So, I just installed a gear reduction starter in the 66 F100. I switched the starter wire to the battery side of the starter relay/starter solenoid as I head seen done by several online sources, then ran the 2nd wire to the "Start" side of the relay as shown on the same sources. To my surprise, I have tried to start the truck several times now, and only had success once. The truck is doing nothing at all when I turn the key. I even pulled the starter and re-tested it on the bench and it runs beautifully. Anyone have experience or suggestions for this?

Bellow shows the wiring of an OE starter over top of the wiring of a gear reduction... but it's just not working in my case. I seemed so simple

 

Why use two starter solenoids?? Just hook up the lead from the ignition switch to the starter itself, as well as the cable from the battery.
In other words, hook it up as you would a GM starter.

Cosmo

 

Dual solenoids are preferred and Ford does the same thing on plenty of vehicles because the ignition wire can't handle the higher current required by lots of the starter mounted solenoids. So have you tried jumping hot to the s terminal?

 

Battery to "S"... I'll try that tonight. I'm going to have my wife turn the key and I'll check voltage as well.

 

Do you have proper engine ground cables? The coil circuit won't close on the starter without it.

 

It appears to be connected correctly, and if it cranked and started on one occasion, it must be. Your diagram shows the starter wired in the GM (some Fords and others too) fashion. On a GM car the "S" wire is purple and comes out of the firewall harness, and the heavy power wire runs straight from the battery "+" terminal. You don't have to run your heavy power wire to the Ford solenoid but it saves you the effort of adding a different 12v supply, say a 10ga, to that terminal.
I like the solenoid on the fender myself, but it appears you weren't given that option.
Eric

 

I believe that the ground on a starter is achieved by bolting directly to the bell? The starter has a ground wire going from the built in solenoid into the starter, so that should be correct right?

I am running all through the fender mount solenoid as shown on the bottom half of the picture, and yes it did actually start and run once... then never again. So confusing.

 

Yes the starter is grounded to the bellhousing, but you need to make sure the engine is grounded correctly for it to work. The draw of the starter solenoid relay coil is low and a bad ground will not allow it to close the contacts.

 

To clarify the grounds that are supposed to be on your truck, and, truly, NEED to be for it to work properly.
A) The battery MUST be grounded to the engine block at least. Direct to the starter is best.
B) There must then be a ground cable from the block to the body. (An additional cable between body and bed [or frame] is necessary on trucks with taillights attached to the bed).
C) An additional ground from the body to the frame is also necessary.

Copper is a good conductor of electricity. Steel is not. Do NOT run starting power through any steel structure, other than the block.
All grounds MUST ABSOLUTELY be through adequate cabling (for high performance, I highly recommend 00 gauge welding cable with appropriate ends staked and soldered) The 4 gauge sold in ready-made cables is barely adequate for stock engines.
Further, all grounding points MUST be through CLEAN, BARE metal, and star washers between cable end and attachment point do help.

Failure of any of these can lead to weird electrical problems.
Failure of some of these can lead to moving parts welding themselves through trying to conduct electricity, a process similar to fretting.

Hope this helps.

Cosmo

P.S. The fact that it cranked just once indicates to me that the grounds are not adequate.

 

This is gonna sound kinda stupid but the last time that happened to me (two weeks ago) I didn't have the battery cables tight enough at the terminal. Felt tight, thought they were tight, they weren't tight.
That was also on a gear reduction mini-starter, on my 69 galaxie not my 63 4x4 (the ol 292 v8 doesn't need that stuff lol) and is wired per the diagram that came with the starter.

 

So, has anyone run into a battery that read 12.5 Volts or higher and wouldn't turn over the vehicle? Maybe amps were down? Last night I brought out a spare battery with a low charge (still read 12.5 like the one in the truck)? I jumped it to the truck and got it to turn over once before dying... far better than most previous attempts. After that, I placed the old battery on the trickle charge and found that it still read 12.5v but was only 77% charged. Tonight I'll try again with a fully charged battery.

If it works, I might imagine there is something drawing on the battery since it was only down for a week during the trans swap. It seems maybe Cosmofennema and sqettin may be on to something. The first thing I ever learned was to check the battery for volts and voltage drop... but for some reason that continues to embarrass me, I cant put it into proper practice.

I'll update once I've got results.

 

Voltage is also referred to as "Potential Difference" and is not an indication of Amperage a.k.a. current flow capability. A battery that is flowing no current (no leads hooked up to it) will often show 12+ volts as a potential difference as long as two or more plates (each plate supplys approx 2 volts with 6 plates for a typical 12 volt battery) are not fusing together. So, voltage across the terminals is not an indication of the cranking ability of the battery. To test the cranking ability of the battery you have to put it under load - meaning you have to apply a draw on the battery. Many of the battery chargers also have a battery test switch on them which allows you to push a button or switch causing the charger to put an appropriate draw on the battery to see if there is anything more than a Potential Difference between the terminals.

Voltmeters have an internal resistance often in the Megohms or higher range - So, when checking voltage with a meter there is approximately zero current flowing through the meter and it doesn't give any indication of the available current flow - only the potential difference between the terminals.

 

So all your saying here manifested in a great startup last night! Fully charged battery resulted in pure awesomeness. I just have to remember my lessons and look for voltage drop with cranking. I'm going to leave the battery disconnected now as I work out the issues with my hydraulic clutch setup.

THANKS!