John Deere 644B losing power

[ssrider]

Hi I have a 197? John Deere 644B loader. Overall the machine runs pretty good but it started having an issue a few years ago that is getting worse.

The machine randomly loses power when running it. To the point where it won't even push into a pile. It will be running great one minute and then all of a sudden no power. Even in neutral it will only rev up to half of what it should.

Sometimes if I keep running it, it will "clear up." If I shut it off and re start, it will usually run ok again for a while.

Seems like it's not getting fuel so I changed the fuel filter but that didn't help at all. Anyone know what it might be?

 

[Delmer]

The screen in the tank is collapsing on you from getting gunked up.

Or air, or a blockage somewhere else.

 

[YouBrokeWhat?]

Take the fuel line off and blow back through it with an air compressor and look/listen at/to the tank for bubbles. See if that works.
Also if you're in a warm climate get some humout, you might have algae growing in your machine fuel tank and wherever you fill it from.
Algae is a pain in the ass and if that's the problem get used to blowing the line out because after you put the humout in you're going to be doing a lot of it.
Last machine I got that had algae like that I wound up running a separate fuel line down the filler neck after I drained the tank, and stuck a dollar small engine filter on the end and stuck it in the tank so that'd get plugged before the expensive filter did and I could just rinse it out and use it again. Take a week or two to get all the algae out.
I doubt your machine even still has the screen, that probably was gone 20 years ago.

 

[ssrider]

Thanks for the reply's. I pulled the fuel pickup out of the tank. There's no screen, and I don't think there ever could have been. Here's what it looks like. I blew through the lines and they don't seem blocked at all. What else should I be looking at?

 

[thepumpguysc]

Does it have a lift pump on it?? replace it.
Does it have any rubber lines anywhere from the tank to the injection pump? replace them.
Do the ENGINE rpm's drop?? or does it stay the same & it wont move or pull??

 

[ssrider]

It does have a lift pump. And has all rubber lines between the pickup and injection pump.

The engine won't pull rpms when this loss of power happens. Even in neutral.

 

[thepumpguysc]

Deff. sounds like a fuel supply problem.

 

[ssrider]

Ya it definitely seems like it. What's the purpose of changing the rubber lines if they aren't leaking? Here's a picture of the setup

 

[thepumpguysc]

I don't get it.. is the square glass filter still in play or is it by-passed.. it looks like it hasn't been changed??
Is that an electric lift pump behind the bracket? Make sure its working..
To answer your question.. the rubber lines will collapse internally under a load.. the pump is calling for more fuel & the rubber will "suck down".. & when the load is taken off, the line expands back..
I just reread your post.. it does it in neutral too..after it happens.. HMMM
WHEN does it get "better".??

 

[funwithfuel]

Good eye pump guy. I completely missed that old water separator. I used to service those things all the time in the 80s into the 90s. Haven't seen one in a while. I 'member those little grommet seals getting dryrot and the little tubes it sits on rot off so it doesn't sit just right letting air in. Mostly saw em on 3208 scaterpillars

 

[funwithfuel]

BTW, just cuz fuel don't leak out, don't mean air ain't getting in. If it's under negative pressure (vacuum) hows fuel gonna leak out?
I have seen rubber fuel hose less than 2 years old split wide open when flexing into a U . Never trust a rubber fuel line.

 

[ssrider]

Hey thanks for the reply's. Ya the glass filter is still in play, and that's an electric lift pump behind the bracket. Lift pump sounds like its working, bit can't say for sure. In this photo neither fuel filter had been changed yet. Fuel system goes like this - Fuel tank pickup, rubber line, spin on filter, rubber line, lift pump, rubber line, glass filter, rubber line, injection pump.

Makes sense with what you guys are saying about the rubber lines collapsing. They definitely don't look in the best shape. I'll try pick up some new lines and try changing them this week.

As for when it runs "better". Last year it was pretty random. Would be running good for a few hours and then would lose power. Sometimes just restarting it would run good again. This year ive only ran it about an hour, and its running more bad then good. Today it wouldn't make power at all when I tried it.

 

[funwithfuel]

Make sure rubber is UV stable. Don't want your repair to go south right away.
Any banjo screws in the system? They like to trap debris like sand and grass

 

[thepumpguysc]

CHANGE the dam filters before you change the rubber lines.. geesh..
Sorry, long day out in the sun.. AND the wifes pizzin me off... AND asked "ME" to cook dinner.!!!
I do make a MEAN MEATLOAF tho..

 

[Bls repair]

We had a machine that would bog down or stall. Let it sit for a couple minutes and then be ok . Did it more when fuel was low . Found clear plastic wrapper that would float in tank ,when got close to pickup tube would get sucked up to it slowing or stopping fuel.

 

[ssrider]

The filters are changed. That was an old photo. Took a look in the tank and there doesn't look to be anything floating around which could block the fuel pickup.

Today it won't even stay running. Starts good, revs up, then back down and slowly dies. Since I got it, it's always done that where it revs up when first started. Sometimes it took a blip of the throttle to bring the RPMs back down.

I've cofirmed the lift pump is pumping fuel to the injection pump, and bled the system again. No change.

Possibly the fuel injection pump is toast?

Here's a short video of it today

 

[Delmer]

Before you touch the injection pump, put a tee in the supply line and use a pressure/vacuum gauge to see what fuel pressure the injection pump is seeing when it dies. This should be easy to diagnose, it happens right away.

Also, check the fuel return IF you have good fuel supply pressure as it dies.

 

[ssrider]

Ok I replaced all the rubber fuel lines tonight. Bled the system again. Fired right up no problem, seemed to be running good.... until it warmed up a bit, then back to the same problem.

I put a tee in before the injection pump with a pressure/vacuum gauge. The lift pump is supplying a steady 7-8 psi right through even when it dies.

I checked for return fuel and am getting steady return right up until it dies.

 

[Bls repair]

If it has an electric fuel shut off it could have bad electrical connection letting the shut off to partially or fully shut off fuel.

 

[ssrider]

Hi, just an update for everybody. Found and fixed the problem. It was the injection pump. I took it apart and the "flex seal" or whatever its called between the weight basket, was totally gone. It broke apart into pieces, and plugged up some fuel passages. I replaced it with a solid weight cage and fully cleaned and rebuilt the pump. It runs great now! better than ever actually, and idles perfect as well. Thanks for the advice. Hopefully this can save somebody some headaches in the future.