Mechanical Fuel Pump Issues with a Comp Cam Install (4.9L) - Ford Truck Enthusiasts Forums



Mechanical Fuel Pump Issues with a Comp Cam Install (4.9L)

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Old 01-20-2018, 01:24 PM
pyromunky pyromunky is offline
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Mechanical Fuel Pump Issues with a Comp Cam Install (4.9L)

Installed a new comp cam high energy kit (K66-236-4) as part of a 300 I6 rebuild for my '80 F100.

Went to install the stock fuel pump and and the cam isn't producing enough lift on the pump's rocker arm to move fuel.

I called comp cam's tech support and they said I should install a pump with a slightly longer arm to make up for the cam's shallower eccentric. Stock arm is ~2 3/8" long. They suggested I try one 2 1/2".

I'm having a hard time finding a replacement pump, most part store's descriptions don't make a point to specify the arm length. Has anyone come across this before? Hoping someone out there may have some insights into what I should be looking for.

Appreciate any help in advance!
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Old 01-21-2018, 10:37 AM
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BaronVonAutomatc BaronVonAutomatc is offline
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That's a new one. I've got the Comp 268 cam and the pump works fine. Don't remember which brand pump, but I tend to order from Rock Auto. I don't think there's a lot of variation on 300 fuel pumps, though. Possibly bend the pump arm a bit?
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Old 01-21-2018, 11:48 AM
Harte3 Harte3 is offline
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Nary a problem with my Comp 260H cam and fuel pump...
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Old 01-22-2018, 03:35 PM
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Would 1/8" matter?

Quote:
Originally Posted by pyromunky View Post
Installed a new comp cam high energy kit (K66-236-4) as part of a 300 I6 rebuild for my '80 F100.

Went to install the stock fuel pump and and the cam isn't producing enough lift on the pump's rocker arm to move fuel.

I called comp cam's tech support and they said I should install a pump with a slightly longer arm to make up for the cam's shallower eccentric. Stock arm is ~2 3/8" long. They suggested I try one 2 1/2".

I'm having a hard time finding a replacement pump, most part store's descriptions don't make a point to specify the arm length. Has anyone come across this before? Hoping someone out there may have some insights into what I should be looking for.

Appreciate any help in advance!
I am sure that CompCam's tech knows what he is talking about, "but", 1/8" is a very small amount of arm. My build was done by a shop that has built several successful for the Salt Flats. He used a Chevy pump in the tank, not the OEM Ford pump. However, the build was with injectors, so don't know if that would be of any help on your build. Just an idea. Good luck with your build, the big-sixes are gems when they're all done.
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Old 01-22-2018, 05:44 PM
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The Frenchtown Flyer The Frenchtown Flyer is offline
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Are you sure you are installing the pump correctly. I seem to remember that somebody installed the pump with the lever on top of the lobe instead of under the lobe.
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Old 01-22-2018, 11:58 PM
fordman75 fordman75 is offline
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I second what FTF mentioned. I've seen multiple people install the fuel pump the wrong way.
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Old 01-23-2018, 07:13 PM
pyromunky pyromunky is offline
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Appreciate all the advice so far.

Here's the pump I'm trying to install.

It was installed on the original block with the fuel connections up and the arm riding on top of the cam. It started and idled before the rebuild. But wouldn't surprise me is it was installed wrong originally.

Turning the pump crossed my mind. The two manuals I own show it with the arm below, but it's hard to tell if they referencing a 300 or 302.
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Old 01-23-2018, 08:29 PM
fordman75 fordman75 is offline
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That's your problem. It goes below the cam lobe/eccentric not above it.
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Old 01-23-2018, 09:07 PM
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The pump arm may offer stiff resistance depending on how the cam lobe is oriented. It may take two hands to compress it while starting the attachment bolts.
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Old 01-26-2018, 12:14 PM
pyromunky pyromunky is offline
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Quote:
Originally Posted by The Frenchtown Flyer View Post
The pump arm may offer stiff resistance depending on how the cam lobe is oriented. It may take two hands to compress it while starting the attachment bolts.
No doubt - it's putting up a hell of a fight. Having a hell of a time just getting it past the engine mount.
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Old 01-26-2018, 01:00 PM
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It looks like there's two different types of mechanical fuel pumps.

On mine, I'm 99.9% certain that the arm went on TOP of the cam lobe. You can tell which side it's supposed to go on by the smooth side of the arm.

(Mine was this style: https://www.summitracing.com/parts/a...UaAnM5EALw_wcB)

I rested the arm on the top of the cam lobe and then pressed down to move the arm and get it into place. Of course, if the cam lobe is in the position to activate the pump, it's going to be harder since you'll have to move it further. Then get the bolts in.

Either way, even on my engine with a big 0.504" lift cam, fully ported head, 4bbl, etc. etc. etc. the stock fuel pump has no issues keeping up, even at 5000 RPMs WOT.
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