Good idea to remove a working mecanical fuel pump.

Bob Dunahugh

New member
Sep 17, 2012
2,784
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On Barb's 73 GMC. The pump is working fine. But if it quits on the road. Not simple for her to change. I can make an electric simple to change. I think it's a good idea for her. Any thoughts out there? Bob Dunahugh
 
> On Barb's 73 GMC. The pump is working fine. But if it quits on the road. Not simple for her to change. I can make an electric simple to change. I
> think it's a good idea for her. Any thoughts out there? Bob Dunahugh
Mechanical pumps can fail in a way that results in gas in the crankcase. I don't see a downside to an electric fuel pump. Might fail more often, but
easy to change balances that out.
--
73 23' Sequoia 4 Sale
73 23' CanyonLands Parts Unit 4 Sale
Upper Alabama
"When I grow up I am going to be a curmudgeon."
 
Bob,

For my part, the only configuration I'd even consider is two electric pumps
(preferably Carter 4070's) with one connected to each tank and NO selector
valve.

Because of the possibility of having to replace a pump with something
unknown on the road, I'd tie the two outputs in the line forward with two
check valves into a tee.

A pump power selector relay powered by the tank selector switch can be used
to power either pump from that switch.

Definitely bypass and remove the mechanical pump.

It's not an expensive upgrade yet gives redundancy, eliminates the
hard-to-change mechanical pump, eliminates the possibly troublesome old
ethanol-susceptible selector switch, and helps minimize vapor lock.

JWID,

Ken H.

> On Barb's 73 GMC. The pump is working fine. But if it quits on the road.
> Not simple for her to change. I can make an electric simple to change. I
> think it's a good idea for her. Any thoughts out there? Bob Dunahugh
>
 
Thanks for the input. Makes me feel better to recommend it. This working o=
n her GMC is working out great. She's paying me $90 an hour to fix her GMC=
. And I'm paying her $90 an hour for help Linda. So we're both making good =
money. RIGHT? This is a fantastic situation for all of us. As we're gettin=
g some great things done for all. As to Barb's GMC. I'm finding it to be in=
good condition over all. PO did a good job of timely grease jobs, and oi=
l changes. Plus many parts have been serviced. So now I'm looking to head o=
ff problems as best as I can for see. New starter, ignition switch, and s=
ome battery cables. Change engine oil, and FD gear lube. Fan, fan clutch=
, shroud, and new belts. Check front wheel bearings along with all steerin=
g components, and adjust steering gear box. Check rear pins for tightness, =
clean out grease, and lube. Raise up, and power wash undercarriage, and fro=
nt suspension. Next replace trans, check gas lines, brake lines, install el=
ectric fuel pump, and get the generator running. Paint window frames satin =
black, then buff, and wax body. This GMC is her full time, and only home. =
North in the Summer, and the South in the Winter. So this GMC Glacier is e=
verything for her. My hats off to her for living her dreams. Not everyone =
has the guts to do that. Bob Dunahugh ____________________________=
____ On Barb's 73 GMC. The pump is working fine. But if it quits=
on the road. Not simple for her to change. I can make an electric simple t=
o change. I think it's a good idea for her. Any thoughts out there? Bob D=
unahugh
 
Reliability on most electric pumps is not as good as mechanical ones. I have several examples of that.

1. I have replaced one electric fuel pump on a GMC and no mechanical ones.

2. On low wing airplanes they will not fly with a bad pump. So we have 2 pumps in series just like most people do on an GMC. On aircraft I have
replaced at least 10 electric fuel pumps and 0 mechanical ones.

3. In my life, I have replaced exactly one mechanical pump. That was on a 1954 Ford in about 1964. I have replaced 15 or 20 electrical pumps on
various vehicles.

So by going to electric only, I suggest that you have increased your chances of an on the road failure. If I were to go to electric only pump
solution on a GMC I would definitely go with TWO PUMPS plumbed in a way that the engine will run on either one by itself.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
I've only had a mechanical fail once in a 1973 Chevy suburban with a 454 , somehow it was leaking gas into the oil and the engine suffered a crankcase
explosion, blowing out all the gaskets, at least once those were replaced the engine ran fine for years, but with that in mind I plan on putting my
pumps in the tanks and if I keep the mechanical I'll put a surge tank in as well

David
--
78 Royal #749
74 #136
Oversteer is when you hit the wall with the rear of the car, understeer is when you hit the wall with the front of the car. Hp is how fast you hit the
wall, and torque is how far you take the wall with you when you hit it.
 
Forgot to mention though had about a half dozen or so fail though
--
78 Royal #749
74 #136
Oversteer is when you hit the wall with the rear of the car, understeer is when you hit the wall with the front of the car. Hp is how fast you hit the
wall, and torque is how far you take the wall with you when you hit it.
 
