87 TBI troubles, please help

[AyWoSch Motors]

I'll try that

 

[AyWoSch Motors]

So in re-reading your first post this started happening after doing the ignition system work, and I reading that correctly? I'm wondering if you got a new module that isn't giving the computer a strong enough RPM signal? If you have a spare I'd swap it out just to see, especially if it was lower cost or off brand module.

Make sure that none of the wiring is damaged where the injector wiring leads to the injectors especially where it passes from the outside to inside the throttle body sometimes it gets rubbed in that little rubber bushing it passes though or someone damages it putting the air cleaner one, some times it take a while for a wire crimped for that to actually become a problem so if one or more of the wires has been flattened even if it didn't break though the insulation it could be a problem. Feel free to post pictures of the wiring and engine it might not tell us anything but maybe we'll spot something.

I checked that those wires weren't damaged, they look to be in good shape.

This all started when it stopped running, did work to it to try to get it running again.
I didnt replace anything in the TBI, just took it apart to clean and inspect it.
Which Module do you mean?.

 

[AyWoSch Motors]

Ok here's another thought for you. There should be some ground wires attached to a stud on the thermostat. These ground wires the computer uses. The injectors are constantly fed power, and the computer completes the circuit creating the pulse though those ground wires at the thermostat.

Hmmm, didnt know that. I will have to inspect it.
On the thermostat?

 

[SirRobyn0]

Hmmm, didnt know that. I will have to inspect it.
On the thermostat?

Yes, IIRC one of the two bolts that holds the housing down is a double stud with a nut, should be some ground wires on that but I think the number varied from year to year.

 

[WP29P4A]

My son's 87 TBI truck has that ground, it was covered in oil and it was lose. I pulled it off cleaned and tightened it. Truck ran more consistent after.

 

[Originalthor]

There are also two ground wires on the back of the passenger side head aswell. Also just on a whim here check the bulkhead connection at the fire wall. Theres some wierd tar stuff in there thats like to hinder connections.

I just did a stand alone harness on my tbi and it runs 10 time better once I redid those grounds and just give it 12v power straight from the battery. So I'm assuming it was something to do with those grounds and bulkhead connection.

 

[Redfish]

On the back of the engine, right against the firewall and partially hidden there is an oil pressure switch. It is tied into the FUEL circuit and will not let fuel get to the engine if there is no oil pressure. I haven't looked at a schematic to see where it ties in but I do know what it does. On my all stock '87 when I turn the key I can hear the electric pump come on and prime but the engine won't run if that switch is bad.

Just a thought.

If you do replace that switch pay careful attention to the plumbing it is attached to. Otherwise you will find yourself using an EZ Out to remove a piece of broken brass pipe and raiding Home Depot to fabricate a new pipe and elbow assembly.