Hi all,

I've got an '89 with the 5.7L TPI that's got an odd issue that I think is fuel related but not sure. It will start on ether and once running will run and drive just fine with good throttle response. I can hear the fuel pump prime at key on, though only if the car has been sitting for at least 20 minutes since it was last shut off. Once I turn it off, it will not start again without the ether regardless if it's within the 20 minutes or more than a day and the pump primes again. I'm stumped. Any ideas?

Thanks,
Jason

 

If you are looking for a new engine, keep spraying ether in that motor with its lite duty aluminum pistons and aluminum heads. You'll get one, especially spraying in a hot engine....

But, if you like the engine you;ve got,. and just want to fix it, I';d start with some basics.

Get a noid lite and test all injectors with it. Then Ohms test all 8 injectors.

Fuel pressure test. Gauge on the rails. This tells you about the pump, electrical system, IF there is sufficient pressure to start & run, and about the filter if you watch the gauge.

Next, go thru the engine harness and check EVERY electrical plug and connection. These are fragile and the ECM operates on the smallest bit of electrical resistance. Dirty corroded connections make for poor signals and the ECM does not know if its hot/cold/ thirsty or what. Get your FSM out and locate and clean all the harness grounds. Power source connections at the jumper as well. I've seen similar issues over the hot source wires being bolted tight...but dirty.

Engine/coolant temp sensor. Good for weird start up problems. Harness is more likely but it happens.

Are the injectors the originals? <--- 10:1 thats an issue
If so, you need Jon. Bad.


Whats the VATS status? has the enable relay been bypassed/jumped? if so, whats to say that the EFI drivers are not being locked out due to a VATS event? Thats why I hate seeing half assed VATS bypasses....if it turns the starter how does anyone know if the EFI is working? FP should run 2 seconds EVERYTIME the key is turned to ON...with a 10 second break between attempts.

A fuel pressure gauge would show whats really happening. A FSM would show how to fix it.

 

The ECM takes roughly 10 seconds to shut down because it does the IAC reset, MAF burnoff and MAF burnoff test before it turns itself off. I have seen an ECM take more than 30 seconds to shut down, but that's very unusual.

Since the 2 second fuel rail prime is not happening EVERY TIME, I suspect that the ECM grounds or power have problems. The ground wires (5 or 6 black wires) are connected to the side of the engine block by a large bolt above the oil filter. The negative battery cable connects here and there is also a braided ground lead that goes to the frame. I have heard that later years had a ground connection to a bellhousing bolt, but I don't know if that's true or not. There are two power inputs to the ECM. One comes from the ignition switch, and turning it on is what triggers the ECM to run the fuel pump for 2 seconds. The second power input is always on, and maintains the ECM memory. It connects to the battery through a fusible link and the ECM reset connector by the battery. Your ignition switch or this connector (and its wiring) might have a problem:

 

Thank you for the info guys! I certainly had no idea I could damage my engine. Fortunately I've only started it that way three times and all three were cold starts.

I'm curious, after the 10:1 original injectors comment you say if so, I need Jon. Who's Jon?

Unfortunately I think most of what you guys have told me is over my head a bit. Guess I'll tow it in to my favorite mechanic and hope he goes easy on me.

 

No need to run for the shop YET...but IF you DO, make sure you go to a shop with known C4 experience. Contact your area vette club for references. This is like finding a good dentist...you want to talk to someone thats been there before...

the 10:1........ ----> ten to 1 odds....that the injectors are at least partially responsible. These are classic points of failure. They age, performance in every aspect goes south. Till it barely runs....

Jon...
national hero to the Corvette DIY crowd... sells new style Bosch fuel injectors at a very resonable price and has the kind of customer assistance that people dream about...good dude.
Look up FIC fuel injector connection. Check his you-tube videos as well.
You tube "fuel injectors"