We got this thing ready to go to the dyno, which is all I really wanted. And I think along the way, we've hopefully taught you guys
how to diagnose some stuff. And the fact is, diagnosis
is a very deep well, there's a lot of stuff, so we've really only
scratched the surface. When issues pop up, we'll
cover some more diagnosis. I hope you guys liked this
one, I appreciate you watching, follow me on Instagram @Zachjobe, follow donut @Donutmedia and I'll see you guys next week.
I enjoyed this, except he kinda forgot to check the final thing a car needs to run, which is timing. You can have fuel, air, compession, and spark, but if your engine's timing is off, you will not be going anywhere.
This is really helpful I’m trying to learn a lot more about cars lol
Really good troubleshooting video.