bykerboy

I've read all the threads on here I could find and did not find the answer to my issue.

My '96 C4 will start, run a few seconds and then immediately die. It will start right up again and exhibit the same behavior. It will do this as long as the battery can crank the car over. Here are the things I know.


The fuel pump primes when the key is first turned on.

After the car dies I can still hear the fuel pump run for a couple of seconds.

I tried jumping the fuel pump relay so the pump is on all the time and it still behaved the exact same way.

VATS is disabled in the in the PCM.

I disconnected the MAF and it still behaved the same way.

I've been at this all day and can not figure it out!

Any help is greatly appreciated.

Scotsman

Have you pulled the codes? That's a great place to start. Since you have jumped the fuel pump relay out, I'm figuring you're fuel is fine. Once you get the codes, you'll be able to narrow the search down, but I'm betting you're going to get ignition codes. Let us know what codes you get and I'm sure someone will be able to direct you in the right direction.

bykerboy

I'll do that this weekend and post them up, I'm out of town for work all week.

surfer92

When my FP went south, it did about the same.

surfer92

Check fuel pressure, you might have a clogged filter or a bad FPR.
If you are hearing the FP after the car dies, chances are the pump cannot keep the fuel pressure high enough to keep the car running.

engle1147

Check the fuel pressure at the rail first. If you've got the appropriate fuel/rail pressure ensure you have 10+ PSI for oil pressure showing up on the cluster once the engine is running.

bykerboy

Would either of these throw a code?

I'll definitely go ahead and replace the filter as that should be an inexpensive thing to do?

bykerboy

Oil pressure was good before it started acting this way.

Will the CCM not pulse the injectors if the oil pressure is low?

engle1147

No but low or no oil pressure will shut off the fuel pump.

bykerboy

So the drama continues. I went out and bought a very nice ACTRON code reader. I go to pull the codes and I get a "link failure". For some reason the reader can not communicate with the PCM. I checked continuity on the serial data link to the PCM and all looks good there.

Any ideas on why this might be happening? I am sure this no run condition is related but after having poured over the FSM for hours I am still at a loss.

onedef92

I wonder if you've got a bad connection or faulty/loose PROM chip in your car's ECM?

bykerboy

I'm open to any suggestions at this time. How would I check whether or not it is faulty.

The PCM is from a '95 fbody. Does it have a PROM or an EEPROM?

surfer92

Did you have the PCM reflashed for your 96, from the 95 fbody?

Yours does not have a PROM, 94 and later PCM's can be tuned on the car and earliers have a PROM, which must be removed to be programmed.

bykerboy

Yes, it was reflashed for a y-body tune with my performance mods.

surfer92

Have you pulled codes yet or checked FP?

bykerboy

I checked FP and it is between 40 and 50 PSI. I can only pull CCM codes as I have had no luck getting a code reader that can read my OBDI computer with my OBDII data link connector.

I just went through and rechecked everything, I did have a history DTC 54 (FEDS enable) that was not there before.

After clearing the CCM DTC codes and once again checking all my connections, miracle of miracles, it started up and ran.

I have decided to buy the datamaster software and an AKM cable so I can start seeing PCM codes as well as collect history.

I HATE problems like this!

bykerboy

The DataMaster software showed very clearly that my fuel enable bit was not being set. The FEDS security system controls this.

Problem solved! I had TC at TunerCAT disable the FEDS in my PCM and it will now run the car without the CCM.

TC is a great guy to work with and really knows his stuff! Highly recommend him and his software.

Danny King

Had to change a heater core. First thing we did was disconnect the battery for 10 mins, because we had to remove the airbag on passenger side. Several connections had to be unplugged and re connected during the process. Now the car will start and run a few seconds and shut off. My code reader says cannot link. HELP PLEASE Thanks in Advance This is a 95 model C4

mixalive

Did your optispark get wet?

KyleF

I know, old thread... but doing some research today for another "Won't keep running thread" I actually came up with the electrical schematics and this thread came up in my research.... the switch is wired in parallel with the fuel pump relay. For any one coming across this in the future, the oil pressure switch is a secondary switched power to the fuel pump, not a primary breaker switch in the power.