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Fuel pump lever arms and what they mean for flow.
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56D500boy
Posted 2019-06-17 6:34 PM (#583597)
Subject: Fuel pump lever arms and what they mean for flow.



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I had an Audi parts garage sale and purge on the weekend to free up some shelf space for my 56 Dodge parts. I've spent most of the morning and the afternoon out in the garage sorting through the parts and organizing them.

In doing so, I found my fuel pump (FP) box that contained the FP I took off the car when I got it in Sept. 2016 and a new in box Airtex 4280 FP. They are pretty much identical including the length of the lever arm. For some reason, I am running a new old stock 4280 FP that has a shorter lever arm, I guess because I bought it from a knowledgeable Chrysler 300 owner/tuner. Based on this photo that I annotated before (for a fuel pump thread), I am wondering if the shorter arm NOS 4280 isn't providing enough fuel at higher speeds (the car seems to "hit the wall" at 70-75 indicated mph). Hmm....

Previous thread: http://www.forwardlook.net/forums/forums/thread-view.asp?tid=48369&...

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ronbo97
Posted 2019-06-17 8:59 PM (#583603 - in reply to #583597)
Subject: RE: Fuel pump lever arms and what they mean for flow.


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56D500boy - 2019-06-17 6:34 PM . I am wondering if the shorter arm NOS 4280 isn't providing enough fuel at higher speeds (the car seems to "hit the wall" at 70-75 indicated mph).

I had a similar experience with my 58 Plymouth. Around the same speeds, it seemed to be holding back a bit. I had my distributor rebuilt by my friend, who has an old tyme distributor machine. He found that the shaft was wobbly and had a few other problems. He flawlessly rebuilt it and demonstrated the improvement at simulated high speeds, on the machine. Now the Plymouth accelerates nicely past 70. I had it up to about 85 before letting off the gas. The car is very happy.

Ron

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wayfarer
Posted 2019-06-20 12:24 PM (#583777 - in reply to #583597)
Subject: Re: Fuel pump lever arms and what they mean for flow.



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The overall length of the arm has nothing to do with pump operation. The pump is mounted in a fixed location and operated by an eccentric also in a fixed location.
Now, the shape of the arm is a different story and can/will affect operation if it sits too low in relation to the eccentric.
Place one of your pumps on the edge of your workbench and draw a line around the arm, then sit the next one on the same spot and compare arms.
Use the mounting bolt hole to note pump location. Also, if they have been used, note the location of the wear patch from the eccentric.
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normsclassicradio
Posted 2019-06-20 5:01 PM (#583801 - in reply to #583597)
Subject: Re: Fuel pump lever arms and what they mean for flow.



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Notice in the photo the NOS one. The arm is higher in relation to the mounting holes. More stroke?
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56D500boy
Posted 2020-04-11 2:13 AM (#596668 - in reply to #583597)
Subject: RE: Fuel pump lever arms and what they mean for flow.



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Old thread I know (sorry) *BUT* earlier this week it was suggested to me that my NOS fuel pump (the second from the left in the photo below) might NOT be putting out enough flow/pressure. So today, while in the garage, I dug out the box with the fuel pumps in it and checked out the original OE pump (the one on the left) and the new AirTex 4280 (still in the box) on the right side of the photo below. The lever on the original OE pump could be moved easily and a significant distance per stroke. However, I couldn't much if anything is regards to pumpy suck/blow noise.

In contrast, with the new Airtex 4280, I could barely move the lever about 1/8" *BUT* I could hear a strong pumpy such/blow noise.

I am concerned that something is wrong with the Airtex pump. It felt like the lever was jammed internally and that if I installed it on the engine, there would be bad things happen to either it (the pump) or the "eccentric" on the crank noise. Something would have to give.

Or it's fine and I wasn't trying hard enough (and the internal diaphragm spring is pretty strong (??))



