Starting squeal only when warmed up
 

Was hoping that the collective heads out there could help diagnose a problem I encountered. I have a 79 thats been in storage for awhile. It starts fine when cold but after warming up ( 3 minutes or so to release the manual choke) I'll begin to get a squeal when starting. At first, I suspected the starter so I swapped in a spare I have. No change, fine when cold but squeals after it warms up. I purchased another new (remanufactured) starter that again, acted the same. Next, I took the car and both previously installed starters to the only remaining automotive electrical rebuild shop in the area. I let the old guy listen to it but he had no firm suggestion. I left the original starter with him to replace the drive grear and bearing and give it a once over.

Again, there was no change after reinstalling the freshly rebuild starter. Next, I swapped out the starter with one from one of my other 79's that starts fine cold or hot. This time, the starter from the other car acted just like the previous three. Absolutely perfect when cold but squealed like a pig when warm. The starter that was making noise, worked fine in the other car hot or cold. This pretty much rules out the starter in my opinion.

Are there any other thoughts on what could be causing noise? Something from the flywheel or clutch? To me, it sounds more like a bearing squeal or electrical strain sort of whine. It does it if the clutch is depressed or not. There is no grinding to the noise. It goes away as soon as you release the key and sounds perfectly normal when running or at idle. It doesn't seem to affect actual staring either, just sounds bad. Once the engine cools back down, it starts normal again every time until you let it run for a few minutes and you get some temperature back in the engine.

From the witness marks on the starter gear, I've got plenty of engagement with the flywheel (1/4 or so) so I tried shimming the starter out from the bell housing with .060 washers at the two mounting points. No change. I ran a jumper cable from the positive battery terminal directly too the main hot lead on the starter (to eliminate a bad or weak starter cable), plus tried a different battery. Here's a link to a video of the noise:

my guess would be check the bushing in the nose end of the starter.

Definitely the starter making that noise....

Maybe you missed it in the original post. I swapped starters between two cars. The starter that made noise was fine in the other car, (hot or cold) while the one that made no noise, squealed just like the previous one, but (again) only after warming up. Besides, if it was in the starter, I'd think it would make the noise regardless if the engine was cold or hot.

Each of the 4 starters I've had in the car made absolutely no noise when starting from a cold engine. Even repeatedly, successive cold starts. Only after 3 minutes of warming up at idle, I get the noise, regardless of which starter.

The bushing in the end seems fine. No excessive clearance, plus I've lubed it.

oh is it the hot start assist thing? they make like a grinding noise sometimes, unplug it and see if anything changes

Hmmmmm, then maybe it's the starter solenoid?? The more I listen to it, it sounds like you said, electrical strain....

I was going to say that too! It looks like the noise starts and stops when the cable on the hot start thing is pulling

Yes, I found that the hot start mechanism is the culprit. Un plug it and it starts normally.


https://cimg4.ibsrv.net/gimg/www.rx7...abc135dbc5.jpg


You could feel it vibrate when making noise. Sounds a lot worse than it felt. Next step is to see if it can be repaired......I opened it up and nothing seems stripped or broken.


https://cimg2.ibsrv.net/gimg/www.rx7...9fc7ae0142.jpg

Just replaced one on a customer car. Same issue. I knew the problem when she said it only happens when the engine is warm. These commonly fail. If you need one I have more in stock and would be happy to drop one in the mail!

What exactly does the hart start mech do? Just crack the throttle for hot starts?

I believe it opens the throttle valve for better air flow during hot starts. You can do the same thing by depressing the pedal, but I suppose the natural tendency is to have your foot on the brake when starting. Looking further, I don’t think the noise is coming from the motor itself. It appears to have a tiny centrifugal clutch. The motor turns the inner hub which contains 4 small metal shoes. The shoes are thrown out to contact the inside of the outer hub which drives a larger gear which acts on the large gear arc to pull the cable.


https://cimg0.ibsrv.net/gimg/www.rx7...ab5075bba7.jpg


Its kind of delicate, like a big watch and is meant to operate dry with minimal friction. Not sure, but I think all the noise is clutch slippage. I sparingly lubed axle shafts for the gears with WD-40 as well as the actuation shaft at its joint and where it passes through the rubber boot. When you press the actuation shaft, it cycles everything down to the outer clutch hub and then reverses to return to its extended position mostly powered by the rubber boot returning to its relaxed shape. Did I mention it was delicate?

Re installing it, I tried it first without hooking up the cable to the carburetor. The arm was pulled in without any noise. I made sure the cable action was free and lubed the arm where it attaches to the carburetor. Re attaching the cable brought back a small noise. It's a lot better but not totally gone. I don’t think Its friction in the cable itself, the only resistance is a light return spring on the carb arm itself.

I’m wondering if something in the clutch is worn to the point where the carb return spring makes it slip and chatter. Since all it does is open the throttle during hot starts, it seems simpler to just unplug it and press the gas pedal down when cranking a warm engine. If anyone has any additional info or thoughts, I’m all ears.

Thanks for that description of the operation, It sure seems like the long way around doing something akin to a solenoid and a bell crank.

As far as its functionality versus a press of the gas pedal, I don't know. I always tap a couple of times on a start anyway.