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Posted by: solex Jun 20 2020, 10:41 AM

I have done a lot of work and had the car running fine for serveral but now I have an electrical problem that I cannot seem to find.

Symptoms:
Starter will turn a few degrees but will not turn over the engine when I release the key the starter will turn over a few more degrees as though I still have the key in the start position.

What I checked:

1. Battery was tested and showing 12.58 volts
2. Checked current draw looking for a dead short on negative side of battery (no current draw indicated)
3. Also had a charger (in start mode) hooked up while starting
4. The starter was rebuilt and a new solenoid was installed the starter was bench tested
5. The starter relay was also removed and bench tested
6. Visual inspection of the wiring in the engine bay and underneath the car, I could not see anything obvious

Recent work done (may not be relevant):

1. Installed 123 D-Jet distributor (using curve D)
2. Rebuild Fuel Injectors (Mr. Injector)
3. Adjusted Fuel Pressure was 26 psi is now set at 28 psi
4. New cap, rotor and wires
5. New spark plugs W7C W175T2
6. All new vacuum lines
7. Compression checked #1:145 psi, #2:135 psi, #3:145 psi and #4:145 psi
8. Replaced activated charcoal in charcoal canister (no more gas smell)

Posted by: solex Jun 20 2020, 10:48 AM

I just went out to check the distributor and turn the engine over and noticed that the accelerator cable in the engine compartment was hot...

Posted by: yellowporky Jun 20 2020, 10:51 AM

If you cross the main power lug and the terminal with the yellow wire from the ignition switch will the starter crank fine?
If no you have an issue with the starter
If yes you have something wrong with the ignition switch or the feed from it.
Good luck

Posted by: falcor75 Jun 20 2020, 10:52 AM

Check your ground between engine/gearbox and body. put a startercable between the gearbox and body to rule it out being poor.

Posted by: Spoke Jun 20 2020, 11:38 AM

The accelerator cable is now the ground for the engine/starter/distributor for some reason. That's why it's hot. As others have said, check the cable from the trans to the chassis.

If you want to measure the bad ground, connect your voltmeter between the engine case and chassis and crank the engine. Likely you'll see several volt drop.

Posted by: solex Jun 20 2020, 12:07 PM

Thank you for the suggestions.

yellowporky: I bench tested the starter and it works fine, bridging the power to the ignition results in the same problem, this has be puzzled

Falcor75: The ground between the body and the transmission is relatively new and has been thoroughly cleaned.

I just ran an endoscope up an down the center tunnel and other then rust I do not see any obvious shorting.

Posted by: solex Jun 20 2020, 01:10 PM

I cannot believe that the ground strap was the problem. I replaced it two years ago.

I removed the strap, checked the resistance at 0.1 ohm, cleaned up the strap (it did not need much cleaning) replaced the nuts and washers with stainless, chased the threads on the chassis stud, the car started right up...

Thank you all for the quick replies, I was getting really frustrated, all I wanted to do about 3 weeks ago was dial in the timing with my new digital timing light and it turn into a likely unnecessary starter rebuild and tearing in to my interior showing me the minor rust I need to repair.

Have a happy fathers day all.

Posted by: dr914@autoatlanta.com Jun 20 2020, 01:34 PM

you did not connect the rear transmission ground lead, that is the problem

Posted by: Superhawk996 Jun 20 2020, 02:00 PM

0.1 ohm is too high of resistance

Ohms Law voltage = current x resistance

Stating can draw several hundred amps

Let’s use 100 amps to keep the math easy

100a x 0.1 ohm = 10 volt drop

You can see how even a 50a starter current will drop 5 volts across that strap. Not good.

Posted by: solex Jun 20 2020, 02:21 PM

I just checked the specs on my meter and 0.1 is the lower limit of the meter so I would need to get a better meter to confirm the actual resistance of the strap but will order a new one

Posted by: Spoke Jun 20 2020, 02:21 PM

Good news!

Likely it wasn't the strap but it was the connections to the chassis. It doesn't take much dirt, oxidation or rust to create a very large resistance even if the bolts are tight. You did exactly the right thing by cleaning up all the metal around the connection. One thing you didn't mention was if you wire wheeled the chassis around the stud.

About the 0.1 ohm resistance of the cable, it is very difficult to accurately measure resistances below about 0.5 ohm. Many times touching the 2 probes together will yield 0.1 or 0.2 ohm so the DMM has to be zeroed out. At least you didn't measure 5 or 10 ohms.

Posted by: solex Jun 21 2020, 09:25 AM

Thanks Spoke, I cleaned the pad with 220 grit and steel wool. Seems to be running well.

Again thanks for all your help

Posted by: Bartlett 914 Jun 21 2020, 10:55 AM

I would agree with that. Measuring very low resistance has too many variables and is often unreliable. I am sure the cable is fine but the problem was properly cleaned and seated connections. Glad you are up and running

Posted by: Mark Henry Jun 21 2020, 11:48 AM

Buy a spare accelerator cable, in certain areas the cable itself has a teflon like plastic coating to make it slippy and snag free, you likely melted that coating. The cable will eventually fail.

Posted by: solex Jun 22 2020, 04:40 AM

will do, looks like the clutch cable took a shot at being the ground as well, fortunately I have one in stock.

Posted by: ClayPerrine Jun 22 2020, 08:21 AM

I like to add a second ground cable from the right front corner of the motor to the stud where the negative battery cable attaches to the body.

Just in case....