: Hot start...but not the FPR!



weister42
11-06-05, 01:31 PM
If you have been tracking my posts I have a hot start problem when my car's been parked for at least half an hour after the engine warms up. First I thought it was my stereo and I ripped it all out, then I had a shop run a cleaning agent to clean my fuel injectors, replaced the fuel pump relay & filter, plugs & wires are 8 months old and the car runs perfect when it's running. I replaced the FPR this weekend and the problem did not improve a bit (60 dollars down the drain:banghead: ). One thing I noticed when I removed the old FPR was a coat of very dark red oily substance under the FPR and probably all around whatever else that's connected to the underside of the FPR, my friend and I couldn't figure out what it is but I don't think it should be there (should be just fuel).

So, I'm confused. I'm wasting my money. WTF???

zonie77
11-06-05, 03:49 PM
The suggestion was to buy a vacuum tester and test it before replacing it.

I would test the fuel pressure next.

weister42
11-06-05, 04:19 PM
Actually my mechanic told me the FPR is fine...he followed the vaccum test on this forum but I just want to eliminate all the possible faulty parts. Fuel pressure comes out to be 42psi. Again the car drives perfect when it's running.

:bighead:

weister42
11-06-05, 04:24 PM
However I do have one question...what are those wires running into the passenger side of the engine compartment? It's a black plastic wire organizer and that's where my power wire for the stereo goes through (wires were the only component I didn't remove when I took everything out). I trimmed the plastic part so the thick wires can go through and it's really close to the factory wires.

eldorado1
11-06-05, 04:45 PM
Could you explain in more detail what it's doing?

When you start it, it turns over... does it try to fire? Do you hear a couple puffs? Does it just crank? How long does it take until it does fire up? Does it start up if you let it cool down? (is that the only way it will start?)

What happens when you push the pedal down when you try to start it? Does it start easier? Not effect it at all?

zonie77
11-07-05, 11:09 AM
The wires go to the computer, it's behind/below the glove box.

CadillacSTS42005
11-07-05, 11:47 AM
I had the same problem with my Trans AM but thats a crossfire lol. (AKA designed by those who had developed the caddy 4 6 8 motor so you kno the set up is shit) i had to replace the ECM worked fine ever since

weister42
11-09-05, 09:49 PM
It takes about 3~5 seconds to start when it doesn't want to, starter spins rapidly and everything is normal, car drives perfect when it's on.

My car does start better when I press on the gas pedal (at times when it doesn't start right away), so does this mean I have a fuel leak somewhere?

eldorado1
11-09-05, 09:58 PM
So it doesn't even try to fire?

And it only happens when it's hot? No stalling or hesitation or anything when it's running?

zonie77
11-10-05, 02:20 PM
I'd hook up a fuel pressure gauge and check it every time I started it. It would be nice to have it sticking out of the hood where you could easily see it.

The check ball in the fuel pump could be leaking and letting the fuel drain back to the tank. I realize this should be true on cold starts also but this is the next step I'd take. If it showed 40+ while no start it would eliminate pump.

coppertop
11-11-05, 06:03 AM
I thought the fuel pressure was not to be under 45- 50 PSI? Is that just pre starting the motor? I was ready to change the fuel pump because my car running is at 35 PSI.:suspense:

zonie77
11-11-05, 09:36 AM
I said 40 without checking. Don't take that for gospel.


to Weister, check what the pressure should be. If it's even a few pounds low it can give hard start problems.

eldorado1
11-11-05, 11:53 AM
I thought the fuel pressure was not to be under 45- 50 PSI? Is that just pre starting the motor? I was ready to change the fuel pump because my car running is at 35 PSI.:suspense:

Fuel pressure should be at least 40psi idling, and it should rise 5psi if you disconnect the vacuum line to the FPR. If that is not the case, you need to investigate and/or replace the fuel filter, FPR, or fuel pump.

El Dobro
11-12-05, 12:17 PM
I've had a similar problem with my 98 SLS. The car will not start after approx. 5 min. when hot. It wil start before and after that time period and it doesn't do it all the time. Everything checks out. Now, to play it safe, I depress the throttle slightly to ensure that it starts when I fill up for gas.

weister42
11-14-05, 12:40 PM
My fuel pressure is at 42psi so it's normal, I now have to tap the gas pedal halfway down to get the car to start. My car does the long cranks mostly when the engine is warm but sometimes cold. I'm guessing there might be some sort of gas leak that drained the gas out so it takes time for the fuel pump to refill the gas line?

weister42
11-14-05, 12:46 PM
So it doesn't even try to fire?

And it only happens when it's hot? No stalling or hesitation or anything when it's running?

