1990 z24 shuts off after driving for a little bit - Maintenance and Repair Forum

Forum Post / Reply
You must log in before you can post or reply to messages.
1990 z24 shuts off after driving for a little bit
Thursday, June 25, 2020 1:40 PM
I replaced the fuel filter, plugs and wires are next. It seems like it's not getting enough fuel. The battery is 11 years old (also on the list of things to replace) could that do it? The fuel pump primes when I turn the key so I don't think it's the issue. What else could it be?

Re: 1990 z24 shuts off after driving for a little bit
Thursday, June 25, 2020 8:13 PM
Two things come to mind. Fuel injectors or ICM. Often the fuel injector issue engine will die at higher rpm's. Engine will start right back up.
ICM will often die at idle, but can sometimes die at normal cruise. It too will normally start back up and may run fine for awhile, then just cut off again.
To check the fuel inject, you have to pull the plenum and check the Ohms of each injector. If you find one that is quite low, that is the problem. I don't know of any check for the ICM. I think they have to be tested on a diagnostic machine.

Please explain, in detail, exactly what is happening.
Re: 1990 z24 shuts off after driving for a little bit
Friday, June 26, 2020 12:48 PM
It would make sense if it is the fuel injectors. I thought it was the sending unit but what you said about it dying at higher rpms for injectors sounds about right. The car will idle perfectly fine for extended periods of time but usually dies or sputters (silently, just fluxuates rpms so the only noise is the exhaust) if I press the gas too hard or get it above 30. Yesterday was driving fine around my small town for about 20 mins then it died. Started right back up, got another block and died. Every time it died it started right back up but died quicker and quicker. Eventually it gave up on starting and I had to walk home. Started right back up a couple hours later and ran fine. This situation has happened multiple times. Before I replaced the fuel filter it would not start back up when it died. Giving it gas does help when it doesn't want to start but is not a guarantee.
Re: 1990 z24 shuts off after driving for a little bit
Friday, June 26, 2020 9:23 PM
Might want to check your fuel pressure. If you don't have a fuel pressure gauge, you can get one at O'reilly in their Loner Tool. You pay for it, but will get your money back when you return it.

It does sound like it may be an injector out of specs though. The ECM will shut down the fuel if an injector is too low. They should be at around 12.5 Ohm, or so.
What is strange is that if it was a fuel injector that cause the engine die, it should have cranked right back up. At least that is what I've read from others that had a bad injector. I had this happen with my 88 Z24 around a year ago. It died at maybe 42-4500 rpm. I left it in gear but it did not run. Only when I pulled over ans switched it off and then cranked it did it run again. Switching it off reset the ECM, and it would crank again. I read a lot over at v6z24 and saw where other people posted the same problem and it was nearly always an injector issue. Best I remember, the cars would always crank right back up and run again. My 88 did too, but after the third time it did it, I parked it when I got home. I did the reading up on it and concluded I most likely had a bad injector. I ordered a new set of Standard FJ105's. Problem solved.

Now, if the ICM is overheating, that could cause a delay in the engine not restarting. The ICM would have to cool off before it would work again.
I had an ICM go out on me on my 92 Z24. The first sign something was wrong was one morning it died while I was letting it warm up. It cranked back up, no problem. Then it would sometimes die at a red light. I recall it died when I gave it the gas (just normal amount) when a signal light went green. it cranked right back up. This happened a few times and reading pointing to an ICM problem. I took one off my 94 RS and put it on the 92. Problem solved.

Hopefully something I've wrote here will point you in the right direction as to is it a fuel injector or ICM.
Re: 1990 z24 shuts off after driving for a little bit
Friday, June 26, 2020 9:43 PM
Thank you for the advice. Is the icm the sending unit? My buddy was telling me something about a rubber diaphragm that might be going in a sending unit.
Re: 1990 z24 shuts off after driving for a little bit
Saturday, June 27, 2020 7:41 AM
No, the ICM is a processor that is between the coils and the mounting plate.

Not sure what sending unit your friend is talking about. Maybe he means the Oil Pressure. Or the fuel pressure regulator. See if he can give you more details on what it is he is suggesting.
I've read that the oil pressure sender/switch will cut off fuel pump, if oil pressure is below around 8psi. However, I've also read this not true. That the oil pressure sender will cut run the fuel pump if the fuel pump relay fails. I really don't know which is true. I suppose this could be tested by unplugging the oil pressure sender connection and see if the engine cranks and continues to run.
If your oil pressure gauge is reading normal, then I suppose the sender must be working correctly.

If you friend is talking about the fuel pressure regulator, you can find a video on how to check it. It is a quick and simple test.
Re: 1990 z24 shuts off after driving for a little bit
Monday, June 29, 2020 2:56 PM
He was talking about the fuel pressure regulator. I looked into it. It seems to be the problem but I still gotta run a test. My spark plugs were kind of black, it's misfiring while accelerating, and has poor acceleration.
Forum Post / Reply
You must log in before you can post or reply to messages.

 

Start New Topic Advanced Search