eccentric lobe question

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Aug 7, 2016 | 11:23 AM

betheldb57

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eccentric lobe question

I am trying to get my 1974 camper special running.

Long story shorter:

It has the 390, I rebuilt the carb, but it wasnt getting fuel so I assumed the pump was bad. Before I bought the truck, it has sat for about 10 years and I knew the tank was rusted from visual inspection. So I got a new tank and new pump replaced everything but still wasnt getting fuel. I disconnected the pump from the tank and instead ran a line down to a gas can about two feet away, cranked it over for ~ 20 seconds several times - still nothing. So Finally I disconnected the line from the output side of the pump and cranked it over - not a drop.

So I assumed either the pump was bad or it wasnt getting actuated.

Next I took the pump off and manually actuated the pump arm and everything seemed fine. So I am starting to think it must be the eccentric lobe. I reached in and found I could spin the eccentric with just my finger: I feel dumb asking but I should not be able to do this correct?

I just want to know if it is safe to assume that the eccentric is bad before I tear everything apart to replace that. Does any one have any insight here?

Thanks in advance for your help.

Aug 7, 2016 | 11:30 AM

KsHighboy

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On a 390 the eccentric is held by the timing chain bolt. Also, the cam has a pin that sticks out and the eccentric has another hole that this pin slides onto to keep the eccentric from spinning. I'm betting your gonna need to pull the timing cover and see what's happening.

Aug 7, 2016 | 11:32 AM

mikeo0o0o0

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From: Stanley, VA

Quote:

Originally Posted by betheldb57

I reached in and found I could spin the eccentric with just my finger: I feel dumb asking but I should not be able to do this correct?
I just want to know if it is safe to assume that the eccentric is bad before I tear everything apart to replace that.

The answer is "maybe".
There are two types of fuel pump eccentrics on Fords. There is the one piece eccentric that you should not be able to spin. The second type is a two piece eccentric where the inner eccentric spins and it has a sleeve that spins freely on the eccentric itself but still has the orbital action that will allow the pump's arm to stroke.
The most common one is the two piece unit. The reason Ford went with this design is now, there's not the rubbing friction between the eccentric and the pump arm, the outer shell is fairly stationary while the eccentric spins within it. With the one piece design the eccentric is constantly rubbing the arm as it spins.

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Aug 7, 2016 | 08:33 PM

dlburch

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From: Kansas

not sure on the past history of the truck, has it ever ran since you bought it? are you able to watch the eccentric to make sure its moving while someone cranks it (or confirm the rotor under the distributor cap is turning?