TN75F Injection timing

[svcguy]

I have a TN75F that ran fine during the winter, but doesn't run well in warm weather. Even in the winter, as soon as the needle indicates normal operating temp it began to miss, not heavily, but noticeable. I haven't used it much since I bought it, but I have a lot of loader work to do and thought I might use it now, but after warming up in summer weather it's worse than a miss, it's downright brutal. I suspected the filter in the fuel transfer pump might be sketchy, so I removed the pump and cleaned everything up, but the filter was fine. Then suspected the injection pump. While the transfer pump was off I was able to lift the fuel line and noticed the injection pump marks were not even close. I loosened the injection pump, lined up the marks and it seemed to run better, but still was not running well once it warmed up. I decided to properly time the pump with the indicator to confirm a 1mm rise at 9 degrees advance. Brought number 1 to TDC on the compression stroke and removed the injection pump gear cover only to find the number 4 on the pump gear in the right place and the number 4 on the gear below trailing it by about two inches. I am thinking at TDC, the two 4's should be matching as timing marks - am I correct? Not knowing the tractor's history, I am now wondering if the timing gears have been fiddled with and were replaced incorrectly. I realize the gear below the injection pump is just an idler that acts as a cam for the fuel transfer pump and drives the hydraulics, but am concerned that if someone was sloppy enough not to line up the 3's (4's not lining up), they may have missed the 2's or the 1's. Would the engine run if someone missed by a tooth on either the 2's or the 1's in the timing sequence? Also, wondering if the timing gear cluster cover is able to be removed with the engine in place. It appears to me it might be able to, but the manual onlys shows removal with the engine out. Anyone done this or might be able to comment?

 

[RickB]

You aren't going to take the timing cover off that engine without splitting the front bolster from the front of the block. And if the tractor is a SuperSteer, that is no small task. If you have improved the way the tractor runs by adjusting the timing in one direction but it isn't right yet, why not move the pump some more in the same direction, especially if you don't trust the timing marks. Fact of the matter is, it wouldn't be the only TN in the world that was timed by ear, not by a long shot. Half the problem is those Bosch injection pumps sometimes were not internally timed correctly so timing the pump "by the numbers" won't guarantee it isn't going to run like crap.

FWIW the lift pump is operated by the engine's camshaft.

 

[svcguy]

I am going to try and run the dial on it just to see what it's saying, but if others have timed it by ear and it's worked - that's a whole lot easier than splitting the bolster. I really like the tractor, but it has been a challenge. Thanks for the info Rick, really appreciate it.

 

[svcguy]

Well, it's one for the "Duh" files. I tried timing the injection pump by hand, but it lacked power no matter what I did. I removed the lines and properly timed the injection pump to spec using a dial indicator. Got it dead accurate, which really made it run nice for about 10 seconds or so. I overhauled the fuel transfer pump again to no avail. I was about to pull the front end to check all the timing gears when it dawned on me that perhaps they used a filter sock for the tank pickup, so I thought I would blow it clear and see if that would help. Removed the fuel line inlet side from the transfer pump and blew it clear with compressed air, although nothing happened. I tried blowing in the line myself to try and hear bubbles in the tank, but couldn't get anything. I followed the rubber line back beneath the floor board to the lower tank, but couldn't see where it went. I removed the lower bolts and pryed slightly on the floor board so I could shine a flashlight underneath only to hear fuel flowing freely. I dropped the bar and saw it was running out of the hose where I disconnected it from the transfer pump. When I dropped the bar though, it stopped. I pryed it again and watched another dump of fuel. The previous owner must have had the floorboard tray off and pinched the fuel line when he reinstalled it. I pulled the fenders and unbolted the floorboard tray to find the fuel line squashed between the floor board and the frame. Moved the fuel line over to the tunnel and Bob's your uncle. The TN has been unleashed. Power is unbelievable. This was not a New Holland problem, it was definately sloppy work by a previous owner or mechanic. I am more than impressed by the power and smooth running of the Iveco diesel. Wonderful tractor.

 

[Jerry/MT]

Well, it's one for the "Duh" files. I tried timing the injection pump by hand, but it lacked power no matter what I did. I removed the lines and properly timed the injection pump to spec using a dial indicator. Got it dead accurate, which really made it run nice for about 10 seconds or so. I overhauled the fuel transfer pump again to no avail. I was about to pull the front end to check all the timing gears when it dawned on me that perhaps they used a filter sock for the tank pickup, so I thought I would blow it clear and see if that would help. Removed the fuel line inlet side from the transfer pump and blew it clear with compressed air, although nothing happened. I tried blowing in the line myself to try and hear bubbles in the tank, but couldn't get anything. I followed the rubber line back beneath the floor board to the lower tank, but couldn't see where it went. I removed the lower bolts and pryed slightly on the floor board so I could shine a flashlight underneath only to hear fuel flowing freely. I dropped the bar and saw it was running out of the hose where I disconnected it from the transfer pump. When I dropped the bar though, it stopped. I pryed it again and watched another dump of fuel. The previous owner must have had the floorboard tray off and pinched the fuel line when he reinstalled it. I pulled the fenders and unbolted the floorboard tray to find the fuel line squashed between the floor board and the frame. Moved the fuel line over to the tunnel and Bob's your uncle. The TN has been unleashed. Power is unbelievable. This was not a New Holland problem, it was definately sloppy work by a previous owner or mechanic. I am more than impressed by the power and smooth running of the Iveco diesel. Wonderful tractor.

Glad to hear you found the problem. Insufficient fuel delivery, for whatever cause, is the usual reason why low hour diesels don't develop adequate power.