87 chevy truck prob

[mjc]

I have an 1987 r3500 tbi truck and have a question. It is stock to when I try to put it in base timing mode to set timing it will not run with the connector disconnected. Does any know what will cause this?

[EagleMark]

Probably just idling to low! Stick a few feeler gauges in behind the throttle blade stop screw to raise idle a little. On these old trucks the way the throttle blade shaft wears it closes. You could probably just turn in throttle stop screw, also known as Minimum Air Adjustment screw 1/4 turn. Do not try and use this as an idle adjustment though.

[mjc]

It will not even fire up. If i start it and open the connector up while running it will die immediately. I have no spark when connector is opened.

[EagleMark]

That funny! We just helped a guy who had the exact opposite issue?

Without the bypass wire the EST should run off the pickup coil. The pickup coil generates it's own power to run the EST. What you do when disconnecting the bypass is take away the 5 volt to EST.

So either the pickup coil or EST are faulty. Pickup coil replacement is cheap but it requires pulling distributor and taking it apart to replace.

[mjc]

I will get some time tomorrow to go look at that stuff I have another module i can try. Does anybody know what the timing is if you do i without the bypass opened.

[EagleMark]

Depends on if engine is up to temp and RPM... but around 16 stock.

[budweiser_man]

check your wiring and grounds. I had the opposite problem. turned out to be 2 wires grounding out to each other.