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StillOutThere
Posted 2020-04-11 10:59 AM (#596672 - in reply to #583597)
Subject: Re: Fuel pump lever arms and what they mean for flow.



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To my knowledge no factory OEM fuel pump EVER has a laminated arm. Arms are always either a solid casting or a one-piece stamping. Factories did not install, nor offer as replacement parts laminated arm pumps because they caused higher rates of wear to the driving part, whether that be the camshaft or an eccentric elsewhere in the motor like in the timing cover. An old factory trained, respected mechanic went ballistic on me multiple times regarding use of aftermarket pumps with laminated arms.

I know today it is almost impossible to find a solid arm pump. But if you have one, rebuild that before using any laminated arm pump.
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wizard
Posted 2020-04-11 12:24 PM (#596677 - in reply to #583597)
Subject: Re: Fuel pump lever arms and what they mean for flow.



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The diaphragm spring is very hard to depress if the pump is not mounted in a wise. Also, if there is a rubber/plastic plug, or something that blocks the intake, it's next to impossible to move the arm - the pump will feel "seized"
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56D500boy
Posted 2020-04-11 12:28 PM (#596678 - in reply to #596672)
Subject: Re: Fuel pump lever arms and what they mean for flow.



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Thanks for your thoughts on the lever arm Wayne. I guess (and I am not surprised) that the "OE" pump that I removed from the engine was already an after market pump when I got the car (the odometer had 119,000 miles on it). Furthermore, the "NOS" pump that I replaced it with must also have been aftermarket, not factory.

So two questions:

1. Where would one find a NOS pump (or a rebuildable pump) with a solid lever arm?

2. My original question: Is there a reason why I can only barely move the lever arm on the new Airtex 4280? Am I just not trying hard enough or is there something wrong with it? (I was keeping it as a spare)

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Mopar1
Posted 2020-04-11 2:35 PM (#596680 - in reply to #596678)
Subject: Re: Fuel pump lever arms and what they mean for flow.



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There's been F/P problems for @ least a decade with the Hemis. I got the HH adaptor for the LA pump.
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56D500boy
Posted 2020-04-11 3:17 PM (#596682 - in reply to #596680)
Subject: Re: Fuel pump lever arms and what they mean for flow.



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Mopar1 - 2020-04-11 11:35 AM
There's been F/P problems for @ least a decade with the Hemis. I got the HH adaptor for the LA pump.


I see now what Wayne meant by stamped lever arm:



And I see what Mopar1 is suggesting (from Hot (hemi) Heads):



All that said, I forgot that the "NOS" fuel pump that I am using has "cover" on the tip of the laminated lever arm, making it very similar in action to the stamped lever arm



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samstrader
Posted 2020-05-01 4:14 PM (#597603 - in reply to #596682)
Subject: Re: Fuel pump lever arms and what they mean for flow.


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I have a 1955 Plymouth 259 V8 and looked into the Hot Heads adapter so I could use a LA Pump. The Hot Heads adapter and LA pump will not work on the early blocks that have the one point motor mount set up in front. The water pump housing is too close to the top of the fuel pump. I made a 1/8 inch adapter and was able to get a LA pump mounted and tried it out. The pump worked but I pulled the pump back out to see where the eccentric was riding on the lever arm and it was riding right at the top of the bend on the eccentric arm and it was wearing badly. It is impossible to put a thicker adapter (thicker than 1/8 inch) to get the lever arm farther out on the eccentric.

Bottom line is that it is not possible to make a LA pump work on a 1954-1955 Plymouth / Dodge 241/259 block.

Thanks,

Sam
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samstrader
Posted 2020-05-01 4:15 PM (#597604 - in reply to #583597)
Subject: Re: Fuel pump lever arms and what they mean for flow.


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A very trusted adviser told me the only way to go on fuel pumps for these cars is to get an electric pump and mount it near the gas tank. Mechanical pumps for these cars are a design issue.
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