1996 Collector Edition Corvette

Update your progress on your various car projects.

Moderators: MostMint, wxo, Fred32v, Basement Paul, ttamrettus

User avatar
wxo
Posts: 1754
Joined: Mon Jul 18, 2005 9:09 pm
Location: Raleigh, NC

Re: 1996 Collector Edition Corvette

Post by wxo »

Here's are the comments I received from Rich Jensen:

Okay, there's only four places the fuel pressure could be bleeding off.
1: Through the injectors but if you had the fuel rail lifted and no fuel was coming out of them, then it's not that.
2: An external leak in one of the hoses or fittings but since you didn't see any fuel dripping anywhere, and that would be evident if the pressure is dropping off quickly so that eliminates that.
3: Through the pressure regulator. You would need to block off or pinch the return hose to the tank to determine if that's where it's going.
4: Back through the check valve in the pump. You would need to do the same to the feed line from the tank to determine if that's it.

It's worth checking out to see why you're losing pressure so quickly but none of this explains how you would hydro-lock a cylinder with fuel because that would only be caused by the injectors leaking.

Rich J.

So, when Maverick and I were testing, with the fuel rail lifted, I noticed a few drips of fuel from one of the connections to the fuel pressure regulator. I will take a closer look at that. But the real issue here is the fuel in the crankcase and as Rich said, "that would only be caused by the injectors leaking". Another point...When I lifted the fuel rail, the first thing I did was touch the outlet of each injector. Every one was wet. This was after sitting for almost 24 hours. I didn't expect them to be wet.
User avatar
wxo
Posts: 1754
Joined: Mon Jul 18, 2005 9:09 pm
Location: Raleigh, NC

Re: 1996 Collector Edition Corvette

Post by wxo »

After several long diagnostic phone conversations and some testing with Rich Jensen, we know we are dealing with two different symptoms related to the fuel system:
1) Fuel pressure not holding in the fuel rail
2) Fuel dumping into a cylinder by one of the injectors

Through the process of elimination, we have isolated the quickly dropping fuel pressure to the fuel pump check valve, but the dumping fuel/hyro-lock problem is still a mystery. Rich thinks they could be related in that fuel debris could possibly cause both. So the short term plan is:
1) Change the oil and filter to remove the gas contamination
2) Remove the spark plugs to try to determine which cylinder is involved (just to gather more info)
3) Change the fuel filter and cut it open to inspect for debris.

Rich also suggested installing an in-line fuel check valve in the fuel feed line to avoid dealing with the administrative chaos of trying to return the fuel pump assembly for replacement. He also thought that our testing of the spray pattern yesterday may have already flushed out any offending debris in the injectors if, indeed, debris is the source of the problem. In addition, he didn't think the wet injector tips I noticed yesterday were NOT unusual.

So...on we go...
User avatar
wxo
Posts: 1754
Joined: Mon Jul 18, 2005 9:09 pm
Location: Raleigh, NC

Re: 1996 Collector Edition Corvette

Post by wxo »

I spent this afternoon gathering more info on this cylinder flooding problem. I removed all the spark plugs starting with the most difficult, #8 (pass side rear). They were all wet to some extent, but #6 was obviously the cylinder with the problem. Number 1 was the last one I removed. You can see in the photos that it is still wet. The gas had evaporated from the others. On the drivers side where I could see the plug hole for #3, I snapped a picture showing the evidence of the fuel running out when I removed the plug. Since they all came out wet to some extent, I think this was the case for all the plugs.

#6 just after I removed it.
IMG_3897.JPG
From the passenger side
IMG_3907.JPG
#3 hole
IMG_3909.JPG
When I put the car on jack stands to change the oil, I noticed a big 2ft pool of gas on the floor. I looked at the dipstick and it was waaaaaay over full. I drained over 8 quarts out of it! The specs call for 4.5 quarts for a fill, so I had about 3.5 quarts of gas in the oil pan.

