The Blue Beast Blues

I apologize for the length of this. But here is how this all started. I’ll try to include everything even those I think are irrelevant.

‘94 Z28 6spd. – 75K mi.

I replaced the OptiSpark complete because it was running really lousy, new plugs & wires. New MSD coil. Modified the OptiSpark with the GM vacuum hose assembly, new Hypertech 160 deg. thermostat. Water pump was in good shape so did not replace.

Probably irrelevant info: I changed the oil and filter, power steering fluid, fuel filter, air filter. Put new coolant in when I reassembled, 50/50 with distilled water.

Here are the current repeatable problem/symptoms, none of which happened before the above maintenance: When I start it it takes a few seconds to crank and finally starts. When it does start the SES light and fans come on and run continuously. The AC compressor also will not turn on. So when I go to start it I think that it checks all the cylinders to see if it has spark, fuel etc. and then says it is OK to start and then starts. If I turn the key all the way off and wait it will take the same time to start, but if I just turn the key to the accessory position for a few seconds it will start a little sooner depending on how long I have it off. When I pull the fuse to clear the faults in the PCM and then start, it still starts the same, i.e. slow, then the SES light comes on about 2 seconds after it starts and then about 7 seconds later the fans come on.

I have an old, simple SunPro code reader [that just jumps the pins], but I can’t get it to give any codes. The fans will also run when I plug in the reader. AutoZone said that if I can’t get any codes with what I have then they would not be able to do anything else to read it.

I know from searching around that the fans come on when you jump the pins with a reader and that they also come on when the SES light is on. But since I cannot get it to give me any codes with my little “pin jumper” I don’t know if anything is actually related to a bigger problem or separate issues. I have also heard people say just to leave the fans run, but that is not solving any of the problems.

When it does start it runs better then it ever did…. like new! It is absolutely great except for this puzzling issue. Drivability is absolutely fantastic all the way thru the RPM range in every gear.

Things I have checked in a futile effort to fix the problem(s):
Both Coolant temp sensors, compared operation at cold and hot to new ones, same.
All Relays except Fuel pump relay (but fuel pump turns on and primes fuel rail) to the stop point.
EGR Valve (applied vacuum works fine)

Is there anyone who has had these problems or heard of anything like this that can give me some assistance? I would really appreciate it. If jumping the pins with the reader can’t give me any codes will a shop with a computer be able to get any info from the PCM?

 

ya kinda i have a 93 z28 and when i turn it to accesery it will flash a coad 12 over and over agen. so i have no clue what it is. but other then that iput a new opti in it and it dident fix any thing.

 

From your description, it seems to me your car has an internal fuel leak and and the FI system is not holding pressure once the engine is turned off. To verify this (do after the engine has been turned off for several hours) Turn the ignition key ON & OFF several times about 2 seconds between each cycle, this will cause the pump to prime the system even if it has a leak. On the 4thtime try to start the engine. If the engine starts right up, it indicates that the system was not holding pressure and had to be primed to get the pressure back up. This problem could be due to a leaky injector, an injector stuck open, or an injector that stays on continuously due to a false ground, a fuel pump that has a bad check valve, a bed pressure regulator, or even an external fuel leak. If this is the problem you can break it down more by doing the fuel pressure test as indicated in the LT1 section.

 

i also have a similar problem but sometimes it starts right up. and others it takes a bit of cranking, i have tried to turn the key on and off a few times but didn't seem to help so like pete said maybe i have a injector sticking open sometimes so system can't build pressure.