Slow Cranking
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Slow Cranking
Me and a friend of mine have been working on his truck (79 f-150 351m). When he first got it it didnt run, we cranked it alot and the starter worked just fine, but it wouldnt start. One day we decided to swap motors since his cousin had a 400 for it. After our swap was complete, and we had put the original 351m starter back on, we hooked up a battery and now the starter just turns over really slow-not fast enough to start it, it almost act like a dead battery but we're sure it isnt. His dad thinks the starter is bad but how could a starter work fine on one motor then not work on the next, the motor isnt really tight or anything, could the problem be in the solinoid or the wiring anywhere? What should we check? Thanks
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From: Virginia
Take a voltmeter and put it on the battery and you should get around 12 volts. Keep the meter on the battery, and crank the engine. The voltage should stay at 8 volts or above. If it falls below 8, then the battery is getting weak.
If that checks out ok, charge the battery well, and then try cranking it some more. Feel all the large connections from the battery to the starter. If any of them are hot or smoking, then that is the spot where you have a bad connection.
One other thing that I have done myself during a motor swap is install the starter without cleaning the metal surface where it mounts. The starter wasn't making a good ground connection where it mounted, and gave me trouble. I had to take the starter back off, and clean the area with a rag, and that fixed it.
If that checks out ok, charge the battery well, and then try cranking it some more. Feel all the large connections from the battery to the starter. If any of them are hot or smoking, then that is the spot where you have a bad connection.
One other thing that I have done myself during a motor swap is install the starter without cleaning the metal surface where it mounts. The starter wasn't making a good ground connection where it mounted, and gave me trouble. I had to take the starter back off, and clean the area with a rag, and that fixed it.
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Ok I was wondering if the starter had to ground against the tranny, because i know, in the hurry I was, in I didnt clean it up. When this happend to you did the starter turn slow like I explained? This would be a very logical explanation, I hope this is the problem. Thanks for the help.
Last edited by mattselland; Feb 6, 2006 at 10:39 PM.
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I think you are going about this wrong. It is possible too that the stater is binding against flywheel and causing a lot of drag too. I serious doubt that the starter not grounded to engine because if it was not the heat form the voltage drop in that connection would make itself known. It is also possible motor is stiffer to turn over too and may need a stronger starter. Do check all of the cable and the battery voltage while cranking and it shouls stat above 10.5 volts while cranking, if it drops below that you have a bad battery or excessive current draw from something binding.
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From: Virginia
When I had the starter grounding problem, it would crank slow and then stop. Then it would do the same thing again. It was just luck, that out of the corner of my eye I saw a spark jump down near the starter.
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How long has that 400 been sitting? Could the cylinders be corroded?
Also since the engine was just changed, the first thing that comes to mind is that the engine to chassis ground was left off.
Also since the engine was just changed, the first thing that comes to mind is that the engine to chassis ground was left off.
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