justavetteguy

:banghead: I have an 89 vette that is having an on/off NO START condition. I have replaced the fuel pump relay,throttle position sensor(adjusted to specs),and idle air control valve. When the car runs it couldn't possibly run any smoother or better in gear or out, with or without air conditioning load. If I allow the car to sit overnight it will start guaranteed the next day, I could bet my life that it would. After starting the car it jumps to about a 1000 rpm's and then slowly comes down to 600 and stays there idling perfectly. I can take it anywhere and do anything until I turn it off. Once off, the car will start back up right away if within a minute or so. But if I wait any longer than that it will just crank over and over and over till I wear out the battery. But strangely enough if I let it sit overnight it will start again the next day. The other weird thing about its starting pattern is if I let it sit overnight it will start the next morning but if I only let it run a few minutes instead of letting it get to operating temperature as I described above and cut it off it will not start back up. Every now and then in the no start condition it will start but sounds very starved of fuel and if you pump the accelerator it will run EXTREMELY rough and backfire and shake violently until it stalls back out. I've gone over the car and inspected everything and have hit a brick wall. I'm stumped. The only other thing that I thought it could be is the fuel filter or pressure regulator. This is the original filter and I have had water in the gas before.
UPDATE: MORE INFO TO AD:
This is what I have done: I bought a fuel pressure guage with the schrader valve attachment and decided to diagnose my car using the Hayne's Manual. I came out in the morning like all ways and started the car. And sure enough as grass is green the car started like always. So I immediately turned it off and then I unplugged the Fuel Pump fuse and tried to start the car a few times to depressurize it. Then I replaced the fuse. I took a rag and screwdriver and let the rest of the pressure off the fuel rail which was just a few dribbles which is what I expected. I connected the Fuel pressure gauge up and turned it so that I could see the gauge from inside the car. I turned the key and I heard the fuel pump click behind me in the trunk area and the fuel pressure shot up to 41psi. So far so good. I then started the car and let it run. It immediately came down to 35psi and stayed there just as I had expected. So far still good. So then I cut the car off and I watched the pressure gauge start to fall, not very quickly but at a steady rate that would probably take 15 minutes or so to make it back to 0. Maybe more. Now that the car has been started after sitting over night and ran up to operating temperature this is usually where the problem starts to happen. I have just never known what that problem was.(Read above posting) So my first thought is the injectors are leaking. But I know more tests need to be done to rule that in or out. So I turn the key on again and the fuel pressure jumps up on the gauge straight back to 41, so then I continue to turn the key on and off on and off on and off and each time I do that I can hear the fuel pump click in the rear and the gauge climbs to 41. (Sorry this is so long but I figure the more information you know the easier it will be for you to come up with a possible solution) At this point in time is where something changes, what changes I do not know but the very last time I turn the key to the start position I still hear the click in the rear but this time when the fuel pressure rises on the gauge it stays at 41 forever. IT DOES NOT FALL!!! So I go ahead and start the car figuring that something has changed and it probably won't start. Well it does. BUT!!!! I turn it right back off again and try to start again and nothing,nada,zip,zero,zilch, uh-uh. The car just cranks over and over and over like its usual pattern that it does everyday and it won't restart till the next day. The only clue that I have on my side this time is that when I try to start it in this no run condition I DO still here the fuel pump click behind me when I turn on the key but absolutely NO MOVEMENT on the pressure gauge at all. No matter how many times I try the fuel pressure is gone. I mention in my first post I thouhg that it might be the pressure regulator but the car would have to be running first correct ? Its the pumps job to create the initial pressure to the rail correct? This problem would certainly rule out any leaking injectors or cold start injector correct? I did not do the test where you crimp off the fuel to and from return lines to see if it was the filter, but I seriously doubt it could be. Even though I am gonna replace that! Thats leaves the fuel pump going wacky ! Do fuel pumps go dead and stay dead or do the work and stay working ? What I'm trying to say is can there be an on/off working pump that just works when it wants to? LOL I'm gonna check juice going to the fuel pump connector under the rubber boot and will pull the fuel pump and turn the key on and make darn sure the pump is getting power all the way down to the pump itself. If it isn't i'm going to replace it. Just hate to replace parts that I don't need to. Could this problem be related to temperature ? When the car is cold it starts fine and the pump has plenty of pressure according to the gauge. Once the car is nice and hot and the pump has run a while with the car idling up to operating temperature, could the pump overheat and then just want to die ? Just one of my many questions. LOL I AM SO SORRY this is such a long posting but I just wanted you to have all available information and maybe you can help me or steer me in the right direction with what i'm doing. I know I asked a bunch of questions, so do the best you can. As you can see I'm going cross-eyed dealing with this car :crazy:


Anyone else out there with an opinion I would love to hear it!
But please don't mention V.A.T.S. LOL I have 3 sets of keys 2 which have never been used. Both sets won't start the car any better than the set i'm using. The engine does crank and starts.

