Fuel issue?

[npaden]

I *might* have found the problem. Last night I found a schematic online for the Zexel pump. It showed a screen at the inlet line. Pulled it this morning. It was pretty well clogged: almost to the point of not being able to see light through it. I blew it out with air (hold tighter next time so I don't lose it across the barn floor!). Reinstalled it, tightened things up, purged the air, and started it up again. Way higher RPM! No surging or "missing". I'll have to go mow a field or something to see if this truly fixed it or not. Keeping my fingers crossed.
View attachment 480947

Here's a pic inside the bottom of the old fuel filter I took off. Pretty ugly.
View attachment 480948

Now, as to the red fuel line: that's how it came from the factory. I don't know. If it has deteriorated inside, maybe that's why that small screen was clogged instead of that stuff being caught by the filter? I'll get a new piece today.

Where was that screen? I have the same pump and have been having very similar problems. I also had a red fuel line. Is it that fitting right there at the inlet? Just pull it off and the screen is under it? Thanks!

 

[npaden]

I found the diagram. It looks like it is under the return instead of the inlet. Right at the top of the injector pump?


Here's the diagram (the screen is part 251):

Here's where I think the screen is located (circled in red):

 

[PatMcD]

I found the diagram. It looks like it is under the return instead of the inlet. Right at the top of the injector pump?


Here's the diagram (the screen is part 251):

Here's where I think the screen is located (circled in red):

Your pump looks different than mine. See post #13 and the photo. The screen filter I cleaned was right at the inlet from the main fuel filter.

 

[npaden]

It is the same pump, just a different angle on the picture. It was in the inlet not the exit like I was thinking.

Right here circled in red:

The spring and the filter screen were down in the injector pump housing:

It was a little tricky to get them out. I used a tweezers for the spring and then a wood screw for the filter. Put the screw down inside the filter and pressed it to the side and pulled it out. I'm sure there is a better tool for the job, but it worked.

The filter screen itself is tiny! The size of an eraser head on the end of a pencil. Mine was dirty.

Now it is clean!!

As soon as I got it repaired (it took about 30 minutes start to finish) I disced 5 acres of damp soil and it worked great for the hour and a half that it took me.

Thank you VERY much for figuring this out and reporting it here!!! This saved me hauling my tractor to a different repair shop at a minimum and possibly $2,000+ to replace the injection pump which is what the mechanic that had been working on it was telling me the problem was.

Thanks!!!!

 

[PatMcD]

No problem. I just don't understand why this info isn't in the owners manual.

 

[crackerjack222]

No problem. I just don't understand why this info isn't in the owners manual.

Maybe they don't put stuff like that in the owner's manual so their dealers can make a few bucks on service?

 

[Pierce5225]

Thank you very much for this thread. I am lucky to finally find it before I ripped my pump apart. I had a similar issue with my tractor. Lost 1000 rpm and never could figure out what it was. I cleaned injectors and fuel lines, changed fuel filter, disassembled and clean injectors again, bypassed the filter, and installed a 4-7 psi fuel pump from the tank to the injector pump which helped a little bit. I removed the injector pump and decided it needed rebuild. I was searching for a rebuild kit online when I came across this thread. Your pump is the same as my pump. I pulled the screen out and holy **** was it clogged. My tractor is back in Mississippi but I have the pump with me here in NC so I won稚 be able to install it and test it for 3 more weeks. No doubt in my mind this was my problem.

Thanks again

 

[Walter L]

Here is a manual on the Mitsibishi S4S engine that shows the little screen in the injector pump

MITSUBISHI S4S SERVICE MANUAL Pdf Download.

 

[Pierce5225]

Thank you sir. I found the screen and cleaned it out. Very clogged.