Mopar gear reduction starter cranking RPM

[JimKueneman]

Does anyone have a definitive answer to what is the normal RPM these old starters crank the engine at? I am in the heat of trying to figure out why the FiTech takes so long to start when the engine is cold and we have discovered that the unit does not actually kick off until it sees 200 RPM cranking. It turns out the Coronet with the original starter that I rebuilt with correct parts, brand new wiring harnesses and a brand new correct battery cranks at about 120RPM when cold (Arizona garage cold bout 60F) for the first 6-8 revolutions before it loosens up and tickles over the 200 RPM mark. Once it hits that point the FiTech starts squirting fuel and it fires right up. I will tell you it is not really possible to tell by ear. I can't really hear a difference but the data shows the RPM increasing.

 

[Frank Mopar]

I would think it your initial shot of fuel when cold is the problem

You can change that setting unfortunately I dont remember what setting it is

My workaround is to cycle the ignition 2 or 3 times when cold. Give that a try

 

[JimKueneman]

I would think it your initial shot of fuel when cold is the problem

You can change that setting unfortunately I dont remember what setting it is

My workaround is to cycle the ignition 2 or 3 times when cold. Give that a try

We have been working this problem on the FiTech FB page for a while. It is clear from the logs that the FiTech unit does not shoot ANY fuel until it hits 200 RPM. There are a significant number of FiTech owners that have the same problem. Cycling does not do it either.

 

[69Bee]

You might look into a mini-starter. They are direct drive instead of a reduction drive, so this might net more turning RPM. I do not find an engine rpm spec, but the reduction spec is 1925 to 2600 RPM for the starter and do the math for the number of starter teeth to flywheel teeth.

 

[JimKueneman]

You might look into a mini-starter. They are direct drive instead of a reduction drive, so this might net more turning RPM. I do not find an engine rpm spec, but the reduction spec is 1925 to 2600 RPM for the starter and do the math for the number of starter teeth to flywheel teeth.

Thanks Dave

 

[threewood]

We have been working this problem on the FiTech FB page for a while. It is clear from the logs that the FiTech unit does not shoot ANY fuel until it hits 200 RPM. There are a significant number of FiTech owners that have the same problem. Cycling does not do it either.

Soooo, if FiTech is aware of the situation why don't they offer to flash a workable patch on their control units?

 

[oldbee]

I LOVE CARBS, most of the time!!!

 

[threewood]

I LOVE CARBS, most of the time!!!

Oh boy, me too! Jim knows his stuff too and if he is having problems I know I would have pulled my hair out and stuck some tools in the drywall by now

 

[Cranky]

Been a long time since messing with the old gear drive starters but is it really a gear reduction setup? IIRC, the two gears are the same size? If the starter motor is turning 1925 to 2600 and has a reducing gear drive and then deduct the ratio on the flywheel, the engine wouldn't be turning very fast at all.

 

[69Bee]

The reduction is 3.5:1 per 69 manual. I reduced the 1925-2600 by 3.5, then divided that number by 13 (10:130), and the result was too low. I have to assume the 1925-2600 is the 3.5 reduced value, so therefore, dividing by 13 results in an engine RPM of 148-200. On a cold day, the battery is shivering, and I will bet the number is lower...

 

[JimKueneman]

The reduction is 3.5:1 per 69 manual. I reduced the 1925-2600 by 3.5, then divided that number by 13 (10:130), and the result was too low. I have to assume the 1925-2600 is the 3.5 reduced value, so therefore, dividing by 13 results in an engine RPM of 148-200. On a cold day, the battery is shivering, and I will bet the number is lower...

That is about what she does, thanks Dave.

 

[wyrmrider]

On the older factory starters you can install 4 fields instead of 3 fields and a shunt- there are other tricks
you need heavy battery cables
Best is a later small starter from a late truck
they use permanent magnets and will spin faster than a built big heavy starter- more header clearance too shield your starter from exhaust heat if you want reliable hot restarts

 

[oldbee]

Well here’s another. Looking in my ‘68 FSM the direct drive hemi starter turns at 3800rpm,compared to 1925-2600 for reduction gear. I’m getting more confused every day.

 

[mopar 3 B]

I have not seen a hemi direct drive in years. If memory has not failed it is huge even by gear reduction standards.

 

[RJRENTON]

Gentlemen,
I have used both types of starters on my GTX. Presently i have the mini starter installed. The Mopar reduction gear unit develops more torque at a slightly lower RPM, where as the mini starter, because it is a permanent magnet motor (no field coils), it will draw less cranking amps than the OEM starter. Armature current produces the torque required at little loss of battery voltage drop so the EFI system should be unaffected...except for the minimum cranking RPM it needs to begin fuel turn on. I would guess there is a Hall switch or similar crankshaft sensing device sending pulses to the ECM to determine RPM. Unfortunately, because of the fixed starter pinion to ring gear centerlines, changing gear ratio may be difficult or impossible. If one could reprogram the ECM's turn on point to slightly lower threshold value....but what software would be necessary to do this??? I wish I could be more helpful.
Bob Renton

 

[Frank Mopar]

http://fitechefi.com/faq/cranking-fuel/

 

[old guys rule]

HELP! have an 11" clutch behind my 440 and the starter gear teeth are too big to fit the ring gear and grinds and hangs up. Any answers out there?

 

[Cranky]

HELP! have an 11" clutch behind my 440 and the starter gear teeth are too big to fit the ring gear and grinds and hangs up. Any answers out there?

Since this thread is a year old and the title doesn't fit what you are looking for, you might start a new thread about the problem you're having.....and it should get more views/comments.

 

[old guys rule]

Thanks,
I didn't notice the date.