Mustang 940E sputtering/loss of power

[rfpowerman]

I have a Mustang 940E with the Yanmar 4TN82E diesel engine, about 1300 hours on the engine. Occasionally it seems like it has run out of fuel and starts to sputter and sometimes stall, even with 1/2 to 3/4 tank of fuel. It sometimes can be recreated when going forward down an incline but not always. If you stop all movement and let idle, sometimes it will recover. Then it seems to go away. This problem is very intermittent. I can run for hours and it is fine, then do this for a while, and then be fine again. I have tried fuel additives (diesel 911, biocide, cetane boost) incase of water, etc., and that does not seem to help. I purchased the machine with about 950 hours on it. I do not know much of the past service record. Has anyone come across this type of behavior? Do the injectors need replacing at some interval? Does anyone know a good Mustang skidsteer mechanic in the Western Massachusetts area? The closest one to me which is supposedly a dealer (in Springfield) seems to know nothing about diesel engines and the next closest dealer is quite far.

Any insight would be great!

Thanks in advance

 

[Delmer]

In general that's common behavior for simple diesels with fuel system blockages, like a plugged inlet screen, collapsed/cracked hose, etc.

Since yours isn't dying and it's so intermittent, it's a little harder to diagnose. If you could tee into the fuel line from the filter to the injector pump and run a line to a gauge in the cab, you could see how much pressure there is when it acts up, and go forward or backward from there.

 

[rfpowerman]

How much pressure do you think would be normal there? Isn't that an area of the line which would be basically gavity feed and very low pressure?

 

[Delmer]

Generally, because I don't know mustangs, or much about Yanmar for that matter, there's a lift pump or electric pressure pump that sucks the diesel out of the tank, pumps it through the filter and into the injection pump. The exact pressure isn't critical, but if you have 5 psi running and then gets low and bounces as it's sputtering, that's a pretty good sign it's a fuel pressure issue. If it's 3psi running, but stays the same, it's time to look closer at the injection pump. If it is gravity feed use a vacuum gauge tee'd into the line to see if it pulls more vacuum than it should, meaning the suction is plugged. Another possiblility is the suction is leaking air, a clear hose or filter is the easiest way to see if there's air.

 

[iwillhaveacrack]

i had the same problem with mine,
mine has not had the the problem after i had completed my service.
things i fixed / adjusted on mine durning service
-changed air filter this a common cause or spluttering
-changed fuel filter
-there is also a tap on the top of the fuel filter bowl check that this is all the way open and if it is open and close it a few times there maybe some grit in it
-there is a little injector priming pump on the back of the injector block pump that a bit and could also free up and build up in the lines or show you where some possible leaks are..dont stress about pumping this a few times the excess just returns to the tank.
hope my two cents might help..cheers

 

[rfpowerman]

Hello to you from down under! I did pull the air filters and they seem fine, not much dirt at all. I blew out the outer filter from the inside with an air gun, minimal dust so I dod not bother to change it. The inner one was really clean. The tap/shutoff on the fuel filter bowl was stuck on mine the last time I changed the fuel filter. I just pinched off the hose to change the filter but perhaps I should check into this further. I did look for the priming lever in the past because it was in the service manual to re-prime after the filter change but I could not find it. I purged the air in the system by loosening the fuel fittings on each of the injectors afterwards. I'll re-check into these this weekend.

Thanks much for the info mate!

 

[Delmer]

-there is a little injector priming pump on the back of the injector block

This is where you find the priming pump, it sounds like it will be a 1" round cap that unscrews, pops up and you pump that piston to prime it. Might have plastic bellows.

If you don't have a separate transfer pump, the system is even more sensitive to plugging/leaking on the suction side, because the whole system is under suction typically.

 

[iwillhaveacrack]

i was looking for a cap as a priming pump btu it was a little lever ...if you put your hand on the injector distrubution...spelling... block at the back of it you will find a lever that the the priming pump.

 

[OG52]

hello. im new to the forum and i wanted to know the outcome of this particular situation. im having the same issue with the same unit and it seems to always happen when its on a hill. but not all the time, the issuew comes and goes and its driving me crazy..... i have done all the typical maintenance and such but it just seems to keep happening... any insight?

 

[rfpowerman]

I still have not found the cause yet. It's still eludes me and seems stable when I run at about half throttle. I am suspecting something possibly with the timing going on but have not tried to adjust it yet. I am not sure how to do that yet either.

