Reposting with same problem on NH 1715

[mikelh]

I posted this about a week ago, so will try again. Last fall I went to start my old dependable 1715 and it would not start. Changed the fuel filter, checked all the bleed vlaves, and checked the resistance on my glow plugs. All was OK, so I put on the battery charger and went back an hour later. Still nothing although it turned over better, so I replaced the battery. Meanwhile my neighbor came over as he had wanted to borrow it. We tried for about 15 minutes and then when we manually pumped the injector pump it caught and took off. It died again so I used the foot throttle and at full throttle I got it started and away we went. The next day same thing, so I called our local NH dealer and he suggested bringing it over. They doublechecked my fuel lines, glowplugs, and air in the lines. All checked out. They found one injector tested at low pressure so I authorized them to install a new rack of injectors. The tractor now runs better then before, but they and I can still not start it at an idle. It has to be started at full throttle and them backed off slowly over 10 to 15 seconds. Once it is running and warm I can start it at an idle. The injector pump has also been checked for correct pressures and no leaks. Pretty darn puzzled at this point and quite a few dollars poorer. IDEAS?????

 

[rsallen]

Did they check the compression while they had the injectors out?

How long since the last valve adjustment?

 

[DJ54]

Might be grasping at straws here, but what is the fuel level in the tank, compared to the level of the fuel line going into the injection pump?? If it's lower in the tank, could be an air leak, letting fuel siphon back into the tank. Looked at the exploded view of the 1715 fuel system on the New Holland parts page, and looks like the pump is mounted pretty high on the block.

A buddy of mine has the same problem with his 5400 Deere. Although their tank is located behind the seat, the system has a check valve at the low outlet of the tank. Talked to a pretty decent Deere mechanic, and he told me the check valves are known for having problems.

His suggestion was to keep the fuel tank filled above the level of the injection pump, of it's going to set for a while. No problems since...

Strange thing about fuel & hydraulic systems. They have been known to siphon air in, but under pressure, or vacuum, not show leaks.

 

[mikelh]

Yes compression is at the top end and all of the injectors are brand new and tested all showing around 180 to 210 which according to the mechanic is very good. The injector pump also was completely broken down, cleaned, and new seals put in and retested and all was excellent.

 

[rsallen]

This is a diesel?
210 psi for a diesel isn't right.

 

[mikelh]

I may have misstated pressures, I will check with the mechanic and let you know

 

[mikelh]

All I got from the mechanic that worked on it, was that when he put the injectors on an apparatus to test the pop off of the injector, they were all working at correct pressures. He never gave me a number, but if I find it out I will repost the correct info.

 

[rsallen]

Will probably be in the 1800 to 2100 psi range for the injectors.
I'd consider 350 psi boarder line for a compression test on a diesel engine. Though I seem to remember the specs on one engine (sorry can't remember which) that ran as low as 320 psi.

 

[mikelh]

I can't find my paper work from the NH shop, however I distinctly recall without numbers that engine compression was well above average especially with 1000 hour engine. The injector pressures were also more then adequate. We replaced the injector rack at their recommendation as one was barely popping off when on the injector tester. The new rack is operating above what the two good ones were at originally. i appreciate your response as it is starting to be a challenge now. We have considered that the timing for the injector pump may be off, but that requires opening the front of the engine according to the mechanic and I am not willing to spend that kind of money yet.

 

[rsallen]

Okay they were well above average. So what were the engine compression figures?

I'm not asking out of idle curiosity.