out of ideas... STARTER problem

[RustyBucket]

My neighbor built a '51 pickup approx. 10 yrs. ago. Moderate performance 350, 700r4, Camaro 10bolt posi rear., Heidt frt. suspension, P.S., P.B., A/C, EFI ... nice truck. Sometimes it won't turn on the starter when it's hot... not always though. He's changed many starters... big ones, little ones, all brand new. New #2 cables w/factory ends. New batteries. Rigged it so he could turn it on the starter w/o the ignition firing.. didn't help. Recently installed a remote FORD type starter solenoid.. same crap. The engine isn't a big compression race motor.. prob. 9.1 comp. Don't have the cam specs but it's not crazy. Runs cool enough, doesn't use or loose oil or coolant.. Any fresh ideas... we're not experts but both of us have always had & built old cars & trucks.. I'm 68 & he's 75.

here's his '51 & my '71

[Dead Parrot]

Use a volt meter or test light and verify that you are getting juice to the starter when it is hot. Possible the failure is somewhere upstream from the starter.

[dmjlambert]

In addition to Dead Parrot's idea, let's see pictures of how close to the starter is the exhaust pipe or header. Try putting a piece of metal roofing flashing or coffee can metal or something like that between the exhaust pipe/header and the starter see if the problem goes away. Ideally you would have a little bit of air space on both sides of the shield. If that fixes it, get a more permanent and prettier heat shield.

[rpmerf]

Has he used starter heat wrap like this? They help with heat soak. When you have issues hot, but not cold, this could certainly help.
https://www.summitracing.com/parts/sum-350118-1

Has he used a gear reduction starter?

Is he using QUALITY batteries? I had 'starter' problems for years that turned out to be a cheap battery. Bought a 750 CCA battery and it cleared up some of my problems. Might watch voltage drop at the battery while cranking.

Is every connection clean and tight?

What grounds do you have? I added a second ground wire from the battery to the case of the starter. There is a stud on the back of the starter. This seemed to really help.

[RustyBucket]

In response to your kind suggestions..... It's hard to get a meter on it at the starter when it screws up... It has good voltage at the newly installed remote solenoid and at the battery. It only does this "sometimes" which doesn't make it easier to diagnose. He's got a variety of ground straps on it but not one from the stud on the starter case. We'll try that. I'll bet he's tried 10 different new starters, geared, big, little, high tq. He's tried a variety of heat shields both store bought and fabricated. Header clearance is not particularly tight.. compared to my two trucks. I don't recall if he's tried one of the "blanket" shields. It's had lots of batteries, has one in it less than a month old now.. not sure what the CCA is on it. It's almost like the engine "binds up" and just won't turn sometimes. THANKS for the thoughts & suggestions. He just installed the remote solenoid kit and was pretty disappointed that didn't cure it.. might be a few days before he can bear to mess with it again.

[franken]

Define "sometimes it won't turn on the starter when it's hot." Cranks slowly or no crank? Those are two different issues. If no crank does the solenoid click?
Ground the battery to the engine block via the big negative cable, not to the frame, head, bracket, etc.
Measure the battery voltage to the nearest tenth of a volt when cranking and with the key off.
Measure to ground at the starter on the big cable while cranking. Make the same measurement at the lug from the solenoid to the starter.
Scrap the remote solenoid. It's a waste and only makes for more parts to troubleshoot.

The starter runs on the high current side, meaning the two big battery cables.
The solenoid switches the starter on and engages the Bendix. It runs on the low current side.

[RustyBucket]

The starter engages and it turns the engine slowly, not fast enough to start it. It will stay engaged til you release the key, but it will stop turning the engine. We'll see where the Batt. ground is attached tomorrow. Awhile back he jumped it w/cables when it screwed up and it didn't make any difference. We'll check some voltage per your suggestions. Thanks!

[Getter-Done]

Had the same problem with a SBC in my 63 Impala.
I routed a (single) wire from the solenoid(The post you touch with the screwdriver to start it)
to a good quality push button switch mounted under the dash,
Then to a Illuminated on/off switch so I could remember to turn it off
Then wired that to 12 volts at the fuse block.
Started every-time I had that issue.
Hope this will help your problem.













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[Wgesnerjr]

I know this is probably a long shot, but maybe the ignition switch? Maybe a power drop when in start position?

[franken]

The ignition switch and solenoid have already done their duty once the starter turns.

If the starter cranks slow, it's the big cables that aren't passing the current, poor connections on the big cables, the solenoid contacts are burnt, the battery is dead/discharged, or the starter is the problem. Nothing else is in the circuit driving the motor other than the extra solenoid.

Clean all cable ends of the big cables. Try using one lead of jumper cables from the battery negative and connect the other to the starter body to somewhat bypass the big cable. Try the same from the pos terminal to the big connection on the solenoid. Lots of current capability so be careful not to do any welding...

If the distributor has too much initial advance it can cause a slow crank issue.

[Dead Parrot]

Where is the negative cable connected? Frame, block or other? Even if it is on the motor block, might try a different bolt just in case the current one isn't making a good connection hot. If it goes to the frame, make sure there is a good frame to block cable.

Odd thought - is there enough clearance between the starter and flex plate? Thinking if they are too close - they might bind once things get hot and expand. (I would think that one of the many starters tried would have had enough clearance by blind chance but might check anyway)

Sometimes the mechanical advance on a dizzy will intermittently stick in the advanced position. If you have a good amount of initial advance, the added from the stuck mechanical can lead to hard hot starts.

[El Dorado Jim]

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