Home » Public Forums » GMCnet » Electric fuel pump and Carbs don't mix
| Electric fuel pump and Carbs don't mix [message #79816] |
Thu, 08 April 2010 21:33  |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
Karma: -3
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Well we are half way through our trip to LA, Vegas, LA and home to Fremont. 3 issues I need to fix - double pulley on the alt, dash a/c, and fix my crappy carb setup.
I have Jim K's electric fuel pump and I think it overpowers the floats particularly when I pull a long grade and everything is hot and maleable. I want to go to fuel injection late this summer but can't wait to fix this rich-running stuttering at idle stinky beast.
Should I pop for a pressure regulator in the mean time or tap my daughter's college fund and do the fuel injection now?
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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| Re: Electric fuel pump and Carbs don't mix [message #79823 is a reply to message #79816] |
Thu, 08 April 2010 22:07  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Turn off the electric pump and see how it runs that way.
Are you using the correct 5 PSI electric pump? Carter 4070 works very well with a carb.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Electric fuel pump and Carbs don't mix [message #79827 is a reply to message #79824] |
Thu, 08 April 2010 22:33 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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| ljdavick wrote on Thu, 08 April 2010 22:19 |
I only have the electric pump. It's the one from Jim K with the
external filter. I was not comfortable pumping gas through the
mechanical pump.
Ljdavick at comcast.net
On Apr 8, 2010, at 8:07 PM, Ken Burton <n9cv@comcast.net> wrote:
> Turn off the electric pump and see how it runs that way.
>
> Are you using the correct 5 PSI electric pump? Carter 4070 works
> very well with a carb.
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
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That is to bad. Your installation kind of defeats the redundancy idea. Every low wing airplane I know of uses two pumps. One mechanical and one electric. In fact it is required in order to be certfied. This is in case one fails you can still get to your destination on the other one.
I guess your only option now is to install a fuel pressure gauge to see if the problem is the fuel pump or the carb.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Electric fuel pump and Carbs don't mix [message #79839 is a reply to message #79816] |
Fri, 09 April 2010 00:48 |
bobby5832708
Messages: 237
Registered: November 2006
Location: Winter Springs FL
Karma: 3
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Larry,
When I got my coach in 2006 it had a Carter 4070 as it's only fuel pump, the mechanical one on the engine was disconnected. A previous owner apparently had it installed in 1986 according to the stack of receipts I have. I replaced it with a new Carter 4070 just because it was over 20 years old and I kept the old one as a spare. The Carter 4070 pump feeds the QJet just fine. The engine starts quickly, idles perfectly, has good power, and never misses a beat.
In experimenting with Carter 4070 pumps I have found that if you wire and plumb it backwards it will pump fuel fine but will not have any pressure regulation. If I remember correctly, it puts out about 10 - 12 psi in this state. Also, since the pressure relief port is relatively small, a bit of gunk can restrict it leading to too much pressure. I would check the actual pressure of your pump. You want about 5 to 6 psi. Much more than that and the QJet will not be happy. I like this particular series of Carter pumps as the fuel flow is very smooth, not pulsing like some other types of electric pumps I've seen. Also, they've been around a long time and seem to be quite reliable.
Disclaimer: What works for me may not necessarily work for you. JWID, YMMV.
Bob Heller
2017 Winnebago 29VE
Winter Springs FL
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| Re: [GMCnet] Electric fuel pump and Carbs don't mix [message #79876 is a reply to message #79824] |
Fri, 09 April 2010 09:54 |
powerjon
Messages: 2446
Registered: January 2004
Karma: 5
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I have had only an electric fuel pump on the coach since 2002. I use
the carter P4070 pump and I also have a low oil pressure shut down. I
filter the fuel twice before it get to the carb. First filter is
located just after the selector valve and before the pump and the
second is located where the mechanical fuel pump used to be located
at just before the carb.. I do not have a filter in the carb. I
change the filters twice a year. This has worked well since it was
installed.
J.R. Wright
GMC GreatLaker
TZE Zone Restorations
77 Eleganza Custom (For Sale)
1975 Avion (Under Reconstruction)
Michigan
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J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
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| Re: [GMCnet] Electric fuel pump and Carbs don't mix [message #79877 is a reply to message #79827] |
Fri, 09 April 2010 09:55 |
Luvn737s
Messages: 1106
Registered: June 2007
Karma: 2
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| Ken Burton wrote on Thu, 08 April 2010 20:33 |
That is to bad. Your installation kind of defeats the redundancy idea. Every low wing airplane I know of uses two pumps. One mechanical and one electric. In fact it is required in order to be certfied. This is in case one fails you can still get to your destination on the other one.
