# ford 3910 CAV injection pump



## brad kopp (Jul 24, 2017)

i need help on a tractor injection pump ...i had some small leaks and removed pump to replace all light gaskets i could without diving into pump , before i removed it it was pumping fine .
so after installation just like it was it wouldnt start tractor . i bled all line and did everything i have done for past 20 years . when i opened the bleeder screw and turned it over to bleed it used to spray out 3 feet ...now it was just drizzling out ...
removed all fuel lines to make sure i was getting fuel all good . then a mechanic said it was hooked up wrong . that the fuel filter assembly was pushing fuel to 2 separate ports the pump end and the middle of the pump labeled #3 ...so he bypassed the fuel out in #1 and said that #3 was an over flow and shouldnt be hooked to the pump ...tractor started right up 

its been hooked this way for years and ran and all pics i see on web is like mine , i think there is something wrong or something small not working please help


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## BigT (Sep 15, 2014)

Howdy Brad, welcome aboard the tractor forum.

Wait for the pumpguy to comment. He is an expert on injection pumps. Below are my comments FWIW:

The hose connection pictured from #3 to#1 is correct, based upon my tractor's hookup.

There should be a steel tube from the inner connection of the filter (not in the picture) to the inlet to the pump. See attached parts diagram of the fuel system on your tractor. Line #24 runs from the filter to the pump inlet.

See attached diagram of your pump. Item #12 is the inlet of your pump. Is the metal tube from your filter hooked up to the pump? I think I see it up in the air just below the hose in your picture.


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## brad kopp (Jul 24, 2017)

you are correct it is there and i have the head off , when i connect that from the supply and disconnect the front one the tractor runs its when i connect that first connection it doesnt 
something is not opening or a valve is bad


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## BigT (Sep 15, 2014)

While you have the head off, check filter #7 on the pump diagram.


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## BigT (Sep 15, 2014)

I'm wondering if you have the seals in the filter installed wrong? See attached diagram.


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## brad kopp (Jul 24, 2017)

BigT said:


> While you have the head off, check filter #7 on the pump diagram.


do you have a pump diagram


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## BigT (Sep 15, 2014)

Pump diagram attached....See fuel screen/filter item #7.


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## BigT (Sep 15, 2014)

If the small CAV filter is plugged, go back to post #5. Make sure that your primary filter is installed correctly.

If the CAV filter is plugged, it means that dirt got past your primary fuel filter. Most likely due to filter bypass/incorrect installation.


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## thepumpguysc (Jan 25, 2015)

There "should be" arrows on the filter head.. in & out.??
2 is IN & 3 is OUT..
3 is a pressurizing valve on the pump.. if its been knocked out or worn out/ fallen out, that may be a problem..
I cant tell weather or not that's a new fuel filter but.. MAKE SURE the top oring is UP IN the filter head & NOT ON the filter..
IF it aint broke, don't fix it.. if it runs, run it..


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## thepumpguysc (Jan 25, 2015)

SORRY, I'm still in fuel injection mode..
2 is INTO the INLET of the injection pump..
3 is OUT FROM the inj. pump, back to the filter..


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## duke7595 (Jan 23, 2012)

thepumpguysc said:


> SORRY, I'm still in fuel injection mode..
> 2 is INTO the INLET of the injection pump..
> 3 is OUT FROM the inj. pump, back to the filter..


You did everything but go to his house and repair it for him, good job on your part. He didn't seem to appreciate all the leg work you put into this.


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