 

[partsandservice]

Don't over do it, it's not a timing issue I can tell u that from here. It is a fuel blockage or suction side air leak more than likely. Also inner air element only has to have turned grey to be stopped up it does not have to have any dirt in it.

 

[Swannny]

I'd agree that it is a fuel supply issue. I've had them start running rough due to air getting into the system because the lift pump can't supply enough fuel for the demand....causing air to be sucked in rubber lines between the clog and the injectors...one or two cylinders will get air entrapped/start missing...lowering the rpm's sometimes allows it to catch up, if not, cracking the steel line before the injector does. Lift pump may be weak. Lift pump may have pre-screen that is clogged. I've dug crap from hoses disintegrating out of lines before. Crap in the tank floating around blocking outlet to fuel filter/pump.

 

[OG52]

does anyone have any insight as to finding the fuel primer everyone speaks of. i have looked and cant find it for the life of me. any photos or videos to that would be helpful. someone was saying that if the primer gets stuff clogged in it, that that to can be the problem

 

[iwillhaveacrack]

does anyone have any insight as to finding the fuel primer everyone speaks of. i have looked and cant find it for the life of me. any photos or videos to that would be helpful. someone was saying that if the primer gets stuff clogged in it, that that to can be the problem

its tucked away left hand side as your looking from the back just behind the injector block... if you follow the fuel line from the filter housing to the roundish diaphragm looking thing it is a little lever on the rear side of that. poor area for a primer level took me a while to find it and every time i run out of fuel it takes me a while to locate it again even when i know where it is.

 

[iwillhaveacrack]

what direction does the tap on the filter housing need to be pointing?
nothing in the manual that i can find?

i have also found this to be weaping fuel may also suck air from there.

 

[Rcorn1031]

I have a Mustang 940E with the Yanmar 4TN82E diesel engine, about 1300 hours on the engine. Occasionally it seems like it has run out of fuel and starts to sputter and sometimes stall, even with 1/2 to 3/4 tank of fuel. It sometimes can be recreated when going forward down an incline but not always. If you stop all movement and let idle, sometimes it will recover. Then it seems to go away. This problem is very intermittent. I can run for hours and it is fine, then do this for a while, and then be fine again. I have tried fuel additives (diesel 911, biocide, cetane boost) incase of water, etc., and that does not seem to help. I purchased the machine with about 950 hours on it. I do not know much of the past service record. Has anyone come across this type of behavior? Do the injectors need replacing at some interval? Does anyone know a good Mustang skidsteer mechanic in the Western Massachusetts area? The closest one to me which is supposedly a dealer (in Springfield) seems to know nothing about diesel engines and the next closest dealer is quite far.

Any insight would be great!

Thanks in advance

I know it has been a very long time since you first posted your issue . I have reviewed all the other replies and What appears to be happening in your case and one of the other readers is there is likely something in your fuel tank that intermittently blocks (either completely causing the engine to stall ) or ( partially causing the engine to "splutter" from restricted fuel supply) It is definitely NOT a timing issue as that is accomplished with a fixed set of gears inside the gear housing .
My personal recommendations here are to (1) Drain the fuel tank . (2) Replace the flexible fuel lines and In-line fuel filter. (3) while the tank is empty inspect it for an loose debris that could interfere with proper fuel delivery . This is suspect due to the issue occurring for the both of you . I do not suspect fuel tank removal would be an easy task but may be necessary to end up with a clean tank .

I have this same engine in another Mustang 940 that I am trying to locate a step by step static engine timing procedure for because the "Yanmar" "Service Manual" is intentionally VAGUE about it.

Hope you have found your issue and repaired it .

 

[Rcorn1031]

Your fuel primer

its tucked away left hand side as your looking from the back just behind the injector block... if you follow the fuel line from the filter housing to the roundish diaphragm looking thing it is a little lever on the rear side of that. poor area for a primer level took me a while to find it and every time i run out of fuel it takes me a while to locate it again even when i know where it is.

Your Fuel Pump Primer Lever is a Small lever on the fuel Transfer/Supply pump it is located on the Flywheel side of the pump which is located on the Left side of the injection pump as viewed from the Water Pump end of the engine . It is very difficult to locate . you can use this lever at any time because the excess fuel will be returned to the fuel tank.