Intermittent Hard Starting

[RonnieH]

The weather here in central Va. has turned nice so I started driving the vette to work a couple of days. No problem with starting in the morning. When I go to leave work in the afternoons, car fires right up and then shuts down in a matter of microseconds. If I try to start it back immediately, no luck. Let it sit for 5-20 minutes and it starts back up after turning over for a few seconds - acts like it takes awhile to pump the fuel up. The car is a 90 coupe with only 27,000 miles and has never given me a problem until now, but then again there's always the 1st time. I am getting ready to troubleshoot some of the most obvious things, i.e., check fuel pump pressure (after I get a gauge), check fuel filter, have already added injector cleaner, etc.

Anyway, hopefully someone has experienced/solved a similiar problem or someone add their $.02 worth regarding items to troubleshoot.

Maybe just a coincidence, but the problem just seems to occur on warm days (80 degrees and above) and when it is sitting in the sun. Years ago, similiar symptoms indicated a vapor lock. However, with electric fuel pumps, that problem pretty much ceased to be a problem and just sitting outside, I can't imagine it getting hot enough to vapor lock.

Just grasping at straws, is there anyway to do a quick electrical check on the fuel pump when I have the problem next time. First time I had the problem, first thing I did was check the fuses for the fuel pump and injectors. There are two fuses for the fuel pump - one of them is for "secondary fuel pump". Can any of you explain this - that's a new one on me.

The only other variable I can think of - a couple of weeks ago, I clay barred the car, dewaxed and waxed it and treated the rub strip with peanut butter. She sure looks good, but I'm pretty sure this is not the source of my problem, but darn, it sure looks good sitting there when it doesn't start!!

Thanks for any help you can provide. I'm sure with the knowlege level on this forum, someone will be able to help me resolve the problem. By the way, I already considered the easy fix - stop driving te car to work and leaving it outside all day. Not an option. I look forward to 4:00 for two reasons: 1. getting away from the office 2. Enjoying the cruise home

 

[WhalePirot]

The secondary fuel pump may only be for the ZR-1.

The pump runs for four seconds when the ignition is activated, triggered by an ECM circuit. It takes oil pressure to keep it running.

Maybe your relay is sticking, in the heat only, and starting to fail. If you had a 4+3, you could swap relays, as they are the same. The relay can be carefully opened up and cleaned, as can the connectors, which may help.

The relay an easy place to begin before getting into sending units and more; plus they are mechanical and more prone to failure than the electronics.

 

[6speeder]

You might try to recover any trouble codes.

Need a fuel pressure gage? .... http://minimopar.knizefamily.net/quickfpg.html

 

[RonnieH]

I'll Add To Troubleshooting List

The secondary fuel pump may only be for the ZR-1.

The pump runs for four seconds when the ignition is activated, triggered by an ECM circuit. It takes oil pressure to keep it running.

Maybe your relay is sticking, in the heat only, and starting to fail. If you had a 4+3, you could swap relays, as they are the same. The relay can be carefully opened up and cleaned, as can the connectors, which may help.

The relay an easy place to begin before getting into sending units and more; plus they are mechanical and more prone to failure than the electronics.

Great idea to add to my list. I think this is going to be a difficult one to isolate and I am certainly open to any/all suggestions. For my year model, where is the relay located? I agree it is something starting to fail. Just hope I can identify the exact problem and be pro-active in repairing the problem.

 

[RonnieH]

You might try to recover any trouble codes.

Need a fuel pressure gage? .... http://minimopar.knizefamily.net/quickfpg.html

Never ceases to amaze me the resources on this web. Looking in the garage, I already have most of the fittings, etc. needed to make the gauge. I only need the 0-100 psi gauge and I have a friend who has just such a gauge at work. Thanks for the feedback!

 

[WhalePirot]

For my year model, where is the relay located?

According to the factory manual: on a multi-use bracket, passenger compartment, under the dash, passenger side. There are five relays on it, the fuel pump relay being the middle one.

When you get the fuel pressure gauge, you might tape it facing inwards on the windshield, so you can watch it while you start the car.


If you need an expert, who owns a very helpful shop, perhaps nearby --->>
http://www.jimsperformance.com/

Jim quickly pointed me to the solution to a unique fuel problem, from across the country, while my newly-running hot-Vette was a non-starter at the DMV parking lot. He also was 'there' time and again, when I tackled the TBI to TPI conversion of my car. Highly recommended! Needles to say, I gave him as much business as I could from the other end of the country. ( I see you're 172 miles south of him.)

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