I had an issue a couple of weeks ago that just bothers me. 1990 A4 starts and runs well except for once two weeks ago. I get back from a drive, park in the driveway before pulling into the garage and let the car sit for about 30 minutes. Go to start the car and it does not start. Turns over but when I first turn the key I do not hear the fuel pump kick in. Try on and off for 20 minutes with no luck so I push it into the garage figuring I will troubleshoot it in the morning. Except it starts right up the next day and has ever since then with no issues. New fuel pump two years ago. Relays check OK but are old and I have an FSM to troubleshoot.
So now I just keep wondering when or if this will happen again and if I will have cell phone service when it decides to act up again. I know I should just keep driving it and not worry about it but intermittent issues bother the hell out of me.
Anyone else ever had this happen and figure out what caused it?

 

Check if it has fuel pressure at the time of problem with a gauge and not the ear

 

I have and it was the wiring on the sending unit itself, inside the tank. In my case it was because the Racetronix pump sucked so much juice that it eventually melted the wires. But it does seem to be happening with others due to the age the cars now. It only happened intermittently, so I'd have full fuel pressure or it would plummet and then come back up. Some days it fired up fine, some nothing at all.

If the relay is good, you can power directly through terminal G, the fuse is good, then its basically got to be either the pump or the wiring to/from somewhere, assuming you checked fuel pressure of course when you couldnt get it to fire.

 

Thanks for the quick replies. Fuel pressure is good now but I did not have a chance to check it the one time it did not start. If I could get the same issue again I would check it immediately. Happened once and never again.

I think I will just keep driving it and hopefully it never happens again (yeah right).

 

Pressure is good as in it holds at 43 psi for a while and is good at WOT?

 

Yes fuel pressure is good at WOT. Car runs strong, modified as indicated in my profile, pulls very strong up until theTPI runners run out of breath.

Just that one time that it did not start, cured itself, and has perform as expected since. I am just one of those people who need to know why something happened and it drives me nuts until I figure it out. Old engineer who needs to know the “why’s “.

 

First, I would like to Welcome You to the Corvette Forum! This is the place to be if you have a Corvette.

Try replacing the Fuel Pump Relay as that can cause intermittent issues. This relay is used on several places in my 1988 so I keep a spare with me in the glove box.

Take a reading of your battery voltage and then measure the voltage at the fuse panel. They should be the very same or close. If there is a difference with the readings and the fuse panel readings are lower than your battery readings then you might want to check the post where the battery supplies voltage to the Fusible links on your Corvette.

On my 1988 C4 the post was covered in corrosion and caused a near 2 volt drop between the battery and the fuse panel. The post is located behind the battery under the side panel cover in front of the drivers door. There should be a fairly large RED wire leading you to the post. This is the point from which the power is distributed throughout the Corvette. On my C4 the low voltage was making the relays hold and then let go intermittently. After re-supplying them with full battery voltage everything worked much better.

These C4's need clean electrical connections to operate at their best so I suggest that you clean all major connections and reconnect them. I bought some DeOxIt which is an incredible electrical component cleaner and it will wipe away decades of corrosion in seconds. I have a bottle in my Tool bag and one at my bench just because it works so well. It is available on Amazon.

If you don't already have a set of Factory Service Manuals for your specific year you should get a set. For my C4 it consisted of two books, one mechanical and one electrical. They are available in print and on DVD by aftermarket suppliers. The other important tools would be the Fuel pressure testing Gauge and a good Volt Ohm meter to get going with your Corvette.

 

And a scanner

 

I do have FSMs and a parts and illustration catalog for the Corvettes.

I have cleaned all ground locations, replaced both positive and negative battery cables, battery voltage is great. This was all before the issue popped up. I have a wide variety of electrical test equipment including a little used oscilloscope, more machinist measuring devices than I care to inventory but no scanner. That will be next on the acquisition list.

Retired engineer with both mechanical and electrical disciplines that has worked on vehicles since high school so troubleshooting and correcting this issue should be in my wheelhouse. The problem is it happened once so unless it happens again I have no starting point for troubleshooting. I will replace the relay even though it tested OK.

It is the one time gremlin that just bugs me.

Thanks for everyone’s suggestions..

 

When it comes to older Corvettes it helps to have a scanner like mentioned above as I had left it off my list. (Thank You Aklim!)

Your Fuel Pump relay tested okay? Mine would not hold the relay closed for very long and I suspect it was damaged by the low voltage operation. It would just randomly shut off and stop the flow of fuel. Did you try to see if full voltage is making it to the actual fuel pump? That is important, if it is then I still would suspect the relay. The possibilities are kind of limited

I found a Snap On MT2500 for a deal on the Corvette Forum and it is priceless. It came with the one cartridge that works on the OBD1 Corvette and several for Asian cars. It allows you to see in live time what is happening in your Corvette. You mentioned having an oscilloscope and if you want to see some things working you could use it. I still miss my Fluke Digital portable oscilloscope from work.

I too am a retired engineer with a lot of tools. I built Solar Photovoltaic systems for Westinghouse around the world. I don't miss the traveling but I loved how people around the world reacted when I told them about my C3. They could not accept that we need a 7 liter engine for a 2 person vehicle.

Unexplained gremlins are very hard to trace at times. This is when it is nice to have OBD2 tell you the history versus the limitations of OBD1. I am glad the new Holley EFI I put on my C3 has the potential to data log so I can watch the problem IF you can catch it happening. If you need something like a scanner there are folks on this Forum who can help you know what works best with our C4's. I keep hearing about Tuner Pro and a Moats adapter to connect to the OBD1 port.