B7800 wont run

[pps]

I've purchased a 2003 B7800 HST with 250 hours a few months ago. The tractor ran fine until a few weeks ago when the engine started loosing power on a very cold night. It sounded that the engine didn't get enough fuel. After a couple of hours I was able to restart the engine but the problem reoccurred just a few minutes later.

Fearing that the problem was caused by dirty/plugged fuel filter I replaced it. The filter was indeed very dirty, some water accumulated at the bottom of the cup and the metal bottom of the filter element has separated from the paper body. Afterwards, I bled the injector lines (several times) but the problem persists.

When the tractor sits idle for a night, I can start the engine without any problem. It will run on idle for a few minutes, but after the engine warms up a bit the RPM starts oscillating (up and down) a bit slower each time. within a minute or two the engine finally stops.

The problem happens before the engine gets hot. It's barely warm, pleasant to touch - probably in the range of 80 to 90 deg.

I tried a few diagnostics steps:

- The fuel pump seems to be working OK. I tested it by hand when removed as well when the pump is installed on the engine. When cranking the engine the fuel flows through the pump and the pressure builds on the output of the pump. I haven't tested the pressure with any instrument it seems reasonable for a tiny diaphragm based pump.

- The problem persists with the fuel cap on or off.
- The fuel lines are free of dirt kinks or other obstruction.
- The fuel flows feely out of the return line into the tank.
- The fuel cut-off solenoid is working correctly.
- When the engine is running the fuel gets to the injectors. I bled them many times.

I will appreciate any advice on the possible root cause of the problem or how to further diagnose the issue.

PPS

 

[skeets]

Did you happen to refuel it at all during this time before it started to RLS?

 

[pps]

Yes, I did refuel it last week.

 

[North Idaho Wolfman]

Sound like you have sucked dirt into the injector pump and or Injectors.
You need to pull the injectors and clean them, and at least the top of the injectors, and clean all the ports and holes.

 

[65specialk]

There is an o ring in the filter. Sounds like it is not in place and sucking air. Do not pull injectors till you are sure there are no air leaks. Dave

 

[tthorkil]

Symptoms are very similar to what I have read on this forum when it has been discovered that 'Gasoline' was accidentally used to refuel rather than diesel.

 

[SteveF]

Given your thorough description and trouble shooting, I'm with those who are thinking the injector's or pump may be fouled with residual dirt.

If the o-ring is the cause, why did it occur before changing the filter?

I don't know about the gasoline contamination thingy.

 

[bruceatlam]

I assume that you checked the air filter. Since the fuel filter was so neglected, the air filter may have been neglected too ----- a plugged air filter will also cause that symptom.

 

[Tx Jim]

I would check a lot of things before pulling injectors!!!!!!!! Have you checked for good flow of fuel coming from tank to inj pump? What is the temp where you live? Could fuel be gelling?

 

[Dan_R_42]

I would check a lot of things before pulling injectors!!!!!!!! Have you checked for good flow of fuel coming from tank to inj pump? What is the temp where you live? Could fuel be gelling?

...

It looks like he is in the same very cold temps I am experiencing. You will most definitely need to be adding something like "Diesel Fuel Supplement" to the fuel to keep it from gelling.

http://www.powerservice.com/default.asp


PPS - Welcome to OTT...

 

[kuboman]

Eliminate the simple things first. Indeed if the o-ring is missing or any kind of air leak will give you the symptoms you describe. You may well have had a plugged filter but now you have a different problem.

 

[pps]

Thanks to all for your advice.

I decided to try simple solutions first. I dumped the fuel and replaced it with new. This immediately fixed the problem! My B7800 runs like new. It didn't even require bleeding of the fuel lines or the injectors.

I neglected to mention earlier that when I refilled the tank two weeks ago, I did add some anti-gelling additive "super-tech winter diesel fuel treatment". Even though I added the appropriate amount, the additive must have made the fuel difficult to burn, especially after the engine warm up. So while the original problem was caused by dirty filter being plugged by crystalizing paraffin on filter's paper element, the latter issue was due to the "bad fuel" which is often described on this forum.

Can anyone offer an explanation why an additive which is make for diesel cars or trucks would spoil the fuel for a tractor?

PPS

 

[North Idaho Wolfman]

Glad to hear you got it going!

One reason additives can spoil the fuel, is that the additives will bind with all the junk and contaminates in the fuel tank and lines and try and move it on down the line.