I'm popping fuse #11. I own an '86 gl wagon, and I was tinkering around with this damned carb when the motor stopped firing up. Ign. coil/fuel pump relay fuse was blown, so I replaced it and turned the motor over, fuse popped again.

 

I checked the coil and capacitor by swapping both parts onto my EA81, the motor fired right up, no problem.

 

Sounds like I have a short somewhere. Think it might be the fuel pump relay (rev)? I don't know if this is a common failure or not. Btw, the fuel pump relay is bolted up just under the steering wheel and it has a mitsubishi symbol on it. It looks like someone has been inside this dash before.

Edited June 30, 201015 yr by Mantis_Toboggan

You don't state what year and model car you have. I assume you are talking about a EA82 engine of some sort. Data for the wiring shows that fuse 11 ties to the fuel pump and coil areas as you said and you are correct about having a short on the line. Since the trouble seemed to happen while you were working on the engine I would look for a pinched blk/wht wire going the coil. To isolate things remove the fuel pump relay and the blk/wht wire going to coil. Hopefully you have a test light probe to work with. Connect the clip lead to a power source and then place the probe tip on the protected side of the fuse connection. If the short is still there the light will turn on. When the short is removed from the circuit the light will go out and you can replace the fuse back in the slot.

Yeah sorry, it was late, haha. It is an EA82 that I'm working on.

I began test-lighting at the coil end (fuse out/blown), and checked each wire on the positive end.

disty, ok

condenser, ok

fuse#11, bad

Then I went back inside and took the power supply wire from my off road lights, and checked the fuse slot.

The black/white wire lit up, so I disconnected the fuel pump relay, and checked that, no light.

Also no light when I try #11 fuse again, unless I plug the harness back into the fuel pump relay. I'm gonna try a few more things..

UPDATE:

I started working on the connector to the fuel pump relay (rev). The only prongs that did not light up were the yellow prong and the black/white prong.

The blue/red prong lit up.

I disconnected the fuel pump and checked again, blue/red did not light up.

 

So it looks like it's the fuel pump.

To make sure the trouble is with the fuel pump I suggest you disconnect it and then try a new fuse to see if that works ok. It seems strange that the trouble is with the pump but it's possible. It is more plausable to me that the trouble would be at the coil area where you were working. Using the test method I gave you needs to be used on circuits that are normally disconnected from ground. Since the pump motor is grounded on the return side the test light will glow even if nothing is wrong with the pump circuit. The current from the test light will find ground through the motor wingings of the pump motor.

Edited June 30, 201015 yr by Cougar

Hmm, so you think I should put in a new fuse, then check the fuel pump connector?

So if everything is connected, except the fuel pump connector, and I test the "blue/red", it should not light up. If it does, I may still have a short?

I wonder if it's the relay that's gone bad.

Yes, remove the fuel pump connection, put the relay back in, and then see if a new fuse works ok. Relays don't usually cause a short problem so I doubt it is bad. They generally have bad switch contact issues due to a burning of the contacts over time.

So I plugged the relay back in, unplugged the fuel pump and turned her over. Fuse popped.

I've taken the dash out and the driver fender to put a new wire in the harness (coil to fuse box). I think I'm going to build it as a separate circuit and test the functions before I start splicing into the factory harness.

Back in post 3 you indicated that the test light would not light if you removed the fuel pump wire harness. If that is still correct then the trouble is with the fuel pump wiring and not the coil wiring.

Yeah.

Well, If the fuel pump connector is the only piece disconnected, the light does not light up. When it is reconnected, the circuit lights up.

If I disconnect the fuel pump connector, and turn the motor over, with the fuel pump relay connected, the fuse pops.

Now, if I have the fuel pump relay disconnected and turn the motor over, no fuse problem.

 

So Yeah, it looks like the problem is between the fuel pump relay, and the harness that attaches it to the fuel pump, or the fuel pump herself.

 

When I was under there, it looks like the pump sits on a metal plate that is isolated by rubber bushings, is this for vibration or for circuit isolation?

 

Here's what I've done so far:

 

Added new wire to harness:

 

Coil side:

 

Firewall side:

 

Fuel pump relay connector:

 

Connect alternate circuit:

 

Splice into new wire from harness, firewall side:

 

Protect circuit, and tap into fuse panel ground:

Edited June 30, 201015 yr by Mantis_Toboggan

So I'm testing the Fuel pump relay now.

I've ran some intermediate wires from the harness to the relay, I've placed all except for the wire that goes to the relay.

The fuse pops when the relay minus fuel wire is connected.

Edited June 30, 201015 yr by Mantis_Toboggan

The trouble is between the relay and the wiring to the pump. It may be a good idea to swap the relay just to confirm it isn't the trouble. It would be the first time I have heard of a relay fail like that if it was the cause. I would think it would be easier to track down the trouble on the original wire rather than replace it but it looks like you have done that already.

Fuel pump harness is fine, triple checked that.

So I went over the wiring diagrams for a while, followed the wires out.

I've isolated the blue wire from the harness and the motor turned over without popping a fuse.

 

It seems the blue wire is connected to the auto choke.

Good deal. You have pinned down the trouble. Either the choke is bad or the wire to it has a connection ground. This makes more sense than having a problem with the pump.

Thanks for your help man!

You're welcome.