Fuel pump eccentric

Shulaps · Jan 12, 2018

I am trying to clean up a fuel suppy issue and wonder if anyone has ran into this issue.

I have what I think is a 71 Block. Has the bigger valves etc. BTW is has a different firing order than most 302’s.

If I prime the pump it will run fine. But if it gets a gulp of air it won’t pull gas. Switching tanks etc.

I have tried running a new line into a tank on floor and it won’t pull unless primed so Not tank issue.

I think it is a bad eccentric or possibly I have the wrong fuel pump? I have a Holley on it that is new as I thought the old one was done. It does work if primed but won’t pull from Dry similar to old pump.

Do early 302’s require different pumps?

Any thoughts?

DirtDonk · Jan 13, 2018

Shulaps said:
I have what I think is a 71 Block. Has the bigger valves etc.

So it's swapped in from a different vehicle maybe? Any idea what it's from?
You mean the heads have larger valves? Larger than what? I'm not sure that any Bronco with a 302 got larger valve heads than any other. What size are yours? Maybe they've been worked on and warmed over?

Shulaps said:
BTW is has a different firing order than most 302’s.

Then the cam has been changed. No other reason would have given you the other firing order.
All early 302's had the same firing order, which changed in the early eighties if I remember, to the 351 firing order.

Shulaps said:
If I prime the pump it will run fine. But if it gets a gulp of air it won’t pull gas. Switching tanks etc.

Hmm, never run into that before. Sure, they suck (not literally unfortunately) when first trying to prime them, but once that's done the little bit they get during a switch-over does not usually cause them to lose their prime.
You sure you don't have any leaks anywhere else? Just a small one in an old hose for instance?

Shulaps said:
I have tried running a new line into a tank on floor and it won’t pull unless primed so Not tank issue.

Is all the line new? Both stock tanks? Maybe the valve is getting old and leaking. Some discussions about that lately.

Shulaps said:
I think it is a bad eccentric or possibly I have the wrong fuel pump?

Never heard of an eccentric wearing out, but it's probably not impossible. But it would have had to take a lot of abuse in the lack of oil changes department I would think.
It's maybe possible that you have the wrong pump, but given that most Fords that I've seen either used the same pump style (for the Windsor family) or a completely different one that would not even fit a 302, I'm not sure.
Hopefully someone knows more about the different pumps than I do though.

Shulaps said:
I have a Holley on it that is new as I thought the old one was done. It does work if primed but won’t pull from Dry similar to old pump.

Holley pump? Guessing it would be the correct one for the engine then, but I wonder if Holley is the same as all the other crap we get these days from the parts stores, and maybe you just have a new bad pump.
The old one acted the same it sounds like?

Shulaps said:
Do early 302’s require different pumps?

I know of the vacuum type (for the windshield wipers) and the non-vacuum type that came later, but not sure how many different pumps were used.

Good luck.

Paul

bmc69 · Jan 13, 2018

Sounds to me like a small leak somewhere between the pump and tank. I had that happen to my '89 F-250 recently..drove me nuts finding it because the leak would let air in but never let any fuel out.

In all the years I've been building Ford engines (40+), I've never seen an eccentric completely wear off/out.

And like Paul, I'm curious what you meant by "has the bigger valves"?

Shulaps · Jan 13, 2018

It is an early Block and has the bigger spark plugs so I believe those stock heads also had bigger Valves?

It has different firing order than my 74. Figured it out when i was googling, so very early 302’s did have different order.

Anyways, I have tried a completely different hose and fuel out of a canister so to isolate the problem, tanks completely bypassed and still have issue?

I think it was rebuilt prior to me getting the engine as it has great compression and runs like a top when getting fuel.

I an thinking that since the pump is likely not the issue as I have tried 2 different brands I am down to the eccentric? Sounds rare but possibly not put in right after rebuild?

