2002 Mustang GT doesn't want to start when it's warm

[Viper GTS]

I've got an 02 Mustang GT that doesn't like to start when it's fully warmed up. It has never failed to start on the first try when it's cold but if I drive it somewhere & get it fully warmed up it will frequently take 3-4 attempts before it will re-start after it's been sitting. Once started it runs fine. It's never failed to start eventually but it's getting old - Not to mention slightly embarrassing.

Anybody have any brilliant ideas? If I can save myself a trip to a dealer/mechanic for something minor that would be preferred.

It's the 4.6L V8 of course, with ~62K on it. I believe it did the same thing when I first got it 20K ago but I think it's getting worse.

Viper GTS

 

[exdeath]

All solid state ignition with COP so you can rule out ignition since it's highly unlikely it would affect the whole engine at once unless your ECU was going out (highly unlikely).

Running fine when it's running, doesn't stumble, idle bad, or smell rich or anything? Likely able to rule out cold start temp sensor, crank position sensor, and fuel rail pressure sensor.

I'd guess something fuel system related like the or fuel pump/FPDM (fuel pump driver module, driver side in the trunk, controls fuel pump voltage based on computer PWM, known to overheat and shut down); something that gets hot and works fine, but just doesn't want to start up right away when it stops.

Fuel pressure test is also about the easiest tests you can do and rules out 50% of possible issues.

There is also the CCRM (constant control relay module) which is a sealed/riveted black metal can either near your radiator or inside the passenger fender that contains all the main relays like the EFI and FP relay; relays can act funny with temps and starting/stopping.

Some things to get you started. Also check if you have any non-MIL codes that might be logging a history of something.

 

[alkemyst]

could be coil packs. I believe the mustang uses them and that has been a problem of a couple cars I fixed that would start fine in the morning but had a hard time starting mid day.

 

[TehMac]

I had actually started having problems with my '99 Mustang V6 in late Jan 2010. The problem occurs every now and then but its behaving itself lately.


The car's engine would not turn on, the ignition would work, but it'd keep turning over with no spark. So I'd hear these revolutions over and over again, but nothing.

I'd get this nice burnt smell, but a few minutes later, I could turn the key and away I'd go. I have noticed this usually happens if its a bit cold out.

I had started the car up in the morning though, drove off to some place no problem, left it in the parking lot from 8:00 am - 10:45 am, car wouldn't start initially, tried again a few minutes later and it started up no problem.

My friend suggested I had some impure fuel, but I get my fuel at 7/11, not sure that'd be it.

 

[brblx]

if the problem is simply a longer crank time after sitting, i would look at fuel pressure. if the car uses a mechanical fuel pressure regulator (has a vac line going to it), a torn diaphragm inside it could cause a loss of residual fuel pressure. bad drainback valve in the fuel pump or a leaking injector could also cause the same thing.

edit: nevermind, i somehow interpreted the OP's problem backwards.

when it's hot and not starting, what exactly is it doing? just cranking? any sputtering?

 

[Vette73]

Yep I was gong to say check the fuel pressure first.

If it is low, or not there, after it has sat watm then it could be a bad regulator, leaky F/I, etc...

 

[jlee]

I poked around a bit and some people suggest fuel pressure regulator - may be worth a look.

 

[AdamK47]

Starter

 

[Viper GTS]

Sounds like something fuel system then. That's probably beyond what I'm willing to attempt by myself, so I'll take it somewhere to get it checked out. When I said something minor I really should have said stupidly simple, I don't pretend to be a mechanic.

Thanks for the suggestions & I'll update when I get it fixed.

Viper GTS

 

[Viper GTS]

Starter

I don't think so, it cranks just fine it just never catches.

Occasionally when I think it's good & let off it will die unless I can catch it with gas. So I'm inclined to agree with the lack of fuel.

Viper GTS

 

[exdeath]

There is no fuel pressure regulator on those cars since '99. It uses a PWM returnless system.

Instead of a pump working 100% and a regulator returning fuel that isn't needed, the computer pulse width modulates the pump (through the FPDM) based on a pressure reading from a pressure sensor (FRPS) on the fuel rail. There is only one feed line from the tank to the engine. Only the fuel that is needed is sent, hence returnless.

