1256 Pump Timing ?

[d282]

Friend has an early 1256 with 10,000 hrs that was bought from the original owner. The tractor was a dealer demonstrater for the first 300 hours, and had the C4 block update before being sold to the original owner. Tractor starts and runs great, has good power but has a tick higher up on the engine around the injectors. Figured we would send in the pump and injectors as they are original to the tractor (previous owner said he never had any engine work done all the years he owned it). Turned engine to get the injection pump timing marks to line up and noticed that the flywheel is at 15 degrees. The book says timing should be at 6 degrees. Did IH do somthing to the pump for the demonstrater 1256's? Thanks!

 

[Dieseltech]

Post the complete pump DBGFC637 number so the spec sheet can be checked, IH 361/407 engines did not all use the same pump advance piston travel/degree. No way 15 degrees, either before or after TDC is right.

 

[DeltaRed]

My early 1256 has that tick.Had it as long as I've owned it.Even after an overhaul,still there.Even took it to a shop to findit.Pump and injectors were rebuolt or replaced.If it was going to blow up it would done it a long time ago.My 1456 on the other hand is as smooth as glass.

 

[used red MN]

Coming from left field, any chance the dampener has slipped? Not sure I if you time those models on the flywheel or the front pulley. If read on the front pulley and if I am thinking right the timing would show more retarded if it had slipped. Just assuming due to fan, alt and water pump loads it should slip the opposite direction it is turning.

 

[DeltaRed]

Timed by flywheel.However the damper can move and unbalance things.Extreme cases the cam gear will break.

 

[caterpillar guy]

If it is doing it's job and not smoking or rough running I would check the valves and run it. If the timing was off much it would be hard starting. Since you don't say anything about hard starting I'd say again run it.

 

[d282]

DBGFC637-3DH
DBGFC637-3JW

 

[Dieseltech]

The 806 used DBGFC637-3DH, 8DH, 6GS, and 8GS pumps, all time 8 degrees BTDC. The 1256 used DBGFC637- 2GS, 12KC, and I've seen 3JW also. The 1256 is timed at 6 degrees BTDC. Both pumps have seven degree advance piston for 14 degrees crank advance.

 

[pete 23]

First off, IH never put out a special over powered demonstrator model. You could pick one off the lot, get the serial number and make arrangements with IH to do demonstrations with that machine.

However, a whole lot of dealers, (had one 12 miles away) that would give them all they could get out of them for horse power to make that so called better impression. They did it with the 8 cylinder model and later when a customer bought a new one after running their demo he wondered where all the snort went.

They didn't know how to read a dynamometer either which caused a few arguments among dealers and customers.

Now, as far as the timing of that engine. There are three things that could give you the reading of 15 degrees BTC that you are getting.

One is that the automatic advance in pump could be stuck fully advanced or adjusted that way. The stationary timing mark should be near center of the window.

Two, the governor carrier on pump could be marked wrong when calibrated.

Three, the timing marks on flywheel may not correspond with the piston being at TDC. Had that happen on a 806 that was a full 8 degrees off. Problem is, finding true top dead center with head on is difficult. You need to measure piston travel with a dial indicator and it would be difficult through the injection nozzle hole in head.

Piston stops moving a few degrees on either side of TDC so you have to find the spot where it no longer moves on both sides of TDC to mark .

I would sure want to see if auto advance is working by installing a window on pump. I would also, if you intend to take pump off, try setting it at six degrees before removing pump and seeing how engine responds to that.

There were several changes made on the DT407 pump, lines and nozzle tips mid way through production. All those changes have to come together.

Lines were changed from .082 hole to .062 hole, retraction valve (delivery valve) changed from 35cc to 20cc disp and hole in nozzle tips changed.

Throw in that some pumps incorporated a injection relief valve in head of pump and you have all kinds of mixing and matching possibilities.

If block was changed, there had to be a reason and most possibly some of the other changes took place. Who knows.