1990 TBI, Starts but dies immediatly. Sparks & FP runs but inj. pulse stops?

[keykey]

Have a 1990 with 3.1 TBI engine. Fuel pump + filter replaced about a year ago. Well maintained (plugs, wires, dist. cap+rotor replaced/in good shape). Fuel pump relay energizes when key on and when engine runs. I hear the fuel pump whirring in tank while relay is energized. It always starts, but only runs for a few seconds each time (about 2-5 seconds).

I removed the plastic cover on Fuel Pump relay and looked at the relay while engine stalling. It stays energized all the time, and is still energized while the engine stalls. De-energizes about 4 seconds AFTER the engine has stopped completely.

Spark is obviously there because if I spray starter fluid into throttle body bore when it's about to stall, it will stay running until i release the spray can BUT i can see that the injectors quit spraying at that point so it only continues to run on the starter fluid!

What could cause the ECM to stop the ground pulses to the injectors? If the Ignition module isn't sending any reference pulse to the ECM, shouldn't the spark be gone too? Why the heck do i have spark and power to the Fuel pump relay but no injector pulses?

Even more interesting, why do i have injector pulses for the first 5 seconds after starting and then they disappear but sparking continues???

[Jrs3800]

IIRC the ignition module in the distributor controls spark, you can have spark from the distributor, but the ECM will control the timing of the spark.. I think if the EM isn't controlling spark you will be at a default for spark timing...

The Injector is controlled by the ECM... Not 100% sure if you have a Ignition control issue or an ECM issue or an issue between the two... Hard to say...

[keykey]

I've now replaced the Pick-up coil AND the Ignition Control Module with brand new parts (both are located in the distributor housing).

The problem is still there. Starts everytime, but stalls after a few seconds when it's cold. If you start it over and over it will run longer and longer, and all of a sudden it just continues to run without stalling, after that no driveability problems of any kind.

Connected +12V to fuel pump test connector, listened to tank with stethoscope, can hear fuel pump whirr, started, but still stalls. So it doesn't seem to be a fuel pump problem (the pump was replaced 2 years ago because of another problem back then).

Seems to be a problem related to cold temperatures. It was much easier to get it running when it had been parked inside @ work over the weekend than it was when parked outside in freezing temperatures.

Anyone have any ideas?
Best regards,
/Erik

[Jrs3800]

No real ideas at this point... Can you scan the computer in it to see what the ECM is seeing? I am thinking a sensor issue or an isssue with the ECM.. But can't promise you thats where your problem is..

[keykey]

Originally Posted by Jrs3800

No real ideas at this point... Can you scan the computer in it to see what the ECM is seeing? I am thinking a sensor issue or an isssue with the ECM.. But can't promise you thats where your problem is..

No fault codes. I think ive found out now WHY the engine stalls. There seems to be a intermittent blockage of some kind in the fuel delivery system between the tank and the TBI...

When the car is in it's "working as it should"-condition, if you send +12V to the fuel pump via test connector, the pump is whirring with a constant sound, and fuel is circulating through the TBI and back in the return line (i can feel the warm pressure regulator housing getting cold pretty quick from the cold gas in the tank when starting pump test)

When the car is in it's "stalling after starting"-condition, i can hear the fuel pump building up a pressure against something (whirring fast at first but quickly slowing down and getting more quiet).

I haven't found the blockage though, i changed the fuel filter yesterday, the car started fine before and after the change. I called it a night, and left it inside overnight, and this morning it was stalling after starting.

Does anyone know if any part in the TBI can fail causing this behaviour? Pressure Regulator? Where do i start looking? It's so frustrating to look for because it's so intermittent!

[keykey]

I found the culprit, it was the in-tank fuel pump again! The strainer had rips in it around the mounting point, the pump probably sucked up some foreign material and partially siezed. Drained & cleaned tank, replaced pump again with new strainer (I'm actually not sure if i replaced the strainer last time...).

Lesson no. 1 learned: Don't assume that the pump "should be okay" because you replaced it not so long ago.

Lesson no. 2 learned: If you don't have a new strainer, don't put in the new pump with the old one. Wait until you've gotten hold of a new strainer instead. Saves a few headaches and a lot of work. (The tank was just filled up when I had to remove it. Therefore, I had to raise the car on a lift, place a table with wheels under the car, lower it, remove bolts, then raise the car up from the tank.)