Oil & Fuel MT372D fuel shutoff issue.

[Boomer16th]

Now that I have the thing (MT372D) up and running, I need to address a few issues. If I shut off the fuel line between uses, air gets into the system making startup a pain. If I do not shut off the fuel line, it starts right up but, since I see no external leaks I'm worried that fuel may be draining into the crank case. I have not noted a fuel smell in the oil but, I'm not sure if that could become a problem. Is there a sequence of checks to go through to find this problem?

Thanks from So. Oregon

 

[radios1]

you could check the oil level on the dipstick, if it shows above full you could be getting fuel in the crankcase, not good at all your fuel shutoff may be leaking in air when turned off, it may have to be replaced, but the leak could be somewhere else too.. a seal on the injector pump or lift pump for example..

 

[CausticUrbanCoast]

Start with the easy stuff, undo and reseat all the line nuts you opened and look for seal problems on the flares.

 

[Boomer16th]

you could check the oil level on the dipstick, if it shows above full you could be getting fuel in the crankcase, not good at all your fuel shutoff may be leaking in air when turned off, it may have to be replaced, but the leak could be somewhere else too.. a seal on the injector pump or lift pump for example..

The shut-off is on the bottom of the tank (with the filter bowl) and it is dry as a bone on the outside. A rubber hose runs across to the pump area with no signs of leakage.

This is my first diesel, so though I understand the function of the pump, I do not know how they are constructed and if they can leak into the crank case like some older automotive pumps could. Leakage into the crankcase at this point would make sense.

The pressure lines from the pump run up and around the block to the injectors, also with no obvious leakage.

If there is a slow leak in an injector then with the shut-off closed, fuel could leak into the cylinder and be replaced with air from the cylinder until the fuel from the highest point in the line has emptied leaving about 2 or 3 inches of air in the line (messing with the startup until the air is pumped out)? With the shut-off open, fuel would drip into the cylinder but no air could be drawn into the line because the the fuel in the tank is slightly higher than injectors?

The leak is slow, there is no startup problems if the shut-off is closed and the tractor is used every 3 to 5 days but, if the shut-off is closed for a week or so, it will try to start and quickly die several times. The longer it sets with the shut-off closed the more start & die cycles are needed to get it going.

I have left the shut off open for several weeks in a row and found no noticeable change in oil level (it is hard to be exact with the dipstick location and the bucket frame in the way), no diesel smell in the oil that this old nose can detect and no start & die cycles needed.

It seems that diesel would have to come out for air to get in the line? If the diesel is not on the outside (I will double check next chance that I get) then it's on the inside? If in the crank case, through the pump? If through the injector(s) into the cylinder(s) will it cause problems?

Is it better to use the shut-off and stress the start cycle, rather than chancing too much diesel in the wrong place? I think we are talking teaspoons here, but over time!

Sorry for being so wordy and thanks for your attention.

 

[CausticUrbanCoast]

I am curious, how long are you running the glow plugs before trying to start?

And you verified that it is air by opening the bleeder?

 

[Boomer16th]

My glow plug indicator does not work (yet) so I give it a 15 count in warm weather and 20 to 25 count on cold mornings. With all things the same the only difference between a typical startup and the start & die cycles is if the shut-off has been closed for more than 3 to 5 days.
I have not opened the screw at the pump or cracked the line at the injectors to check for air. Is there something else I should consider?

side note: I replaced the copper wire in the glow plug indicator with Ni-chrome but, no glow. I plan on changing the Ni-chrome length and/or diameter until I get a glow timed with my count (or current/voltage drop numbers if I can find them).

Thank you

 

[CausticUrbanCoast]

How were you determining that air was getting into your system?

 

[Boomer16th]

What I call the "start & die" cycle begins with opening the shut-off valve, setting the throttle at about the 2200 rpm location, running the glow plugs for a 15 to 25 count and keying the starter. It will crank maybe 4-8 times, fire, rev toward 2200 rpm and stop flat (die) as if the throttle was shut down. I will pause a moment and key the starter again with the same results. I usually repeat this 2 or more times and then the engine will catch and stay at 2200 rpm. I then lower the rpms to around 1500 rpm or so to warm it up and it runs great for the rest of the day. Air in the line is the only thing that I can think of that would do this and the longer it has set with the shut-off closed the more start & die cycles I will have to go through.

The start & die cycle has lead me to believe that air pockets in the line was stopping the engine and that the air was removed from the line after several cycles. The pattern that the longer it has sat with the shut-off closed, the more start & die cycles were required to remove the air supported this idea.

When I first got the tractor I would forget to open the shut-off valve, start it and it would die after a few moments. I would open the shut-off and try again. After several start & die cycles it would catch and run well for the rest of the day. This added to my thought that it was air or starved for fuel.

As I am new to diesels does this make sense? What else should I check?

Thanks

 

[CausticUrbanCoast]

Mine does the same thing, however it just means there wasnt enough warmed diesel.

 

[Boomer16th]

Why would the closed shut-off cause this, while leaving the shut-off open between uses stops it? It happens summer or winter.
My worry is that fuel may get in the crank case oil (or ?) if I don't keep the shut-off closed between uses and cause other problems.
I just went through the starter because it was getting overworked from the extended starting procedure.
I can live with it if there isn't a fix. I am just not sure where to start. I would hate to dig into a working pump for no reason and make things worse.

Thank you for helping.