Hi everyone.

When I bought my Bronco it ran great. Recently, it has developed a no start condition - the starter just spins and spins but the engine never fires. When I initially put the key to the run position, the fuel pump sounds like it's running, except it doesn't shut off after 1 second, it keeps humming - and it'll run forever if I keep the key in the run position. When I spray some starting fluid into the engine, it sits and coughs and sputters and belches out black smoke. It will not start without the starting fluid, but once started it does not stall.

What's weird is that on rare occasions, like after I do the KOER test, the truck will run GREAT, without any problems at all - no hesitations, full power, no sputtering, no smoke. So I am assuming the PCM might be getting an intermittantly bad input value and going into limp mode, or the PCM itself is freaking out itself.

I have been pulling codes for a week or so, and the latest tally is the following:
21 - ECT out of self-test range
33 - EGR valve opening not detected
87 - Fuel pump primary circuit failure
95 - Fuel pump secondary circuit failure - PCM to ground

Today is the first time that code 87 came up. Does anyone know where to start? I have replaced the fuel pump relay, the battery cables, plugs/wires/cap/rotor (and triple checked the routing of the wires), and I have 12v on the input and output of the fuel pump relay.

This is a 91 Bronco, 351W, MPI, E4OD.

Thanks,
Dan

 

a W.A.G. on my part; look for a small gauge black wire that connects to the batty.'s Neg post; that's if I recall correctly is the pcm ground