My truck has been a real pain lately, if I leave it sit for a day it will fire up and idle horribly and want to die and then if I turn it off after driving or even while driving it will die and not wan't to restart at all and I have to let it sit. When I put my fuel pressure tester on and it starts it rarely gets to 60psi and idles around 55psi unless I get on it and accelerate. The fuel pressure does bounce around alot but never really goes below 52psi. I can see when it wan't to dies it drops from 58-52psi. If I turn it off then on again the pressure usually stays the same and doesn't jump to 60psi.

Now when I check the fuel pressure when it doesn't want to start if I turn the key off and on it jumps to 60psi every time and won't start. I can crank forever and get nothing but it always jumps to 60psi which is strange since it won't start but when it does start again it doesn't jump to 60psi when turning the key off and on.

I have spark, I just replaced my coil pack, wires, cap, rotor, and had my ICM tested and it passed. Is there something that might make my fuel pressure act weird and cause a no start?

 

Sounds like a spark issue to me. I believe those FP numbers sound about right.

Try tapping the coil with a hammer to see if it helps (mine quit once, and tapping it with the hammer got it back running until I ordered the new one). Other than that, it's difficult to diagnose poor spark without proper testers. You could check the plugs to make sure the gap is correct, and check the timing... but they are likely OK.

 

I just cleaned up this post and changed some stuff, someone please re-read my first post and try to help me please, this is driving me crazy and I am sick of throwing more parts at this truck! On a side note I keep having problems with my 4x4 not working and resetting it by pulling the plug on the transfer case has helped in the past, I will try resetting it again today to see but can a TCU cause strange problems like I am having? Maybe its the ECU?

 

Have you tried gently tugging on the wires that go into the manifold & connect to the fuel injector? Many have chased no-start conditions and found that the $15 connector was providing intermittent contact with the injector pins.

 

I actually replaced that connector last year when I replaced my spider and regulator for the second time after reading about it I figured might as well.

This is really strange and I am beginning to think maybe its my fuel pump or oil/fuel pressure sensor.

Today, It starts and runs on a cold start, my fuel pressure was around 55psi when I would turn the key to on, cranking and starting the truck it was around 60psi when I would give it gas. I could turn the key off and on and the pressure would drop a little when it was starting and eventually if I waited long enough with the key off I could turn it to on and the pump kicks on and my pressure goes back up to 55psi or so.

Now with the truck not wanting to start my fuel pressure is a constant 60psi if not 62psi, it's actually going over 60psi. If I turn the key off and on it is always 60psi, even if I wait for a few second with it off and get the pump to cycle it is 60psi up wards of 63psi which is way higher then when the trucks actually starts.

So is it possible that I am getting to much pressure and my truck won't start? Should I maybe replace the ebay fuel pump I put in last year? I should have listened but it was only $20. Could the fuel pump relay cause something weird like this or if the relay is bad it never starts?

Also, do you happen to know the correct ac-delco fuel pump id number, advanced auto has a few different pumps. Or should I just get the delphi and be done with it?

Does this look like the right ac-delco pump? http://www.ebay.com/itm/New-AC-Delco...8f2112&vxp=mtr

I was gonna get this one for sure http://www.ebay.com/itm/1992-1995-S1...fb4b09&vxp=mtr

 

SO after talking to some guys at the shop it seems the fact that I have fuel pressure and enough of it I should look other places then the fuel pump and if the relay is bad it won't turn on at all. So, the best guess was the ICM even though I had it tested. After that it could be the crank or cam sensor but the only thing about that is I would be getting a code thrown. So at this point I guess I will just start throwing parts and see what happens. I read another post where a guy had similar problems and replacing the ICM helped him so what the hell, time to throw parts at it. Also I don't think it's my computer but at some point it might get replaced.

 

You are not testing your pressure properly. Put your gauge on, and follow these steps.

Key on - 58+ psi and HOLDING at this value (62 is fine too)
Cranking/Running - Should not change much, still 58-62, it will go up a little when you press the gas pedal, thats the nature of the beast.
Key off - Should not drop more than a couple points over 5 minutes. Even overnight it should still have pressure held and should still be over 40psi. If you are losing pressure that is noticeable on the gauge, you have a leak. Leaks start out small before they get big.

Here is a fuel test video link I made to show you what a leaking "nut kit" looks like on your gauge. This is a good example of a very bad leak, this vehicle was running, but didnt make enough power to climb my driveway without a run at it and i couldnt get up over 25kmph.
4.3 V6 CPI Fuel Pressure Test - YouTube

Wow, its had a poopload of veiws since last time I checked it.

And BTW, your pump doesnt determine the pressure, the FPR does (Fuel Pressure Regulator)... Your pump puts out much more than 58 psi, that pressure is goverened and the excess pressure is dumped back down your return line to the tank via the FPR.

Notice how my engine runs all shaky and not smooth at all? It doesnt have enough running pressure for the batch fire injector to function properly, does not mean the injector is bad, it means I have insuficient pressure to operate the injector. My problem was a leaking fuel line in the plenum.

If these are your symptoms, then open up the top of the intake and look for gold spots where fuel has washed away the black soot inside the engine. If its gold on the passenger side, its the FPR leaking, if its gold on the drivers side, its the Nut Kit leaking.

If neither of these are your issue, then stick your gauge on the tank side line at your fuel filter and turn the key on. Should hit about 80+ psi and HOLD THERE, if it bleeds off then the leak is in your gastank and will be the 2" long black hose that will be popped off the pump or laying in the bottom of the tank.

Throwing parts at a problem never fixed anything but your sore hip from sitting on an empty wallet. Diagnosis is the key to proper repair and spending the least.

ICM or spark problems are going to throw a code for you. FUEL problems wont throw a code... Hope that narrows it down for you. If you get no engine light, its a fuel problem. You have a fuel problem, and I know this cause you mention that your pressure drops off more than a couple points. You dont ahve a cam sensor, and if you did, it would throw a code as well as your crank sensor or EGR system will.

Also be very careful when ordering parts and make sure you arent getting the pump for a TBI engine, they only need 13psi to run... You must have the pump and parts for a CPI engine. Sometimes the parts guys sell you the parts for a fullsize "Blazer" which only had a TBI engine. Stress this and have them triple check for you. Also you can find the part numbers for delco parts around here if you use the forum search button.

 

Thanks for the reply,I've looked in the plenum and it looks ok from the top but I am at the point where I'm gonna take it off anyways. I replaced the ICM and that did nothing so I am beginning to think you are right about it being fuel. It's just strange that there is enough pressure there for the truck to start but it won't. Maybe an injector popped out or something, it does bleed pressure alot faster then it probably should. It's nothing like the video where it drops right away but it does drop over time. I'm not seeing fuel in the oil and I am not seeing any inside the plenum looking in from the top so that is why i am doubting its the problem. I also disconnected my MAP sensor just to make sure it threw a code and it did so I am guessing the ECU is ok. If the spider ends up being my problem once again I am really going to hate this truck considering I have replaced it so many times.

 

Hooked up a noid light and I have power and pulse and after getting my hands on some starting fluid I sprayed some into the intake and she fires up so once again my regulator or spider injector has failed. I am going to buy a new one and then put an add in the paper to sell this headach and buy a subaru.