Many cars have been going returnless for the past decade as an evaporative emissions measure.

Common causes for fuel issues on those cars: CCRM (relay module), FRPS, FPDM, and fuel pump itself. Hooking up a fuel pressure gauge can rule them all out in less than 5 minutes, provided you experience the problem at that moment.

 

[Vette73]

There is no fuel pressure regulator on those cars since '99. It uses a PWM returnless system.

Instead of a pump working 100% and a regulator returning fuel that isn't needed, the computer pulse width modulates the pump (through the FPDM) based on a pressure reading from a pressure sensor (FRPS) on the fuel rail. There is only one feed line from the tank to the engine. Only the fuel that is needed is sent, hence returnless.

Many cars have been going returnless for the past decade as an evaporative emissions measure.

Common causes for fuel issues on those cars: CCRM (relay module), FRPS, FPDM, and fuel pump itself. Hooking up a fuel pressure gauge can rule them all out in less than 5 minutes, provided you experience the problem at that moment.

There is a "Fuel Injection Pressure Regulator". Cost $130 at rockauto.

 

[alkemyst]

There is a "Fuel Injection Pressure Regulator". Cost $130 at rockauto.

he's a bench racer and loves to throw out acronyms and technobabble.

 

[Viper GTS]

he's a bench racer and loves to throw out acronyms and technobabble.

Seriously? What the fuck happened to you that this is how you behave?

Go back to the gym or something, piss off unless you're done with your petty flamewar.

Viper GTS

 

[alkemyst]

Seriously? What the fuck happened to you that this is how you behave?

Go back to the gym or something, piss off unless you're done with your petty flamewar.

Viper GTS

not petty, I really...I mean really seriously think he is clueless. I have only been back to the gym for 3 weeks now, but I am glad you are following me.

That last post was total idocity. Are you saying there is no Fuel Pressure Regulator? (resisting just saying y0 an FPR dude).

thx.

 

[Pacfanweb]

Viper:

You say once it tries to start, it might shut back off if you don't keep it running with the gas pedal, right?

Have you tried, when this condition is occurring, cranking the engine with the throttle cracked open slightly?

Try it...just give it a bit of pedal when it won't start, and see if it does then. If so, the IAC (Idle Air Control) Valve is the problem.

Now, usually the IAC causes this problem when the car is cold, not hot....but I have seen a few do it hot, too.


Other things that come to mind: Fuel pressure. Do you hear the pump run when you turn the key on and this condition is occurring? When you first turn the key, the pump runs for a couple of seconds to make sure there's enough pressure to get fuel past the injectors. You turn the key to 'on', and leave it there...you should hear a buzzing or humming noise for a few seconds from the tank area....you also might hear the relay click on and off.
If you do not hear this, you might want to take a rubber hammer or something non-pointy and tap the bottom of the gas tank...see if that makes the pump run. If so, the pump is the problem.

Could be an ignition concern, but I don't know of any easy way a non-mechanical person could self-diagnose that.

 

[exdeath]

There is a "Fuel Injection Pressure Regulator". Cost $130 at rockauto.

Are you saying there is no Fuel Pressure Regulator?

Correct, there is no fuel pressure regulator on 99+ Mustangs, or any vehicle using a RETURNLESS fuel system. The item shown on Rock Auto under "Fuel Injection Pressure Regulator" is called an FRPS (fuel rail pressure sensor).

The traditional fuel pressure regulator is replaced by a rail pressure sensor and a digital pump driver module and lacks a return line. The main engine computer regulates fuel pressure electronically, based on the input on that sensor by altering a signal to a variable speed fuel pump.

 

[exdeath]

he's a bench racer and loves to throw out acronyms and technobabble.

You can blame Ford for the acronyms and "technobabble", that's what those parts are called and anyone who has worked on a Ford in the last 10 years would know what they are.

 

[Pacfanweb]

exdeath is correct, there is no fuel pressure regulator on that car at all.

He's also correct about the Fuel Pressure SENSOR...that's the only thing to do with fuel pressure that's mechanically connected to the fuel rail.

Fuel pressure is controlled by the ECU by duty cycling the pump through the FPDM (Fuel Pump Drive Module)


Talking to my Mustang expert buddy just a minute ago (this guy is one of the premier Stang tuners on the East Coast), he echoed my idea of cycling the ignition key....to see if the pump can be heard running, and also, if it is running, cycle the key on/off a few times and see if it fires right up....that'll tell you the pump isn't holding pressure at rest.

