Ford 641 missed bad when you try to rev it up!????

[tysmobiletractor]

I have this good old 641 Ford 4cylinder gas engine.
Been running weird last few times I used it. Don't use it often.
Now it missed really bad if you try to give it throttle.

What I've done:
New-points-condensor-rotor-cap-wires-plugs-pulled the carb and disassembled and cleaned it - reinstalled - new fuel filter-tank is clean- lots of gas flowing to carb-
just reset the timing -
sprayed around intake while running to see if there is a intake leak-nothing obvious
Starts weird when cold - I think because I give it a bit of throttle to get it going. Idle and up to about 400-800 rpm runs great- above that missed terrible!
When its warm it starts great with the throttle low. Runs perfect at idle and just above.

Is there some sort of advance in the distributor that could do this?
Just seems electrical.
If I fool with the distributor timing, I can get it to run better at mid higher rpm, but never the way it should.

 

[Rob Mo.]

Sounds like the distributor is not advancing time when the engine speeds up.

 

[showcrop]

Starting weird--- running weird.... I can't find those symptoms in my trouble shooting manual. Can you come up with any more description? I would run a compression check. Quick and easy to do.

 

[tysmobiletractor]

Thanks for the responses...

This makes sense, because it runs nicely at low rpm. The more you try to raise rpm, the worse it seems to run.

I may do a compression test just to make sure. But symptoms don't make sense for cylinder or head issues.

If it is distributor, can it be repaired?
Or is a new purchase best choice?

I actually have a spare distributor from an 800 that was converted to electronic ignition. Maybe I will install it if it looks good after a visual inspection. See if it solves the problem.

 

[tysmobiletractor]

I understand your question. But If you are like me we all know how our tractor motor sounds. And easily can tell when things are going south.

Starting weird - Sputters, backfires, .... once I get it started, if I idle it down it seems to clear up.

Running weird - giving it throttle, it runs awful, and worse and worse the more throttle you increase. Really won't even rev up, just starts misfiring, sputtering. Let throttle back down it definitely runs better, after a few moments at idle it clears up and idles with ease. I suspect it gets the cylinders a bit loaded up from misfiring, and after slowing the rpm's it clears the cylinders out and begins idling as it should.

I had done a compression test about 2 years ago

#1 115
#2 112
#3 115
#4 115

But I can recheck that.

 

[WayneIA]

Remove the air cleaner hose from the carburetor and see what happens!!

 

[tysmobiletractor]

Thanks
I ll try that.

 

[showcrop]

Well ty, it sounds like you have eliminated compression, so since you are concerned with spark advance, go ahead and check that. Checking the advance system is quick and easy. Just remove the plate that the points sit on, and there it is. Most likely you will have some cleaning to do by spraying with carb cleaner. Then just check the parts for free movement. While removing it pay close attention to the condition of the metal strip that conducts the current into the distributor from the coil.

 

[tysmobiletractor]

I did a new compression test. All in 110 lb range.

Also, I did remove the intake air rubber hose, and sprayed carb cleaner into the carb while running to see if it was starving for fuel and it ran worse. I don t think it s a air intake blockage.
But I may pull it off again to verify this.

Then check on the distributor issue.

Thanks for the posts guys.

 

[D F S.D.]

Have you tried different spark plugs and not champion ones

 

[tysmobiletractor]

Just a few weeks ago I pulled out champions that were less than 1 year old and installed new Autolite plugs.
I m not a fan of champion brand either, though they do work.
Thanks
Though

 

[LarryMaine]

I'm no expert, but if it were me, I would put a timing light onto it and check timing at idle speed. Correct number is in the IT manual. Then increase engine speed in increments and check timing using your timing light on the flywheel each time to confirm whether or not your distrib is properly advancing. Correct numbers are also in IT manual. I might also remove individual spark plugs just one at a time to see if misfiring is linked to any single cylinder. Larry

 

[Tim PloughNman Daley RIP]

Don't guess and start replacing parts with all new until true root cause problem is determined ---oops--- too late. Did you get the firing order correct? 1,2,4,3 CCW.
It's not the Champion Plugs. OEM spec for FORD Tractors, 39-62 are Champion H10, 14mm. That's 14mm x 1.25mm THREAD SIZE. The plug hex size is 13/16". I crack up every
time someone says this brand is better than that brand. BS. How does one gage spark plug performance? I've used both Champion and AUTO-LITE plugs for over 40 years
with no issues whatsoever. The H10 plug was released with a hotter plug, the H12 and the AUTO-LITE 437 plug was also released as well, and both perform equally as
well. My elderly buddy was a Ford tractor mechanic until they closed in the 80?s and he still repairs Fords and always uses the Champion H10 and has never had any
complaints or problems. Did you perform the fuel flow test before you rebuilt your carb? Did you set the point gap at .025?? Did you set the timing correctly using a
timing light? Did you set the spark plug gap set .025? - .028?? Is your system the OEM 6V/POS GRN setup or has a 12V switch out job been done? Is the entire wiring
correct regardless which operating voltage you?re using? Do you have the essential Owner/Operator/Parts/Service Manuals? If not the OEM operator?s manual and the
Clymer I&T FO-20 manual are valuable tools. Best to read them and get your wiring, plugs, and distributor set and timed correctly. I guarantee it is one or a
combination of these items and has nothing to do with whether you are using Champions or Auto-Lites.

FORD 600/800 TRACTOR IGNITION TIMING & ELECTRICAL WIRING:

Tim Daley(MI)