I need to understand why all the cylinders had gas in them if the flooding was in cylinder #6. Looking for evidence of why this happened, I plan to remove the fuel filter, cut it open and look for debris that may have caused #6 injector to stick open.
User avatar
MostMint
Posts: 2714
Joined: Thu Jul 21, 2005 12:11 pm
Location: planning a race

Re: 1996 Collector Edition Corvette

Post by MostMint »

That is a lot of gas to leak past the cylinders. might want to lower the fuel pressure and see if that changes anything

I also wonder if the low pressure return is not working forcing the pressure up and the leaks
[quote="Basement Paul"]Is that a mint rocketship on the hood?? :shock:
-BP[/quote]
User avatar
wxo
Posts: 1754
Joined: Mon Jul 18, 2005 9:09 pm
Location: Raleigh, NC

Re: 1996 Collector Edition Corvette

Post by wxo »

The fuel pressure is where it is because that's were it needs to be to run without the bog. That engine has been running really strong and reliably with the current fuel pressure set at 58 psi until I suddenly got the P00300 code.

One thing to keep in mind, is that the engine may have been running with a stuck open injector for as much as 5 minutes. Some of these symptoms might be related to that.

If an injector sticks open, a lot of gas sprays out of it all at once as opposed to the short, millisecond sprays while running normally. When Maverick and I tested the injectors wide open, there was an impressive spray of gas coming out of each one.
User avatar
MostMint
Posts: 2714
Joined: Thu Jul 21, 2005 12:11 pm
Location: planning a race

Re: 1996 Collector Edition Corvette

Post by MostMint »

Is that higher than stock spec? What I read is 42/48 psi but that is on the internet. While the higher PSI does clear up the bog it might not be the best way to solve that problem. I really don't know Walt just putting ideas out there for you to consider in the process.
[quote="Basement Paul"]Is that a mint rocketship on the hood?? :shock:
-BP[/quote]
User avatar
wxo
Posts: 1754
Joined: Mon Jul 18, 2005 9:09 pm
Location: Raleigh, NC

Re: 1996 Collector Edition Corvette

Post by wxo »

I appreciate your help Andy and I keep in mind all the suggestions as I go along toward the solution. Right now I'm focusing on the assumption that the only way all that gas could have gotten in the cylinder is by way of a malfunctioning, stuck open injector, either mechanical or because of debris left over from the original contaminated fuel system. This engine was been running well and strong when something out of the ordinary happened that tripped the P00300 (non specific misfire). I think that at that point, the flooding started. It ran normally after that until I turned it off at the grocery store about 5 minutes later. It is likely that my attempts to restart it made things worse as far as the flood of gas to the cylinders is concerned. If the injector was stuck open, any time I turned on the key, which may have been as many as 10 times, that #6 injector flowed fuel for 2-3 seconds. I plan to change the fuel filter, the #6 injector and the spark plug. I will cut open the old filter to see what it caught .
User avatar
Basement Paul
Posts: 3372
Joined: Sun Jul 17, 2005 9:27 pm
Location: In the dirt.

Re: 1996 Collector Edition Corvette

Post by Basement Paul »

It may be worth checking with the fuel injector manufacturer to see if there's a pressure rating or range that should not be exceeded.

-BP
User avatar
wxo
Posts: 1754
Joined: Mon Jul 18, 2005 9:09 pm
Location: Raleigh, NC

Re: 1996 Collector Edition Corvette

Post by wxo »

That's a reasonable idea, BP, just to cover that base.
Furthermore, I found this blurb from an Accel article on the web that is talking about raising the fuel pressure with an adjustable fuel pressure regulator for tuning purposes. At 58 PSI I am pushing the limits of factory fuel fittings if this is correct.

"As a point of reference, most GM factory fuel pressure regulators are preset at 3.0 BAR or 44.1 PSI. If we were to increase
the fuel pressure from 39.6 PSI to 45 PSI, what will be the new flow rating of the ACCEL p/n 150121 injector?
New flow rating = [square root of (new pressure /old pressure)] x old flow rating
New flow rating = [square root of (45 PSI / 39.6 PSI)] x 20.0 lbs./hr = 21.3 lbs./hr
This increase in flow rating would support about 15 additional horsepower on our GT-40 engine. An adjustable fuel pressure regulator is an excellent tuning tool as long as the fuel pressure does not exceed 55 PSI, which is the limit that the stock fuel line fittings are designed to handle. So let’s say we increase the fuel pressure up to 55 PSI, then the ACCEL p/n 150121 injector would be flowing 23.6 lbs./hr. But because ACCEL offers p/n 150123 that flows 23.1 lbs./hr at 39.6 PSI and 150124 that flows 24.3 lbs./hr at 39.6 PSI, radical increases in fuel pressure are not required to find the perfect match for your engine. The key is to make power efficiently, choosing the correct injector for your intended needs and using the adjustable pressure regulator as a fine tuning tool."

