535 Ford Backhoe/Loader problem

coastbuster · Mar 30, 2020

Hi people.
I have the above mentioned machine for many years now. It's a 1975 unit. The machine will start and run great for about 5 minutes then will slowly start to lose power so it seems like it's running on only 1 cylinder. I have changed fuel filters,cleaned the fuel tank,and observed the return line pumping fuel back to the tank. I also cleaned the filter in the CAV injection pump. New fuel doesn't make any difference. I'm a decent self taught mechanic on my machines as I have a dozer,excavator,payloader and Massey ferg tractor which I fix and maintain when needed. This ones driving me bats. You might say it's a bad injector pump except that it runs great for the first five minutes so I am tending to rule that out. Anybody have any thoughts to help me out would be greatly appreciated. Thanks,Dan

Tinkerer · Mar 30, 2020

When it is running at it's absolute worse, slowly loosen the fuel tank filler cap and listen for a hissing sound. If the vent in the cap is plugged there will be a vacuum in the tank.

Delmer · Mar 30, 2020

When did the problem start? and how did it progress?

You could try a piece of clear tubing in the fuel return to see if there's bubbles, or if the flow drops when the engine starts dying.

Is this a mechanical pull shut off, or electrical shut off?

coastbuster · Mar 31, 2020

It's a mechanical shut off.

Tinkerer said:
When it is running at it's absolute worse, slowly loosen the fuel tank filler cap and listen for a hissing sound. If the vent in the cap is plugged there will be a vacuum in the tank.

I'll try that today if the rain ever stops in upstate NY.

thepumpguysc · Apr 1, 2020

The filter oring.?? has to go UP IN the filter head NOT ON the filter..
You end up sucking the filter dry & it shutting off.. let it sit & it slowly fills the filter & again, runs till the filter drains.. Its a vicious cycle.. lol
Whay about a supply pump.?? or is it gravity feed.?? Have u pull the line off at the inj. pump INLET & hold it over a 5 gal bucket & WATCHED the flow.. ya gotta watch it for any slow down for like 5 MINUTES.. fill that bucket 1/2 way.. your looking for any debris in the tank that might be covering the outlet pipe in the tank..
Go to a Ford NH website & see if u can find a breakdown of the fuel tank..
A LOT of'm had filter screens on the outlet tap.. could be clogged..
HOW was the filter inside the pump inlet.?? THAT right there, will tell u the conditions your working with..

Tinkerer · Apr 1, 2020

Have you cleaned or changed the screen ? #9 in the image.
It is part of the petcock assembly on the bottom of the fuel tank.

coastbuster · Apr 1, 2020

thepumpguysc said:
The filter oring.?? has to go UP IN the filter head NOT ON the filter..
You end up sucking the filter dry & it shutting off.. let it sit & it slowly fills the filter & again, runs till the filter drains.. Its a vicious cycle.. lol
Whay about a supply pump.?? or is it gravity feed.?? Have u pull the line off at the inj. pump INLET & hold it over a 5 gal bucket & WATCHED the flow.. ya gotta watch it for any slow down for like 5 MINUTES.. fill that bucket 1/2 way.. your looking for any debris in the tank that might be covering the outlet pipe in the tank..
Go to a Ford NH website & see if u can find a breakdown of the fuel tank..
A LOT of'm had filter screens on the outlet tap.. could be clogged..
HOW was the filter inside the pump inlet.?? THAT right there, will tell u the conditions your working with..

I think I have installed the filter ORING correctly but I will check it again. Hte screwing with the fuel. If not done correctly,priming the system again is a nightmare.I don't get why Ford didn't put a primer pump on the inj. pump. Any way,I could probably use the INJ. pump supply line into a clean can of diesel and bypass the filter. The only problem I see is that there are 3 filter lines,1 supply and 2 going to the Inj. pump. Which one feeds the pump? What is the other ,a bypass,return ? Here's a pic. Also it is a gravity feed. I have cleaned out the tank and its petcock filter. Also the Inj. pump filter. You may have a point about the O ring though. I notice that when it starts running lousy and dies,I wait 5 minutes and start it,It will run good for about 30 seconds and dies again.I wish HE Forums would install a voice chat option. So much easier. Dan

coastbuster · Apr 1, 2020

Tinkerer said:
Have you cleaned or changed the screen ? #9 in the image.
It is part of the petcock assembly on the bottom of the fuel tank.
View attachment 214252

I just cleaned it. Its in great shape now. Not the problem

Tinkerer · Apr 1, 2020

Good flow of fuel to the filter when it was removed ?
Still a good flow out of the filter and at the inj. pump ?

thepumpguysc · Apr 1, 2020

100 bucks says its the oring.. those napa filters are known for it..
U GOTTA physically put it UP IN the filter head & MAKE SURE it doesnt fall when your assembling the rest..

coastbuster · Apr 4, 2020

Would anyone have an electrical schematic for this machine. I want to get all of the gauges and warning lights working again while trying to figure out the power loss problem too.

tractormech · Apr 4, 2020

thepumpguysc said:
100 bucks says its the oring.. those napa filters are known for it..
U GOTTA physically put it UP IN the filter head & MAKE SURE it doesn't fall when your assembling the rest..

