Hi, new to the board, but have been absorbing alot of info. The knowledge on here is great. Prior to owning this car, my skills were limited to oil changes, brake work, hub work, and other basics. I'm starting to feel like I know a thing or two, which is great because my 12 year old daughter and I are doing this project together.

The car: 89 Iroc 5.7 tpi, 71,xxx miles. Bought the car in the spring to restore and she would run beautifully one minute and like death the next. She also would only start with starting fluid.

What I've done: Read a lot of posts on here and then did alot of diagnostics. Had a low and high coolant code, a high and low air flow code. I subsequently replaced engine coolant sensor (sensor only, not the pigtail), wires and plugs, distributor and cap, replaced injectors with 22# Bosch from South Bay, cleaned and tested MAF, tested O2 sensor, tested TPS sensor, replaced both MAF relays, and fuel pump relay, adjusted throttle cable and kick down cable. BTW I tested the injectors hot and cold before I changed them. They looked stock and 5 or 6 had resistance of 8 ohms or less.

Current status: runs beautifully, like a whole new car...once she starts. If I crank it over for 3 or 4 times for 5 seconds or so each time she'll eventually start. Once she has been started and running, it fires up instantly every time and runs beautifully. I have 45# of fuel pressure at the rails. No vacuum leaks.

I have my suspicions of whats wrong, but I'm laid up for a few days and figured I'd ask for advice. If you have a diagnostic process to add please feel free.

Thanks! Matt, Lafayette, NY

 

Also, oil is new synthetic and yes I let the fuel pump and relay do their thing before turning it over.

 

Had the same problem. Was practically waking any late sleeping neighbours cranking so long every morning. ...New oil sender = starts like a charm since.

GM even printed a clue as to its ‘other’ function on startup:

 

a quick test would be to bypass the ops. The wire colors should be orange and red or orange and tan.
This could also be injector issue needing battery voltage offsets changed in the tune. Or a ignition issue pickup coil and or icm. It’s normal for 89 tpi to take 3-5 seconds of cranking to fire off. The ecm has to see two engine revolutions to enable the injectors. This perimeter can be changed in the tuning but doesn’t make a huge difference in crank time.

 

Looks like a 3.1l , the ops is in the same place above the oil filter in the block.

 

I can verify that the OPS has voltage, but how do you know the sensor actually works short of replacing it? Should it have 5 volts?

 

It’s a 12v switch. The switch closes at 4psi of oil pressure.
there should be 3 wires one that’s blue goes to idiot light or gauge.

 

 

If you can’t find the ops above the oil filter it’s behind the intake manifold. I can’t recall what year they changed it’s locat.

 

Thanks. It'll be a few days before I crawl under. I had a blocking mishap with a friend's truck last week and it fell on me. My wife has asked me to stay out of the garage for a bit! I'm going to listen.

 

Sounds like things could have been much worse. Glad your doing ok

 

If you have long crank times, you need to verify the fuel pump is actually running when you first turn the key to 'on', and that you are building fuel pressure. The oil pressure switch is backup power for the fuel pump, in the event the ecm controlled relay fails. The ecm doesn't really care what oil pressure is, and will happily continue to run the engine, even with zero oil pressure.

 

What ploegi posted! Make sure that at key-on, engine-off the fuel pump runs for at least 2 seconds then shuts off. A short crank on the starter should have the fuel pump run again for 2 seconds.

If not then need to make that happen. Could be the ECM, the fuel pump relay, or a wiring issue.

RBob.