This is way too interesting to not keep up on. Great advice for a seemingly impossible issue. This is why this is my favorite forum.
To the OP, I like your attitude. Totally willing to dive neck deep into your car. Good luck with this. Just please remember to let us know when you find the problem.

 

I uploaded a video to youtube.

 

That is some fucked up ****.

Wow.

Great vid, you got the gauges on there, pump is unhooked.....IDK how or where the car is getting fuel from.

 

My plans are pulling the fuel rail, hooking everything back up and watch what the injectors are doing. With the pump hooked up the gauge hold at around 43 psi. When the car is off it holds fuel pressure like it should.

 

Before you do that I would check for gas in the vacuum line to the regulator. I'm guessing your (new) regulator has a ruptured diaphragm and before you unplugged the pump it put a bunch of fuel in the intake, cylinders, and oil pan. The engine might be running on fuel puddled in the intake manifold.

One way to test it would be to pull the vacuum line off the regulator, reconnect the fuel pump and turn the key on for a 2 sec pump. If the diaphragm is ruptured, you'll see fuel out the vacuum nipple.

 

Just to give a little background about myself. I have been around cars and trucks all my life. I grew up working in my fathers shop and switched over to heavy trucks about 10 years ago. I also have a 2,400 square foot side shop that I restore old cars in. I just hit 50 years old and I have seen some odd stuff but this corvette has been a challenge.

I have checked the fuel pressure regulator. The only Thing I can think of is the new injectors are letting too much fuel pass and burning off what is left over in the fuel rail. That is why I want to see what the injectors are doing out of the intake. I only posted this thread to see if anyone has had this happen to them.

 

Robert,

OK, once more and I'll stop beating a dead horse. Your experience is better than mine, even though mine is longer. A friend had a VERY similar thing going on with his Vette. Bunch of gas in the oil. He did a quick check of his NEW regulator by pulling the vacuum hose off, pump not running and, finding no gas, he decided the regulator was OK. It wasn't. Later, when the vacuum hose was removed from the regulator and pump run, gas squirted out of the regulator vacuum nipple. New regulator had a torn diaphragm. Another thing caused him to remove the intake manifold and it had a LOT of gas puddled in it. Probably enough to make the engine run some with no fuel pressure. Just continuing these questions in case your check of the regulator was, like his first one, without running the pump. Your issues are so similar to his, I just hope you checked the regulator with the pump running. Now I'll shut up.

Jim

 

Jim I don't mind the input. I have already done that test. If the diaphragm was ripped or bad, the fuel pressure will bleed down after the car is turned off. It holds fuel fuel pressure according to my gauge even after the car has been shut down for a while. I'm going to get back on the car in the next few days and start taking video of what I come across.

 

More vid will be interesting.

 

Right, with the ruptured regulator diaphragm my friend's fuel pressure dropped INSTANTLY when pump shut off. The mystery to me is how your engine can run with no fuel pressure. Pooling in the intake might explain it, but nothing else seems likely to me. I'll be following.

Jim

 

Is that the same fuel pressure gauge you've been using all along? Is it possible that the gauge is faulty and you actually have pressure in the rail? Because, and I'm just spit-balling here, what if there is another (backup) fuel pump in-line somewhere that is getting power and running the engine, but the gauge doesn't show the pressure?

 

Electrical bypass some place is all that would make sense to me as to why it's still running.

Bubba sure do get creative sometimes.

 

Any possibility it dumped a ton of fuel and the brake booster has fuel in it?

 

Time to call a Priest and get ready to perform an Exorcism on that Corvette!

IF the fuel was pooling in the intake How long would the engine run?

My L98 shuts off very quickly once the fuel pump is turned off. The 1990's don't have the Cold Start Injector do they? That would be a good source of fuel IF the car was built with a CSI, I don't think they did in 1990 but I am not sure.

If it did have that much fuel in the intake I sure would not want it to backfire at that point, that could get Ugly real fast.

Like suggested by Natty C I would bet there is alternate electrical route for power to the fuel pump.

 

This^^^. I've only seen engines go from flooded, to lean out and stall, when the intake is full/puddled of fuel -not run on and on. That time frame from flooded/standing fuel, to stalled out lean is typically seconds....like 5-10 seconds. That engine in the vid ran way, WAY longer than 10 seconds...and ran rather smoothly and nicely to boot. Weird.


It sure does seem like that! I wonder about the suggestion that there may be an inline pump? I mean, in the vid, you can see that the OP unplugged the pump. Then he held up the pump's pigtail. It's unplugged. No extra wires. It don't make no sense!

 

Have you tried this? Clamping off the hoses and see if it keeps running? Will it run indefinitely like this or does it eventually die (did you look inside the valve cover via the PCV hole for pooled fuel)? If it eventually dies with FP off I would, at this point, completely ignore this...and concentrate on the flooding itself...treat the cause

Going back to your original issue to re-summarize, and correct me if I'm wrong:
1 - Your car was running fine
2 - At some point while driving it, it started running very poorly (diagnosed as rich/dumping fuel into the engine? what were the exact original symptoms?)
3 - As a result the following were replaced with no effect whatsoever (correct?):
- Fuel pump
- Fuel filter
- Injectors
- Fuel pressure regulator
- Plugs/wires
- Distributer (cap/rotor?)
- 02 sensor
- ECM
- Coolant temp sensor
4 - You have verified that the fuel pressure goes to 43psi and holds there with key off (which points to no FPR or FI stuck issue)

That is a LOT of stuff replaced in item 3 to have no effect...was there gas in your Oil and was the car running with FP disabled BEFORE you started swapping parts? Right now it's very hard to know/separate what may be a new problem introduced vs your original running issue...so any clarification or behavior change along the way (when you noticed what) would be helpful. Also, where are you located? Perhaps a second set of eyes could help...and unfortunately it may be necessary to start swapping some of those parts back to the originals to diagnose (particularly the FPR and FIs)...

I am going to throw out some things you didn't look into that maybe could point to original problem (and can be verified without new parts):
- Clogged catalytic converter
- exhaust manifold leak ahead of O2 sensor
- Compression test
- MAF sensor

Apologies for the long post and all the questions!

 

What ever happened with this?