TR6 TR6 Only starts when being jumped

[John-Glen]

Hello Everyone,
My 1972 TR6 is having dificulties waking from its winter slumber. It will only start when jumped from another vehicle. I tried 3 different batteries all same result. It would then run on its own but die when I removed the ground from the negative terminal. While running it would show higher charging voltage though. Just bought a new battery today as old one had bin in there for 12 years. Installed then put key in ignition and nothing happens at all, no lights, no guages no starter nothing. I have 12.6 volts at battery, at starter post, at ampmeter and at ignition switch. That's as far as I have gotten. If I pull wires from the ignition switch and leave the Brown/White from ampmeter connected and connect one white wire I get the brake warning light to work. When I connect the White/Red to starter and turn key brake warning light goes away but nothing else happens.
Any suggestions or ideas?
Cheers,
John-Glen

 

[NutmegCT]

John - a couple thoughts.

1. bad grounding strap(s).
2. voltage regulator fried
3. bad battery cables
4. is the new battery fully charged?
5. is the generator/alternator functioning right?

When you say it won't start unless jumped - do you mean the starter won't turn unless car is jumped?

With all in place, how does the horn sound? Turn the headlights on and start the engine. Do the headlights really dim when the starter turns?

Tom M.

 

[Gliderman8]

I agree with Tom. The first thing I would check is the ground strap. Maybe remove and clean the ends of the strap and reinstall. Check with a continuity meter to make sure you have a good ground. Let us know how you make out.

 

[John-Glen]

Thanks for the quick replies, when I say it won't start unless jumped: I mean that I get nothing, absolutely nothing with battery in car. When I connect a jumper from running vehicle battery posts to battery posts everything works. Lights, guages, hazards, starter, everything.
Cheers,
John-Glen

 

[dklawson]

Clean and inspect the main battery cables and their terminals. Since the battery is new and you said it was charged to 12.6V, look for problems with those main cables and their connections. If nothing else you should be able t get the headlights to work since they do not involve the ignition switch.

As a footnote.... In college I had a roommate who owned an AMC Gremlin that would NOT start unless we connected 3 cars to his via jumper cables. We couldn't figure it out so the car went off to a shop where they promptly diagnosed the problem as corrosion of the main cables UNDER the vinyl insulation. The cables were full of corrosion byproducts... not copper.

 

[John-Glen]

I removed and cleaned all main cable ends, still nothing... Will run some cable parallel to see if that helps next.
Cheers,
John-Glen

 

[glemon]

Disconnect the ground, then clean all connections at the starter solenoid, all power runs through there, you have have resistance that can only be overcome by extra juice from another battery. I had a similar problem years ago. Car and all electrics would die, it was intermittent, PITA to figure out, but easy fix.

 

[John-Glen]

Thanks everyone, it ended up being the main power cable from battery to starter. Will need to replace. Lots of corrosion on all electrical connections as well, spent a lot of time cleaning today. Time to order some parts for tune-up anyway. Then will need to pass TÜV again here in Germany and all is good for another 2 years.
Cheers,
John-Glen

 

[NutmegCT]

Congrats on the victory - and thanks for sharing the solution with us.
Gratuliere!

Tom M.

 

[Gliderman8]

Glad to hear you got it sorted out. Enjoy the drive!

 

[dklawson]

Thanks everyone, it ended up being the main power cable from battery to starter.

Sounds just like the problem I mentioned in my last post. Corrosion can hide in many places!

I'm glad you got it figured out!