Oldsmobile Doctor

Started truck to warm up ran for a while than died. When you cycle the key you can hear fuel pump running. Checked and don’t have spark at coil. Plugged in known good ignition module still no spark.
Plugged in good coil still no spark. Hooked up computer reader and cranked engine no codes or tack reading while cranking. Replaced crank position sensor and still no start. Checked the power feed to coil, ing module, crank position sensor and cam position sensor. Checked all fuses to ignition and computer. Replaced Computer and still no spark. Was working on 98 Bravada and swapped crank sensor the one from blazer worked in Bravada. Checked for spark on Blazer and it had spark swapped it back and it still had spark. Tried to start and it starts and dies. If I put gas in the throttle body it will run until it runs out.
Was running the fuel pump and it died replaced pump it still starts and dies. Purchased a fuel pressure gage and checked fuel pressure at the filter and it is 75 psi. Checked the pressure at the engine and it is 63 psi when starting than drops to 55 psi when it starts. I looked at other posts and others wouldn’t start for 10 min mine will start but die over and over.

old_master

If you put fuel in the throttle body and it runs, you have a fuel delivery problem. Key on, engine off, pump running, must be 60psi to 66psi. Must remain above 55psi for 3 to 5 minutes after the pump shuts off. Post your results.

Oldsmobile Doctor

Turned ignition on gage went to 62 psi dropped to 55 psi and was holding for 10 min when I came it to post results.

old_master

In the underhood fuse panel, directly in front of the fuel pump relay, there is a vacant, single, recessed terminal. That terminal comes from the fuel pump relay and goes directly to the fuel pump. Cycle the key several times to make sure that terminal is activated every time, and that it remains powered when the engine is running. You can also run a fused 10 amp jumper wire from battery positive to that terminal, the pump must activate every time you apply battery voltage to that terminal, (watch fuel pressure).

Oldsmobile Doctor

The pump runs while it is running though rather short . When jumping to the prime connector pressure goes to 62 1/2 psi then drops to 56 psi when I unhook it. When starting while jumpered pressure drops to 55 - 56 while it runs than jumps back to 62 - 63 after it stalls

old_master

Will the engine remain running if you keep the jumper wire connected?

Oldsmobile Doctor

No it dies

old_master

Is the SES light on when the engine is running?

Check TP voltage with key on engine off, must be below 1.0V

Check MAP voltage with key on engine off, must be at least 4.0V, then decrease when cranking.

post your results.

old_master

Before we go too much farther, does this vehicle have a security system, anti theft system or remote starter, either factory installed or aftermarket?

Oldsmobile Doctor

SES light goes out when it starts and stays off.
Tps voltage is .575
Map voltage is 4.75 drops to 2.something when it start
I have a MT 2500 and can give live data from the sensors but I only have a generic cartridge

Oldsmobile Doctor

No remote starters, No sercurity besides the passkey system that they all have

old_master

Just for grins, stick a test light in the negative coil terminal and fire it up. Make sure it stays on, (pulses) when the engine is running and DURING the stall.

Do the same thing on the coil positive, (pink) wire, and see what it does.

(just want to make sure we're not losing ignition)

old_master

If the SES light goes off and stays off, the problem is most likely NOT in the OBDII system. Primary and secondary ignition and fuel delivery are not directly monitored by OBD so they can't turn the SES light on.

Oldsmobile Doctor

The light hooked to the pink wire to ground stays on while while cranking but won't start. When removed it will run longer guessing do to injectors firing while not starting. When hooked to white & black wire to batt it flashes weakly while cranking. tries to start but dosen't. Also runs longer before dying.

old_master

The coil connector must be connected when you probe. (You want the engine to start and run while probing each of the terminals.)