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Most use it as a boost pump, not running continuously only for starting and takeoff and landing when you want critical redundancy.
Randy
1973 26' Painted Desert
Ahwatukee (Phoenix) AZ
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| Re: [GMCnet] Electric fuel pump and Carbs don't mix [message #79879 is a reply to message #79877] |
Fri, 09 April 2010 10:09 |
Steven Ferguson
Messages: 3447
Registered: May 2006
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I have a single ele pump, (4070) and even though it has a regulated
output, I still run a FP regulator. I removed the mechanical years
ago and ran the fuel lines up the rear of the eng compartment and used
foam insulation covered with reflectix tape to keep exhaust manifold
and eng comp heat from having any effect on fuel delivery.
I have a cannister type fuel filter mounted ahead of the ele pump and
after about 8 years, I changed the filter. From the looks of it, it
was a waste of time.
JWID
On Fri, Apr 9, 2010 at 7:55 AM, Randy <Acrosport2@hotmail.com> wrote:
>
>
> Ken Burton wrote on Thu, 08 April 2010 20:33
>> That is to bad. Your installation kind of defeats the redundancy idea. Every low wing airplane I know of uses two pumps. One mechanical and one electric. In fact it is required in order to be certfied. This is in case one fails you can still get to your destination on the other one.
>
> Most use it as a boost pump, not running continuously only for starting and takeoff and landing when you want critical redundancy.
> --
> Randy
> 1973 26' Painted Desert
> Ahwatukee (Phoenix) AZ
> _______________________________________________
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--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source
www.bdub.net/ferguson/
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| Re: [GMCnet] Electric fuel pump and Carbs don't mix [message #79896 is a reply to message #79879] |
Fri, 09 April 2010 11:54 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
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Steve,
Sounds like my filters. Since I put the Cad in, I'm having intermittent
drops in the EFI fuel pressure. Locating and correcting the cause of that
is today's task. The first step was to R&R the fuel filters right after the
4070's on the Main & Aux tanks (I know, I know, they should be before the
pumps -- I just didn't want the plumbing hassles). After replacing them, I
stuck their 5+ year selves in the lathe and cut the ends off. Not a sign of
any debris at all. The tanks must be pretty clean.
Then I temporarily connected my new 0-30 psi, $29.95, electric pressure
gauge between the surge tank and the filter before the EFI pump. I thought
I'd be able to monitor there whether the 4070's were keeping enough fuel to
the EFI pump. No such luck! The pressure is not enough to wiggle the
needle, even without the EFI pump running. Apparently the 3/8" return line
from the top of the surge tank is bleeding off all of the 4070's pressure,
leaving the EFI pump to feed by gravity+suction. That shouldn't be a
problem, but now I'll have to move closer to the 4070's with the fuel
pressure sender to check their operation.
Ken H.
Americus, GA
'76 X-Birchaven
www.gmcwipersetc.com
On Fri, Apr 9, 2010 at 11:09 AM, Steven Ferguson <botiemad11@gmail.com>wrote:
> I have a single ele pump, (4070) and even though it has a regulated
> output, I still run a FP regulator. I removed the mechanical years
> ago and ran the fuel lines up the rear of the eng compartment and used
> foam insulation covered with reflectix tape to keep exhaust manifold
> and eng comp heat from having any effect on fuel delivery.
> I have a cannister type fuel filter mounted ahead of the ele pump and
> after about 8 years, I changed the filter. From the looks of it, it
> was a waste of time.
> JWID
>
> On Fri, Apr 9, 2010 at 7:55 AM, Randy <Acrosport2@hotmail.com> wrote:
> >
> >
> > Ken Burton wrote on Thu, 08 April 2010 20:33
> >> That is to bad. Your installation kind of defeats the redundancy idea.
> Every low wing airplane I know of uses two pumps. One mechanical and one
> electric. In fact it is required in order to be certfied. This is in case
> one fails you can still get to your destination on the other one.
> >
> > Most use it as a boost pump, not running continuously only for starting
> and takeoff and landing when you want critical redundancy.
