chevysrule94

i have a 95z, and the other night when it started it took alittle longer than usual to start, and when it did it was idleing at like 500 rpm's. then when i hit the gas it almost stalled , it was like that for a few minutes, then it stalled. after about 3 minutes of cranking, it started and ran fine the whole way home, although the service engine soon light came on. the next day i tried to start it and it just cranked . so i disconnected the batt to reset the ecu, the fuel pump still wasnt comeing on with the key. so i checked for power at the harness that goes to the fuel pump relay by the rear axle.... no power with the key???? i tried to pull up the codes with a scanner i have , but since i disconnected the batt., there were none. i checked all fuses , and also noticed that with the scanner that the fuel injectors were pulsing while cranking just like they should so i dont think it could be VATS.



please help any suggestions are greatly appreciated.



thanks, matt

shoebox

If the engine is not started, there will only be power to the pump for 2 seconds when the key is turned to ON. If you did not check voltage during that time, you won't see any.

OBE1 95Z28

I'd suggest you hook up a fuel pressure gauge and see what's going on a the fuel rails. You could have a clogged fuel filter, FPR going bad, and/or a marginal fuel pump.

chevysrule94

ummm, i know that the fuel pump only primes for 3 seconds....and it DOESNT have any power at all. if it doesnt have power to turn it on and make pressure why would i hook up a gauge to figure out that theres no pressure?????

shoebox

Well, I don't know what you know. Sorry, I was just trying to help. :blah: You might check at the f/p relay.

385LT1

i think what these seasoned enthusiasts are trying to explain to you is....

assuming there is no pressure and verifing there is no pressure on a gauge are two different things.

also, assuming there is no power, and verifying there is power on a multimeter is two different things.

it could be possible that you are not hearing the fuel pump because it is failing, or failed.

start with the basics,

verify pressure then power to the fuel pump relay located underneath the passenger side dash panel.

then verify that the relay is functioning properly.

is your security light on? it could be the VATS system. if so, let me know i can explain how to bypass it.

good luck

chevysrule94

sorry, i didnt post that i used a test light and a multi meter to verify that there was no fuel pressure....also, not trying to shoot you guys down or anything but im just alittle frustrated with this thing, and i pretty much ruled everything out except for a broken wire or somewhere else the power goes first, before it reaches the fuel pump.


thanks for your help guys.

chevysrule94

wait the fuel pump relay is on the pass side frame rail above the axle???? is there another one under the dash? and yes the security light goes out within 5 seconds.

385LT1

i am not aware of any relays located on the passenger side above the axle.


the fuel pump relay is grounded by the VATS system FYI.

shoebox

F/p relay

385LT1

now thats strange.....

where is it located on a 94?



my 95 z was under the passenger side dash. same color wires.
as well as a friends 94.
weird.

385LT1

check this out Rob......

link


are there 2 relays for the starting system? starter relay and starter enable relay?

in this schematic it show the starter enable relay with the appropriate wires prpl and ylw, being grounded by the VATS module. could these be in line with each other?

shoebox

Are you sure you are not thinking of the theft deterrent or hatch relay that is to the right of the glovebox? Under the dead pedal is the only place I have known the f/p relay to be.

385LT1

My VATS died, so i grounded the Ylw and blck wire, and it bypassed the VATS system, so i unplugged the VATS module and tossed it...... the VATS module also controls the SECURITY LIGHT on the dash, once removed it no longer illuminates.

385LT1

Then the theft detterent relay controls the starter relay, because it has 4 wires... yellow and black, brown, purple and yellow.

edit..... the ignition switch enables the starter relay, but power stops at the theft detterent relay, untill it is grounded by the VATS module......

if this is correct then that schematic is wrong... the purple and yellow wires should be routed through the theft detterent relay... because the yellow blck, and brown wires are simply control circuits. brown, power from ignition, yellow and black is ground to energize the relay.



if this is the case, then it is baisically redundant other than the fact the theft detterent relay is grounded by the VATS module once the appropriate key is inserted......


it makes sense to me that there would have to be 2 relays in line... one controlled by the ignition switch the other by the VATS module.