Also, go to a parts store and get the codes scanned...if you have a P 0190, that's a bad FPS that we mentioned before.

 

[Viper GTS]

exdeath is correct, there is no fuel pressure regulator on that car at all.

He's also correct about the Fuel Pressure SENSOR...that's the only thing to do with fuel pressure that's mechanically connected to the fuel rail.

Fuel pressure is controlled by the ECU by duty cycling the pump through the FPDM (Fuel Pump Drive Module)


Talking to my Mustang expert buddy just a minute ago (this guy is one of the premier Stang tuners on the East Coast), he echoed my idea of cycling the ignition key....to see if the pump can be heard running, and also, if it is running, cycle the key on/off a few times and see if it fires right up....that'll tell you the pump isn't holding pressure at rest.

Also, go to a parts store and get the codes scanned...if you have a P 0190, that's a bad FPS that we mentioned before.

If the fuel pump was not holding pressure at rest wouldn't it exhibit the issue in the morning after sitting all night? I can certainly handle that level of troubleshooting though, I'll give it a shot. Would the P 0190 throw a CEL? I'm not getting that, but I can go scan the codes too.

Viper GTS

 

[exdeath]

If the fuel pump was not holding pressure at rest wouldn't it exhibit the issue in the morning after sitting all night? I can certainly handle that level of troubleshooting though, I'll give it a shot. Would the P 0190 throw a CEL? I'm not getting that, but I can go scan the codes too.

Viper GTS

Could involve something overheating that doesn't want to start up again when it's shut off hot (pump driver module and pump itself). The driver module (FPDM) is what takes the low voltage digital signal from the computer and sinks the high current to the fuel pump; they are known to overheat and shut down when they fail.

Again, a fuel pressure test will quickly rule out all of those common problems. If you can hook up a scanner, you can hook up a gauge; just connect to the fuel rail through the valve stem, turn the key on, bleed fuel through the gauge until all the air bubbles are gone and you have a fixed reading, then wait for the problem to occur. If the needle stays ~38 psi when the car doesn't start, then you can rule out fuel system entirely. Alternately you can use a scanner to monitor rail pressure provided the FRPS itself is not the cause.

 

[Xed]

Sounds exactly like the symptoms my old 98 mustang was having. It got to the point it wouldn't start up at all unless it sat for a few hours. Turned out to be a fuel pump going bad.

 

[alkemyst]

You can blame Ford for the acronyms and "technobabble", that's what those parts are called and anyone who has worked on a Ford in the last 10 years would know what they are.

but you see that's not going to be your typical audience and you are assuming more home mechanics are going to spend their free time researching all these things instead of just fixing the problem to get back to driving rather than shopping for parts.

 

[Pacfanweb]

but you see that's not going to be your typical audience and you are assuming more home mechanics are going to spend their free time researching all these things instead of just fixing the problem to get back to driving rather than shopping for parts.

True in a lot of cases, but I know, and assume ExDeath knows, that Viper isn't your "typical audience", and this is HIS thread

 

[exdeath]

but you see that's not going to be your typical audience and you are assuming more home mechanics are going to spend their free time researching all these things instead of just fixing the problem to get back to driving rather than shopping for parts.

No, but if you are going to ask for or look up parts at a dealer, look them up in a service manual, or talk to anybody who works on that car, it helps to know the basic systems you're dealing with. Also I assume someone asking for advice on a forum is hands on and willing to learn something and get technical. If the poster didn't care and just wanted the car fixed, he wouldn't be asking questions in a forum and the car would already be at the dealer for service.

CCRM, FRPS, and FPDM = Ford specific and common Mustang terms relating to starting and fuel system that aren't applicable to common fuel injection knowledge.

For example, there is no fuel pressure regulator on a 99+ Mustang, nor does a Mustang have a typical user accessible FP relay or EFI relay (they are part of the CCRM). If someone comes on here with generic advice saying "check your fuel pump relay or fuel pressure regulator" on a '02 Mustang, the OP is going to be extremely confused when there isn't one, vs. having to Google an acronym well known to the Mustang community.