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My ‘48 is HARD to start


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My dear ‘48 V12 had a hard starting problem when the engine was hot.  The issue was that the engine turns over far too slowly.  Because I have a new battery and good clean tight cables, I figured the starter must need to be rebuilt.  So I did that and now the engine turns over even slower than before the rebuild!  Any ideas on where to go from here? Thanks!

Edited by John_Mc (see edit history)
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Posted (edited)
10 hours ago, billorn said:

How big are your cables? Did you add a ground from starter to frame or battery ground?

My heavy duty braided ground strap runs from the starter bolt to the frame and then on to the battery.  Thanks for all the replies.

Edited by John_Mc (see edit history)
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John,

I will assume that your battery is fully charged and is in good condition and that you have cleaned the battery cables and posts.

 

Connect your volt meter COM lead to the NEG battery post and the + lead to the starter terminal. Crank the engine with the ignition OFF. The meter should read 0.3Volts or less while cranking the engine. If the reading is higher, you have excess resistance in the circuit.

 

If the reading is higher than 0.3V, move the + lead of the meter back to the starter cable side of the solenoid and repeat the test. The meter should read 0.2V or less. If it does, replace the cable to the starter. If the reading is higher, move the + lead to the battery side of the solenoid and repeat the test. The meter should read 0.1 V or less. If it does, replace the solenoid. If it is higher, replace the cable from the battery.

 

Now that you have the battery side of the circuit in good condition, you need to check the ground circuit. Connect the + lead of the meter to the POS terminal of the battery and the COM lead to a mounting bolt of the starter. Crank the engine and read the meter. It should read 0.1V or less. A higher reading means excess resistance in the grounding circuit. Move the COM lead to the point where the grounding strap is connected to the engine and repeat the test. If the reading is now 0.1V or less the starter is not grounded to the engine correctly. Remove the starter and clean the mounting surface of the starter and the oil pan and repeat the test. If the reading is still high, replace the grounding strap.

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19 hours ago, 19tom40 said:

John,

I will assume that your battery is fully charged and is in good condition and that you have cleaned the battery cables and posts.

 

Connect your volt meter COM lead to the NEG battery post and the + lead to the starter terminal. Crank the engine with the ignition OFF. The meter should read 0.3Volts or less while cranking the engine. If the reading is higher, you have excess resistance in the circuit.

 

If the reading is higher than 0.3V, move the + lead of the meter back to the starter cable side of the solenoid and repeat the test. The meter should read 0.2V or less. If it does, replace the cable to the starter. If the reading is higher, move the + lead to the battery side of the solenoid and repeat the test. The meter should read 0.1 V or less. If it does, replace the solenoid. If it is higher, replace the cable from the battery.

 

Now that you have the battery side of the circuit in good condition, you need to check the ground circuit. Connect the + lead of the meter to the POS terminal of the battery and the COM lead to a mounting bolt of the starter. Crank the engine and read the meter. It should read 0.1V or less. A higher reading means excess resistance in the grounding circuit. Move the COM lead to the point where the grounding strap is connected to the engine and repeat the test. If the reading is now 0.1V or less the starter is not grounded to the engine correctly. Remove the starter and clean the mounting surface of the starter and the oil pan and repeat the test. If the reading is still high, replace the grounding strap.

Tom, thanks for the fantastic reply!  Last night I removed the all the connections starting at the starter relay and after reassembly the engine turns over much faster.  I’ve yet to try it when hot, but I suspect that was my trouble.  I’m going to print up your answer for future reference.  

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