7520 Fuel Problems
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Thread: 7520 Fuel Problems

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    7520 Fuel Problems

    I've recently acquired a late s/n 7520, when I first went to look at the tractor the previous owner told me that occasionally when the tractor sits for more than a week the fuel lines drain back and you have to crack the line on the injector pump to prime it before starting the tractor. Not a huge deal but I'd like to try to fix the problem. Looking at diagrams the earlier s/n tractors had an inline check valve installed between the tank and the filters. However the later s/n tractors do not have the check valve and have a different model of transfer pump. Now it'd just be my guess that the newer style pump must have an internal check valve that has failed on mine and the last owner didn't want to spend the $ to replace the pump. I'd think a guy could simply get the old inline check valve and put it in somewhere but i'm also wondering why the previous owner didn't do that. Does anyone here know why that would be a bad idea or any other insights to this issue? Is it possible that the old check is too restrictive for the newer pump? Thanks.
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    1010's Avatar
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    The type I'm familiar with has a canister filter with a twist on collar that holds the canister in place. Seems like there is a smaller rubber O-ring (like a garden hose type) that goes up on the tube that inserts down inside the canister. The traditional bleeder is above the collar so I don't get why you'd need to bleed off at the pump?.. I mean the filters should stay full of fuel.
    Does the tractor run for a bit and then run out of fuel?
    Does you're tractor have the elec primer pump?

    Before I did anything major I get the correct filters and hardware and install them. and see what happens after a few days.

    The 7520 we have had a starving problem under a load when it got hot. I believe it was a strainer or a clogged elbow that was the culprit. But when ever there was a fuel pressure problem you would get a light on the dash and you'd start to feel the machine slowing.

    I'll do some looking tomorrow!

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    Quote Originally Posted by Birchcraft View Post
    I've recently acquired a late s/n 7520, when I first went to look at the tractor the previous owner told me that occasionally when the tractor sits for more than a week the fuel lines drain back and you have to crack the line on the injector pump to prime it before starting the tractor. Not a huge deal but I'd like to try to fix the problem. Looking at diagrams the earlier s/n tractors had an inline check valve installed between the tank and the filters. However the later s/n tractors do not have the check valve and have a different model of transfer pump. Now it'd just be my guess that the newer style pump must have an internal check valve that has failed on mine and the last owner didn't want to spend the $ to replace the pump. I'd think a guy could simply get the old inline check valve and put it in somewhere but i'm also wondering why the previous owner didn't do that. Does anyone here know why that would be a bad idea or any other insights to this issue? Is it possible that the old check is too restrictive for the newer pump? Thanks.
    if its original, the transfer pump is close to the front of the block, the discharge side has the check valve, then up to the filters. It could have been relocated ahead of the transfer pump, but either way, i like it between the filters and the transfer pump. I have seen the flare fitting crack upstream of the check, which allows fuel to bleed off, if thats the issue look at the top of the filter and see if it is bubbling, that means one of your lines is cracked and sucking air, which will allow the filter to bleed down and wont run till you get the air out and to the pump.
    BigJim55 and em14 like this.

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    Had similar issue with my 6400. Replaced fuel lines and check valve and firs right up now. JD oem fuel lines are junk and won’t last long.

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    Definitely start by replacing all rubber fuel lines from tank to filters, pump and fuel cooler. Use the best quality 5/16" fuel hose you can find so you don't need to do it every 3-4 years. That alone usually prevents fuel drain back on the later system with 2 filters. Your primary filter should have a glass bowl on it. Many times I have found that the oring that seals the bowl to the filter is missing. It sticks to the bottom of the fuel filter when swapping it to the new filter and gets lost. That can cause fuel drain back as well. If you still have problems after that, then install a AL117189 check valve in the hose between primary filter and electric transfer pump. It won't hurt a thing but usually not needed if the system is tight. The fuel hoses get dry rotted and allows fuel to drain back due to air leaks.
    BigJim55 likes this.

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