V-12 Starting Problem

[Guest James Cook]

I have a 41 Zephyr I bought a couple of months ago. The engine has been rebuilt. Car starts and runs fine. As soon as I shut it off (after it is hot) and try to restart it, it won't turn over at all. I have put a new Optima battery in, checked the generator, insulated the starter from heat, all to no avail. The engine seems very tight when I shut it off but it doesn't over heat (as far as I know). I am totally baffled. any thoughts as what may fix this?

[peecher]

These devils can be pretty tight when freshly rebuilt. If you are satisfied the engine was correctly rebuilt ( proper clearances) then you might look to the starter for weakness. The 6 volt starter draw a lot of amps so the connections including the grounds are important. If you remove the starter check the mounting surface on the pan and starter motor. The mounting surfaces should be bare metal and free from paint. Check the grounding lug on the right cylinder head for corrosion too.

The "tightness" should subside after a hundred or so miles of running.

Edited May 13, 2013 by peecher (see edit history)

[trimacar]

Have you checked you battery cables, are they heavy enough for the 6 volt duty? You need the heaviest cables you can find, not skinny 12 volt cables, and it's best to run ground cable directly to a starter mounting bolt. This solves the majority of all starting problems with a 6 volt system.

I never have agreed with the "newly rebuilt so tight" idea, if an engine is rebuilt correctly it's not going to be tight until broken in....part of my aversion to this comes from having my first car, in the mid 1960's, have an engine rebuilt that was "tight", and it failed in the first 200 miles of use.....

[Tom_Overfield]

double what has been said here about the battery cables, a 12 volt cable will NOT start the car under heavy load conditions. Go the the vendors section, Narraganset Restoration, and you can order the proper cables from them. Also make sure your connections are spotless clean and tight and as also stated, remove the starter and make sure the mounting area is clean and dry.

I had the exact same problem with my V-12 and once I put on the original cables, problem solved.

Tom

[Guest 65Starfire]

James,

I'll chime on in favor of cables too. The draw is high and once the cables start to warm up resistance eats up amps and adds heat to the cables which ups the resistance which heats the cables more...

Please post the results to your efforts so the rest of us will know.

[TexasJohn55]

Have you tried to turn engine with a wrench after hot shutdown? It may indeed be too tight. Check cranking voltage at battery versus at the starter cold and compare that to voltages when hot. Post those rusults. After engine is hot, raise hood and watch while someone turns the key off, if engine is too tight, it will stop immediately with a shudder, may even squawk the fan belt. Compare that to your cold shutdown. Even a properly built engine will sieze at abnormally hot conditions from thermal expansion of the pistons in the bore. If you built it with too little piston clearance or inadvertently have the ring gaps too small, it will do the same thing after reaching "normal" operating temperature. TexasJohn

[Guest James Cook]

Just an update on the V-12 starting problem. I got the heavy cables as suggested and cleaned the engine and starter where they mate and problem appears to be solved. Turned over faster when cold and turned over and started when hot. Thanks for all the input.

[rockitdoc]

Just an update on the V-12 starting problem. I got the heavy cables as suggested and cleaned the engine and starter where they mate and problem appears to be solved. Turned over faster when cold and turned over and started when hot. Thanks for all the input.

Just saw your post and got serious deja vu. I had same exact issues. Tried everything and even found out that some repo cables are not copper! So, I fabricated my own out of 0 ga from a welders supply. Still didn't help. Pulled plugs and car spun fine. plugs in, very slow. NOS starter. New battery. Turned out to be binding between the starter and the flywhee when starter bolted tight. Shimmed it to make room and poof! Works. Something else to consider if problem comes back.