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New Starter & Ground... Still no start

T

thevinman99

New member
Joined
May 30, 2019
Location
Jackson, NJ
Got a 1990 M47 240 that runs beautifully. But last week the starter sounded like it was struggling. The car started for a few days and now the starter won’t even engage. So I put a new Bosch in and replaced the crusty ground connection between the block and firewall as per the Bentley gods but still nothing. Multimeter says the starter cables are getting 12 volts and the excitor cable is also getting power. Battery in good shape and the car maintains 13.5 volts once it’s running after bump starting. So now I’m stumped. Anyone encounter this??
 
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I chased similar symptoms for a few days until I replaced the multimeter with a test light. The issue was an ignition switch that would pass voltage but not enough current to operate the solenoid.. I assume you mean the solenoid rather than exciter.
 
The gray/silver wire between the block and firewall is NOT for starter current, it's just for the current the rest of the car uses. The main ground cable (that the starter uses) leads from the battery to the engine block.

But really, if that was the issue it might crank, just *very* slowly.

But yeah, make sure the starter wire is plugged into the correct terminal. If it's on one, try the other. I *think* the correct one is the one closer to the engine, not the one on the outside, but could be wrong. Some types of injection systems used the other terminal to tell them when the engine was cranking (for cold start valves and such).
 
kyote said:
Check the gray firewall connector out, test voltage on both sides.
Click to expand...

Good idea. Using a meter here will expose voltage drop across corroded pins in this 8-place connector exposed to the elements.

Gray firewall connector doesn't mean braided ground strap between cam cover and firewall, which is strictly radio noise suppression, not meant to carry any of the car's DC current.
 
JohnMc said:
But yeah, make sure the starter wire is plugged into the correct terminal. If it's on one, try the other. I *think* the correct one is the one closer to the engine, not the one on the outside, but could be wrong. Some types of injection systems used the other terminal to tell them when the engine was cranking (for cold start valves and such).
Click to expand...

You've got it backwards. The outboard terminal (green circle) is the correct one for the starter trigger. The inboard terminal (red circle) is for cold start injector/ballast resistor bypass.

StarterSolenoid.gif
 
kyote said:
Check the gray firewall connector out, test voltage on both sides.
Click to expand...

Where would you probe for this test? Meaning, where do you suggest the positive and the negative test lead would each go and what should the reading be?
 
ZVOLV said:
Where would you probe for this test? Meaning, where do you suggest the positive and the negative test lead would each go and what should the reading be?
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Do you follow me around to second guess my advice? My free advice? On a forum I've been a part of for 16 years?

If so that's your red wagon brother.

I'm sure you'll love my answer to your question too:
https://www.amazon.com/Automotive-T...t=&hvlocphy=9027615&hvtargid=pla-846575674517

As for me and my house, we use a power probe III for almost all electrical diag these days.
 
And if you get 12v on the chassis side and 9v on engine side, there's yer sign!

Bypass with a blue butt splice and call it a day :-P
 
kyote said:
And if you get 12v on the chassis side and 9v on engine side, there's yer sign!

Bypass with a blue butt splice and call it a day :-P
Click to expand...

And if you don't see any drop, I bet a roll of Smarties you follow up closing the puncture wounds with a drop of cyanoacrylate gel. :-P
 
apachechef said:
post 2
Has confounded me before.
Click to expand...

After my AW71 - M47 swap I spent an embarrassingly long amount of time trying to figure out why it wouldn't crank. I was sure I'd screwed something up with the simple task of bypassing the neutral switch wiring.

Yep, after replacing the starter I'd plugged it onto the wrong terminal.
 
Kyote- I was just clarifying if you meant probing both sides of the connector, which you didn't. CFT thought that's what you meant. That would be a voltage drop test.

I AM critiquing your method. 12v on a meter isnt a valid test. 1 strand of wire will pass 12v, but not operate a circuit. That's why I have been formally trained to use a test lamp. I am trying to educate the forum to use a test lamp instead of a meter for checking power circuits.
 
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