Weird EFI wiring problem - no crank unless EFI fuse removed (1 Viewer)

[msahr]

This has got me confused. 86 22RE 4x4 manual trans... I bought this truck not running, so I don't know much history. When the EFI fuse, EFI relay, 30A fuse in engine fuse box are all connected, the truck won't crank at all and there's a clicking coming from the driver's side near the top of the dash. If I remove either the EFI fuse OR the EFI relay OR the 30A AM2 fuse... it will crank. I've looked over the wiring diagram and even have the FSM wiring diagram supplement. I have another 86 truck and have moved the EFI relay to that truck, cranks and starts no problem.

Any thoughts?

 

[gnob]

will it crank with only the ecu uses unplugged ?

 

[CJF]

there's a clicking coming from the driver's side near the top of the dash.

That sounds an awful lot like when I was a dumb kid and drove into the ocean at Pismo. Stalled and wouldn't start. Fortunately I had some good sleuths with me and we figured out the clicking was the coil shorting to the body (due to the water in my case). Worth a look...

This was on an 80 22R (or maybe 20R? Too long ago...)

 

[msahr]

will it crank with only the ecu uses unplugged ?

Any combination of any of the 2 fuses allows it to crank

 

[gnob]

ok. pulling the efi or am2 kills different things.
you have a short somewhere behind those fuses, possibly the ignition switch.

you need to start unplugged things behind the fuses to eliminate your options.

 

[msahr]

ok. pulling the efi or am2 kills different things.
you have a short somewhere behind those fuses, possibly the ignition switch.

you need to start unplugged things behind the fuses to eliminate your options.

I've tried a different switch and have pulled the kick-panel fuse box out, it looks fine and the wiring to it is clean. The other reply about the coil and igniter got me thinking and I started tracing all that wiring, only to find several nightmares. Gonna sort all that out and hopefully after I fix all that I can at least have a good starting point.

 

[gnob]

I've tried a different switch and have pulled the kick-panel fuse box out, it looks fine and the wiring to it is clean. The other reply about the coil and igniter got me thinking and I started tracing all that wiring, only to find several nightmares. Gonna sort all that out and hopefully after I fix all that I can at least have a good starting point.

cool. the coil definitely on the circuit.
i also noted the injectors and resistor are there as well potential spot for short.

 

[vipergrhd]

Look for aftermarket alarm, I have chased my tail before only to find out the alarm is the cause of all the electrical issues.

 

[msahr]

Update, with partial success: Fixed all the nightmare interesting wiring from who knows where (broken 3-wire connection from coil to wiring under intake plenum, wires were broken, they jumpered across the connector but poorly. Also found a broken ground wire. Fixed all that, no help. Removed the fusible link box and opened it up, all looks as clean as an 86 can, went ahead and replaced the 80 AMP FL, still not fixed. Decided to pull the ECU and disconnected it, nope. Considering how big a deal the circuit open relay plays I decided to disconnect it... success! The engine cranks with the EFI fuse and all other parts connected. Hmmm... so decided to disconnect the fuel pump, reconnect the COR, the damn thing cranks now. Reconnect the fuel pump... no crank. So there must be a short to ground between the COR and FP. Next step, remove the bed (because I hate dropping fuel tanks) which I need to do anyway. Pull the carpet, etc. I seem to remember a harness connector between the cab and the bed. Maybe that's it, we'll find out.