Hey guys i have been having this problem for some time and I'm just really stuck. I have a sock 88 with a 2.8 automatic. The problem I'm having is that I'm loosing fuel pressure in the fuel rail once i sit the car off. it drops slowly to 0 pressure and i can watch this with my fuel pressure gauge. It seems to be running slightly rich. When i shut off the car I'm having it over run slightly. so it doesn't just turn right off like it should. So here is what i have done. I have a new fuel pump and good pressure. I replaced the rubber seal in the block of the fuel rail. I put in all new injectors and a new fuel pressure regulator. And still having this problem. I thought the cold start injector could be leaking so i plugged the hole in the block and capped off the fitting at the fuel rail. I checked for leaks and had no leaks. I also bench tested the fuel rail with another fuel pump to see if the injectors were leaking and everything looks good. The fuel rail pressurizes and then fuel ejects from the return tube. So my question is can this seal in the square block of the fuel rail be leaking or can i have got a bad pressure regulator? This is got me crazy and now I'm thinking about changing the whole fuel rail to one i have from another car. Please help.
I installed a new fuel gauge sending unit for my VDO gauges. In doing so i removed the pulsator all together and patched it with a piece of fuel line and clamps. It seems to be a super snug fit. Could it be possible that something is bleeding off in the tank? Is there a check valve anywhere, or is there one inside the fuel pump. The fuel filter is new and I'm getting plenty of fuel to the fuel rail but it just won't hold pressure for more than 20 seconds.
Why does it bother you that it doesn't hold fuel pressure?
I know it's a standard test in GM manuals but I don't really see it as a valid test. Unless it is the injectors that is leaking I don't see how it makes any difference, as long as the engine has proper fuel pressure while running.
A leaking injector will make it hard to restart after shutting off the engine and restarting a short while later. In your case no longer than it takes for the fuel pressure to drop to zero. The fuel if it was leaking out of an injector would stop once the pressure drops.
If the leak is past the FPR, but the proper fuel pressure is maintained while running who cares? If the leak is back past the fuel pump but proper fuel pressure is maintained again who cares. You said it's not leaking into the FPR vacuum line, and by now I am sure you have checked and made sure it's not leaking on the engine.
[This message has been edited by phonedawgz (edited 11-30-2014).]
I guess your right , it does have enough pressure to run and it isn't very hard to start. Im just having a problem with the motor still running for a few revolutions after the key it turned off. I thought i was losing pressure from a internal fuel leak that was making the cylinders keep firing. This may be caused by something else all together. I did a valve adjustment and ever since its had this over run problem. I may have adjusted them wrong. Im not a professional mechanic and struggle to resolve some of these issues so thats why I'm here looking for advice. I wish i could afford to just take it to a shop. But anyway i do thank you for your advice.
The over-run may be leaking injectors due to dirt or varnish or some other stuff....and you may be able to get rid of it with the usual injector cleaner or SeaFoam treatments. It may take some time though, I was after that in my car for about 2 months before it went away.
So if there is a leaking injector would that make it run slightly rich? and if so could i pull out the spark plugs and check them for deposits or discoloration. Would that help to determine witch cylinder is leaking if any?
Chances are slim that there is just one injector that is fouled. The usual procedure here is to have all 6 cleaned and tested ('matched' they call it) and re-installed. There are a number of on-line services that do this. If you use the fuel additives, all 6 injectors will get the benefit too.
edit: Yes, the car would run rich. You can also clean them yourself...there are demos on U-tube.
The last time I replaced Injectors, I made one mistake, I forgot to grease the o-rings and had fuel all over the top of the motor. Do you see or smell any fuel? Allso there should be an o-ring on the cold start injector....Bad fuel pump (wrong pump)? What brand pump did you buy?
[This message has been edited by James Bond 007 (edited 12-01-2014).]