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EFV-8 Club Forum / 1940 Ford Discussion / Weak starter motor when engine up to temp

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Posted By Discussion Topic: Weak starter motor when engine up to temp     classiclover 08-31-2021 @ 4:07 AM reply profile send p.m. Member Posts: 73 Joined: Aug 2021 Gents My newly purchased 40 coupe, stock, appears to have a weaker starter than when cold. Starts strong when cold, but much weaker when warmed up. Any thoughts Thks Much Dale 40 Coupe 08-31-2021 @ 4:48 AM reply profile send p.m. Senior Posts: 1678 Joined: Oct 2009 Go over the ground path of the starter and make sure the front to the pan are clean and the two mounting bolts are clean under the heads and the threads. Sometimes too much paint is put on the starter main body ends. The front end plate of the starter needs a good ground path. Then go over the battery cable to the solenoid and the solenoid to the starter are clean and tight. Look for any signs of a loose battery terminal on any of the battery cables. Check battery voltage, charge the battery and then take it to the auto parts store to have it load checked. Check the charging voltage to the battery should be close to 7.2V TomO 08-31-2021 @ 8:00 AM reply profile send p.m. Senior Posts: 7256 Joined: Oct 2009 Slow starter can be caused by wrong or corroded cables, weak or undersized battery, poor grounding, bad solenoid or bad starter. Check the battery: Measure voltage at the battery posts to make sure that it is fully charged. It should have at least 6.3V Leave the meter leads attached to the battery and crank the starter with the ignition off. A reading of 5.5V or higher is good, a reading of 4.75V or higher is marginal and a reading below 4.75 should be investigated by having a load test performed on the battery. Check the cables, do this after the battery passes the test: Connect the black or COM lead to the NEG post of the battery and the red or + lead of the meter to the starter terminal. Crank the engine with the starter off and read the meter while cranking. The meter should read 0.3V or lower. If the reading is higher, you may have excess resistance in the circuit. Move the red or + lead to the starter side of the solenoid to check the cable leading to the starter. If the cable is good, the reading should be 0.1V less than the previous reading. If the reading is higher, replace the starter cable. Next move the red lead to the other side of the solenoid and repeat the test. Again the reading should be 0.1V less than the previous reading. If it is the solenoid is good. The cable from the battery to the solenoid may be bad or the starter may be bad. Continue to the grounding circuit. To check the grounding circuit, move the red lead to the POS battery post and connect the black lead to the case of the starter motor. Crank the starter with the ignition off and read the meter. The reading should be 0.1V or lower for a good ground and starter. If the negative cable test failed and the reading at the ground circuit is higher than 0.3V, you should remove the starter and have it tested and repaired if necessary. If the negative cable test was OK and you have a high reading, replace the grounding cables that come from the battery and the one to the motor. If the negative cable reading was high, the grounding test showed less than 0.3V and the starter cable and solenoid tests were OK, replace the battery to solenoid cable. I know this looks complicated, but once you do it, you will find that it is easy to do. Tom classiclover 08-31-2021 @ 9:45 AM reply profile send p.m. Member Posts: 73 Joined: Aug 2021 Thanks for the detailed advice, can you advise me as to WHY this would occur only when engine is hot Dale TomO 08-31-2021 @ 5:05 PM reply profile send p.m. Senior Posts: 7256 Joined: Oct 2009 Dale, I have never tried to analyze what could be cause of it only failing when hot, but assumed that the starter motor draws more current when the windings are hot. Tom RAK402 08-31-2021 @ 9:35 PM reply profile send p.m. Member Posts: 438 Joined: Jul 2015 classiclover, My 40 behaved as you described for years (cranked slowly when warm)-I couldn't find the problem. It turned out to be one of the issues that Tom described-bad connections (in my case the battery ground to the firewall). It cranks very briskly now. This message was edited by RAK402 on 8-31-21 @ 9:36 PM classiclover 09-01-2021 @ 4:15 AM reply profile send p.m. Member Posts: 73 Joined: Aug 2021 Thanks much to all 1931 Flamingo 09-01-2021 @ 4:53 AM reply profile send p.m. Member Posts: 388 Joined: Nov 2019 Physically remove the NEGATIVE battery cable and inspect it. Earlier this year I had a NO-START condition on my 40, had voltage at the batt and the sol. Removed the neg cable and somebody decades ago had wrapped the sol end with electrical tape, pulled the tape off and very corroded. Had the cable cut back and new end soldered on. Hasn't cranked this good since I've owned it. Paul in CT alanwoodieman 09-01-2021 @ 5:26 AM reply profile send p.m. Senior Posts: 868 Joined: Oct 2009 slow starter when hot is also the result of the engine temperature and the pistons fitting tighter in the bore and of course too small of cables when the need for more AMPS to start a hot engine classiclover 09-01-2021 @ 11:06 AM reply profile send p.m. Member Posts: 73 Joined: Aug 2021 Greetings I just finished removing/cleaning all the cables, batt, starter, sol, so we will see. Going to my first local show on Sat, interested to learn how it does. Thanks to all for the advice Dale

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