Six volt flathead resistance

I put a new 6 volt battery and starter in my 36 Ford 1.5 ton but still had very slow cranking, so I installed all new "00" cables and all was well for a week, then back to the same problem. With a multi-meter, I determined that I had 6.3 volts at the battery side of the starter switch (floor push rod type), but only 4.5 at the starter side if the switch, so I replaced the starter switch, but there has been no change.

I routed the ground cable (positive) direct to the engine pan and have moved it to other locations without seeing a change.

Is the voltage drop at the starter side of the switch normal? Any ideas?

 

are all your ground connections good and clean ?

 

I moved the ground cable from a transmission to engine housing bolt to a cleaned area on the pan with no change. I believe the original set up was a ground strap from the positive post of the battery to the frame and then another strap from the cowl to the engine. I assume that going direct to the engine is best?

 

You want both - chassis to engine & engine to battery - with the shortest possible runs of the largest possible wire (esp for 6V). But I'm not sure it'll fix your problem. Also, be sure your starter mounting area is clean so your starter makes a good ground with your block.

 

had same problem with my 6 volt system and did a good cleaning of connected area's.seem to fix problem

 

You didn't mention if that starter has been rebuilt by a an expert auto electric shop. That can make a huge difference ! 4T

 

I have checked all connections and added a ground wire from engine to frame, but problem remains. The starter was new with the modern bendix from Streed Rod & Performance supply. It seems odd, however, that when I put a hot jumper cable right on the starter wire post it doesn't turn at all. On the other hand, when operated from the starter switch, it gives maybe one turn, and only shows 4.5 volts at the starter.

 

The six volt battery shows 610 CCA and 750 CA. Is that enough?

 

Perhaps you could post a drawing of what you did in the above post. I myself would take the starter to a good auto electric shop and have them go over it to find out if it is any good.

 

I put a 1,000 CA Optima battery in with no change. I will have the starter checked and let you know the outcome.

 

Some times the stater armature bushings wear oval and allow the armatue to drag on the field coils. Try running a ground strap from the cab to the engine also.

 

Go buy yourself an amp guage and know how many amps your starter is pulling. they sell really nice ones that just clamp over your wire and have a digital readout. as a general rule, if the starter is pulling over 500 amps you have a problem with the starter. with a low compression flattie i would expect around 350 amps. a starter with a short in the armature or dirty brushes will pull too many amps and cause your voltage drop.

 

I pulled the starter and bench tested it and it turned fine. I put the old starter back in (which I had pulled because it was getting jammed up) and it turns the engine great. I'll have the new starter tested to determine the problem and hopefully get warranty help.

The old starter was major rusty and ugly looking and the new one all shiny and bright, but obviously something wrong inside. Thanks to all who offered ideas.