Thanking everyone in advance,
Sean

AGENT 86

Welcome to the forum :seeya
Your fuel pump may be getting tired. Your pressure loss may be the check valve on the pump. What kind of pressure is there with the vacuum hose removed from reg. ? When you do have no pressure I agree you should check for voltage at the pump. At the start of your post it did sound like a leaking injector but with the zero pressure something else must be whacky.
Hopefully someone with a similar situation will chime in and set you straight.
Good Luck
:cheers:

brookman

My first guess is the fuel pump is bad. Electric motors exhibit this kind of condition just as the brushes are getting to their limit. My wifes exploder(Explorer) did this to me twice and I promptly replaced the fuel pump. If you want to prove it beond a shadow of a doubt - put a multi-meter on the leads to the fuel pump and make sure you have voltage when it wont start. Relays do go bad - but if that is the original fuel pump - I would place my money on that.

vinnies87

:iagree: sounds like fuel pump, to me... :thumbs: :thumbs:

justavetteguy

Thanks for the advice. I am going to replace the fuel pump,pulsator,and pickup screen. I will let you know how things turn out just as soon as I do so.

While I am here I would like to tell you one other test I performed on my car today. It was something I just thought of and decided to try. I put the pressure gauge back onto the fuel rail. I checked for power at the fuel pump connector under the rubber boot next to the fuel filler neck. There was power there. I turned the key and the pressure on the gauge went up to 40 and then I started the car and it ran fine while the gauge read 36 the whole time it was running. I let the car get up to operating temperature and then I cut it off. When I cut it off I noticed the fuel pressure shot up from 36 where it was running back to 40 and held there and did not drop. This is something I had not seen it do before.(I know I kinda already did this test but I'm getting to the part that I did different) I then waited a few minutes and the gauge was still at 40. I turned the key to start and the pressure went to 0. The car would not start. I then left the key on and went back and checked the connector at the fuel filler neck and there was still power there. So I know now that electricity is getting to the fuel pump. So then I decided to see if I could energize the pump by sticking a wire into terminal G on the communications link and the positive on the battery. When I did that there still was no pressure on the gauge. The key was off when I did that test. Then I tried it with the key on and still no pressure. Did I do that right? What did I possibly rule out as a potential problem other than the fuel pump itself?
Something else happened during the test that I didn't understand and I don't know if this has anything to do with my problem or not. But each time I touched the wire to the positive on the battery and the G on the communications link with the key off I heard a clicking sound coming from a relay behind the battery. I could even put my fingers on it and feel it clicking. I could make it click every time I touched the wire to the battery. BUT when I removed the wire and turned the key on sometimes the relay would click and sometimes it would not. Maybe 1 out of 10 times it would click. Could this be part of my problem? The relay that was clicking was the inner relay of the two towards the engine not the outer relay. I believe from what I read that these are the MAF power and burn off relays. Sorry such a long posting again. :) Just thought I would get your input. Thanks for your help :thumbs:

Sean

pablocruise

whew! took me a couple tries to get thru the posts :D but seriously, welcome to the forum-glad ya could join
now,
how is oil pressure? Their is an oil pressure sender behind the distributor. Check that it's wiring is not frayed or shorted out. The ECM needs to see certain pressure from it before it will send the signal to ok fuel flow. The relay is as you discovered on the driver side wheel well aft.
Do you have a 6 speed car or an automatic? There is a switch that tells the ECM you are pushing in the clutch and it's ok to turn over. Not sure if the autos have something similar.
The starter itself might warrant some attention. Is it original? How many miles on the car? You can put a remote start switch between the two connector studs on the starter. Key can be on or off and you can bump the motor while standing outside the car(not in gear). Check it's connections too.


[Modified by 89 Paul in Cal, 9:08 PM 12/11/2003]

brookman

What you did is narrow it down to a problem between the point you measured the voltage and the fuel pump itself. I have heard that the connections from the pump to the connector do go bad. But....If that is the original fuel pump - 13 years is a pretty good run.