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Confirm / correct: possible mechanical fuel pump difficulty

Started by John Barry [CLC17027], April 29, 2018, 01:26:27 PM

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John Barry [CLC17027]

Background: I own a '40 La Salle (matching numbers; engine rebuilt in 2003 to use latter-day fuel) that seems to be starved for fuel occasionally.

Symptoms: when accelerating from a standing start, often partway through the acceleration in second gear (most commonly but not always) the engine will almost quit.  A quick letup on the accelerator followed by a quick push may remedy the situation.  I've also noted that if I use the electric fuel pump (installed some years back to help with starting, etc.), I don't get that sort of engine-nearly-dies syndrome.

So:

  • Is this indeed a mechanical fuel pump problem, most likely caused by latter-day fuel with ethanol?  I suspect it is, with ethanol doing some violence to the diaphragm.
  • Would this warrant a fuel pump rebuild?
  • If so, is that something I could do myself or would I do better to send it for rebuilding?
  • I wonder if there are more robust diaphragm materials available, like Viton, that while more expensive, would stand up to gasoline with ethanol?

Thanks.
[/list]
John Barry (CLC 17027)
Now-retired editor/Publisher of the Valley Forge Region newsletter, The Goddess
1940 La Salle series 50 four door sedan

Bobby B

John,
Hi. Sounds like the pump. You can put a pressure gauge in-line to see what it's putting out. If it's good, maybe your accelerator pump in the carb is on it's way out, garbage in the float bowl, float bad, etc. Mike Gadeleto has kits or can do it for you. They're ethanol ready.....
                                                   Bobby
1947 Cadillac Series 62 Convertible Coupe
1968 Mustang Convertible
1973 Mustang Convertible
1969 Jaguar E-Type Roadster
1971 Datsun 240Z
1979 H-D FLH

John Barry [CLC17027]

Thanks for the advice.  Now the big question: is a fuel pump rebuild something easy to do? Never tried it.
John Barry (CLC 17027)
Now-retired editor/Publisher of the Valley Forge Region newsletter, The Goddess
1940 La Salle series 50 four door sedan

Bobby B

Quote from: John Barry [CLC17027] on April 29, 2018, 03:39:13 PM
Thanks for the advice.  Now the big question: is a fuel pump rebuild something easy to do? Never tried it.

Not difficult. Just make sure you mark the body so you clock it back the same way, or else it won't work/mount. Take a few pics for reference. Good Luck!
                                                                                             Bobby

http://www.cadillacpartsltd.com/19calafupure.html
1947 Cadillac Series 62 Convertible Coupe
1968 Mustang Convertible
1973 Mustang Convertible
1969 Jaguar E-Type Roadster
1971 Datsun 240Z
1979 H-D FLH

76eldo

I've got decent mechanical skills.  Have done major restorations, engine swaps, etc in the past.  Detail work like rebuilding carbs, generators, fuel pumps, etc in my opinion, is best left to those that do this all the time, day in, day out. a few little tips and tricks like staking the valves in the pump and other things are not apparent to someone that never did a pump before.

There are many good people that do this work.  You send it to them dirty and nasty in a plastic bag in a box and get back a beautiful like-new part for not a lot of money.

I know my limitations and only like to put parts on once, not open myself to breakdowns on the road.

Brian
Brian Rachlin
Huntingdon Valley, Pa
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

Caddy Wizard

Rebuilding fuel pumps is not terribly hard.  LOTS OF PICTURES during disassembly is a big help.  Nothing worse than staring at a new component and not remembering if it goes in one way or the other.  Hardest part of most fuel pump rebuilds is hooking the actuating arm onto the spring. Some folks are better at this than others.

