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My car always took an extra second or two to crank over but it always fired up just fine and drove alright, I assumed that it was just old.
I have an 85 stock motor, stock everything.
so I was driving today and the oil puressure hit 0 and my car cut fuel. Now it won't start. My oil is perfectly filled on the dipstick and I remember my oil puressure being 42ish psi on the freeway and 21-32 ish psi around town.
when I crank the motor it cranks but no starting oil puressure starts at 0 but after a few seconds of cranking goes to 44 ish but still no starting. It's throwing a few codes one of witch is my egr witch is just disconected and the other is "fuel pump circuit voltage low" I took an volt meter to is and the voltage just before the fuel pump seems fine?
Few people are saying its a oil puressure sensor/ switch some people say its the oil puressure sending unit? I can't seem to find anything maybe a fuel pump relay?
Please help
Edit:
new fuel pump, mas, plugs, cap and rotor, iac, tips, fuel filter, radiator
Last edited by Tony Thompson; May 29, 2018 at 05:32 AM.
My car always took an extra second or two to crank over but it always fired up just fine and drove alright, I assumed that it was just old.
I have an 85 stock motor, stock everything.
so I was driving today and the oil puressure hit 0 and my car cut fuel. Now it won't start. My oil is perfectly filled on the dipstick and I remember my oil puressure being 42ish psi on the freeway and 21-32 ish psi around town.
when I crank the motor it cranks but no starting oil puressure starts at 0 but after a few seconds of cranking goes to 44 ish but still no starting. It's throwing a few codes one of witch is my egr witch is just disconected and the other is "fuel pump circuit voltage low" I took an volt meter to is and the voltage just before the fuel pump seems fine?
Few people are saying its a oil puressure sensor/ switch some people say its the oil puressure sending unit? I can't seem to find anything maybe a fuel pump relay?
Please help
Hi
The ecm does not cut power to injectors with low oil pressure, the ecm wont care less if you have no oil pressure.
Check the fuel pressure, when you turn ignition on the fuel pump will prime a few seconds then go off unless the ecm can see the ignition pulses.
The ecm does not cut power to injectors with low oil pressure, the ecm wont care less if you have no oil pressure.
Check the fuel pressure, when you turn ignition on the fuel pump will prime a few seconds then go off unless the ecm can see the ignition pulses.
Fuel pumps can fail at any time,
Good luck
so upon further examination I found some intresting stuff...
The fuel pump isn't pumping you're right, I figured id check the relay for good measure and found that well... It wasn't there... Just gone, the previous owner had taken it out and did some funky wireing. So I'm assuming the fuel pump takes voltage from the fuel puressure switch and that's why it takes a while to crank before starting (it has to build oil puressure) so would you think that the fuel pump died and isn't pumping or the switch died so it's not sending voltage to the pump?
Can I point out that this seems low to me? I'm usually at ~50psi even just around town, maybe hit 40 at idle.
I read online that it's fairly normal? I think I'm running 10w 30 and I live in the mountains so I'm farther up in the air, my car runs almost 5° hotter consistently then compared to when I'm inthe city
A healthy 350 can idle at 25. Mine sits around 30 at idle at temp (oil 260 degrees). I idle around 600 though. Add 1000 rpms to that and I'm about 60 psi. Moving I'm never below 50. Cold I'm 65. As long as you're between 25 and 50 youre well within reason.
- sounds like a fuel pressure issue. start with the basics -
I agree with pressure check. Now the 85 has 2 oil pressure sensors behind the dizzy. one is for pressure guage and one connects the power to the fuel pump after oil pressure builds. Make sure the wiring is good they look like this
I agree with pressure check. Now the 85 has 2 oil pressure sensors behind the dizzy. one is for pressure guage and one connects the power to the fuel pump after oil pressure builds. Make sure the wiring is good they look like this
Good luck diagnosing.
after days and days of poking around and replacing the fuel pump. The fuel pump fuse isn't getting any power and I can't hear a click from the relay when I turn the car on. So is it the relay or could the fuel puressure switch stop the fuel pump from getting power if that went bad?
In the racing world - a rule of thumb had always been you need 10 psi of oil pressure per 1,000 RPM. So - at 1,000 RPM - if you have at least 10 psi - you're OK. An OEM small block Chevy should make a bit more than that - but I wouldn't be too terribly worried about 20 psi of fuel pressure at idle.
I'm not the expert on the earlier C4's but on the LT1 era C4s if either the PCM commands the fuel pump relay to "on" OR the car has 10 psi or so of oil pressure (which closes the contacts in the oil pressure switch) - power is supplied to the fuel pump. Power goes through the fuel pump fuse - so pull the fuse and supply + 12V directly to the pump and see if you hear it run.
Who knows what the previous owner did wiring wise - but if you are supplying +12V to the fuel pump, it should be running. The longer than normal cranking you were experiencing could have been the lack of a fuel pump relay to get the fuel pump running before oil pressure came up.
PLEASE HELP (oil puressure?)
- sounds like a fuel pressure issue. start with the basics - 
