GMC starting issues

[Jeepman272]

Hi,
Drove my GMC at the weekend, not an issue. Parked her up, came to start her today and nothing, dash instruments on, lights work but nothing at the starter. Checked the 6v battery and all ok. Took the solenoid of the starter and it tests ok. whilst it was off I put the battery lead onto the starter direct and it turns over!!
My guess was it must be the solenoid but it looks good so took it to an electrical engineer and he said it's fine.
I put it all back together and noticed when I press the starter pedal, the fuel gauge drops from half full to empty (never noticed before so could be normal), and I can hear a slight humming.
When I find someone to help me i'll get them to press the starter whilst I am under the bonnet, but has anyone had similar issues?

Cheers,
Alistair

[jesse]

The battery terminal(s) could be dirty. They may conduct enough juice to run the accessories, but not the starter. Take them apart and make sure all the connections are spotless and tight. Put it in neutral and see if you can turn the engine by hand to make sure its not locked up.

[fernando mendes]

https://www.youtube.com/watch?v=blAYOE2f9xk&t=43s

[fernando mendes]

https://www.youtube.com/watch?v=sa6XpeUVAYE

[kw573]

Hi Alistair,

It sounds like a solenoid issue to me, but a few questions/observations:

1) The starter will turn over when the solenoid is bypassed = starter is working well enough for now.
2) The solenoid can fail internally and still look good and throw in ('click') as expected, but not make hi-amp connection. When you tested it, did you test for a closed circuit as opposed to just hearing a 'click'?
3) The fuel guage behavior probably reflects the dead short that a starter motor is, but not noticed before because of concentrating on the routine starting procedure, dunno.
4) A humming sound can be high amps in a device of some sort.
5) GMC = CCKW?? If so, I thought they used a floor switch like an MB Jeep, is this so or am I mistaken?
6) Did the engineer test the solenoid under load, eg, on another starter?
7) A solenoid can fail due to dirty/burnt contacts inside. I have occasionally disassembled them, even the crimped ones, cleaned, filed and polished the contacts and re-assembled them with good results.

Hope this helps find the problem.

Sam.

[mudflap]

CCKWs do not have starter solenoids (as built). The starter pedal connects directly to a linkage that actuates a high current switch on the starter motor when the pedal is depressed.

So... Maybe this is not a CCKW ? If, not, what kind of GMC are we dealing with ? Or has there been some modification performed to the electrical system?

A quick and dirty check for solenoids is to put a voltmeter across the battery input and motor output terminals while the solenoid is energized. You should see virtually no drop across the solenoid - maybe 0.1 volts. If you see like 6, the solenoid is not working correctly.

Besides that, hard to provide guidance until we know more about the specifics of your vehicle.

Although... That fuel gauge movement might have me checking and cleaning grounds - battery to frame, frame to engine, body to frame, etc. etc..

Best Regards...

[Jeepman272]

Thanks folks!
All advice useful
Its a cckw floor starter, i call the contact switch on top of the starter a soleniod.
The contacts in tbe switch are so clean they look new.
It wasnt tested under load only for circuit when closed by pressing the switch in.
I will now check all wires earths etc..
Again thank you

[fernando mendes]