Anyway, I need to sort out the current mess at hand and get it running again. I will be sure to settle the fuel pressure issue before I hit the road again. Although, Randi and I enjoyed the tow truck adventure, I don't want to do it again. Nothing like riding three up in a rollback cab. 8)
User avatar
wxo
Posts: 1754
Joined: Mon Jul 18, 2005 9:09 pm
Location: Raleigh, NC

Re: 1996 Collector Edition Corvette

Post by wxo »

This conversation has teased out some thoughts regarding this problem. Just before we took this doomed test ride, I had removed the throttle body and did a deep cleaning. Even though I had cleaned the throat while on the car, it was really dirty everywhere else. What if the dirty TB was the cause of the bog and not the fuel pressure? What if I had raised the fuel pressure to compensate for flow problems in the throttle body? When I get Silvia back running again, I will certainly adjust the fuel pressure lower to see if the bog still exists. Thanks for your input, guys.
User avatar
MostMint
Posts: 2714
Joined: Thu Jul 21, 2005 12:11 pm
Location: planning a race

Re: 1996 Collector Edition Corvette

Post by MostMint »

hopefully we can help shorten the repair time. I don't have a huge experience base with injectors but stuck open is not something I have seen yet.

the TPS on mine is a bit out of adjustment which makes a slight hesitation off idle. while yours may not be out of adjustment it could be dirty/corroded (that is unless you replaced it already)
[quote="Basement Paul"]Is that a mint rocketship on the hood?? :shock:
-BP[/quote]
User avatar
Maverick
Posts: 1801
Joined: Sun Apr 26, 2009 6:29 pm
Location: Raleigh, NC

Re: 1996 Collector Edition Corvette

Post by Maverick »

What if the dirty TB was the cause of the bog and not the fuel pressure? What if I had raised the fuel pressure to compensate for flow problems in the throttle body?
I like this theory. It would explain the error code with multiple cyl misfiring, multiple cyl overly rich, and fuel in the crankcase after key on running the fuel pump 10 or so times overpowering multiple injectors for a total of 20 or so minutes.

Also, MostMint suggests TPS as another cause for the bog. What ever caused the original bog, increased fuel pressure might not have been the right solution.

The theory doesn't explain continuing fuel accumulation in the crankcase while the injectors were removed from the cylinders.
Maverick
User avatar
wxo
Posts: 1754
Joined: Mon Jul 18, 2005 9:09 pm
Location: Raleigh, NC

Re: 1996 Collector Edition Corvette

Post by wxo »

MostMint wrote:hopefully we can help shorten the repair time. I don't have a huge experience base with injectors but stuck open is not something I have seen yet.

the TPS on mine is a bit out of adjustment which makes a slight hesitation off idle. while yours may not be out of adjustment it could be dirty/corroded (that is unless you replaced it already)
I replaced the TPS a while back.
User avatar
wxo
Posts: 1754
Joined: Mon Jul 18, 2005 9:09 pm
Location: Raleigh, NC

Re: 1996 Collector Edition Corvette

Post by wxo »

Just to get back to the garage and reality, I have a lot of work to do to get this car running again. The problem of fuel pressure not holding needs to be addressed. It appears to be a failing check valve in the fuel pump. I'm thinking of plumbing in an inline check valve to verify the theory.

I also need to change the fuel filter, but I'm not looking forward to getting dowsed with fuel from the feed line when I open it. I need to figure a way around this.
User avatar
MostMint
Posts: 2714
Joined: Thu Jul 21, 2005 12:11 pm
Location: planning a race

Re: 1996 Collector Edition Corvette

Post by MostMint »

you could disconnect the line at the tank and at the fuel rail and put compressed air through it
[quote="Basement Paul"]Is that a mint rocketship on the hood?? :shock:
-BP[/quote]
Post Reply