Electric fuel pumps fail all the time. If they dont faill, the wiring/filters, relays do. I am surprised Bob, that you would suggest going away from
a mechanical pump for her after your experience with your coach out to shawnee. Electrical pumps are good for efi, vapor lock, but i would not ever
believe them to be more reliable. As far as gas in crankcase, a good new pump should not cause that worry. Electric pumps are also one of
thise PO things that if you are. Ot the one to install them, having someone else work on them can be a pain to get it right the second time.

With that said, the gmc does need some sort of electic pump for vapor lock backup. But i put my reliability in a mechanical pump. I put on a new
one on my coach because it was 40 years old, not because it did not work.

Like ken stated above, use two so you have a backup is the only way i would send someone else out on the road without the mechanical pump.

--
Jon Roche
75 palm beach
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
Been driving GM cars since 1969. Never been stranded by bad mech pump. Replaced one once (1) as return spring was weak and sounded like a lifter
noise. Done 7 in tank pumps in the years since they have been factory installed.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
I would go with Ken Hendersons suggestion of the 2 P70 pumps and no mechanical pump. True mechanical pumps are more reliable but they tend to vapor
lock real bad in many warm parts of the country with our cramp gas these days. With the 2 P70 pumps all you need to do is switch tanks with a failure
and replace the bad pump when you get a chance with the spare that you carry. I have used the P70's in my GMC and hot rods for manny years with out a
failure but you never know. As far as I know most vehicles use electric these days rather then mechanical ? Vapor lock will leave Barb on the side of
the road in a bad location.
--
Roy Keen
Minden,NV
76 X Glenbrook
 
Need to know that until few years ago, mechanical pumps had the old
standard rubber diaphragm and not the newer ones that can tolerate ethanol.
Also the age of the pump.
Also your tank selector switch has the old rubber and need to be replaced.
Best to address it before it happens on the road.

> I would go with Ken Hendersons suggestion of the 2 P70 pumps and no
> mechanical pump. True mechanical pumps are more reliable but they tend to
> vapor
> lock real bad in many warm parts of the country with our cramp gas these
> days. With the 2 P70 pumps all you need to do is switch tanks with a failure
> and replace the bad pump when you get a chance with the spare that you
> carry. I have used the P70's in my GMC and hot rods for manny years with
> out a
> failure but you never know. As far as I know most vehicles use electric
> these days rather then mechanical ? Vapor lock will leave Barb on the side
> of
> the road in a bad location.
> --
> Roy Keen
> Minden,NV
> 76 X Glenbrook
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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>

--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk
http://www.appliedgmc.com
1-800-752-7502
 
> I removed the mech. pump in the GMC and replaced with two Facet 40104s So far so good but they are a bit noisy.
>
> JP

So is my P7040.
--
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
 
Only fuel pump I ever had go bad since 1956 was the in-tank pump in our 2002 4WD Explorer! Repair cost was somewhere around $1,000!

My own belief is that external pumps mounted as close as possible to the fuel tanks is probably best solution overall and I will eventually go that way.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~~ ~ D C "Mac" Macdonald ~ ~~
~ ~ Amateur Radio - K2GKK ~ ~
~ ~ Since 30 November '53 ~ ~
~ ~ USAF and FAA, Retired ~ ~
~ Member GMCMI and Classics ~
~ ~ ~ Oklahoma City, OK ~ ~ ~
~~ ~ ~ "The Money Pit" ~ ~ ~~
~ ~ ~ ~ TZE166V101966 ~ ~ ~ ~
~ ~ ~ '76 ex-Palm Beach ~ ~ ~
~~ k2gkk + hotmail dot com ~~
~ www.gmcmhphotos.com/okclb ~
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
______________
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"--OO--[]---O-"

________________________________
From: Gmclist on behalf of John R.Lebetski
Sent: Sunday, April 16, 2017 08:21
To: gmclist
Subject: Re: [GMCnet] Good idea to remove a working mecanical fuel pump.

Been driving GM cars since 1969. Never been stranded by bad mech pump. Replaced one once (1) as return spring was weak and sounded like a lifter
noise. Done 7 in tank pumps in the years since they have been factory installed.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
I you would have installed aVain driven pump it would have been better. Pump is not just a pump

Get Outlook for iOShttps://aka.ms/o0ukef
________________________________
From: Gmclist on behalf of Steve Southworth
Sent: Sunday, April 16, 2017 1:45:33 PM
To: gmclist
Subject: Re: [GMCnet] Good idea to remove a working mecanical fuel pump.

> I removed the mech. pump in the GMC and replaced with two Facet 40104s So far so good but they are a bit noisy.
>
> JP

So is my P7040.
--
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI

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On these old coaches your going to see more failed as they are old and the diaphragm cannot handle Ethanal.
Don't believe me, keep on running those old pumps

Get Outlook for iOShttps://aka.ms/o0ukef
________________________________
From: Gmclist on behalf of David Morrison
Sent: Sunday, April 16, 2017 2:49:05 AM
To: gmclist
Subject: Re: [GMCnet] Good idea to remove a working mecanical fuel pump.

