- 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.