Vintage Tractor Motor Help Needed

[Jay H]

My father has a 1963 Allis Chalmers D-17 tractor. It’s been in use almost daily on my dad’s farm since the ‘70’s. Since my dad retired 8 years ago from farming, it no longer gets used daily, however he uses it once a month or so. He used it in November for cutting brush and parked it in its spot in the shed as he always does. He went to use it again in December and it would not start.

We tried to pull start it using another tractor (which we’ve done a million times over the years with everything), but it just wouldn’t run. I’m wondering if any of you engine guys would have any idea what is causing this non start problem on this simple motor.

It’s a 50 hp, 4 cylinder, carbureted, 2 valve pushrod motor. When trying to start it via the starter or pulling it, it’ll smoke gray smoke, but won’t fire. The plugs get wet from fuel. Timing is correct and has been checked. The plugs spark nicely and at the correct time when you test them by grounding them on the outside of the block. The points are clean and the cap, rotor, wires and condenser are relatively new. Compression testing with a basic compression gauge reveals ~120 psi per cylinder on all 4 cylinders. The carb looks clean and in good adjustment. The fuel has been drained and replaced with fresh fuel. The air cleaner is cleaned (oil bath type cleaner) and the air intake tubing is free from obstructions. The plugs are brand new Champion J8’s. The tractor was parked after he used it in November and the thing ran fine at that point.

The tappet cover has been pulled to check the valves & pushrods to see what’s going on with the valve train and all looks good.

However, the biggest mystery is that if you put your hand over the carb intake area, you’ll get blow back backwards through the carb as you crank the motor. It essentially shoves air (and fuel?) backwards through the carb. The throttle and linkage seems to be O.K., but that is one thing that needs to be checked yet.

Any and all thoughts and ideas are welcomed as to what might be causing this condition.

Thank You!

Jay

90 964

[Rot 911]

Originally posted by Jay H
However, the biggest mystery is that if you put your hand over the carb intake area, you’ll get blow back backwards through the carb as you crank the motor. It essentially shoves air (and fuel?) backwards through the carb. The throttle and linkage seems to be O.K., but that is one thing that needs to be checked yet.

You either have a intake valve stuck open or the engine has jumped timing allowing the intake valves to open on the power stroke.

[dhoward]

I'll bet on jumped timing.

[Jay H]

Thanks guys. My dad checked the timing since he was thinking the same thing. However, the plugs fire (seemingly) at the exact time the appropriate cylinder is at the top of the stroke. You can watch the distributor move while turning the motor and looking down the cylinder since the distributor and plugs are on the same side of this motor and everything is easily accessible.

We could be all wet on this, so we'll probably have a pro mechanic re-check this too...

[Rot 911]

Jumped timing means that the camshaft gear driven off the timing chain has jumped a tooth. Usually due to a worn timing chain. The timing will appear correct as to the relationship between the distributor and the pistons, but the valves will be opening at the wrong time. If you pull the timing chain cover you will see a mark on both the cam gear and the crank gear. At TDC they should be facing each other.

The odd thing is that normally when you jump timing you will get low compression readings. I would first try the following: To check the valve/crank timing just pull the valve cover and observe the valves for the #1 cylinder. Pull the spark plugs, hand crank the engine over with a finger covering the spark plug hole for #1, and wait until it starts up on the compression stroke. Make sure you are rotating the engine in the same direction that the starter motor turns it. You will feel the pressure escaping past your finger. That means that the piston is on the way up towards top dead center (TDC). Now, watch the timing mark on the crankshaft damper pulley and continue rotating the engine until the timing mark is at TDC. Both valves must be completely closed at this time. There should be no doubt of it. You can watch the valve action as they close and make certain that they are closed. If either one is even slightly open you have a problem. A compression test will also reveal timing problems. From the above description it should be obvious that the compression on all cylinders will be low if a valve is still open at TDC. So all cylinders will show low compression values.

[dhoward]

http://search.yesterdaystractors.com/cgi-bin/fastsrch.pl?NumberReturns=25&SearchString=TIMING%20GEAR&SearchArea=4&firstrec=1&lastrec=25

looks like a 3 gear setup on an AC D17

[slakjaw]

Will it run on starting fluid?

Try plugging the carb with your hand or a rag while cranking it over.
If there is any gunk in the carb that might pull it out.

One other thought, did you drain the float on the carb?

[Jared at Pelican Parts]

Originally posted by Kurt V
You either have a intake valve stuck open or the engine has jumped timing allowing the intake valves to open on the power stroke.

my thoughts exactly

[Jay H]

Originally posted by slakjaw
Will it run on starting fluid?

Try plugging the carb with your hand or a rag while cranking it over.
If there is any gunk in the carb that might pull it out.

