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Old 08-22-2007, 12:25 PM
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What caused this?

I finally finished with my external fuel pump conversion project on my Mustang and I turned on the key expecting to hear that momentary fuel pump hum but- I heard nothing! I checked the relay- ok, then I bypassed the relay but the pump still would not run so I removed the wire from the terminal on the pump and got a reading of 12.6 volts (I had 13.8 across the battery terminals). I reconnected the wire and still nothing so I ran a "jumper" wire from the battery and the pump ran just fine, reconnected the pump wire which still read 12.6 volts and nothing! I then checked the wire while it was still connected to the pump and now it reads 2.9 volts, disconnect it and it jumps to 12.6. I suspected a bad connection so starting at the relay I disassembled the relay socket and found corrosion on the terminal on the red wire that runs to the inertia switch so I clipped it intending to solder it back to the terminal end. It was badly corroded even about 6" from the terminal end so I clipped it again about 2' from the end and it was the same thing. To make a long story short this thing (the factory 1987 Mustang wire) was heavily corroded from one end to the other, about 8', so much so that the pump would not run. I replaced the wire with a new one and now the pump runs just fine so my question is what caused this? I have seen this on battery cables but not on regular wiring, is this kind of thing very common? None of the other wires in this circuit look bad at all, why just this one and what do I do to prevent it from happening again?
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Old 08-22-2007, 01:51 PM
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My guess is a bad batch of wire from the manufacturer. There had to be some sort of strong oxidizer present to do that much damage and as you surmise, normal wiring doesn't get exposed to that. Battery leads do with sulfuric acid fumes constantly bathing their ends. The factory must have left an acid wash on the copper or some such. I wouldn't worry about it.
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Old 08-22-2007, 02:03 PM
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First time I have seen this happen and it sure had me stumped for a while, I feel lucky I found the problem before tearing apart anything else. I can only assume that this is the reason the original pump quit running but that is no loss since I have always needed to change back to a factory tank and an external pump. This is in a 65 Mustang that had a modified 87 Mustang gas tank with the in-tank pump and the 87 wiring harness for the pump. The tank looked ok but obviously not stock and only had about 11 gals capacity so as I said I needed to change it anyway and this got me in gear to do so, I just thought maybe I had done something wrong several years back when I did the original EFI conversion that caused that corrosion problem.
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Old 08-22-2007, 03:15 PM
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I had a similar problem with a coil wire on a Bronco I could not find out why it kept stopping. Scan tool said that the primary coil wire was bad but when I checked it with a volt meter it checked good just like what you had.
I connected a bulb to the wire and the voltage dropped to about 3 volts.
Next time you encounter this kind of problem put a load on the wire and then check it.
A small battery checker will work good for this just add a small load 20 amps and watch to see if the voltage drops.
I volt meter won't tell you if a wire is bad unless it is broken in half or has a dead short.
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Old 08-22-2007, 03:18 PM
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Doc here,

Was this a Flat ribbon type cable ? Or a Branch circuit of individual run wires in a bundle?


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Old 08-22-2007, 03:32 PM
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Quote:
Originally Posted by docvette
Doc here,

Was this a Flat ribbon type cable ? Or a Branch circuit of individual run wires in a bundle?


Doc
If your talking about my post it was a multi-wire plug and the problem was were the wire went into the multi-plug.
Since all the others in that plug was fine I just cut the wire on both sides of the plug and installed a spade connector been working like that for 10 years now.
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Old 08-22-2007, 04:27 PM
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Quote:
Originally Posted by Black Bart
If your talking about my post it was a multi-wire plug and the problem was were the wire went into the multi-plug.
Since all the others in that plug was fine I just cut the wire on both sides of the plug and installed a spade connector been working like that for 10 years now.
Doc here,

No, I wasn't ..But I know how the EECV 1 and 2 plugs up , and they are problematic for water and corrosion if left to their own devices..over time

A Volt METER will always tell you what the DROP is..It is the test parameters that determine if you are going to see it..

A Corroded wire or partially open wire will will look fine at 12 volts and ground pulling 1 ma..as will a coil with a ballast will read 12 volts with the points open..the coil is not loaded..close the points , load the coil, the ballast will limit the output to 6 to 9 volts..which is the CORRECT load for that..

So you have to know what parameter you wish to see when testing, for an accurate answer.



