79 JD 644 loader and a 3126 cat engine???

[Cat_man320]

I know for a 1979 John Deere loader 644 . very very low hours and came off an airport .It is in excellent condition. Due to water getting into the exhaust , the engine is seized. I have a new 3126 Cat engine that is totally complete but is electronic . I believe it's a 40 pin computer . Just wondering how many wires I would need to hook to the computer to use an engine like this , oil pressure and water temp and charging system could be hard wired in separately. I know I would have to wire in a throttle as the loader is just mechanical pump but the 3126 uses some kind of rheostat as a gas pedal. would it be worth the time to do this or even could it be done . I'm game for anything as this would save me a bunch of money . I would also love to know what pins on the ECM I would need to hook up to start the engine on the floor . Any help would be appreciated .

 

[fast_st]

I'd sell the 3126 engine and get yourself something a bit more mechanical. have you pulled the head on the JD engine?

 

[lantraxco]

Power, ground, typically one switched hot wire to turn it on and off, and as you say probably a digital throttle, Murphy makes some. It's possible the ECM will have a switched option for resistor type throttle as well, depends on the original program file.

I don't have a pinout for the 3126, run the serial number past your local CAT industrial or genset guy they should be able to send you a PDF file with all the options and pinouts.

 

[Cat_man320]

Thanks for the replies . fast_st , I hate to sell the engine as it is fully complete ready to install in anything that needs comparitable power . the engine I have is 190 hp so it would be fine in place of the JD 6 cyl. I haven't bought the loader yet so I have no way of knowing how much damage or to what extent the rust is .
Lant, I do know that pin 70 needs 12/24 volts on it when the key is in the run position . I do have an electronic pedal out of a rig I parted out . I can see on e bay some of the engines they are selling that there are just a couple of wires hooked up , he also makes the engine rev up. the 3126 is just on the floor hooked to a battery and a few wires from the ECM . I just might try to get it started on the floor and see if I can hook the electronic throttle to it as I also have the harness. only a matter of tracing the wires from the pedal.

 

[Mark250]

Hi Cat-man, it is very difficult to give you the right info with out a serial number for the 3126, as there are machine ,industrial, truck, and military versions and they are different wiring especially the machine engines but I have included a truck engine as an example



Mark

 

[Cat_man320]

Thanks Mark, so are you saying that if I power up pins #6 and#24 and ground 5&4 that the engine would start and idle , then by putting a electronic pedal on it , I could control the rpm ?

 

[Mark250]

yep ,but would need serial number to confirm, the later 3126 uses the ADEM 3 ECM which has 2 x 70 pin connectors ,this circuit uses a digital TPS with an 8 VOLT supply some versions can use an analogue TPS which has a 5 Volt supply
Here is a full schematic in pdf

View attachment 3126 SENR6567SENR6567-01_SIS.pdf
Mark

 

[Welder Dave]

You could run into a lot of headaches switching the engine. How can a machine that got water in the exhaust be in such great shape? There could be more wrong with it and that's why it sat and got water in it. The bad part is you have no way of knowing what condition the rest of the machine is in. It's 37 years old. It might look in great shape coming from an airport but still worn out.

 

[Delmer]

You're looking at the headaches to figure out how to hook up the ecm. What about hooking the engine up to the loader? that's usually enough to make somebody say that they wouldn't do it again, as long as the original engine is repairable or replaceable. The only place a swap makes much sense is a good carcass like you're talking about, but an expensive, difficult to repair/replace engine in it, like a HEUI for instance.

 

[crane operator]

Would vote also against the 3126- its not a great motor. Someone probably has a bad 3126 and would love to have yours. 5.9 cummins is around 160-190 hp in mechanical form and probably the easiest to fit up to something else.

I would not use a electronic motor, would only use a mechanical in a repower. I'm not great with electronics, I'd rather build a throttle shaft with a couple ball joints than wire up a ecm, throttle pedal, sensors etc.

Simplest is fixing the motor in it, or finding another one.

Just for reference- in jan-feb, we repowered 2 cranes, removing 3208 cats, putting in 8.3 cummins. v-8 cats were a poor fit and impossible to work on in the engine compartments. The first 8.3 took around a month or more from start to finish, second repower took a week, because we knew what we needed. I'm glad I did the repower, but probably dropped over $6,000 on each one (motor, flywheel housings, clutch, starter, intake, exhaust, motor mounts, labor, etc).

 

[Cat_man320]

I agree the 3126 is not a great motor and I would like to have something mechanical but I have it and rather than spend 10K to get another good engine or have an old one rebuilt like a Cummins or the JD , I was trying to use it . The ser # is 7AS 75641 , hope this helps .

 

[Mark250]

Cat-man that serial number makes my earlier info wrong as this is a later engine with the 70 pin connectors
to start on the floor you will need to supply power to pins #52 and 53 and ground pins #65 and 67, also you will need to supply power to pin #70 which is usually supplied via the ignition switch
Mark

 

[Delmer]

If your goal is saving money, pull the old engine apart and see what it needs. If you ever sell it the value will be half with a 3126 vs the stock engine. A deere rebuild kit is probably under $2k, probably less time fixing the engine than swapping in an electronic Cat. Now if you're talking about a rat rod engine, or a cobbled up pump/generator/power unit, then the Cat would be perfect. Craneoperator's swaps were a step up, don't go to the trouble of a swap for a step backwards, even if the engine's free.

 

[lantraxco]

A 1979 644 is maybe worth it's weight in scrap metal even if it is a good runner. They were basically junk on a stick new so you really can't worry about lowering the value with mods. Coupling the CAT engine up should be a breeze, the 644 has a rubber isolation coupler in the flywheel housing with a cover plate the output shaft sticks out through, there's a short driveline with the two u-joints back to back. Can't get much simpler probably just a matter of a little adapting I think.

If it was me I would at least drain the oil and see if the pan is full of water, if so, scrap it, if not pull the head and see what you've got and try to break it loose. But I wouldn't hesitate to drop that 3126 in there either if it looks easier/cheaper.

:my2c

 

[Cat_man320]

Thanks for that info Mark sure is appreciated . Now I only have to figure out the two pins for the throttle. This old loader has only 1200 hrs on it . It's not something that I will be using in my quarrys . Strickly for clearing snow in my driveway and also my daughter's driveway .
Thanks Lant and Delmer and the others for your imput . We'll see how this plays out .

 

[Welder Dave]

I wouldn't trust the hour meter. How did it get water in it anyway?

 

[Mark250]

here is electrical schematic

View attachment 3126B RENR1368RENR1368_05_SIS.pdf

Thanks for that info Mark sure is appreciated . Now I only have to figure out the two pins for the throttle. .

Hi Cat_man ,you could try using the cruise control on button and the set/ resume switch's to change speed ,may work to check engine, if it has been enabled in the program (ECM flash file)

 

[Jim D]

Like Delmer and Cat_man and crane operator said, a mechanical engine is the way to go. The electric Cat engine must be worth more to someone who needs it than a good mechanical engine would cost.