1989 corvette hard to start when warm

[Ponch 04]

Car: 1989 Corvette Convertible w/ 96,000 miles.

My dad's vette has been having issues lately.
When it's cold, it starts up immediately and idles pretty good. No problems.
However, once it gets up to operating temperature and is turned off, it does not want to start. It'll turn over for about 10 seconds and finally start but it'll idol rough and the exhaust smells horrid (not sulfur more like a combination of ethanol and some other chemical).

I thought maybe it was the MAF sensor but it's not the stock type one wire design. It's a 2"x3" circuit board with about 6 right angled prongs protruding into the air stream.

The only other thing I can think of was that he got a hold of some poor quality premium fuel and it hasn't run it through completely.


Any thoughts?

[Ultra Boost]

I would check in this order:

Pull the hose off the FPR and look for gas in the hose. If no gas in the hose....

Do a fuel pressure check.
Key on-
Engine running FPR connected-
Engine running FPR disconnected-
Does it hold pressure after key is off?

Report back and we can go from there.

[clm2112]

Sounds like it is flooding.

The MAF is a little odd..I never knew they used a thin-film MAF on any of the TPI engines. Checking fuel pressure at the rail is as good a place as any to start out.

Also, have modifications been done to the motor (oversize TB, different manifold runners, aftermarket calibrator prom, oversize injectors, etc.) I'll have to do some digging on what was "stock" in '89...like if it had the 9th Cold Start injector like the F-Bodies got for a while.

Do you have access to a scan tool that shows the data comming out of the ECM while the car is running?

[Ponch 04]

Well finally had time to dig into the car a little more.
We haven't tested the fuel pressure as of yet.
I do not have access to a scan tool at this time.
We did however found a new clue: My dad took the top cover of air box off and found the air filter to be completely soaked in gas. The base of the air box had a large amount of puddled fuel still resting at the bottom of it. My question is how can fuel work its way upward through the intake runners, through the throttle body and down the flex tube and into the air box?

[RJolly87]

Leaking fuel pressure regulator?

Unless the exhaust is freaking plugged up.

[Ultra Boost]

My guess is something is leaking under pressure. Just pull the hose off the FPR and see if there is gas in the vacuum hose. Otherwise turn the key on and let the fuel pump prime and look for leaks.

[clm2112]

My guess is something is leaking under pressure. Just pull the hose off the FPR and see if there is gas in the vacuum hose. Otherwise turn the key on and let the fuel pump prime and look for leaks.

I would go along with that as well. The FPR is one place where fuel under presure can get into the manifold through the vac lines (tear in the diaphram inside the FPR.) Another possible, but unlikely, place would be the vapor purge line from the fuel tank. The charcoal can is supposed to hold the vapors off the top of the fuel tank and let manifold vac suck them into the motor. If something has been fooled around with in the hoses, you may be getting raw fuel from the tank dumping into the intake manifold.