SPDEMON

Can someone explain to me a properly functioning LT1 fuel system's paramaters?

I.E.:

When you put the key forward how many seconds should the pump prime for?

If you prime the system, then immediately turn the key OFF, then turn it back on, should it prime again? Over and over? Or does the car wait a few seconds before allowing the system to prime again?

Also, what would cause a car to not start with the key forward and turning over, but when you let off the key it starts to fire and will only start with the pedal to the floor?

I am having a hell of a time fixing this issue on my 95 Z28.

RamAir95TA

iTrader: (2)

Do you have in your possession a fuel pressure test gauge? That will help you tremendously.

SPDEMON

Yes, I own one.

Unfortunately that doesn't answer my question.

I don't need to know what the pressure is / is supposed to be, since you can hear the pump prime the system regardless of the pressure. I want to know for how many seconds is the pump supposed to primer the system, and if I was to turn the key off, and turn back on right afterwards, should it prime the system again?

tonskiguy

iTrader: (3)

My pump runs about 3 seconds every time I turn the key on. I do have an Aeromotive FPR though, which does not hold pressure like a stock FPR

RamAir95TA

iTrader: (2)

About 3 seconds with each cycle of the key.

SPDEMON

So on EVERY cycle of the key right? Even if I cycle it 10 times in a row?

Fastbird93

iTrader: (10)

Yes. Just let the PCM power down completely and it'll prime every time.

FAD2BLK93

Unclear on this Fastbird??

SPDEMON

How long does that take (PCM power down)?

StraightTimeStirrups

Is the pump easy to hear on these cars? I never hear my pump prime but that doesnt mean that it doesnt. I do believe I have a fueling issue on my car as well as it never seems to run right all of the time when I start it. The car isnt done yet so I have not done any driving with it as of now.

I have to figure out where/how to test the fuel pressures on my 93 as I only see the 94-97 referenced with a Shraeder Valve.

Joe

sweetbmxrider

iTrader: (13)

I can't find anything definite but I've noticed on my car quickly keying the key on and off won't prime the pump every time. Stick a test light on the ground side of the fuel pump relay and watch to see when the pcm grounds it.

Just because you hear the pump run doesn't mean you have correct pressure.

Fastbird93

iTrader: (10)

Just turn the key off for a couple of seconds. If you flick it off then right back on without a pause, the computer will sort of stay energized and you won't get another prime out of it.

quik95lt1

iTrader: (7)

starts after you let off the key? sounds like something is botched up with the wiring where the pump isn't on durring the "start" positoin but is on durring the "run" position.......maybe a bad keyswitch monitor the +12V to the pump while somebody cranks the motor and make sure it stays on

FAD2BLK93

So the computer grounds the pump to start? Does it also ground the injectors at the same time? Part of the security system after the correct key is used right?

sweetbmxrider

iTrader: (13)

The computer grounds the fuel pump relay which then supplies 12 volts to the fuel pump. The pcm operates the injectors by grounding them.

SPDEMON

Thanks for the info guys.

My FP is priming correctly per your answers. It will prime for 3-4 seconds, and it does prime every time I cycle the key, but it needs to be in the off position for 4-5 seconds before I can turn the key forward again and get another prime out of it.

Now I have to check my pressures one last time before I move back to the ignition system.

Damn car wont start when cold, but will fire 10 times in a row with no coaxing after its been running for 5-10 mins. When it runs it runs great, especially since I just changed the OPTI.

jaycenk

iTrader: (1)

Scanner with live data may help with the cold start problem if it's not fuel pressure related.

sweetbmxrider

iTrader: (13)

Engine coolant temp and air intake temp should be within 4 degrees of each other when starting a cold motor. If there is a large variance, it can give you hard cold starts.

SPDEMON

Thanks for the info.

I have changed out the water temp sensor on the water pump housing already, haven't changed the intake sensor.

Where can I get a decent OBD1 scan tool that will give me live data?

sweetbmxrider

iTrader: (13)

You can buy a cable and download some tuning and live data software like datamaster etc.