I have a 1991 l98 corvette that won't start. It'll run on starting fluid but nothing without it. It seems like the injectors are not working. We tried to connect a multimeter to the injector harness to see if there's power getting to them, there was no reading at all on the multimeter but I'm not sure if this test really works or not. I find it hard to believe all 8 injectors stopped at once (it was running previously). Any help would be great.

 

Take a look at the Ignition related module mounted inside the distributor and be sure it is working. I would check the electrical connections to ensure there is no corrosion. It is something to do with the lack of pulses telling the injectors to fire. I believe it is the Ignition control module and IF I am not mistaken that would be the first place to check.

Be sure that your fuses are still good for the injectors. I have seen blown fuses stop the one batch of injectors from firing.

I am a bit leery when folks use Starter fluid for testing a go/no go on the ignition system. Ether (Starter fluid) will detonate under compression only and does not need to have a spark. We use in Diesel engine is really cold weather to help start the engine. Ether fires inside a diesel which has no spark so how good a test of the ignition system can it really be?

You can test your spark several ways. I have a device that plugs in between the spark plug wire from the distributor and the top of the plug itself. It has a variable gap so I set it for the spark gap and then I test each spark plug at the plug to ensure that I have a healthy Blue spark at all eight plugs. This also helps isolate the bad spark plug wires as the spark will appear yellow versus the blue spark. I had an engine that was misfiring and it turned out that someone got a bit heavy handed with the Die Electric grease and the plugs were not getting all the energy. Some had really weak sparks and others were perfect, I had to test each wire and plug individually.

Hello there sheriffjim! I hope that this helps you a bit! I see this type of failure moderately often as the C4's get older, it is normal due to age and heat. Be sure to buy the replacement parts from a good trustworthy source as some won't take the electrical part back after you buy it and try it. The electronics used in the C4's was designed for a 15 year life expectancy like inside the dashboards.

Good Luck and have an awesome Day!

 

thanks for the help! I wasn’t aware of the starting fluid issue, I might need to get a bit more technical when testing it in that case.

the whole distributor is brand new (including ICM), when the car died we pulled it out and discovered the gear on the bottom was torn up. After replacing the distributor it still doesn’t start.

I have one of those spark testers as well and it’s showing good spark, I’ll go test it again when I get the chance but spark should be just fine.
it could be a blown fuse but I’m not sure. I don’t have much time to work on the car during the week, so I’ll just have to make a list of things to do.
thanks!!

 

Test light is a better tool to check for injector pulse. Try to Google no start trouble tree. Fuel pressure over 42 psi? Injectors use 2 fuses each powering 4 injectors. ECM grounds injectors. Noid light is preferred tool to check injector pulse. Use test light for 12v to injectors. Attach test light clip to battery positive,terminal; light will blink as ECM grounds injectors.

 

It was so long ago I don't really remember but I believe fuel pressure was good but would drop off slowly. I can probably get a test light on it but I'll have to wait until later this week, like I said I don't have much time. When I can get a light on it I'll try your recommendations.

 

You can use a set of these to see if the injectors are getting a signal to pulse from the ECM.
https://www.walmart.com/ip/Wilmar-Pe...5&gclsrc=3p.ds

 

There is a YouTube video from south main auto that goes through the full diagnosis. If you suspect injectors, get a multi meter on it and ohm them out. (Takes a couple minutes and is a good quick test.) I don't recall the specs, but they are around if you look them up. I want to say 15 ohms and they should be about 1 ohms within eachother. Anything less than 10 ohms is suspect iirc. I believe early cars are a little different but those are the numbers we used for an 89 which I believe is the same as 91.

 

I tested my injectors with a noid light, there’s no pulse. I’m not sure why though, anyone know what might cause that?

 

Injectors get signal from ECM. You do have 12v to the injectors? There are- 2 fuses if not. The purple wire of the 4 wire connector at distributor sends reference signal to ECM. Disconnect 4 wire connector attach test light clip to battery positive. With key on. Touch probe to ECM side of connector purple wire terminal. You should hear injectors cycle as probe in removed. If injectors cycle distributor is faulty since its a reman. No cycling ECM, harness , terminal or ECM ground.. You will need to pull ECM to test harness

 

If you have Multitech injectors (they have a light gray body), you could have bad injectors. Ethanol in the gas can ruin them. It can cause them to short and I think take out a whole bank of injectors. I have a 91 corvette parts car and it has the Multitechs injectors from GM.

 

Hello, thanks to everyone for all the help. The car is running now, a new distributor turned out to be the answer. I apologize for going down the wrong path with the injectors, but I did discover the fuel pressure regulator was bad, so it was somewhat useful. Anyways, thanks again to everyone who gave their advice and helped me diagnose this problem. I'm new to car ownership and especially maintenance and all of y'all help is part of the reason why I like this car and the community that goes with it so much.
Now I'm gonna go drive it!