1955 Belvedere mechanical fuel pump still not working!
Drakeule
Posted 2021-04-07 7:31 PM (#610791)
Subject: 1955 Belvedere mechanical fuel pump still not working!


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Posts: 7

This is a new thread to my previous one; I rebuilt the 4280 pump and car started, but died soon afterwards. Hooked up electronic pump and started right up again.

Does my Elec. pump (it's most probably the APDTY one available on amazon) need to be bypassed for the mechanical one to do its job? (I haven't checked the PSI without the electronic hooked up.)
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58coupe
Posted 2021-04-08 11:22 AM (#610801 - in reply to #610791)
Subject: Re: 1955 Belvedere mechanical fuel pump still not working!



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The electric fuel pump has check valves in it as does the mechanical pump. The mech. pump should be able to pull fuel through it if it is in good condition. Since it is a new mech. pump, it could be the cam that operates it is worn. It is rare to find a cam so worn it will not operate the pump, I have only found this one time. You could install a bypass fuel line around the electric pump with one check valve.
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Drakeule
Posted 2021-04-08 1:03 PM (#610803 - in reply to #610801)
Subject: Re: 1955 Belvedere mechanical fuel pump still not working!


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Posts: 7

58coupe- thanks for the response:

Just bypassed the elec. pump, and get 0 PSI when cranking from mech. pump.

When you say the cam is worn, do you mean the actuating lever on the pump, or the engine internal cam?

If you mean the internal device, I too have had the latter above happen with one of my old Alfas; a high end repair shop friend said that when this happened with the old Ferraris, he just installed a elec. pump as the fix.

So, my previous owner (deceased) of the '55 may have known something I didn't...

Thoughts?
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56D500boy
Posted 2021-04-08 2:00 PM (#610810 - in reply to #610803)
Subject: Re: 1955 Belvedere mechanical fuel pump still not working!



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Drakeule - 2021-04-08 10:03 AM
When you say the cam is worn, do you mean the actuating lever on the pump, or the engine internal cam?


The fuel pump on these old V8s was driven by an eccentric cam mounted externally to the engine, behind the timing cover. (See photo below to see the fuel pump drive cam behind that big nut).

I think that you should probably remove the existing mechanical pump and arrange it somehow that you can man-handle the lever arm (move it up and down). You should hear a sucking pop each time you move the lever arm. If not, the diaphragm inside the pump might have a hole in it. That being the case you will need a new pump or a rebuild (there are kits out there if you are game for that).

https://innovationdiscoveries.space/diagnosing-and-replacing-a-mecha...



Edited by 56D500boy 2021-04-08 2:16 PM




(TimingChainOilTrough_1.jpg)



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Attachments TimingChainOilTrough_1.jpg (189KB - 133 downloads)
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ronbo97
Posted 2021-04-08 5:43 PM (#610812 - in reply to #610810)
Subject: Re: 1955 Belvedere mechanical fuel pump still not working!


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The correct part no. for your fuel pump is 1450709 or Carter M2348S. 55 Ply, 55-6 Dodge, 55-6 Chrysler. Get a used one from a parts car. Then get that rebuilt, or rebuild it yourself. I'm not a fan of aftermarket AC, Airtex, etc. And toss that electric pump in the trash.

I assume that you have a V8 in your Plymouth. Is that correct ?

Ron

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Drakeule
Posted 2021-04-08 5:51 PM (#610813 - in reply to #610810)
Subject: Re: 1955 Belvedere mechanical fuel pump still not working!


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Posts: 7

The pump seemed to spritz just fine on the bench. I felt vacuum on the "in" side. However, when installed ,I got zero PSI. Could that rocker arm on the pump be so worn that it can't be "excited" by the cam?

It appears that the cam and eccentric under the timing chain cover would not be the problem (?)

However, I did disturb the exit pipe on the gas tank (looks as if someone did a "quasi donkey" brazing repair in the past on it), and now it's leaking fuel. So I now have a bigger problem. If I can't seal it, expect a new thread discussing options for a new vs rebuilt fuel tank.....
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56D500boy
Posted 2021-04-08 6:16 PM (#610814 - in reply to #610813)
Subject: Re: 1955 Belvedere mechanical fuel pump still not working!



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You might have blockage of some sort in the fuel line from the tank to the mechanical fuel pump. I would use a hand-held MitiVac on the fuel line to the fuel pump at the pump and use the MitiVac to pull some fuel from the tank. No fuel or difficult flow = line blockage.

There has to be a reason. You just need to find it.

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samstrader
Posted 2021-04-09 2:47 AM (#610825 - in reply to #610791)
Subject: Re: 1955 Belvedere mechanical fuel pump still not working!


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I bought one of these Carter fuel pumps last year from Ebay and it works great. A lot better quality than my airtex 4280. Built different but it works great and it matches the one I took off the car that was put on sometime before 1970. the guy has 7 left and the price for a Carter NOS is pretty fair I think.

https://www.ebay.com/itm/NOS-Carter-M2348-Fuel-Pump-For-Chrysler-Ind...

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58coupe
Posted 2021-04-09 11:09 AM (#610832 - in reply to #610791)
Subject: Re: 1955 Belvedere mechanical fuel pump still not working!



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The engine that had a worn out cam lobe was a 6 cylinder chev. and of course the pump works directly on the camshaft, not on an eccentric like your engine. If there was some sort of blockage in your fuel line I would expect the electric pump to not be able to bring fuel to the engine either. It could be the engine was assembled without the eccentric.
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ronbo97
Posted 2021-04-09 7:13 PM (#610846 - in reply to #610832)
Subject: Re: 1955 Belvedere mechanical fuel pump still not working!


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The arm on your replacement fuel pump could be too short, or the incorrect size/shape to work correctly. That's why I encourage folks to find what originally came on the car and work with that.

Ron

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