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955l fuel pump issues

workshoprat92

Senior Member
Joined
Dec 15, 2014
Messages
817
Location
Bois D Arc Missouri
I have a 955L that ran fine when parked. Two weeks later went to start it and it runs for a short amount of time and stalls. Have to let it set a bit and it will fire back up but stalls again. Changed fuel filter and water seperator. No change. Getting good fuel pressure on the gauge. When running you can crack the injector lines at the pump. 1,3 and 4 all have a change in tone and cause a misfire. They spurt a small amount of fuel but nothing extreme. Crack open number 2 and there is no change in tone or rpm. It flows bunches fuel! Not a spurt like a timmed injection but a massive constant flow like an open fuel hose! When it runs it runs like its at high or full throttle and wont idle down till it slows down and dies out. Any ideas?

Machine specs: 955L
serial number 85j10889
Eng serial number 78P31504
Engine was replaced by wagner equipmrnt in denver back in 8
Parts book shows fuel pump to be a 6N281 pump group
 

thepumpguysc

Senior Member
Joined
Mar 18, 2010
Messages
7,445
Location
Sunny South Carolina
Occupation
Master Inj.Pump rebuilder
U have a stuck plunger and barrel or a broken spring ON the p&b..
If your pump has the removable plate that covers the top of the pump.. u can gain access thru there.. BUT.. without the tool to remove the “bonnet” the process is worthless..
 

workshoprat92

Senior Member
Joined
Dec 15, 2014
Messages
817
Location
Bois D Arc Missouri
U have a stuck plunger and barrel or a broken spring ON the p&b..
If your pump has the removable plate that covers the top of the pump.. u can gain access thru there.. BUT.. without the tool to remove the “bonnet” the process is worthless..
The bonnet being the part at the top of the pump where the injector lines attach? I see it looks like a special tool. Wonder how much one is. I do have a manual and a high degree of mechanical skill and experiance. should be able to do any work myself barring any fuel settings requiring a test bench. Have done bunches of cummins pt pumps and a few rosamasters. Havent had to ever mess with a cat pump but it looks like a scroll type pump and meeters fuel much like a detroit injector?
 

workshoprat92

Senior Member
Joined
Dec 15, 2014
Messages
817
Location
Bois D Arc Missouri
U have a stuck plunger and barrel or a broken spring ON the p&b..
If your pump has the removable plate that covers the top of the pump.. u can gain access thru there.. BUT.. without the tool to remove the “bonnet” the process is worthless..
Im guessing that with number two pumping fuel like it is, I am thinking that it is leaking fuel pressure internally and not allowing the other injectors to get proper fuel supply? Is this the basic problem?
 

workshoprat92

Senior Member
Joined
Dec 15, 2014
Messages
817
Location
Bois D Arc Missouri
Ok so i got the side cover off the pump. Right away i see i errored in thinking i had a scroll pump as its a sleve metering pump. Bumped the starter over and sure enough number 2 pluger went up and would not come down. The rack that moves the sliding sleeves was also stuck and very hard to move. Took some carb cleaner and douched the inside of the pump. A pretty nast coating of funk came off everything. Appears I have some fuel contamination. I managed to get the rack clean enough and worked it free while spraying with carb cleaner. It is now fingertip touch free. Still working on #2 plunger. May have to bite the bullet and get the tool to take it apart and clean it. Thinking i need to drain the tank. Flush tank and entire fuel system. Go back with clean diesel and treat with some anti fungal!
 

thepumpguysc

Senior Member
Joined
Mar 18, 2010
Messages
7,445
Location
Sunny South Carolina
Occupation
Master Inj.Pump rebuilder
Find out what cat wants for a pump o/h and to take off and put back on... & I’ll take 10%.. lol
What u don’t wanna do is go tapping on anything with a hammer.
It’s gonna b best to buy the tool AND a new oring that goes under the bonnet..
Once u get things free.. u have to TORQUE the bonnet back down..
Good luck..
 

workshoprat92

Senior Member
Joined
Dec 15, 2014
Messages
817
Location
Bois D Arc Missouri
I think I got it! Kept soaking the plunger and little by little it started to move. It was going super slow and id have to wait for it to slip back down. Standing there looking at the spring i thought man this reminds me of briggs and stratton valve springs. Then an idea hit me like a brick! I went over to my tool box and in a lower drawer all the way to the back, covered up and almost forgoten was my briggs and stratton valve spring compressor. I took it over and sure enough i was able to work it in where i could slowly work the plunger back down the back up. After a dozen or so cycles of work it down, clean, lube then work it back up and repeat it got to the point where it would come down on its own! A little more effort and a bunch of carb cleaner it was free as can be. By this time its dark enough my old man eyes are useless. So i sprayed it with lube and put the cover back on. Tommorow i should be able to clean it out, put new gasket on and put cover back on. Prime it up and fire it! Fairly confident i got er fixed. While i got all the covers off im gona go ahead and change the fan belts, thermostat, oil and filter and wash out the radiator. Been wanting to do that for a while now so its a good time to get it done!
 

Bluox

Senior Member
Joined
Jun 19, 2010
Messages
1,960
Location
WA state
Before you start it take the air system apart so you can block air to motor with a plate or plywood in case you have a runaway, SOP Cat.
Bad Bob
 
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