One other thought, did you drain the float on the carb?

Slakjaw,

It will not run on starting fluid either. Thanks for reminding me of that.

The carb has been drained too.

Kurt and dhoward, it's my understanding that this is a gear driven setup and there are no timing chains. I know the governor disintegrated on this tractor 10 years ago and all the gears were replaced with new since that really screwed things up.

We did get just over 120 psi on all 4 cylinders when we checked it with a guage. The guage is the type where you hold it into the spark plug hole (rubber tip) and crank the motor over and the guage will record the peak compression. All 4 cylinders showed almost identical compression.

Thank you all for your suggestions. I'm relaying this stuff to my dad as well.

Would a stuck intake valve still show these high compression readings though? I would think a stuck (open) valve would not let that cylinder have decent compression at any time.

[dhoward]

Stuck valve would show itself as low compression on that cyl.
Keep us posted on this.
I'm not taking my money off the table, though....

[Jay H]

I'll keep you all in the loop.

It's warm today (in WI), so my dad will probably work on this again after he gets done watching The Price is Right this morning (he's retired, so that's what you do when you have lots of time I guess!!).

He's going to check to insure the throttle hasn't been messed up (which might be affecting carb operation) and then will probably try tackling the timing issue that has been bet on by dhoward and outlined well by Kurt (thank you).

If this is a timing issue, I will be curious to find out when something could have jumped a tooth in all this gear driven timing stuff...since the tractor ran well in November.

Thanks again all!

Jay

[M.D. Holloway]

My Grandfather In-law fixes them. PM me and I will get you his number. Below is a pic of some of his projects. He has about 50 from the 1910's to 1960's.

[Superman]

Yep, there are guys out there who are CRAZY about old tractors. I have one as a friend. They're a blast to operate. Some of the big ones rotate perhaps 100 rpm. HUGE pistons. That's when I realized what a tractor is. It's an engine and transmission and rear end in one case/block, with a seat and gas tank bolted on.

[M.D. Holloway]

Here are a few more that he rebuilt:

[Jay H]

Mike H. PM sent!! Thank you!

Superman, I agree, old tractors are a blast to work on. Everything is SO simple (except this particular problem). I grew up on a farm and we had an Allis Chalmers B, 2 WD's, 1 WD45, 2 D-17's, and other various newer tractors.

They are just a motor, trans, rear diff and a steering wheel! 1500 rpms is WINDING out most of these things. The newer diesels that spun to 2400 was really cranking over.

I've still got the WD45 working at my house plowing snow and with 45 hp, it will push anything with the 6 foot blade on it.

Jay

[Jay H]

Update:

My dad and I worked on the tractor a bit tonight. He took the carb off today and cleaned it out and blew it out a lot with the air compressor. Now, the carb sucks good when you try to start it. The blowing back problem seems to have resolved itself.

The valve cover came off and everything looks good under there and all the valves are functioning (nothing is stuck open).

We also tried cranking it over with everything put back together. She fired a few times, but it seems she's quickly flooding herself now.

We don't suspect it's a timing problem since it seemed to almost catch (fire up) tonight.

My dad's going to have the carb rebuilt by the local Allis Chalmers shop and see what that brings.

Special Thanks to Mike H for the extra help via PM.

Best to All,

Jay

P.S., Since we all like pics, here's my WD45...

[cool_chick]

I keep on thinking that it could be bad gas.

Anyways, let us know what the fix turns out to be..

[Jay H]

Originally posted by cool_chick
I keep on thinking that it could be bad gas.

Anyways, let us know what the fix turns out to be..

Kyle

Kyle,

We too thought it could be bad gas and one of the first things my dad did was to drain the gas tank, clean the glass settlement bowl and clear the fuel line to the carb (it's all right there on the outside of the motor - super easy to access!). He added fresh gas then with no change in results. So, I guess that idea was out. But you are right, bad gas just doesn't combust.

I will keep you updated as we continue to diagnose!

Jay

[wswartzwel]

chech for a clogged muffler/exhaust...something could have built a nest in it while it was setting unused..
My father has an old John Deere A. I still enjoy going to his place and driving it around the field.

[Jay H]

Just a quick update...

My dad was messing with the tractor again yesterday and started moving the distributor to see if he could alter the tractor a bit to help trouble shoot some more based on all the talk of timing problems that everyone has suggested it be.

Moving the distributor allowed the tractor to backfire quite a bit, so we probably have to rethink the messed up timing concept (and I'll have to make good on dhoward's bet that it's a timing related problem!).

To check timing gearing on this thing, the front end of the tractor has to be diassembled a bit, so we'll see how my dad proceeds from here.

Thanks again to all!

Jay
90 964