Hello everyone, I just joined and this is my first post here. I have a 1987 5.7 liter IROCZ, automatic with 49,000 miles. I've owned the car for 5 years. Last year I had the electric fuel pump replaced because the car had no power, low pressure. Seems ever since then whether hot or cold it take 4 to 5 times cranking it over before I'll get it to run. This just doesn't seem normal. Any ideas what could be the problem? Any suggestions? Thanks in advance, Paul

 

Fuel Pump Relay is my guess. What it sounds like is happening is that by you turning the engine over a few times is building up oil pressure in the "Oil Pressure Fuel Pump Switch" that is either behind your intake manifold or right above your oil filter.
This a backup power line for the Fuel Pump in case the Relay goes bad. When the switch sees 4psi of oil pressure it closes the switch and allows power to run to the fuel pump. This switch is wired in parallel with the relay.

To see if your relay is functioning, turn the key to the run position and see if you can hear the fuel pump prime for a couple of seconds. If it does, then the relay is good, if it doesn't, then it is bad.

 

Zepher,

How about the same problem with a carbed car (85 IROC)? The car does have a new fuel pump, but no improvement was made. Any suggestions?

JamesC

 

Thanks Zepher, I've tried what your saing and I do hear the pump running. Does this mean the "Oil pressure fule pump switch" could be the problem instead of the relay? I figure that turning the engine over builds up the oil pressure and alows it finaly fire but what has to be corrected to get it to fire on the first try? Any idea, or is it the oil pressure fule pump switch? Thanks, Paul

 

The Oil Pressure Fuel Pump Switch is only a backup for the Fuel Pump Relay. Car will start and run fine without one. When I converted from carb to TPI, I didn't have the connection for one.
Let me think about this one for a little bit.

About the Carb problem, are you running the stock quadrajet?
If so, it could be the Mixture Control Solenoid going bad.
If the M/C Solenoid goes bad, the car won't start at all unless you hold open the butterflies with a screwdriver or something while you crank it over.

 

Zepher's right, even if we all get into this argument again (over what the oil pressure switch does), all it takes is a look at the wiring schematic to prove that the oil switch is a backup to the fuel pump relay. I ran without mine for a few years when I put my mechanical oil pressure gauge in- I removed the oil pressure switch instead of the idiot light switch by accident. (oops)

MrGilbwrench, how do you start your car? Do you hop in, and turn the key from "off" to "crank"?? If so, this might be your problem. The pump isn't able to work up to pressure fast enough. Next time you get in your car, try this: Turn the key from "off" to "on"- you know, the position right before "crank", where your dash lights come on, the seatbelt light comes on, and you can use your radio and power windows. Listen for the fuel pump "hummm" to stop- that means the fuel lines are pressurized. When the hummm stops, now turn the key from "on" to "crank".

My car starts in a 1/2 second if I do this method. If I go from "off" to "crank" without stopping, it'll crank and crank and crank and crank and not start and I feel like a dumbass- this usually happens when a hot girl is near the car, or some guy parks next to me in his riced-up import.

Don't know why a pump replacement would've done this, though. But give it a shot...

 

I know what your talking about TomP. I've owned a couple IROCZ's, and , yes I do start the car the proper way by waiting a few seconds. Does anyone know if the oil pressure switch is bad because it takes so many tries before the engine will fire. I take it if the switch works proper the oil pressure is high enough the first time to let the engine fire. In my case, by the 4th or 5th time, the pressure is high enough that it alows it to fire and run fine. Does this make sense and I should start by replacing the oil pressure switch? By the way, mine is a TPI 350. Thanks

 

Hey Paul,

Welcome to the board, if these guys can't help you no one can.

Mark

 

dont even bother with the switch. Mine isnt even hooked up and the car runs fine. Have you hooked a fuel pressure gauge up to it to see if the system builds and holds pressure well?

 

One other problem might be the distributor module, if that is going bad, then the injectors won't fire until the RPM gets to a certain speed and the ECM takes over.
It would seem strange that this part would go bad after a fuel pump replacement, but you never know, maybe the original pump didn't fail at all.

You can use a test light in one of the injector connectors to see if they fire up at low rpm when you first crank it, if it doesn't, then the module is bad.

BTW, I learned everything TPI related from Vader, GMTech, John Millican, and others on this site when I did my carb to TPI swap last year.