Electrical Problems Galore- Coil, MAF Sensor, Wipers, Fuel Pump, Short - Defender Source
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  #1  
Old August 20th, 2008, 05:59 PM
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Electrical Problems Galore- Coil, MAF Sensor, Wipers, Fuel Pump, Short

This isn't going to be an easy one.

First the specs>
1995 90 ST- 5 Speed
Mallory Unilite + Mallory Internally Resisted Coil, Mean Green Alternator, 4.6, Tornado Chip (from RPI) in ECU

Problem 1: Coil gets hot... I mean cook an egg hot!
Problem 2: Windshield wipers run fuel pump! (Almost comical) This happens when you turn the wipers on and off. Not on every swipe of the wipers, but only when they are switched off.
Problem 3: there is a short somewhere, but removing fuses, and maxi fuses does not solve it.
Problem 4: Code 12 and crazy idle. Looks like my friend who dropped the MAF Sensor did it in?!?

I will add to the list shortly and fill in details.
I'm going outside to mess with it now.

Please give me some guidance before I rip the whole damn thing down to the frame and rebuild.
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  #2  
Old August 20th, 2008, 08:31 PM
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First thing I would look for is any repairs or changes to the wiring harness. These sorts of problems tells me that somebody has been screwing with things and didn't know what they were doing.

Usual suspects are aftermarket radio installs, foglights, winches and such.

I'd also check to make sure you have the correct relays for the fuel pump and injectors, as they should have diodes in them to prevent back voltage.

-Hans
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  #3  
Old August 21st, 2008, 08:20 AM
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those coils get super hot. Add a balast resistor (yes I know it is suppossed to not need it)
My mechanic put one on mine after I cooked a coil (black gue will boil out, if anyone is curious)

Also, If you ever have to leave the ignition on without the car running (like to run some diagnostics)
I have found it helpful to disconnect the coil. (that was how mine blew)


Don't know if this is related to the other stuff or if you just happened to realize it when looking around.
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Old August 21st, 2008, 10:16 AM
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Hi Hans, thanks for answering so fast! Yes the guy screwing with the wiring harness with no idea what he was doing was ME and Land Rover. They butchered a few things while installing an aux heater and lights and winch back in 1998. I installed an ARB compressor for lockers, a winch, aftermarket headlights, etc.

(Problem 3- short)- I literally disconnected every fuse, radio, coil, alternator, starter... etc. and there is still a short drawing on the battery (about 9.5-10.2 volts) when the truck is off. I tested this by removing the ground cable on the battery and using a multi-meter between the negative battery post and the ground cable. That can't be good... I wiggled the wiring harness back by the fuel tank, where it goes through the frame and the radio was humming. Fixed that by sliding a wiring loom up the wires as far as I could inside the frame... But that did not fix the problem. There was also a mouse nest over the gas tank that I removed while replacing the fuel tank skid plate/holder. Maybe the mice decided to chow on wires?

(Problem 2- wipers run fuel pump)- The wiper problem disappeared when I disconnected the wire that goes from the + coil to the back of the engine/harness that is white with little black stripes. I think that is the famous "hot-wire" that tells it when to fire? Is it also the tach? Well for some reason I can't get the wipers to activate the fuel pump with that disconnected. There is a little black Lucas connector that made it easy to disconnect. Is that just a connector or is it something else? The fuel pump and ECU relays are (I think) located under the passenger seat? I swapped them because they look identical to test them... same problem. Where is the fuel injector relay?

Is it possible that while running air compressor wires through the hole in the center of the firewall that I frayed the wire going to the wiper timer as well as one going to the fuel pump and they are touching? Is it hard to get to the wiper delay unit? This is the only part of the truck that I haven't pulled apart and put back together yet!

(Problem 1- coil hot)- Thanks for the info Bryan. I have experienced the same thing... ultra hot coil while diagnosing issues with ignition on and engine off. I guess it just charges up for the first spark and doesn't know when to stop? Maybe I have it hooked up wrong? I really don't think so though (it does run), but I'm open to anything at this point.