I can't say how many times I checked those filters that they changed and called and said it won't run. Pull the filter and the small oring is in the top of the filter and has the passages sealed shut.

Tenwheeler · Apr 5, 2020

I have pulled my hair out over those filters but they normally are not a problem. Man called me to look at Ford backhoe he dragged home for $700. It had the center of a previous filter stuck up in the the housing with the new filter on top of it. Still runs good.
Laughed under my breath at the guys working on a farm tracker that would not start. Very similar to yours. One of them turned the water hose on the pump for a few minutes. It fired right up and ran. Said " Yep bad pump ". It was fine after the pump was replaced. Best not to laugh. Sometimes you might learn something.

thepumpguysc · Apr 5, 2020

Just for everyones info.. u know the tid-bit that u put away for a rainy day..
When the water hose was ran on the pump.. & Im not saying to do that as a diagnostic tool by no means..
They shrunk the metals in the delicate Head & rotor, & it tightened up enough to pump fuel...
It was actually leaking internally & not pumping the fuel to the injectors..
MOST folks wouldnt do THAT.. they would simply pull the pump & let experienced eyes take a look..
& while were on the subject of water hoses & inj. pumps.. NEVER, NEVER spray a pump down while the engine is running.!! For the exact same reasons as above..
The cold water hits that pump & immediatly locks up the head & rotor..
U can put THAT INFORMATION to the FRONT of your brain.. EVERYBODY NEEDS to know THAT..

coastbuster · Apr 5, 2020

thepumpguysc said:
100 bucks says its the oring.. those napa filters are known for it..
U GOTTA physically put it UP IN the filter head & MAKE SURE it doesnt fall when your assembling the rest..

Hey Pump Guy, I disassembled the filter. There are 4 O rings. 1 for the bottom of the filter can,1 for the top of the filter can,1 tiny O ring that fits on the securing bolt and 1 on the top of the filter itself. I assume that one comes attached to the filter. How does the tiny O ring get installed? As far as I can see,it only rides as far as the top of the threads. Should I push that one all the way to the top of the bolt tube or let it sit on top of the threads, What is it's purpose? Her are some pics.Thanks Dan

thepumpguysc · Apr 5, 2020

The problem is starring u in the face.. the oring is ON THE FILTER!!
Not up in the housing
Remove that oring in #4 picture..
U see the slots under it.?? That’s were your fuel should be coming from.. & it’s blocked by the oring...
Get it NOW.?

coastbuster · Apr 5, 2020

thepumpguysc said:
The problem is starring u in the face.. the oring is ON THE FILTER!!
Not up in the housing
Remove that oring in #4 picture..
U see the slots under it.?? That’s were your fuel should be coming from.. & it’s blocked by the oring...
Get it NOW.?

Got it big time. Was looking at the filter trying to figure out how it filtered with no inlet side to it. Thought that O ring came that way on the filter right out of the box. Now I see that that O ring was blocking the inflow. What a stupid design. I will install it tomorrow the correct way and get back to you. Thanks Dan

thepumpguysc · Apr 5, 2020

I have to disagree.. if u bought the factory filter, it’s not like that filter design..
& just to drive it home.. u were told by SEVERAL people what the problem was..
I’m glad u finally understand..
Happy Tractoring..

coastbuster · Apr 6, 2020

There are 3 O rings with this filter. You guys kept mentioning the small O ring. Check picture #1. To me that is the small O ring being that the other 2 are 100 times larger. There was the confusion I was experiencing.What exactly does that small O ring do anyway?

coastbuster · Apr 6, 2020

coastbuster said:
There are 3 O rings with this filter. You guys kept mentioning the small O ring. Check picture #1. To me that is the small O ring being that the other 2 are 100 times larger. There was the confusion I was experiencing.What exactly does that small O ring do anyway?

I'm sure when I put this back together in a few minutes from now,this machine will run like a champ. Dan

535 Ford Backhoe/Loader problem

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