'86 F150 Starter Solenoid welding

Hi All,
My '86 F-150 is welding shut starter solenoids, and nothing seems to cure the problem. I have replaced both battery cables, the starter, tried three
different makes of solenoids, cleaned out the steering column and lubed the key tumbler linkage, removed and tested the ignition switch, and it still keeps welding the starter contacts in the solenoid. Any suggestions?
AmmonMan
"You can't out-smart stupid."
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On Sun, 16 May 2004 23:59:41 +0000, Ammonman rearranged some electrons to form:

Make sure the ground strap from the engine block is solidly connected on both ends to bare metal.
--
David M (dmacchiarolo)
http://home.triad.rr.com/redsled
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Either the battery is very weak:
Or your starter is going bad and drawing an excessive amount of amperage.
Try running a battery booster cable to the block, from the negative side of the battery to the block, and see if that helps. Which will tell you if your negative battery cable is in the proper place. That might be a start.
If you have access to a clamp on amp meter, try measuring the amperage draw on the positive cable when someone tries to start it, and look in the Haynes manual at the specs chart, then compare the reading to the specified draw.
I hope this helps?
Refinish King

three
the
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Thanks for the suggestion re: amp draw. The starter is a new re-man unit. The battery is freshly charged, but I have not pulled it for a load test. May have a cell going bad. The NEG terminal is connected directly to a stud on the block, so I am wondering if the bond between the engine and the chassis is bad and causing problems.

cure
still
annoys
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three
the
Explain what solenoid you're talking about. Does your truck have a solenoid mounted on the starter? If yes, is that the one screwing up, or is it the small separate one?
The other guys have hit the usual problems. Weak battery, bad cables/connections or a bad starter. Nothing in the circuit that powers the solenoid will cause the contacts to weld. Might cause the solenoid to stay engaged, but will not weld the contacts.
Al
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It has the fender mounted solenoid. I am leaning towards a bad ground in the system somewhere. The NEG terminal of the battery is connected to a stud on the block. I wonder if I am losing the ground from the block to the chassis.

cure
still
solenoid
the
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the
If the negative terminal of the battery is connected to the block, the engine to chassis ground is not so important. It still needs to be there, but it's not as likely to cause the problem you have. Do you have a non-digital voltmeter? If yes, find someone to crank the engine while you measure the battery voltage, and the voltage at the starter. Both should be above 11 Volts minimum. On a 460 Ford I worked on the voltage at the starter was around 6 Volts. Had a bad positive cable. It made the solenoid glow red. This truck would crank fine with the engine cold, but would crank very slow with the engine hot. The owner changed the starter, battery, alternator and solenoid with no change in the symptom. If you would crank the engine for about 15 seconds you could smell the insulation burning on the cable. On this truck the bad cable was between the solenoid and the starter. It was a cheap aftermarket cable and was very thin.
Al
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I have replaced both the NEG and POS cables with good 4/0AWG cables, as well as the POS cable from the solenoid to the starter. When the solenoid contacts weld, it takes me a bit to get the cable disconnected from the battery. I have checked the cables after each event to see if they are getting hot, and they are always cool as a cucumber. I am stumped.
AmmonMan

in
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