The other day, while backing out of my driveway, my 94 vette died. Would not restart for anything. Yesterday I was able to get some time to try to get it back in the garage. I tried starting one more time before working on it and it didn't start, so I hooked up a fuel pressure gauge. There was some air and very little fuel that cam out while hooking up the gauge. It was at zero pressure. I turned the key, it jumped to 40 and started. It ran at about 42 without issue. I pulled into my driveway, shut it off and watched the gauge for bleed down. It started at 40...and went up to 43 over the course of 15 minutes. I tried to start it again and it just turned over. I hit the bleed valve on the gauge and tons of air and a bit of fuel came out. Then, the car started and ran fine.

So...what might be putting air into my fuel line? The gas tank is full and I have no other symptoms. I am going to pull the sending unit/pump assembly and change the strainer and pump as well as the filter, but with no leaks, I am quite confused about how air is getting into a pressurized system.

 

That is where I would start look for bad hoses in the tank but would lean to the fuel filter being plugged up disconnect from the back of the filter and the return line then release it from the top then pull it out to get the filter off will play hell getting the filter off from under the car

 

With a full tank take the lines off on the top of the tank or you will swim in gas

 

Seems odd you would have pressure and a break somewhere. Did the original symptom happen after you had already driven it and then backed out, or did you just start it for the first time that day? I would look at your fuel lines and see if they have gotten close to a heat source Sounds like a vapor lock but if the car was cold its a lot less likely. I dunno, just a thought. I got stranded at Wolf Creek Pass the first time it happened to me.

Good luck!

 

Stone cold...I had not driven it in about 5 days. Started right up and backed out, was running great and just quit when I went from reverse to drive. My foot was not even on the gas. Never happened before.

While troubleshooting, I ran the car for about 8 minutes, shut it off for about 15 minutes and it would not start back up till I hit the purge on the fuel pressure gauge. I am sure the pressure went up because the hood was open at that point and the sun was hitting it heating the air in the lines...but why there was air I do not know.

 

Vapor lock, cycle the key a few times and then see if the car starts up and runs fine. The heat in the engine is boiling the gas in the line when the engine is off and the vapor is filling the fuel rail. My guess is the vapor is pushing the gas backwards out of the fuel pump through the leaking check valve and one cycle of the pump is not enough to fill the line again.

 

The car died cold. I left it and went to work. After work, I tried to start it again, just turned over. Later that night, I tried to start it again, nothing, the next day in the morning tried again, nothing. It was not until I hooked up the fuel pressure gauge which let some air out while I hooked it up that it started. I really don't think its vapor lock.

 

Did you change the pump yet?

 

Yes, finally got some time, swapped out the pump and eliminated the pressure surge reducer. Started right up and ran great for a few weeks, but yesterday she died again. She started right up, idled for a minute and just shut down. Would not start again, just turned over. I am suspecting an opti because she has been a little rough at idle and what I can see from the one in there has concerned me since I got it. I can see RTV where the wires go in... In any case...more work for me!

 

I know this is a 2 year old thread...but its my thread and I am still working on this same problem. Twice over the past two years I got about 2 weeks of good running, then she would die driving down the road. The last time was about 4 weeks ago, waited a few minutes and she started back up, got her home in the garage and she has not started since. I still have not done the Opti because I am a coward and not a very good mechanic. I know enough to be dangerous...so I have blown it off for a very long time.

A few weeks ago...I found a replacement, a 2001, which meant it was time to fix the 94 to make room in the garage. Yesterday I started the replacement...what a nightmare...for me. Huge coolant mess, I drained it, but everything you disconnect and some of the bolts you take out provide more in random locations. I then had to fight the pump because I have an electric water pump and AC which don't work well together. I had to take the pump appart in the car to get it out. Next was the balance, was was actually not too bad. One socket on the center bolt, then remove the other 3, mark, and wiggle to remove...at this point I came to a conclusion, it has not been that many miles since this was done. Everything was pretty clean, had fresh antisepsis compound, and a couple of bolts were even loose (one holding the electric pump to the pump housing, another comes later in the story).

For quite a while I though the opti looked weird. There was a vacuum line coming out of the top and the metal base looked way to thick. The vacuum line went to nowhere, just wrapped around the drivers side valve cover and ended. When I pulled the old Opti out and compared it to the new one...well, it is weird. I would appreciate if someone could tell me what I have. I did find some problems inside the Opti, one of the rotor bolts was out and it and its washer were rattling around, noticed that as I pulled it out. The second rotor bold was only in by one or two threads. Under the cover, there was oil in the pickup area and on the disk. Not much, and not dirty, and I am not sure where it came from. It does not look like it came from the shaft or anywhere else. It almost looks like it came in through the vent line. Here are some pictures, I would appreciate if someone could tell me more about this old Opti.

Outside shows the thickness and the vent line...as well as the shoddy wiring gromet.




Wiring and thickness



Mount is attached, not part of the Opti



Vent and wiring



Loose screw and washer, other screw was almost out



Oil in disk area

 

Doing some additional research, this is definitely an MDS Opti...even that mess of wiring is OEM for that one. It does have an aftermarket cap and rotor...which was the source of my problems. I am replacing it with Petris vented, I hope it lasts a long time!

 

New discovery...the Petris mount points are similar to a stock Opti, but the MSD billet I am replacing has 2 mount points that are MUCH thicker...and require longer bolts. I was able to find replacement shorter bolts at Ace.

 

One thing I forgot to mention that happened a while ago, I did continue to trouble shoot the fuel system which included vacuum testing the fuel pressure regulator...it would not hold vacuum. While doing that, I found some weird plumbing in the vacuum system...the intake lead that goes to the accessories was hooked to the brake booster vacuum line...and there was a line coming from the Opti that went nowhere...just wrapped around the drivers side valve cover and ended open. I know now that it was from that billet MSD opti, but it was never hooked to vacuum...all it did was let oil into the opti.

I believe I had many problems when I purchased the car, I believe the ignition coil was bad, it was cracked when I changed it, I believe the fuel pressure regulator was bad since it failed the vacuum test, and I know the Opti was bad because there were loose parts in it. It was pretty frustrating to fix one problem only to have the car fail to start or shut off again. The car has less than 80k miles on it, none of this should have failed. The Opti was replaced at least twice, and I don't think it was the problem either of those times. The coil was aftermarket too so that had been replaced. I suspect that the fuel pressure regulator was randomly loosing vacuum causing the car to die and the Opti and coil were replace trying to fix that...which actually caused more problems. Is there such as thing as a forensic mechanic?