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engine won't crank over when hot

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Mrpiano45 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mrpiano45 Quote  Post ReplyReply Direct Link To This Post Topic: engine won't crank over when hot
    Posted: Oct/17/2018 at 7:25pm
I know there's a lot of very knowledgeable mechanics on this site, so here's a problem for you to try and help solve.  I would appreciate any possible solutions:  (1971 or 72) 401 in a 68 AMX.  Cranks over and starts fine when cold.  But once the engine gets up to operating temp, and I shut it off, it won't start again.  It tries to crank over extremely slowly, and never does any more than that.  But once it cools down, it cranks over fine again.  Played around with the timing....no help.  Put in a new selenoid...no good.  Was told by a local mechanic to add a heavier ground wire from the battery.....no good either.  I also had this problem a few years back with my blown 70 Camaro....never was able to solve that.  Any suggestions would be welcome.  Thank you.....Myles
R/W/B 69 AMX S/S, 66 Fastback Mustang, 66 & two 68 Chevelle SS 396, 67 GTX 440, 70 AAR Cuda, 70 Vette Conv, (2)69 HOT AMX's, 69 Mach 1, 68 AMX 401
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amc'snjeep's View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amc'snjeep's Quote  Post ReplyReply Direct Link To This Post Posted: Oct/17/2018 at 7:49pm
Pull your coil wire when the engine is hot. If it still will not crank fast your starter or cables are likely bad
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BDCVG Quote  Post ReplyReply Direct Link To This Post Posted: Oct/17/2018 at 9:53pm
If Your comp. ratio is too high You may need a high torque starter. Check the cables first, they do go bad.
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akimmet View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote akimmet Quote  Post ReplyReply Direct Link To This Post Posted: Oct/17/2018 at 11:02pm
I agree that the most likely culprit is your battery cables or their connections.
Don’t forget about the cable running from the starter relay or “solenoid” to the starter.
Also make sure the block to body grounding cable is present and in good shape. People always seem to forget about that one.

However, I also recommend having the battery tested. A weak battery can sometimes have the same symptoms you are describing.

Edited by akimmet - Oct/17/2018 at 11:13pm
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mixed up View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mixed up Quote  Post ReplyReply Direct Link To This Post Posted: Oct/17/2018 at 11:18pm
I agree even if cable looks good on the out side it could be corroded on the in side look for bulges in the cables have the starter tested they can test your battery and check starter amp draw at autozone too much timing can cause it to crank slow try backing it off alittle
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Twisted70amx View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Twisted70amx Quote  Post ReplyReply Direct Link To This Post Posted: Oct/17/2018 at 11:22pm
The first thing that comes to mind would be a heat soaked starter, not sure what you have done to your 401 but if you're running headers it could be a likely culprit. Once you've ruled out the solenoid, cables and battery that would be the next thing Id check. I'm not sure what it's like for room but usually when I'm checking for a bad battery cable I'll just use jumper cables. Hook them up where your battery cables would go and if the problem goes away you know that's your issue. Saves buying parts you don't need and unhooking everything to test.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ccowx Quote  Post ReplyReply Direct Link To This Post Posted: Oct/17/2018 at 11:32pm
My money goes with a starter that is beginning to fail. The windings soak up heat and stop working. If that starter worked before but does not now, then it is failing. If it never did work well, you might need to consider a hi-torque unit and/or a heat shield. 

Chris 
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Mrpiano45 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mrpiano45 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2018 at 2:51am
Thanks to all for your replies.  The starter and solenoid are brand new as well as all the cables.  The battery could be the culprit or it could also be that the headers are very close to the starter.  I won't have the car in my possession for another few weeks but will check it when it comes back.  I appreciate all your help.  Thanks.....Myles  
R/W/B 69 AMX S/S, 66 Fastback Mustang, 66 & two 68 Chevelle SS 396, 67 GTX 440, 70 AAR Cuda, 70 Vette Conv, (2)69 HOT AMX's, 69 Mach 1, 68 AMX 401
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Boris Badanov Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2018 at 7:15pm
Headers?

Hot starter.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote AMXFSTBK390 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2018 at 8:28pm
After you resolve the problem, you may want to install a heat shield over the starter. Good heat reflecting measure if the engine has headers. Summit offers a bunch to choose from,
Questions are powerful tools...what's in your toolbox?
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