Keep in mind that sometimes a fuel pump can be good, but give poor pressure/volume.  Remember to check the lines leading up to the fuel pump for cracks or leaks.  If one allows the pump to draw in a little air with the fuel, it won't pump very well (air, unlike liquid fuel, is a compressible fluid).  So check your inlet fitting, the rubber line leading from the steel line, the steel line, etc.  Any place on the inlet side that feels even slightly wet could be your trouble.
Art Gardner


1955 S60 Fleetwood sedan (now under resto -- has been in paint shop since June 2022!)
1955 S62 Coupe (future show car? 2/3 done)
1958 Eldo Seville (2/3 done)

Jeff Rosansky CLC #28373

Mechanical pump sucks and electric pushes. Turn your electric on to pressurize the lines. Then take a good close look at all your fuel lines-especially under all the clamps. They tend to rust there. If you see any signs of moisture then you have a pinhole which will make your mechanical pump look bad.
Jeff
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

John Barry [CLC17027]

Quote from: Art Gardner  CLC 23021 on April 30, 2018, 08:37:39 AM
(air, unlike liquid fuel, is a compressible fluid). 

  ;D I'm a chemical engineer, so you might say I'm familiar with the concept of compressible and (ideally) incompressible fluids--although liquids do indeed have a property known as the isothermal compressibility.   :D

Thanks for the general advice about rebuilds and the like.
John Barry (CLC 17027)
Now-retired editor/Publisher of the Valley Forge Region newsletter, The Goddess
1940 La Salle series 50 four door sedan

Caddy Wizard

Sorry if my post sounded a bit smarmy.  It wasn't intended to be smart-alecky.  Just trying to point out that even the tiniest of leaks on the inlet side of these mechanical fuel pumps can make them perform poorly.  And since the leak is on the inlet side, the leak often goes unnoticed since it doesn't leak much fuel from the low pressure side of the pump.


Best of luck.
Art Gardner


1955 S60 Fleetwood sedan (now under resto -- has been in paint shop since June 2022!)
1955 S62 Coupe (future show car? 2/3 done)
1958 Eldo Seville (2/3 done)

fishnjim

These "starved" issues are getting more difficult to diagnose as the vehicles age and fuel conditions change.  '03 seems recent but is 15 years since major service.   That would be considered much for a recent car.   Could be just faulty equipment or fuel boiling curve issues, but I prefer to start at the tank and go through entire fuel system to make sure there's no simple/obvious problems; inlet restrictions/dirt/corrosion in system.   Over time things accumulate/corrode, wear, etc.   Rebuild the pump and carb.   New lines and filter, etc. where needed.   Some of these earlier carb systems even relied on vacuum so you have to look at that as well sometimes.   
Most will work just fine after sorting everything to "new" as a few had design issues, but they were updating and improving almost continuously, so it's difficult to know the nuances.   Even at best, they won't run like injection which we're all used now.   Things that were "accepted" back then, aren't tolerated in today's fast paced world.   An old timer would anticipate and drive around/anticipate some issues like hills, etc.   
As we pass time from original to nostalgia, to ain't going to be around forever we have to adjust our thinking as well.
I too like fuel pressure, vacuum, rpm(tach) and voltage gauges on these cars to aid in carbed vehicle diagnostics.
As a ChemE, I dare you understand the importance of systems and doing mechanical maintenance to maintaining efficiency.

Bob Schuman

When reinstalling the pump on a flathead it is very easy to get it cocked as you tighten the two mounting bolts. That will cause the long operating arm to be partly or totally off of its operating cam on the camshaft.
To avoid that problem, get two bolts somewhat longer than the original mounting bolts. Use those to allow you to pull the pump straight against the block as you tighten them. After getting the pump against the block, remove one bolt at a time and replace with the proper length bolts.
I can do much mechanical work, but am not good at fuel pump rebuilding. I prefer sending it to a rebuilder, and my preference is Terrill Machine Works.
Bob Schuman
Bob Schuman, CLC#254
2017 CT6-unsatisfactory (repurchased by GM)
2023 XT5

harry s

" I prefer sending it to a rebuilder, and my preference is Terrill Machine Works.
Bob Schuman"
     I agree, for the small extra cost of rebuilding Terrill aligns the arm and checks the operation of  that part of the pump also. Another helpful part of installing the fuel pump is to be sure the concentric on the cam is at the bottom of the stoke.       Harry
Harry Scott 4195
1941 6733
1948 6267X
2011 DTS Platinum

KenZ

I also have used Terrill Machine with very positive results.  Around $100.00 plus shipping cost.  Well worth it in my book.  KenZ :)