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Old 08-22-2007, 06:06 PM
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This was the 14 ga wire that runs from the fuel pump relay to the inertia switch and there are only two wires that run into the switch plug. If it makes any difference these wires are bundled together (tape wrapped) to form a cable that contains all the wires running to the back of the car, tail/brake lights, etc.
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Old 08-22-2007, 07:38 PM
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Quote:
Originally Posted by oldred
This was the 14 ga wire that runs from the fuel pump relay to the inertia switch and there are only two wires that run into the switch plug. If it makes any difference these wires are bundled together (tape wrapped) to form a cable that contains all the wires running to the back of the car, tail/brake lights, etc.
Doc Here,

No...I was talking about the WHOLE rearward harness..

Some Factory outfits (like 70's Midsized GM for one..)used a FLAT RIbbon TYPE of cable from the front to the rear...looked a Computer hardrive cable..and ran it under the carpet/Rear Seat..

THIS type Cable can not (successfully ) Be soldered , or Crimped..along it's length..It is made from some aluminum Alloy AND is very THIN..like 5 or 6 strands of Brittle wire..If you try to solder it, it just balls up the solder, and if you try to crimp it..It just breaks..) like those "Old" headphone " wires years ago..

Sounds like WHEN the wire Went into the Copper Coating Bath at the Factory, they omitted the neutral Bath next and went straight to packaging!



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Old 08-22-2007, 08:47 PM
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The other wires look ok so I guess the problem is solved now. I made a mistake earlier when I said it was the wire to the inertia switch, it was from the relay to the pump, don't know what I was thinking but I guess it makes no difference anyway. That's the kind of problem that can cause real headaches because it seemed as if I was getting power and if I had not of checked it while it was under a load on the pump I probably would have spent the whole afternoon tinkering with the pump and relays.
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Old 08-22-2007, 08:56 PM
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Oldred, Whenever I am checking something that draws quiet a bit of current I keep an old style(not led,one that uses a bulb) test light to check the power side.
Example:Window regulators,Fuel pumps,fans,door lock actuators,etc.

Your problem is a good example of when it would have saved some time.I am sure it would have been dim or not lit at all. I worked briefly at a ford dealership and it was something that one of the instructors at the school advised.
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Old 08-23-2007, 01:50 PM
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I have one of those things but I never use it much, guess maybe I need to as it would have found this problem with the first check I made. Sometimes the old tech is better for some things than all these digital gizmos we have come to love so much.
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Old 08-23-2007, 03:09 PM
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Quote:
Originally Posted by redlightning
Oldred, Whenever I am checking something that draws quiet a bit of current I keep an old style(not led,one that uses a bulb) test light to check the power side.
Example:Window regulators,Fuel pumps,fans,door lock actuators,etc.

Your problem is a good example of when it would have saved some time.I am sure it would have been dim or not lit at all. I worked briefly at a ford dealership and it was something that one of the instructors at the school advised.
Yes that was what I was trying to say in above post but maybe did not word it very good but I learned that the multi checker digital things that we like will show good voltage but when you put a load on it then it will show low voltage.
You can use a headlight bulb and connect it to a wire and then check the voltage this will tell you more than just using one of those little volt meter checkers
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Old 08-23-2007, 04:23 PM
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Doc here,

It is good to have BOTH in your Tool box AND NEVER get "Lulled" into relying on either, until both Check out...

For Instance, you have a lamp that won't light..shows 14.4 volts..(this is a good thing..) Your test bulb / lamp lights when you probe the pad on the socket and Ground the alligator clip..***?? Pull the bulb thinking the Filament is blown..no joy..Then your light probe accidentally hits the socket ground..both bulbs light dim..***??? Pull out the meter, you'll verify the drop between the 2 is 6 volts...

You have a Bad Ground! Power will be present all the time..!!

KEEP Both, USE BOTH..

Troubleshooting will go much faster.


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Old 08-23-2007, 06:25 PM
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Cable corrosion

I have seen battery cables corrode like this. With old copper, especially under guage (smaller diameter) cables, when you add high heat from cranking, cold winters and rapid heat up, humidity, maybe a chemical reaction from things in the insulation, ...stuff happens.

Throw in dissimilar metals touching one another, and this is the exact reason I solder and not just crimp at the connections.

Quality wire/insulation, larger than needed diameter, soldered joints, and cleaned and dialectric greased connections for me.

Steve
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