# New holland 6635 fuel problem?



## valleyforage (Apr 28, 2015)

I have a new holland that has ran great until a week or so ago, it now acts like it is starving for fuel or surging at all rpm's when it's under a load or not. It will slowly die when driving down the road. I have drained the tank, blew out the fuel lines, replaced the filters and the fuel pump ( the old one was leaking and I thought that was the problem) Could there be a pin hole in one of the lines or could be worse? Im comfortable with most work but have never worked on injectors or internals of fuel systems. Oh and no smoke. I have attached a video of the surge, if it does not work and you want to see it send me your email and I'll send u a link. Thank u!


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## 8350HiTech (Jul 26, 2013)

Probably a long shot but I had that happen (on a different color tractor) and it turned out the new lift pump I installed came with the bolts just loose enough that it still allowed air to intrude. You also might want to try running a different fuel line and drawing fuel from a can to rule out something in your tank or pickup tube intermittently choking off the fuel.


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## mike10 (May 29, 2011)

Did you remove the fuel tank cap and blow back through the fuel lines into the tank? I believe there is also a vent from the fuel tank that runs up the back of the left fender. I do not mess with the tractors only what I have observed.


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## valleyforage (Apr 28, 2015)

ill check the pump out! And good idea for the line I'll also do that. Thank u.

Probably a long shot but I had that happen (on a different color tractor) and it turned out the new lift pump I installed came with the bolts just loose enough that it still allowed air to intrude. You also might want to try running a different fuel line and drawing fuel from a can to rule out something in your tank or pickup tube intermittently choking off the fuel.[/quote]


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## valleyforage (Apr 28, 2015)

I took the line off both sides ( tank and filter) and blew thru. I did not check the vent line but will blow that out too. Could I take the cap off and run to see if venting is the problem?

Did you remove the fuel tank cap and blow back through the fuel lines into the tank? I believe there is also a vent from the fuel tank that runs up the back of the left fender. I do not mess with the tractors only what I have observed.[/quote]


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## mike10 (May 29, 2011)

You can just take off the fuel cap. Did you check the new lift pump for suction and pressure at the ports when you move the lever. Not unusual for the check valves to come loose, but not usually on a new pump.


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## Tx Jim (Jun 30, 2014)

I suggest to check for good fuel flow from tank to inj. pump. Remove return line encircled in blue with engine running to see if engine continues to run or runs better.


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## Gearclash (Nov 25, 2010)

First make sure you have good fuel flow to the injector pump, then be sure there is no air in the the fuel. CIH legacy Maxxums were notorious for developing air leaks in the suction line from the lift pump to the fuel tank. You may have the same problem. Look for wetness on the fuel line somewhere.


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## slowzuki (Mar 8, 2011)

Just went through this on a Kubota - found 2 loose fuel line clamps, bad copper washer on a water separator plug and loose primer pump seal.


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## mlappin (Jun 25, 2009)

Had a land lord that had a 5XXX series IH tractor, it spent a LOT of time in the shop for a similar problem. I don't think they actually found this on purpose, but rather just started throwing money at it, but the fuel line from the tank would eventually get hot enough from engine/hydraulic/transmission heat that it would collapse and cut fuel off. Might run fine for an hour or less but once everything got good and warm it'd act up.

I prefer my older Olivers and Whites for this reason, tanks sat up from the engine, if you had fuel problem disconnect a line and see if the fuel has a good flow from gravity. I've fought similar problems on a few heavy trucks, anytime you suck fuel instead of pumping it from the tank to the engine problems can arise, a small leak under vacuum in a fuel system can be a b*tch to find.


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## rjmoses (Apr 4, 2010)

The fuel line inside the tank split on my NH TS135 and caused similar symptoms. Would run fine with a full tank. As the fuel level dropped in the tank, it would tend to want to die as air got in the line and then surge when the crack was covered and the line filled with fuel.

Had to drain and drop the tank to replace the pickup line.

Hope this helps.

Ralph


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## mlappin (Jun 25, 2009)

rjmoses said:


> The fuel line inside the tank split on my NH TS135 and caused similar symptoms. Would run fine with a full tank. As the fuel level dropped in the tank, it would tend to want to die as air got in the line and then surge when the crack was covered and the line filled with fuel.
> 
> Had to drain and drop the tank to replace the pickup line.
> 
> ...


Our Bobcat did the same thing, got steadily worse until even changing directions too fast on a full tank would cause it to sputter.


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## valleyforage (Apr 28, 2015)

Thanks for all the info, i took off the return line and the cap and it did appear to run better, after blowing out the lines again it came back. So I got new fuel line and dropped the tank for closer inspection. With that being said one of my dads mechanic's suggested that the fuel shut off solenoid could be acting up, could that be a possibility or would it be working fully or not at all? I did not put a meter on it yet as the tank and lines are laying on the floor and can't run it.


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## BisonMan (Apr 27, 2020)

valleyforage said:


> Thanks for all the info, i took off the return line and the cap and it did appear to run better, after blowing out the lines again it came back. So I got new fuel line and dropped the tank for closer inspection. With that being said one of my dads mechanic's suggested that the fuel shut off solenoid could be acting up, could that be a possibility or would it be working fully or not at all? I did not put a meter on it yet as the tank and lines are laying on the floor and can't run it.


Hey, I'm looking into this tractor as a utility tractor that can also handle its weight out in the field. How has your experience been with the NH 6635?

I just saw one online with a cab/loader at a reasonable price.


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