1994 Suburban won't re-start

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wezmykat

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1994 k1500 gmc suburban 350 bought the truck a little over a year ago and it took me this long to figure it out (haven't been driving much partially because of this)
Don't matter the weather the truck seems to start "fine" it will turn over a few times then fire up, it does run rough on cold starts for a few minutes, i let the engine warm up and once at normal temperature, if i turn it off and immediately restart it will start immediately (not even 1/4 turn) and run great. I can drive 5 minutes or over an hour or let it idle the whole time it don't matter - once the truck is shut off, if I wait about 5+ minutes, it work crank, at all, as if the battery is dead. If you boost the truck from another running vehicle, then it will start just fine, battery is shot I'm thinking.
I took off the alternator and went to a guy that rebuilds them, he tested it and said it's putting out over 100 amps and is running great. I ripped out all the wiring from the battery/alternator/starter/frame, sanded down all the metal, put new wires and bolts, issue remains. I went through 3 batteries (under warranty) one was weak, another was defective but the 3rd was excellent (used one of those big fancy testing machines) and the issue remained. New fuel pump, fuel & air filter, fuel lines, cleaned injectors, changed spark plugs, ignition coil, ignition control module, rotor, checked wiring, everything seems fine, issue remains.
After all that I was starting to lose hope.
One day, I dont know how, i fell onto a 60's camaro forum where they said that heat sink on the starter from headers was causing issues just like mine, so i decided to give it a try, even though my truck is stock. Online solutions ranged from 75$+ for shields and wraps and whatnot.
Great timing, my neighbor threw out a broken oven and was kind enough to include a giant aluminium container, so I cut it all apart, used the oven insulation, heavy stuff, about an inch think, disconnected the battery, unbolted the starter, wrapped it in the insulation, then the aluminium plate, then used the copper power wire to strap it all together, then bolted the started back, all out in the street crawling under the truck.

Well, a few months have gone by and the issue is 100% resolved, the 350 will start every time no matter what. Now what i needed to fix the issue ended up costing me 0$ and I wish i knew what the issue was before I went through all that trouble replacing the other stuff but hey. I hope this can help someone else!
 

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Schurkey

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1. Failure to crank at all, when the battery is known-good and fully-charged, is often a problem with the wiring from battery to ignition switch, or from ignition switch to "S" terminal of the starter solenoid. I repaired this wire on my '97 K2500. The original wire had been cut and spliced at the solenoid by previous owner, then it rotted again.

Previous "repair" to the starter "S" terminal wire, that corroded again.
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The wire above was connected to the black end of this wire. Even the "good" end was too corroded for re-use. I had to cut the original harness back about three feet to splice in good, copper wire.
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2. This is so common, that an "aftermarket fix" has been popularized--the "Ford Solenoid on the Fender" modification. The vehicle wire is removed from the "S" terminal of the starter solenoid. A jumper wire is fabricated to go from the battery cable stud on the starter solenoid to the "S" terminal. The main battery cable is cut, with the "Ford solenoid" inserted in series. The wire originally installed on the "S" terminal is now installed on the Ford solenoid. The ignition switch controls the Ford solenoid--an easier load than the original solenoid on the starter. The Ford solenoid and the jumper wire provide full battery voltage to the "S" terminal instead of the reduced voltage of the original, rotted, corroded wire.

For example:
www.summitracing.com/parts/tff-7629

3. The windings in the starter motor and solenoid can be affected by heat. It may be that your starter or solenoid is partially-failed.

4. Installing a bunch of insulation on the starter can keep exhaust heat out of the starter. But the starter generates heat as it operates. That heat is kept IN by that insulation. Given a choice, I'd use a metal heat-shield with an air-gap between the shield and starter/solenoid, rather than fiber insulation actually blanketing the starter/solenoid.

Example:
www.summitracing.com/parts/mrg-3678

 
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