ih 756 gas timing

aksteve · Mar 29, 2011

I have just overhauled my 756, new pto clutch, rebuilt hyd valves. She is all back together but i can"t get it to run. I have timed per the manual but when I turn it over I can tell it is firing before the valves are closed as it is exhausing through the carb. lol I know its a timing issue but I have proved ( i think) tdc by stroking the cylinder till the piston is closing after the intake valve opens. Went so far as to turn by hand and watch pistons close after intake stroke on every cylinder. Then I look at the distributor to see if it is in fact on 1. The plugs are 153624. I have taken apart too may times to count and know it"s something easy. There is no way the cam changed, right? i didn"t take it apart. Thanks in advance.
This site has never let me down yet.

Pls don"t say bring to dealer as there are none anywhere near me.

Icuby · Mar 29, 2011

Did you time the oil pump to the dist? An IT manual will tell you how this is done. i always before tear down of one of these set it to #1 then remve the dist and look in hole to see where slot is and then mark it.

mkirsch · Mar 29, 2011

Rotate the distributor counter-clockwise a little bit at a time until it runs. It sounds like you're just a little bit advanced.

You're verifying that the rotor is pointing to #1 by "calibrated eyeball" right? The calibrated eyeball can only tell you if you're close.

aksteve · Mar 29, 2011

I did set as close to one as i could. I did try moving the distributor but no go.

aksteve · Mar 29, 2011

I didn't time the oil pump. I did not mess with the cam shaft so assumed the timing to the distributor and the cam shaft and rods to the rocker arms would be fine. Am I wrong?

bc · Mar 29, 2011

The procedure in the I & T manual is to get #1 at TDC on the compression stroke. I'd do that by removing the plug and using a straw or dowell. Then adjust the gap on the intake valve tappet to .034. Then put a .004 feeler guage in there. Then rotate the engine in normal direction until it just closes down tight on the feeler guage. At this point is when the intake valve is starting to open. Your timing mark should then show 5 to 11 degrees before TDC. One tooth of the gear out of time will be approximately 13 degrees. When ok, then reset the #1 intake back to .027. Let us know how it goes.

aksteve · Mar 29, 2011

I'll try it again. There has to be something obvious I'm missing. I know it's a timing thing. When I did this with my M I had the same problem but it ws just the distibutor.

bc · Mar 29, 2011

Seems like from the procedure I posted, that you could eyeball it without changing the intake valve gap and know if your gear is off.

If you are having a little backfire while it tries to start, that almost seems normal.

I'd check to see if all your plug wires are firing. Romove a plug and check for fire.

More likely it may be a choke or carb adjustment such as one of the jets to rich or lean. Gas builds up in the cylinders and backfires making you think it is a timing problem. At least on my C-263 it will do that and I've never had to adjust the timing. A recent poster had a similar problem.

aksteve · Mar 29, 2011

i did check from the coil and did number one cylinder with a nice blue spark, sssumed the rest were fine. I won"t start but sounds like extream buld up of pressure so no smoothe turn over byt kind of labored then back presssure into intake manifold. It seems like the firng order is off like one of you guys suggested. Choke is fine although I have not adjusted to carb. It"s not fun anymore.

Brad Gyde · Mar 29, 2011

I have timed per the manual but when I turn it over I can tell it is firing before the valves are closed as it is exhausing through the carb. lol I know its a timing issue but I have proved ( i think) tdc by stroking the cylinder till the piston is closing after the intake valve opens.

From this, I gather that maybe you're not on TDC.. If popping thru the carb you either have firing order off, or are off timing.

From your other responses I annot determine whether you removed your distributor or not..

What I would do is this:

1)Remove valve cover

2) Turn over engine until the intake valve closes, then using a wire or the like in the #1 plug hole, slowly turn over until the wire in plug hole seems to have found "high point" (in other words, the wire seems to drop into cylinder no matter which way you rotate the engine)

3) At this point, I would pull dist. cap, and try to take notice to where the rotor is pointing.. Should be at #1, but I would almost bet you're nearly 180 degrees out of time.

4) Remove distributor and get rotor CLOSE to #1 terminal on cap (if necessary)

5) leave distributor lamp loose, install cap/rotor, ground #1 plug, turn on ignition, and rotate dist. SLOWLY and watch for spark.

That should be "static timed" and should very well be close enough for it to run.. Provided that it is supposed to fire at TDC. I have done similar on several engines, sometimes you set the degrees differently (small block chevy comes to mind) but the process is still pretty much the same.

I'm sure I just told you what the service manual said.. But, hope this will help..

Brad

aksteve · Mar 29, 2011

Yes, I was 180 degrees off. It did start but only when throttle was in lowest speed. when throttled up too much fuel it seemed, plus no oil was pumping into the rockers? when I popped the oil filter there was pressure on it! WTH? Any thoughts?

I"m sorry i"m such a noob. I wish my grandfather was still alive I"d love to be asking him these questions.

Brad Gyde · Mar 30, 2011

Sorry I can't help with the oil issues, as I'm not really familiar with the later IH tractors..

It sounds like you got your timing straightened out now then? I just was looking over my post, and I see in a couple places I kinda "lost" the letter C.. but must have gotten my drift..

You did make sure to line the oil pump drive with the distributor, as others recommended, Right?? (since I'm assuming you pulled the distributor to correct being 180 off) As that would certainly correct not getting oil to the top of the engine.. Or so I would think.

How much "pressure" would you say was on the oil filter? Very little, or quite a bit? That kinda tells me you've got the oil pump lined up and working now.. but makes me want to think that maybe the pressure regulator (if it has one) is messed up, or there is a blockage in an oil passage somewhere, causing pressure to build up and not be able to go anywhere.

Brad

aksteve · Mar 30, 2011

I opened the whole thing back up back to bare bones and am taking the front pulley off to make sure everything is lined up. I"m about to call it a big red paper weight. I like the tractor as it is high and tall and open. Great hay tractor for me. i just to have more patience.

There was enough pressure that it went"pop" when i un srewed the filter. Wierd. It was picking up oil and sending to filter but wasn"t going past the filter which was of course new. It will make sense when I find the problem.

ih 756 gas timing

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