Mechanical Fuel Pump Repair Questions

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cory
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Re: Mechanical Fuel Pump Repair Questions

Postby cory » Mon Feb 01, 2016 1:35 pm

If you have to repair the pickup tube I used a heat gun to soften the plastic screen on the end of the tube. It made it much easier to remove and install.
Cory

250GT
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Re: Mechanical Fuel Pump Repair Questions

Postby 250GT » Mon Feb 01, 2016 5:21 pm

cory wrote:If you have to repair the pickup tube I used a heat gun to soften the plastic screen on the end of the tube. It made it much easier to remove and install.
Cory


Only for info.
perforated metal on all pre 1960 cars without plastic insert made out of copper.
see below.
soldered like the whole metal fuel tanks
ciao
C.
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michaelbalk330
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Re: Mechanical Fuel Pump Repair Questions

Postby michaelbalk330 » Mon Feb 01, 2016 11:32 pm

Thanks Tom and Kerry-
gas must have really sucked in 1967.
Screen filter on the intake tube.
then a fuel filter before the Electric pump.
then another set of screen filters in the pump inlet,
and then the paper filter in the regulator.
LOL -Do new cars even have fuel filters anymore?
M

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John Vardanian
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Re: Mechanical Fuel Pump Repair Questions

Postby John Vardanian » Wed Feb 15, 2017 5:07 pm

Is there a general thickness for the phenolic plate for the block mounted pumps? What general thickness should I start with? Thanks.

john
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michaelbalk330
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Re: Mechanical Fuel Pump Repair Questions

Postby michaelbalk330 » Wed Feb 15, 2017 6:14 pm

mine was about 8-9mm thick ( 330GT)
michael

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John Vardanian
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Re: Mechanical Fuel Pump Repair Questions

Postby John Vardanian » Fri Feb 17, 2017 2:17 am

Thanks. Mine measures about 4.5mm. That might explain why the flat levers were bent.

john
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michaelbalk330
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Re: Mechanical Fuel Pump Repair Questions

Postby michaelbalk330 » Fri Feb 17, 2017 6:57 am

using calipers and some math, I played around with the geometry before I started shaving the spacer. So as to avoid making it too thin and damaging the pump. I actually shot video and turned engine over as I measured the in and out movement of the push rod. and then looked at pump lever to flange distance and did some calculations.....Ultimately, I decided that no matter what, my mechanical pump was never going to pump enough to supply fuel under acceleration. It used to do nothing, so I run an electric full time.
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After I rebuilt the pump and worked on the spacer, I got it to work but not well enough to use full time. So I still run the electric and keep a spare.

If the mechanical pumps were cheap enough and in good supply, I fell pretty confident we could destroy a few and ultimately redesign a few parts and make it work better. For example..My 190SL pump is so simple and works so well. But there just isn't enough movement of the diaphragm designed in the Ferrari pump. from a drivability standpoint my electric works better and I still use it.

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John Vardanian
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Re: Mechanical Fuel Pump Repair Questions

Postby John Vardanian » Fri Feb 17, 2017 4:49 pm

Michael, thanks for those pictures. Do your tabs measure 2mm in thickness?

So, at 4.5mm, mine has to be set at the verge of being right, because there was no starvation with the electric pump off and the glass bowl never had any airhead even at idle speed. If you have an airhead you are a ways from having it dialed in--remember the fuel intake is at the top of the bowl and if you have air there instead of liquid then you are effectively starving the carbs. Judging from the bent tabs, I think I'll reduce the stroke with paper gaskets.

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John Vardanian
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Re: Mechanical Fuel Pump Repair Questions

Postby John Vardanian » Fri Feb 17, 2017 6:35 pm

A question for those who have made their own flat levers from mild, low-carbon steel... have you hardened them before installation? Would appreciate any experiences shared. Thanks.

john
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michaelbalk330
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Re: Mechanical Fuel Pump Repair Questions

Postby michaelbalk330 » Sat Feb 18, 2017 7:41 am

John,
2mm sounds about right... but I dont have it apart right now.
why not hook up a fuel pressure gauge and see whats being delivered to your regulator from the pump.... that way you can objectively measure any changes you make?
wont you decrease the pumping volume if you add paper gaskets and thicken the spacer distance?
the real issue is first the physics of the lever isn't set up ideally and second, with wear, there is some loss of lever function when the tabs transfer some of their "energy" laterally ( i.e. in slop) instead of to the diaphragm.

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tyang
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Re: Mechanical Fuel Pump Repair Questions

Postby tyang » Sat Feb 18, 2017 8:26 am

Hi Michael,

Are you getting fuel starvation or vapor lock? Don't confuse the two.

I'd have to look at the eccentric the next time I'm assembling an engine and see how many times the fuel pump draws a stroke per engine revolution, and despite the bad design, there are thousands of strokes happening a minute. I have a test rig to mount a mechanical pump on the bench to test that it can draw fuel out of a gas can, and there's quite a bit of fuel moved after dozens of strokes. I have not measured the amount of fuel, but it would seem enough to fill the fuel bowls. at 14 miles per gallon of consumption, how much fuel do you need in the fuel bowls?

Tom
'63 330 America #5053

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michaelbalk330
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Re: Mechanical Fuel Pump Repair Questions

Postby michaelbalk330 » Sat Feb 18, 2017 8:30 am

Tom-
definitely fuel starvation--- i can't get the pump to deliver enough fuel to keep the glass bowl filled.
can actually watch the fuel disappear from bowl as you rev the engine. ( supply<demand)
I R&R the pump so many times i got sick of it and kept the electric.
Maybe Ill try again and if not, Ill send it to you!
I probably need to shave the spacer more.

Thanks Michael

DWR46
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Re: Mechanical Fuel Pump Repair Questions

Postby DWR46 » Sat Feb 18, 2017 10:50 am

I have rarely seen a Ferrari V-12 with the glass fuel filter bowl that runs with the bowl full all the time, yet the engines run perfectly well on the mechanical pump only. I would not let the lack of a "full" bowl convince you that you have a mechanical pump problem. You can fairly easily measure the pushrod stroke on the engine and also determine the maximum stroke within the pump before the linkage "bottoms out". With these numbers, and a fuel pressure gauge, you should be able to "dial in" the pump pressure by adjusting the thickness of the phenolic block. I have also found that some of the valves in the latest pump rebuild kits are defective. Do not throw away the old original valves! You may need them.

Don Micheletti
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Re: Mechanical Fuel Pump Repair Questions

Postby Don Micheletti » Sat Feb 18, 2017 12:18 pm

The fuel pump on my GTE drove me nuts after a "rebuild". I added a pressure gage and it led me to a check valve issue. Going back to the original checks solved my problems

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michaelbalk330
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Re: Mechanical Fuel Pump Repair Questions

Postby michaelbalk330 » Sat Feb 18, 2017 2:54 pm

Tom, Dyke, John and menlodon, I suspect you are all correct-
I always felt my old checkvalves, and the diaphragm were OK and saved them. In fact nothing seemed that bad with the old pump except a slight gasket leak and the fact it didnt work, but the lever was a bit sloppy because the pin was a bit worn.
I just got frustrated and stopped playing around, though I definitely made progress.

you have inspired me to go at it again. I suspect with old check valves, plus the rebuild I did to make the lever mechanics strong and in spec, plus a thinner spacer it will work. thanks. Michael


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