Pulling the ignition coil fuse on my '84 EA81 kills the dash but runs the fuel pump.

[PigEqualsBakon]

Carb, EA81. The problem I'm having is strange, the ignition coil fuse, when pulled, Kills the dash (and presumably the coil) but the fuel pump runs a bit. When the fuse is put back in, dash comes back to life, all the dash lights come on then after a second goes back to normal, but the pump won't run when cranking. Putting in a different fuse does nothing, no blown fuses and no new fuses solve the issue. I know it's a wiring issue, but I have no clue where to even begin. Any Ideas? Anyone else had this problem before?

[Dee2]

Is this a new problem ?  Did it happen recently after some changes or did you inherit the problem as part of acquisition.

Best guess is you'll need to get a wiring diagram from a service manual like Chilton's.  Verify if anyone has previously monkeyed with the wiring by checking the fuel pump wire routings.

[PigEqualsBakon]

1 hour ago, Dee2 said:

Is this a new problem ?  Did it happen recently after some changes or did you inherit the problem as part of acquisition.

Best guess is you'll need to get a wiring diagram from a service manual like Chilton's.  Verify if anyone has previously monkeyed with the wiring by checking the fuel pump wire routings.

Bought the car in non running condition, but it ran a few weeks or so before I got it. I have a wiring diagram from a Haynes manual, and it appears that a fuel pump wire might be shorting to ground through the wire somewhere, as the fuse goes to ground. The fuel pump wires vanish into the body and I can't quite locate where they come out, but I do know their colours don't match the diagram. (Not the first time this has happened, only one of the two colors match)

Edited August 20, 2018 by PigEqualsBakon
Spelling error

[Dee2]

3 hours ago, PigEqualsBakon said:

...but the fuel pump runs a bit. When the fuse is put back in, dash comes back to life, all the dash lights come on then after a second goes back to normal, but the pump won't run when cranking.

Almost sounds like the pump itself may be the problem.  Seems like what you're saying is the pump never does run correctly.

Try rapping on the pump with something like a screwdriver handle a few times and see if it comes back to life.  May need to try more than one attempt.  If it does start working, then you likely need a new pump. 

 

[GeneralDisorder]

Start at the fuel pump control unit mounted above the hood release cable bracket - it's either a 6 pin black or 5 pin blue box that controls fuel pump power based on tach pulse (coil neg.) input. 

If you don't have a factory service manual for 84, find one on ebay. Aftermarket manual diagrams are worthless. 

GD

[PigEqualsBakon]

On 8/20/2018 at 8:35 AM, GeneralDisorder said:

Start at the fuel pump control unit mounted above the hood release cable bracket - it's either a 6 pin black or 5 pin blue box that controls fuel pump power based on tach pulse (coil neg.) input.

I found the brain box and bypassed it like you've suggested in  other threads, pumps fine now with key on, and it cranks while the pump is running! Will bypassing the fuel control unit prevent it from starting?

Or cause any running issues?

Edited August 23, 2018 by PigEqualsBakon
Additional question

[GeneralDisorder]

Shouldn't be a problem till the scene of the fiery accident when the fuel is being pumped into the engine bay fire with your unconscious body mere inches from the blazing inferno. 

GD