Hard Starting 790

[Mech]

I bought a new 790 the first of May. I'm really happy with it except that it starts hard the first time each day. It cranks for maybe 5 seconds, then starts smoking and after cranking for another 5-10 seconds it will start. The temperatures here are now in the high 70's but my altitude is 8600ft. I had a Yanmar 1610 that would only start with the Thermal Start so the dealer took it back. It had low compression which is a problem at this altitude. I use to had a JD 1050 which started quickly but at about 7500ft. My salesman says just use the intake heat which does make it start easier but I'm not sure if that is because of the heat or because the electric fuel pump is running before I start to crank. My fuel is new and bought at this altitude. The battery is strong. It runs great after it starts and starts immediately after the first time, even if I just let it run a few seconds. My question is do other people's 790 start hard or should I try to hassle my dealer some more. I'm thinking that maybe the fuel is leaking out of the lines, since 75-80 air temps should be fine.

Thanks,

 

[Mech]

Just bumping up to see if anyone can answer if they have any hard starting issues with their 790.

Thanks,

 

[jbrumberg]

Mech:

I am just curious, but could it be a function of your 8600' altitude? Some people have trouble breathing at that altitude. Jay

 

[irwin]

Mech:

I, also, wonder what the altitude effect is on diesel engines and what adjustments should be done. I find it hard to hear (read) about this new tractor having similar starting problems like your 1610D had.
Do you know anyone at your altitude with a diesel tractor? Perhaps you could call another dealer (JD) located as high or higher than you (you live in Co.!!lots of mountains ) and find out if a injector timing adjustment is called for. Keep us informed..

 

[Mech]

According to my shop manual for the Yanmar the compression is reduced by 3.6% for every 1000 feet of altitude. A perfect Yanmar 1610D has a compression between 568 and 639 psi at 1000 ft altitude. At 8600 feet it is down to between 430 and 485 psi. The book says anything below about 400psi will be hard to start so it is marginal for that engine to start with any wear especially at cold temps. The 1610D has 23-1 compression and I think the 790 only 18-1 but the 790 engine is more modern with injectors at the top of the cylinder and I'm sure other improvements and of course should have perfect compression. In any case, long story but that is my understanding of how altitude effects diesel starting. I have talked to a few people with diesels and apparently you don't want to think about messing with the injector timing on the Yanmar engines. The few other people with diesels don't seem to have an issue but my 1050 didn't either and I don't know anyone else with a 790. In any case my dealer is at about 7000 ft and sells a lot of tractors in the mountains so I think I just need to find a way to get past the salesman and talk to someone in their shop to see if what I'm seeing is expected. I don't mind using the cold start if that is what is required.

Thanks,

 

[irwin]

Mech: I live as close to sea level, and not get my feet wet, as possible. I am interested though, let us know what happens.. good luck