'88 300CID 4X4
Ran fine when parked (in rain). Started next morning, ran about two revolutions and quit. No fuel pump noise. Jumped across FP relay and pump runs but still no start. Inertia switch ok, tried cheap OBD I reader and does nothing. Tried jumping self test to ground - no flashing engine light. Tried snap on engine analyzer and it also does nothing when trying to pull codes. Instrument lights and gas gauge work. Fuses all look ok. Have power to ECM relay but not to FP relay. Battery is charged and engine cranks ok.Have changed both ECM and FP relays, sockets not corroded. Any help would be greatly appreciated.

 

Sounds like the EEC isn't turning on. With the key in RUN, measure voltage between each +12V pin and each ground pin in the EEC connector (unplugged). Refer to the top Left of this diagram:

(click this text)


If each pair shows battery voltage (within ~0.5V), the EEC may be dead. Remove it (you may need to peel the back of the plastic wheel liner forward for access) and look inside.

(click this text)

 

Thanks for the response, the problem was a broken wire between the ECM and the ECM relay. What a time sink for one crummy wire!!

 

Well, it's unlikely that any vehicle will experience several major malfunctions at once, unless it's wrecked (which you'd usually notice ). So naturally, there will be only 1 failure at a time.

But something CAUSED that wire to break. If you don't find the root cause, you can expect a repeat.