The truck also acts weird when I turn it off sometimes. Like it wants to spin backwards or something, or there is a weird noise from the coil or alternator area... This may have more to do with the short that hasn't been located yet though.

Well guys... any help is greatly appreciated and I will continue to post my progress!
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Old August 21st, 2008, 10:51 AM
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I have the wiring diagram at the house and I just rewired the thing when I did the 4.6 swap last week. Had to change some wires out and we neatened thing up.
I will check how I have it if needed....
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Old August 21st, 2008, 11:16 AM
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That would help a lot! Thanks.
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  #7  
Old August 21st, 2008, 12:06 PM
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Well, there is a hot lead that goes to the fuel pump and the negative side is switched.

The fuel pump and Injector relays should be the silver ones next to the computer.

That white/black wire coming from the coil and going to the firewall is the one that gives the computer the firing signal from the coil.

And your tach wire actually goes to the alternator, not the coil.

Have you also tried pulling the under-hood fuses at all, to isolate one of those circuits? Do you have anything wired direct to the battery at all, that bypasses the factory wiring?

-Hans
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Old August 21st, 2008, 12:49 PM
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Quote:
Originally Posted by Hans
Well, there is a hot lead that goes to the fuel pump and the negative side is switched.

The fuel pump and Injector relays should be the silver ones next to the computer.

That white/black wire coming from the coil and going to the firewall is the one that gives the computer the firing signal from the coil.

And your tach wire actually goes to the alternator, not the coil.

Have you also tried pulling the under-hood fuses at all, to isolate one of those circuits? Do you have anything wired direct to the battery at all, that bypasses the factory wiring?

-Hans
Hmm... what does that mean that the hot lead goes to the fuel pump and the negative side is switched? Does that mean that the short could be causing the whole problem?

My bad about the tach wire... I knew that. There are 2 small wires coming off of the alternator... tach and the other one is?

Yes I tried pulling all under hood fuses to isolate the short... the winch bypasses circuits... I will try taking that off! Just a pain though... but it is next on my list!

I'm just not that great at diagnosing

Thanks for all the help!
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  #9  
Old August 23rd, 2008, 01:50 PM
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Update:

I figured out that the only way to make the problem happen is with the Ignition Maxi fuse in...

The "short" was the door being open.

I think the wiper delay / relay might be the problem.
The wipers seem rather slow as well. Maybe it is kicking back current or something?

I replaced the mallory internally resisted coil and added a resistor, problem still exists.

Painting my front bumper, rear swingout and sliders today to give myself a small break...
Electrical problems make me crazy!

The truck is also running with an erratic idle when I start it, but I think that might be the bad Airflow Meter.

Anyone near Mendham, NJ?!?
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  #10  
Old August 28th, 2008, 12:15 PM
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Latest Update...

Thinking I could live with this problem I put the truck back together.
The following is now an issue:

The parking lights, hazard lights, turn signals (blinkers for search), and of course wipers all set off the fuel pump. Both relays under passenger seat must be in to make this problem happen. Also, the white/black wire going from negative coil to the ECU (i guess) must be plugged in, otherwise fuel pump starts normally when vehicle ignition is switched on and does not start with the parking lights, hazard lights, turn signals, or wipers.

What could cause this?

I am also throwing a code 12 airflow meter. And the truck will run with it plugged in or out. My friend dropped the old one on the ground while building a cold air intake. This one is from eBay. It could be bad, but could anything else cause code 12 and surging idle?

Any help will be greatly appreciated!

-H
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  #11  
Old August 28th, 2008, 05:52 PM
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Revalation... Hopefully:

When I disconnect and reconnect the Redish Brown Connector on the firewall next to the heater the fuel pump runs. These two wires go to the starter and the alternator or the coil? I can't remember exactly.

Also, the problem of the fuel pump runinng does not happen with this connector disconnected. How can I tell if the problem is towards the front or inside the firewall? The rubber gromet has come lose in the firewall... maybe one or more of the wires have frayed?

Also, what is the mystery 3rd relay on the right? When I plug a relay into it my headlights turn on.
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