Head scratcher for sure.

langester · Jan 13, 2018

Can you see the eccentric in the hole? I have never had one go bad but I inherited a motor once that the cam bolt backed out and the eccentric was not working.

bmc69 · Jan 13, 2018

Shulaps said:
It is an early Block and has the bigger spark plugs so I believe those stock heads also had bigger Valves?

It has different firing order than my 74. Figured it out when i was googling, so very early 302’s did have different order.

Nope and nope. Valves same size from 1963 through 1980 (289 and 302) and the firing order was too. Not until the "HO" 5.0 came out did the firing order for those change to be the same as 351w.

For a couple years ('69-'71) the 351w heads had slightly larger intake and exhaust valves than the 289/302 heads and the rest of the 351w heads that came after.

bmc69 · Jan 13, 2018

langester said:
Can you see the eccentric in the hole? I have never had one go bad but I inherited a motor once that the cam bolt backed out and the eccentric was not working.

There's ^ another possibility..

Swerve · Jan 13, 2018

langester said:
Can you see the eccentric in the hole? I have never had one go bad but I inherited a motor once that the cam bolt backed out and the eccentric was not working.

This happened to me as well...

amax · Jan 13, 2018

I think I have this exact problem on my 71 right now. I’ve spent the past few hours outside trying to figure out what my fuel supply issue is. I’ve cone to the conclusion is has got to be whatever is driving the pump is not doing it’s job. Only way to fix it is to pull the timing cover off correct?

langester · Jan 13, 2018

Unfortunately it is.

amax · Jan 13, 2018

I figured. Thanks for the input

Shulaps · Jan 13, 2018

Funny, I believe my Block is a 71 also? I plan on tearing into it tomorrow.

amax · Jan 13, 2018

I’ll be right there with ya. Guess the front of my engine will be coming apart in the morning.

B RON CO · Jan 14, 2018

Hi, What I read does not explain how the pump could sometimes work and sometimes not work. Before removing the timing cover I would poke a screwdriver in the opening and see if the eccentric is loose or solid. You could even use the fuel pump arm to jiggle the eccentric. Maybe get a cheap inspection scope, and a balancer puller if you don't have one. In your case I would be so tempted to try a new pump before pulling the front of the motor. Good luck

m_m70 · Jan 14, 2018

B RON CO said:
In your case I would be so tempted to try a new pump before pulling the front of the motor. Good luck

This ^^^.

oldiron · Jan 14, 2018

Are you 100% certain you don't have a 351? Firing order.
Greg

broncnaz · Jan 14, 2018

could be possible that the dowel pin for the eccentric has sheared off possible due to cam gear bolt loosening. which is allowing the eccentric to kinda spin free and not operate the fuel pump correctly. Definetly a good idea to pull that timing cover kinda sucks but its better than having a the cam gear come off at a bad time.

Shulaps · Jan 17, 2018

Pulled my pump out and ran it by hand and it pulls gas no problem. Similar issue as with the last pump. Debating just going electric but it would be interesting to figure out the issue. AMAX did you ever rip into yours?

DirtDonk · Jan 18, 2018

Yeah, it would be very good to find out why.
Especially important if that "why" is that the cam bolt is loose. Even with the cover to keep it inside the engine, it would likely not be a good thing to have it all bouncing around in there!
The good news is that if the timing gear started bouncing around, your engine wouldn't run long after that. Less physical damage that way...

%)

If it was a later engine and the fuel pump had never worked, I'd be tempted to say that someone retrofitted the older front cover and forgot to install an eccentric. But with intermittent pumping and the older engine, that seems unlikely.
Best to keep up the detective work.

Paul

Shulaps · Jan 19, 2018

Well pulled it apart and the eccentric looks fine? Has the 2 piece style. Not sure why the pump would not go full stroke and pump fuel properly? Are the Holley pumps adjustable where the arm starts to engage the pump? Any other thoughts? Hmmm, oh well. Guess I get to paint up the oil pan nice now!

Fuel pump eccentric

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