Hydrobob2006

hard start when cold... crank,crank,crank until oil pressure hits above 20psi on dash guage then fires right up.....thats what is happening...any ideas anyone...after reading posts on here, this is my logical explnation. Am i way off?......please help.......

bluers91

Yes, its potentially the problem. Check your car for codes also. Possibly code 54. I have had the same issue. Replaced the Oil Pressure Sender, ECM, and now it turns out its the Fuel Pump. Got a Walbro 255 sitting here ready to go in.

ECM wont allow the car to start unless it detects proper oil pressure. Also, whens the last time you had an oil change?

Hydrobob2006

going to check codes tonight, I just bought the car-havn't changed oil yet, don't know when it was last done, also tonight for that. where is the OPSU located? also noticed two relays near firewall between master cylinder and fender with really crappy electrical connections, I know one is for the fuel pump, any idea what the other relay is? they are almost identical in size/shape..
thanks

bluers91

Sending unit is located right next to the Oil Filter on the drivers side. Those 2 relays are used for multiple things. Fuel Pump, Fan Relay, etc...

Old dirty old can cause a drop in oil pressure. I would first do an oil change and see if that helps any, along with checking for codes before doing anything. Most likely your sending unit is fine. I changed mine, but really didn't need to. Just needed to change the oil after it sat for 1 1/2 years, and put in a new fuel pump.

Hydrobob2006

thanks, I giv'r a go and let you know how I made out......

mystikkal_69

iTrader: (2)

bad fuel pump relay.

supercrossman

if its TPI then it wont start untill it reaches proper pressure because its a failsafe built into it. that if you get into a crash it stops the fuel pump from just pumping all the gas into the accident.

Toehead

+1

If the fuel pump relay is bad the fuel pump wont turn on until the secondary switch is triggered by the oil pressure.

JP86SS

iTrader: (1)

To clarify,
The distributor pulses are read by the ECM and the ECM energizes the fuel pump relay. IF the relay goes bad, the oil pressure SWITCH (or switch with senser) will directly engage the fuel pump. this bypasses the relay so you don't get stranded in case of failure of a $10 part.
This causes long cranking starts as one side effect.
There is no safety in the ECM for not starting without oil pressure. (at least that I've seen yet)
Nor will the fuel pump stop if you lose oil pressure.
the only way that can happen is if the relay is bad and the car is running on the oil switch.

Urban legends.

supercrossman

urban legends? I read it in a overview of pontiac fuel injection systems in performance pontiac magazine. I dont think they started printing urban legends in tech articles did they?

JP86SS

iTrader: (1)

I'd be curious to see that, I've just never seen evidence that a system was designed to do that. There are several ways it could be done easily. What I've seen is just side effects resulting from another problem and has been interpeted as a safety.

Hydrobob2006

thank you for all the advise, it is much appreciated knowing there is a site like this. the Haynes manual isn't really worth the paper it was printed on. the best advise is coming from all you camaro nuts.........

stitchop

Maybe this will settle the "oil pressure safety" missinformation.

This is a direct qoute from the GM shop manual concerning specifically the 5.0 port fuel injection engine (vin f),
page 6E3-C2-3:


"FUEL PUMP ELECTRICAL CIRCUIT

When the ignition switch is turned to the "ON" position (before engaging starter), the ECM turns the fuel pump relay "ON" for two seconds, causing the fuel pump to pressurize the fuel system. If the ECM does not receive ignition reference pulses (engine cranking or running) within two seconds, it shuts "OFF" the fuel pump relay, causing the fuel pump to stop.
As a backup system to the fuel pump relay, the fuel pump also can be turned on by the oil pressure sensor/switch. The oil pressure sender has two internal circuits. One operates the oil pressure indicator or gage in the instrument cluster, and the other is a normally open switch which closes when the oil pressure reaches about 28 kPa (4 psi). If the fuel pump relay fails, a Code 54 is set in the ECM, and the oil pressure sensor/switch runs the fuel pump.
An inoperative fuel pump relay can result in long cranking times, particularly if the engine is cold. The oil pressure sensor/switch turns "ON" the fuel pump as soon as the pressure reaches about 28 kPa (4 psi)."

the wording is indentical for 5.7 VIN 8 and 3.1 VIN T, and for the TBI 5.0 VIN E, the wording is changed to say; "and the fuel pump builds up pressure to the TBI unit." other wise identical also.

Dan8289gta

Actually if your oil pressure sending unit reads 0 or goes bad it will blow a 20 amp fuse located near the battery (in firebirds). This happened to me once when the sender went bad my oil pressure gauge dropped to 0 and the car shut down and would not restart, i changed the sending unit and the fuse and it was fine. *This is designed to save your motor should you lose oil pressure.* My fuel pump relay is fine, i have no hard starts, you can here the pump activate when you turn the key forward.