I've only had a mechanical fail once in a 1973 Chevy suburban with a 454 , somehow it was leaking gas into the oil and the engine suffered a crankcase
explosion, blowing out all the gaskets, at least once those were replaced the engine ran fine for years, but with that in mind I plan on putting my
pumps in the tanks and if I keep the mechanical I'll put a surge tank in as well

David
--
78 Royal #749
74 #136
Oversteer is when you hit the wall with the rear of the car, understeer is when you hit the wall with the front of the car. Hp is how fast you hit the
wall, and torque is how far you take the wall with you when you hit it.

_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Alex I, and Ken H came to my rescue 2 miles from the Shawnee site. Alex fou=
nd a Mr Gasket 5 to 7 PSI rotary pump. ( GM spec is 5.5 to 6.5 PSI.) Perfec=
t. Got us home. I'm shying away from mechanicals. As I've had three of them=
leak lots of gas into the engine oil in the last 2 years. Then a new one =
fail last Sept coming back from Ohio. Then an electric fail going to Shawn=
ee. So I'm gun shy. I'm putting EFI in our GMC soon with an external pump =
for each tank. That pump system seems safest to me. And Barb's likes the so=
und of that approach too. So now I need to get 2 external pumps to feed t=
he carb for her. The pump that Alex got for me was a rotary. And I've neve=
r had problems with rotary pumps. I think the Carter 4070 is. Who makes the=
P30, and is it rotary? Barb live off the grid with her solar panels out in=
the desert with her dog during the Winter. Her GMC has to be the best it c=
an. Bob Dunahugh p70 4070 Thanks for the input. Makes me feel=
better to recommend it. This working on her GMC is working out great. She'=
s paying me $90 an hour to fix her GMC. And I'm paying her $90 an hour for=
help Linda. So we're both making good money. RIGHT? This is a fantastic s=
ituation for all of us. As we're getting some great things done for all. As=
to Barb's GMC. I'm finding it to be in good condition over all. PO did a=
good job of timely grease jobs, and oil changes. Plus many parts have been=
serviced. So now I'm looking to head off problems as best as I can for s=
ee. New starter, ignition switch, and some battery cables. Change engine o=
il, and FD gear lube. Fan, fan clutch, shroud, and new belts. Check fron=
t wheel bearings along with all steering components, and adjust steering ge=
ar box. Check rear pins for tightness, clean out grease, and lube. Raise up=
, and power wash undercarriage, and front suspension. Next replace trans, c=
heck gas lines, brake lines, install electric fuel pump, and get the genera=
tor running. Paint window frames satin black, then buff, and wax body. Thi=
s GMC is her full time, and only home. North in the Summer, and the South =
in the Winter. So this GMC Glacier is everything for her. My hats off to h=
er for living her dreams. Not everyone has the guts to do that. Bob Dunahu=
gh ________________________________ On Barb's 73 GMC. Th=
e pump is working fine. But if it quits on the road. Not simple for her to =
change. I can make an electric simple to change. I think it's a good idea f=
or her. Any thoughts out there? Bob Dunahugh
 
As Frank Jenkins once told us:

"I carry a spare of everything that ever broke."

Don and Susan Jeffers
78 Eleganza III Cad 507 EFI
 
Out of all of the stuff I use to carry, I only used 1 ignition module and 1 fan belt. I also did a precautionary change to my spare tire once.

A few years back I unloaded most of the spare stuff based on non-usage and weight. The heaviest stuff went first. I need to do the same with most of
the tools that I carry.


--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
I followed Ken Henderson's advice and removed the selector valve, ran two pumps with filters between the pumps and tanks and check valves after each
pump. They are mounted outside the frame. I'm using the old tank switch on the dash with some relays to select which switch (tank) is in use. I
also have a line running from a oil pressure switch that kills power to the relays and therefore shuts off the fuel pump if the engine loses oil
pressure. In the I believe Ken posted a schematic somewhere in his albums. The only thing I did different was put an emergency fuel switch on the
dash. If the engine were to loose oil pressure in the middle of an intersection or somewhere similar and I want to risk the engine in order to get to
a save place, I can turn on the emergency switch, start the engine, and move the coach. I also use it as a fuel primer once in a while.

Oh, and the mechanical pump is removed and blocked off. I believe two electric pumps is sufficient backup. Not to mention the extra 12 MPG I get
because I'm not operating the fuel pump...... :)

I have a drawing in the coach I think.
--
Kerry Pinkerton - North Alabama

77 Eleganza II, 403CI, Manny Brakes, 1 ton, tranny, lots of aluminum goodies.

http://www.bdub.net/pinkerton/

'03 Fleetwood Discovery 39L
 
One thing I have done on other vehicles when I have installed electric pumps is to keep the mechanical pump in place [if its good] and run a loop of
hose intake to output with a little ATF in it to keep it lubricated.
Then if the electric pump fails its pretty easy to bypass and go back to the old pump. Has come in handy for me a couple of times, once on the
roadside in BFE, Georgia mountains.

On the GMC, I have the stock pump with a carter booster. I like the Idea of going to 2 carter pumps and eliminating the selector. and may go that
route eventually.
--
76 Glenbrook