Need help from the pro's. 84 won't start when it's warmed up

[packen]

I had this posted at the Corvette Forum but they ran out of answers so here's my problem.

1984 crossfire, stock. Runs fine when it's cold but once it's warmed up and you shut it off, it will not restart for about 15 - 20 minutes.
No trouble codes from the ECM.
Installed new ICM, new fuel filter.
Fuel pressure holds at 13 psi and stays for at least 45 minutes after shutting down.
Checked injectors with a noid light after recreating the problem. It was hard to see because of being in direct sunlight, but looked like one of them had no signal and the other was very dim. I tried this test while the engine was cold and they both were very bright.
Once the car is at the point where it won't restart, I can spray a little starter fluid and it will fire. If I pump the accelerator after it fires with the fluid, sometimes it will continue to run.
So, anybody have any ideas?

 

[ex-x-fire]

Ohm the injectors when hot & cold. I'm not sure of the spec. When its acting up, have somebody try to start it while you take a long screw driver, put the tip on the inj. body & the handle to your ear. You should hear a loud click a few times a second. I am wondering if the ecm is loosing its grounds as it warms up, I think the ecm grounds are on the firewall side of the heads, sometimes all it takes is alittle loosening & tightening to fix that. You can drop the ecm down & check the grounds at the connector too.

 

[packen]

I will have to get a tester for the ohms. There is no clicking when trying to start. when it runs normal, you can hear the clicking with no problem. I tested with a noid light and there is no power going to the injectors when it won't start, but it will start with starter fluid.

 

[ex-x-fire]

Sounds like the voltge or ground to the injector is causing the problem. Use a 12v test light to test the inj wiring. But hook the tester to the battery terminals to help you figure out which side is weak(causing the dim noid light). The red & white wires to the injector supplies the voltage, the other wires(green & blue?) are what grounds(pulse) the injectors at the ecm.

 

[packen]

Sounds like the voltge or ground to the injector is causing the problem. Use a 12v test light to test the inj wiring. But hook the tester to the battery terminals to help you figure out which side is weak(causing the dim noid light). The red & white wires to the injector supplies the voltage, the other wires(green & blue?) are what grounds(pulse) the injectors at the ecm.

Thank you very much for your help.
I'm not sure I understand what you mean with hooking the test light up to the battery terminals. I am not real mechanical or electrical.
Somebody told me the ecm is probably bad. Do you think that could be the problem? I can get a new (rebuilt) one for about $80. I just hate to throw more money into it if I don't have to.

 

[ex-x-fire]

Try banging the ecm w/ your hand, sometimes they'll act up.
About the test light, what you're trying to do is figure out which side is giving a dim reading. To test the inj. power supply, hook the test light to the battery neg. This is bypasses everything that may give a low reading. For the inj. ground signal, hook the test light to the positive side of the battery & watch how bright it is. Do both when its acting up, & have someone crank the engine while your test them. Most likely a bad ecm, so the grounding side is what you really what to be sure of(that usually confirms a bad ecm), just make sure the ecm has good grounds, which are at the back of the cylinder heads.

 

[geekinavette]

Did you find the problem yet? I have a stock '84 ECM. (auto)

 

[packen]

Did you find the problem yet? I have a stock '84 ECM. (auto)

No solution yet. I replaced the ECM and still get the same results. I have no idea where to look next and the other forum I was posting in gave up.
If you know anybody interested in a 84 vette, let me know, I give up. It's in my driveway now with a for sale sign on it.
I also have a stock 84 ECM for sale.

 

[gmjunkie]

A faulty or out of range temp sensor will damned sure cause the problems your having!!

 

[Buccaneer]

I had this posted at the Corvette Forum but they ran out of answers so here's my problem.

1984 crossfire, stock. Runs fine when it's cold but once it's warmed up and you shut it off, it will not restart for about 15 - 20 minutes.
No trouble codes from the ECM.
Installed new ICM, new fuel filter.
Fuel pressure holds at 13 psi and stays for at least 45 minutes after shutting down.
Checked injectors with a noid light after recreating the problem. It was hard to see because of being in direct sunlight, but looked like one of them had no signal and the other was very dim. I tried this test while the engine was cold and they both were very bright.
Once the car is at the point where it won't restart, I can spray a little starter fluid and it will fire. If I pump the accelerator after it fires with the fluid, sometimes it will continue to run.
So, anybody have any ideas?

Since this happens only when the engine is warm and not cold and you have replaced the ECM already. This could be a heating condition and the HEI module is crapping out when hot. I'm also assuming that you don't get any spray from either injector when hot and cranking it, right? If the module is bad, the engine can crank, but injector signal or the HEI reference is bad which goes through the EST as well. I'd take a look at that module first, then the EST.

Do you have a 84 GM Service Manual? If not and you plan on keeping the car, get one. It's worth its weight in gold for a 26 year old car. Good luck on the sale or fix.

 

[packen]

Since this happens only when the engine is warm and not cold and you have replaced the ECM already. This could be a heating condition and the HEI module is crapping out when hot. I'm also assuming that you don't get any spray from either injector when hot and cranking it, right? If the module is bad, the engine can crank, but injector signal or the HEI reference is bad which goes through the EST as well. I'd take a look at that module first, then the EST.

Do you have a 84 GM Service Manual? If not and you plan on keeping the car, get one. It's worth its weight in gold for a 26 year old car. Good luck on the sale or fix.

What is the HEI module? I can't find anything on a module.
Once it gets to the point where it won't start, I don't get any spray from the injectors and the noid light is dim on both injectors when cranking. I had somebody check the Ohms on the injectors and they said they were fine. Somebody suggested it could be the pick up coil but from what I read, if it is bad, it won't show any RPMs on the tach when cranking and mine shows the RPMs.

 

[elkabong]

The HEI module is the same as the ignition module in the dizzy. It is a 7 pin type. Mine craped out on my and it caused weird things to happen. Also, you say you measured the fuel pressure @ 13psi and it held for 45 minutes. That does not sound right to me. Did you measure it the line that connects the TBs together? You need to tap in to that line some how and measure it there.