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AMC 360 cranks slow when hot

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farna View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jul/09/2018 at 5:53am
You didn't mention if the engine is stock or has higher compression. That could be an issue.  I'd check the connections first, then the cables. If it's a stock motor and the cables appear to be original I'd just change the cables out, and go to the next larger size while you're at it. Don't forget to check the ground cable between the engine and frame! Often overlooked. It needs to be upgraded in size or replaced along with the two on the battery. All three need to be the same size wire, but the strap from engine to frame can be an uninsulated flat braided wire "strap".
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Jul/09/2018 at 12:45pm
Id be looking at that starter...and those cables...if those cables are corroded....it wont crank very well... if that starter is a reman...Id be wary... usually 10 btdc isnt a problem, but you dont know if the ring slipped on the balancer... if so...your timing light wont be accurate.....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jeep9393guy Quote  Post ReplyReply Direct Link To This Post Posted: Jul/09/2018 at 1:02pm
I pulled the battery out , going to take it to the auto electric shop tomorrow and have them load test it .I don't have excess to a vat 40 anymore .  Ill let you know .

Thanks Frank
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jeep9393guy Quote  Post ReplyReply Direct Link To This Post Posted: Jul/09/2018 at 1:05pm
The engine is stock , got 110 ,000 miles on it .
 I replaced a couple ground  cables already, getting the batt tested tomorrow ,If that checks out good ,Going to go with heaver cables .
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jul/09/2018 at 1:07pm
Vacuum indicates his timing isn't "far off".......
Summary of electrical  -
Make really sure there is a ground strap between engine block and chassis, on an AMC car, typically bolts to chassis by or at cross member, depending on car, of course - just so it connects the ENGINE to the CHASSIS and is of adequate size to handle CRANKING load.

Check all connections between (-) battery post and ground, (+) battery post and starter, including the battery end being secure to the cable and that it does NOT get hot while cranking. Hot is trouble and means a loss of connection inside the terminal.

Now here's a kicker -  if it IS a connection and the drop is sufficient, then the solenoid will lose its ability to stay engaged and will typically "rattle" or become a buzzer. It takes some power to keep it engaged and if the voltage drops enough, then it can't stay engaged, it disengages, the starter doesn't get power and then there's enough to engage the solenoid again, then the starter drains power and the solenoid can't stay engaged and this happens several times a second. 
So IF it is a connection, then it's one of those between solenoid and starter or the ground strap engine to chassis. Not that it can't be other places, it's not fitting what's going on here so much as a bad or missing ground strap or a starter issue. 

Again, parts store starters are not likely to be new - they are 99% likely to be remanufactured, and if you've seen what I've seen over my 45 years in auto electric, you'd be wary. Not that they aren't ever good - they are often very good and may last fine but I've seen enough that I know I will never use one personally. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jeep9393guy Quote  Post ReplyReply Direct Link To This Post Posted: Jul/09/2018 at 1:09pm
I checked the starter when the problem occurs , Its not hot at all . 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jeep9393guy Quote  Post ReplyReply Direct Link To This Post Posted: Jul/09/2018 at 1:13pm
Will do some more checking . 
  Thanks 
        Frank
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jul/09/2018 at 2:31pm
All the other checks should be done first but you may have a faulty ignition module.
The only clue to this is backing off timing 10 degrees and it starting or taking off the coil wire and it cranking. Taking off the battery connection and waiting 30 seconds should do the same function to reset the module.
Those DuraSpark modules control the distributor that can push advance up to 55 degrees if left unchecked. That over extended advance can make starting almost impossible.
Swapping modules is the only way to check unless you find someone that has a tester for that module.
Many go to alternate ignition systems as parts for those are hard to get.

  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jul/09/2018 at 2:40pm
So far the only trouble I've seen with those is the typical "we were driving along and it just stopped - if we sat for an hour we could go again, then a few miles later it would stop"

Since we were along I80 and not far from I35 we had a ton of 'em. We kept a half dozen various flavors in stock. Our troubleshooting method was to take a can of R12 along and wait for the car to die then really fast freeze the module and it would likely start again. 
But in Iowa, on the Interstate, on a day like today or even last week, your engine bay temps would get CRAZY, add to that the load of electronics in the little metal box that controlled the ignition and weird things could happen. 
Like I say, we never had one fail in a way other than either totally failing (no spark) or no spark when hot, but was ok when it cooled a bit............ these things are decades old, a lot of on/off/on/off/on/off which is also one thing that destroys electronics. 

A simple test would be to find one to match and toss it in the back seat and if it does it again, plug in the spare and see what happens...........  Or find some really old person who still has a stash of freon and a can tap and pay them the $100 for their can of freon and when that happens, freeze the module. 
Naw, just kidding on the last part............ 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jul/09/2018 at 3:12pm
Cool, forgot about the Dust Off trick.
Used to use it on robot speed controllers when they overheated to get them restarted.
Just turn a can of Dust Off upside down and spray the module (don't let liquid get on your fingers or in your eyes). That would cool the module down pretty quickly!
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