The engine tries to start but sometimes it totally fails as if I ran out of gas. Other than that the car runs great on and off highway and even under WOT with five people in the car. Strange huh?

mcowden
11-14-05, 02:21 PM
Weister42, it sounds exactly like you have a leaking FPR or a leaking injector, especially if you can put the pedal down and it starts fine. When you have this problem again, run to the tailpipe immediately when it starts and sniff the exhaust. If it smells strongly of gas, you have a leak somewhere, be it the FPR or an injector. It's normal for the exhaust to smell somewhat like gas for a while after starting because the catalyst and O2 sensors have to heat up, but if the gas smell is very distinct and strong, it's got to be a leak into the intake. My money is still on the FPR, despite the test results. Mine was the same way. No visible leak whatsoever but it wouldn't hold a vacuum very long.

Ranger
11-14-05, 03:43 PM
If I am not mistaken, holding the pedal half way down does nothing. Holding it to the floor shuts off the injectors to clear a flooded engine. Other than that, the PCM controls the injector pulse width during crank cycle to my understanding.

mcowden
11-14-05, 03:49 PM
If I am not mistaken, holding the pedal half way down does nothing. Holding it to the floor shuts off the injectors to clear a flooded engine. Other than that, the PCM controls the injector pulse width during crank cycle to my understanding.

That's my understanding as well. My point is just that opening the throttle will allow more air in there to burn off the extra fuel that has accumulated. If it's loaded with gas, there might not be enough air to burn it and start. Opening the throttle lets in enough air to burn it properly and start. It's just speculation on my part. Am I wrong?

eldorado1
11-14-05, 04:00 PM
Depends on how far he holds down the throttle... up to about 50% throttle, it will increase the cranking fuel. Past that threshold, it enters Clear Flood mode, and won't fire the injectors until it is running.

I would put the fuel pressure gauge back on it, and try to duplicate the hard start problem. If the fuel pressure holds steady after you turn the key to run (don't start), but it's still hard to start (after you watch the gauge for a few minutes), then you know it's not the injectors or FPR.

zonie77
11-14-05, 07:57 PM
Is that 42lb when it doesn't start? Have you had a gauge on it when it doesn't start?

weister42
11-15-05, 02:19 AM
Well my car doesn't act up at the shop so they can't really pinpoint it:confused: , but I just had the injectors checked/cleaned and the shop says it's not leaking (plus I'll smell/see gas leaks under the hood correct? Which I don't), I replaced the FPR already and that did nothing, and my car seems to get good gas mileage (~13.3 mph in town with heavy foot, 26mph+ on the highway).

I don't have a fuel pressure guage so I had a shop do all the tests, and they seriously aren't lying (didn't charge me for checking the car for two days).

eldorado1
11-15-05, 10:56 AM
it's probably something simple like an intermittant check valve in your fuel tank. But the only way to eliminate that would be to drive around with a fuel pressure gauge on, and try to duplicate it. btw- have you checked your codes?

zonie77
11-15-05, 01:03 PM
it's probably something simple like an intermittant check valve in your fuel tank. But the only way to eliminate that would be to drive around with a fuel pressure gauge on, and try to duplicate it. btw- have you checked your codes?


This is what I've been telling you to do. Harbor freight has a gauge for $8.99. Instead of all the farting around you're doing, this is what you MUST do to be sure it isn't the pump.

No one is saying the shops lying...the gauge has to be on and watched when the car doesn't start.

weister42
11-15-05, 01:07 PM
Okay I'll get get a fuel pressure guage this week, how do I hook up the guage to the fuel system?

eldorado1
11-15-05, 01:24 PM
This is what I've been telling you to do. Harbor freight has a gauge for $8.99. Instead of all the farting around you're doing, this is what you MUST do to be sure it isn't the pump.

No one is saying the shops lying...the gauge has to be on and watched when the car doesn't start.

I'm sure places like autozone might even rent them.

you hook it up to the valve on the front side of your fuel rail, near the throttle body/water pump area...

zonie77
11-15-05, 02:55 PM
you hook it up to the valve on the front side of your fuel rail, near the throttle body/water pump area...


Right! it looks like a tire valve.

Krashed989
11-15-05, 04:57 PM
Why has nobody mentioned the fuel filter yet? :hmm:

eldorado1
11-15-05, 05:01 PM
Why has nobody mentioned the fuel filter yet? :hmm:

back on page 1. but it won't cause an intermittant starting problem.

zonie77
11-15-05, 05:02 PM
I'm pretty sure he put one in. It might have been in another thread.

Krashed989
11-15-05, 05:16 PM
Ohh ok, thanks for filling me in... You guys seem to know what you're talking about, so I don't have much to add. I'm curious to see the outcome of this though.