Intermittent Won't Start When Hot Problem

[kcac]

I have a 1995 Cutlass, 3.4 DOHC engine, 75,000 miles on it. It starts fine when the engine is cold. When hot, it sometimes will crank fine, but will not start. Sometimes extended cranking will get it to start. If I do get the hot engine started, it runs fine. Other times the hot engine will start with no problems at all. 

Does anyone have any troubleshooting advice they can share? I would like to diagnose the problem so I am not blindly replacing parts.

 

[walterdude]

With my 93 Z34 a bad FPR caused The problem you describe... When I went anywhere that I'd only be out of the car for a short time I'd have to leave the car running and lock the keys in... Of course I had a spare in my pocket!!! If the car had time to cool down it started fine... I'd start with Fuel Pressure Guage and check the fuel pressure... Get a Work Shop Manual and a Fuel Pressure Guage and follow the steps outlined in the manual... Most Auto Parts Stores will loan tools,,, you pay for them and get a full refund when you return them...

Hope this helps you out... Post back with your results/progress...

Good luck,,,

Tom B...

Edited July 4, 2019 by walterdude

[kcac]

Thanks, I will check the fuel pressure regulator. I drove the car today. Got it fully warmed up, and made five stops where I shut off the engine and let it sit for 10 - 30 minutes at each stop, and the car started every time.

 

[55trucker]

Without any indepth tools to do some diagnostics

 

try this......when this situation occurs simply pull off any one of the three forward bank plug wires, stuff a screwdriver into the end and with another individual at the ignition key hold the screwdriver close to a ground & watch for ignition spark at the electrode. One can check one of three forward injectors with a noid lamp to watch for the circuit pulsing in the same test manner. If you've both spark & injector pulse then the issue is elsewhere. The fuel pressure should be in the neighborhood of 42psi ign on eng off & the pressure should hold relatively stable.

 

[Cutlass350]

3 hours ago, 55trucker said:

pull off any one of the three forward bank plug wires, stuff a screwdriver into the end and with another individual at the ignition key hold the screwdriver close to a ground & watch for ignition spark at the electrode.

Please, never do that.
That's fine for a car built in the 60's, but not anything built past 1970.
Doing that can damage the electronic spark module and/or coil.
Many times, the damage will be "latent", and will work fine right afterwards.  However, after time and heat cycles, the latent damage becomes greater and greater, until the module or coil fails.

An inline spark tester is under $10.
https://www.google.com/search?q=inline+spark+tester

Many inductive spark testers are also cheap.
So, there's no reason at all to have the spark plug wire/terminal discharge directly to ground.

Fwiw, I agree that the problem sounds exactly like a bad fuel pressure regulator.
Those are known to fail on GM vehicles.  They are often cheap and easy to replace.  So, it wouldn't be a bad idea to replace it anyways.
Get a GM, Delco, or "Standard Products" brand.

Good Luck!

 

 

 

Edited July 4, 2019 by Cutlass350

[kcac]

I have had no issues with the car starting when hot since I originally posted. This is not a daily driver, but I made a point of driving it more often just to see if I could come up with a consistent no-start condition, or at least a pattern to when it failed to start. I will be testing the fuel pressure when the no-start occurs again.

The is parked November through May. I add Seafoam to the gas tank as a fuel stabilizer and fill the tank before storing it. When I was experiencing the no-start issue, the tank was still full with the stored gas. Could the six month old gasoline be the cause of the no-start instances? Three years ago, the same pattern occurred. Engine would not start when warm, and this was right after the car had been put back in service. Neither I nor a shop could reproduce the no-start symptom. The car ran fine for the next six months until it was put back into storage. And it ran fine the next two summers, too. 

[Schurkey]

I guess the answer is to pull the thing out of storage, air the tires, check the oil and brake fluid, then go for a 400-mile drive.

Edited August 2, 2019 by Schurkey

[kcac]

I am thinking along the same lines, except instead of the 400 mile drive, when I pull the Cutlass out of storage next year, I plan to siphon the fuel from the tank and put it in our vehicles that are on the road year round.  Then fuel up the Cutlass with fresh gas and see what happens.

 

 

[jiggity76]

I had the same issue with my 96 CS 3.1 sedan.  It would crank for 15-20 seconds before starting when doing errands around town but would start right up when cold, only crank 2-3 seconds before starting.  I even took it to a GM garage and had to pay the diagnostic fee just so they could tell me it's fine and no issues, just to live with it, it's an old car (78,000 miles at the time).  As soon as I got it home from driving it 40 mins back from the dealer, it took forever for it to start up.  It only sat for about 10 mins.  I got very angry and decided to diagnose it myself.

After watching some YouTube videos and talking to some guys here, I changed out the fuel pressure regulator which only took about a half hour or so.  Never had a problem again and starts right up no matter what temperature.  That was last fall.  Starts up consistently about 2-3 seconds every time.

When I do the gaskets and maintenance work on the International and STE (both LQ1 3.4 cars), I'm changing out the regulators too since I'm in that area anyway.

Edited August 3, 2019 by jiggity76

[kcac]

jiggity76 - did you check the fuel pressure before deciding to change the regulator?

 

[jiggity76]

6 minutes ago, kcac said:

jiggity76 - did you check the fuel pressure before deciding to change the regulator?

 

No I didn't.  I just kinda guessed, seems like it was just starving for fuel when it was warm and running around town doing errands, stopping and starting a lot and struggling to start up.  A guy on YouTube said that if you pull off the little rubber vent hose or whatever it is from the top of the regulator and fuel comes out of it, that's bad.  That's exactly what mine did when I pulled it off.  Still pretty mad that the company who built the car couldn't diagnose it properly and I had to fix it myself.  I mean, they are suppose to be trained GM technicians right?

[walterdude]

That "little rubber hose" is a vacuum line... When the diaphragm in the regulator goes bad it can leak gas and fill up the vacuum line... Doesn't always work that way,,, BUT,,, it is a pretty good indication of a bad FPR... I had actually forgotten about that "trick"... As I said (somewhere not too long ago) I haven't had or worked on ANY GM product in quite a few years... I haven't even had a car or driven since last Feb... Can't afford much,,, but,,, I am looking!!! I'm stuck in a rest home for now and it really sucks not being able to go anywhere!!!

Tom B...

Edited August 3, 2019 by walterdude

[jiggity76]

7 hours ago, walterdude said:

That "little rubber hose" is a vacuum line... When the diaphragm in the regulator goes bad it can leak gas and fill up the vacuum line... Doesn't always work that way,,, BUT,,, it is a pretty good indication of a bad FPR... I had actually forgotten about that "trick"... As I said (somewhere not too long ago) I haven't had or worked on ANY GM product in quite a few years... I haven't even had a car or driven since last Feb... Can't afford much,,, but,,, I am looking!!! I'm stuck in a rest home for now and it really sucks not being able to go anywhere!!!

Tom B...

That's exactly what the guy on YouTube was talking about.  I can't speak for anyone else's situation but like I said, I changed it out and it's been starting up like a champ ever since I replaced it.