Ford 675D Slooooowly Loses Power...

[JCinNC]

Howdy HEF. (Heavy Equipment Forums )

I have a Ford 675D with an issue and any input would be greatly appreciated.

Background: My Dad's backhoe. He was in the business for several decades and passed awhile back. Machine was always maintained fairly well when he was alive. It's not "whipped" or abused. Good power from the engine & hydraulics when functioning correctly. Since then I have kept it cranked and use on the farm from time to time.

Recently it has developed the issue of loss of power like it's starving for fuel.

Symptom-Behavior: You crank it, it seems to run fine. Will run to full RPM and power. Set the throttle for about 3/4 RPM's (Don't recall the exact RPM's. Going by sound I'm used too. Will try to get them if needed.) and it will begin to slow down, down, down and then level off at about 1/4 throttle RPM within roughly a minute.

If you then set the fuel at idle it will begin to struggle and eventually shut off.

Wait about 10 seconds, crank, and it will run normally again even up to full throttle but begin the slowdown cycle again except it's quicker.

If you pump the primer pump when it slows down it will pick back up RPMs.

When it is "good" smoke is black i.e. diesel rich. When the slowdown begins, it gets lighter i.e. diesel lean.

What I've Done: Ran tractor with cap off fuel tank.
No change.

Removed return line & made sure it was clear. Confirmed it is open and returning while tractor running by looking in the tank with a flashlight and seeing the fuel come back into tank.
No change.

Completely dismantled the fuel water separator/filter & primer assembly from the tractor. Cleaned all thoroughly. Replaced the fuel filter.
No change.

Drained and removed the tank. Fuel looked fine and has had stabilizers in it. Drained it through a few coffee strainers while recovering anyway. Removed fuel supply valve at bottom and inspected for any screens or restrictions. Put some Clear Diesel in the tank and swished it around. Let it set. Then washed it out.

Nothing really visible came out of the tank.
Dried tank out. Reinstalled. Removed & cleaned Fuel/Water Separator (nothing really there) and replaced fuel filter again.
No change.

Someone suggested running some Diesel Purge through it. Ran a can.
No change.

Cracked injectors open just for the heck of it to confirm no air and fuel present.
No change.

Dismantled the exhaust system to the turbo just to make sure nothing was in there and the turbo spun freely. Reassembled.
No change.

I'm thinking maybe I should change my name to "No Change" on here. lol.

What ya'll think? Injector pump? Something else? Thanks for any ideas!

 

[Delmer]

Howdy HEF. (Heavy Equipment Forums )
If you pump the primer pump when it slows down it will pick back up RPMs.

With the engine running, the primer pump should be pumping faster than you could with coffee, meth and coke. Pull that pump and inspect, arm movement, free play, look through the hole at the cam. The cav style pump you have should run without a transfer pump, but if the pump is not pumping, then it probably can't suck through the transfer pump.

 

[JCinNC]

Thanks for the input and suggestions. I either may not have the knowledge of what you speak or may have explained/named something incorrectly.
This tractor has gravity fed diesel through the water separator, filter, and then out of the filter directly into the injection pump. There is a hand primer pump for bleeding & priming the system at the filter housing.

I dismantled it, made sure it is clean and all parts are in good condition and put it back on during one of my dismantle & cleanings of things. Appears to just be a couple of rubber baffles in there acting like check valves. Push the pump, pulls and pushes fuel through, crack open the system, and bleed out any air.

Don't know why I decided to do it, but pumped it a few times when the tractor was running and it went into it's "lean" condition, and the engine picks right up for a little bit or as long as you continue to pump.

 

[Swetz]

How about junk inside of a banjo fitting or bolt?

 

[Tinkerer]

Did you replace the filter (#10) ?
Did you dismantle the two shut off valves to see if they have a problem ?

 

[Delmer]

Gotcha, I was thinking of a cam driven pump with a priming lever. Let me think about this for a bit. First, I would reclean everything from the tank back, or run it on a temporary tank to see if it runs better. Replace any rubber hoses. Is the tank full? Did you check the filter in the inlet to the injection pump?

Edit: those filter seals are a common problem also. did you get the old seal out, and put the new seal in the groove, not on the filter? the base can be bent enough not to seal right also.

 

[Honcho]

I d try this. Take a bouttle of clean fuel and conect in to fuel pump. Let him feed the fuel not from the original tank and its line. If there is a differece or not. Or check the pump preassure controler

 

[JCinNC]

Thanks for all the replies.

Tinkerer: I don't see another shutoff. Maybe a different year? Just one at the bottom of the tank. And I confirmed it to be working correctly.

Delmer: Yessir, I removed the old seal and replaced with the new one in the groove. Lubed it with a little diesel. And installed.

Swetz: It could be junk in a fitting somewhere. I've had many loose and haven't found anything....yet.

Honcho: I did that today. Set up a clear tube going straight into the injection pump bypassing the tank, water separator, and fuel filter. Filled it with fuel and cranked it. Still have the problem.
Any help on the pump pressure controller? Not familiar with that.

Thanks again all. Very appreciated.

 

[Delmer]

the pressure controller is under the inlet screen, which is under the hex fitting that is the inlet to the injection pump. carefully use a pick to lift out the inlet screen. I'm not sure how you'd check the pressure controller. Leave that for now.

 

[JCinNC]

Ok, I disconnected the inlet connection to the injection pump with my earlier test. Reached in there but all I got was a spring with a smaller spring and seat inside of that spring out of the inlet. Could have missed the screen. I'll check it again. Thanks.

 

[Delmer]

I don't think you could miss the screen, it was probably missing, which makes me wonder what else was missing, or what else got into the pump with the screen missing.

I guess I'd tee a pressure vacuum gauge into the inlet to see if the pressure drops below zero when the engine slows down. Then if the engine still won't run with the return disconnected, time to pull the pump, or get thepumpguy's advice.

 

[JCinNC]

And the winner is.....DELMER!
I opened up the inlet side of the injection pump again and rehooked in there. There was a screen and I got it out. It had some crud around the lower 1/3 part. The upper 2/3 part was clean as a whistle.
But that lower 1/3 blockage is apparently enough to make the symptoms I had.
Just got done running it. Runs to full RPM and holds it. Idles good. Gonna' be using it soon.

Can't thank all of you enough for the tips and suggestions. And I have some other things I'll likely be bugging ya'll about.

Thanks Again!

 

[Honcho]

some fuel pumps have metalic thimble filter, it is right where fuel line connects with pump but it is a little deep set to take it out one need a tweezers. some pumps have other dont. It might be a little greese with main filter hair. When I change a filter I usually give it a little flash with a diesel, and only after connect it to sistem