> > --
> > Randy
> > 1973 26' Painted Desert
> > Ahwatukee (Phoenix) AZ
> > _______________________________________________
> > GMCnet mailing list
> > List Information and Subscription Options:
> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> >
>
>
>
> --
> Steve Ferguson
> '76 EII
> Sierra Vista, AZ
> Urethane bushing source
> www.bdub.net/ferguson/
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: Electric fuel pump and Carbs don't mix [message #79901 is a reply to message #79816] |
Fri, 09 April 2010 12:08 |
Rick Denney
Messages: 430
Registered: January 2004
Karma: 0
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Senior Member |
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Like several others, I have used the Carter 4070 all by itself for a while now with no issue. But in the past, I did have a problem with the pump overpowering the float valve. The problem was, of course, dirt in the float valve causing it not to seat. That would have been a problem with any pump, of course.
To prevent that dirt in the future, I installed an inline filter in the aircraft-style hose I used to connect the hard line to the carb. That filter is a sintered bronze type that won't turn into crumbs. I have read reports of the carb-mounted filter doing just that over a period of years, and those who install effective inline filters back at the tank may never realize that the carb filter needs to be checked.
I already had inline filters in each fuel line upstream from the selector valve, and it's likely that the dirt in the float was just leftover crap from a range of prior repairs on the fuel delivery system.
Any pump with a 4-6 psi output was designed for the Quadrajet, and being back by the tank, the pressure will be even lower at the carb.
So, it seems to me that a dirty float valve is more likely to be a source of this problem than the electric pump. I would first pull the top off the carb and make sure the flow valve is clean.
Some hate the idea of electric pumps, and some hate the idea of mechanical pumps. Even so, both work and work reliably, though neither will keep a carb with a dirty float valve from spilling gasoline into the barrels and all over the top of the engine, for that matter.
Rick "working backwards from the symptom's location" Denney
'73 Glacier 230 "Jaws"
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| Re: [GMCnet] Electric fuel pump and Carbs don't mix [message #79906 is a reply to message #79897] |
Fri, 09 April 2010 12:41 |
Luvn737s
Messages: 1106
Registered: June 2007
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| Mr ERFisher wrote on Fri, 09 April 2010 09:55 |
>
> Most use it as a boost pump, not running continuously only for starting and
> takeoff and landing when you want critical redundancy.
>
I am not sure most use it for that.
In fact, I know one mechanical pump that killed 3 engines, because it was
moved from rebuild to rebuild..
gene
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I was referring to low wing aircraft installations and how similar useage could be applied to GMC's. You might get all the benefits for a carbureted engine with non-continuous electric pump operation
Randy
1973 26' Painted Desert
Ahwatukee (Phoenix) AZ
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| Re: Electric fuel pump and Carbs don't mix [message #79938 is a reply to message #79816] |
Fri, 09 April 2010 20:03 |
kingd
Messages: 592
Registered: June 2004
Karma: 2
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Let me tell everyone a "story" about my usage of a Carter 4070 in a race car with carbs (because the output pressure from the 4070 could directly feed those carbs with no pressure regulator). The 4070 quit running after not much use. As it appeared to be "dead" but it was passing current, I took it apart by "uncrimping" the motor part from the pump part. A couple of surprises !!!!. The motor is cooled by the fuel as the motor runs wet. I guess a permanent magnet brush type motor can't spark when it is full of gasoline!!! LOL. 2) the magnets had come unglued from the housing, glue was meled by the "race" fuel.
I reglued the magents with expoxy and put it back together and it works, After that episode, I decided to use the low pressure Holley(I forget if the blue or the red was the low pressure pump) that isn't wet and play with pressure relief springs until I got the desired pressure.
I wouldn't depend on the Carter without carrying a known GOOD spare(who knows what the ethanol is doing to that glue!!!)
DAVE KING
DAVE KING
lurker, wannabe
Toronto, Ontario, Canada
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| Re: [GMCnet] Electric fuel pump and Carbs don't mix [message #79943 is a reply to message #79938] |
Fri, 09 April 2010 20:27 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
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Dave,
On the other hand, I had a red Holley literally cook itself a few years
back. I was running it on one tank and a 4070 on the other. The coils were
cooked about like a bad fluorescent ballast.
They can all fail, but I'll stick with the 4070's & won't be using any more
Holleys.
Ken H.
On Fri, Apr 9, 2010 at 9:03 PM, Dave King <kingd@sympatico.ca> wrote:
>
>
> Let me tell everyone a "story" about my usage of a Carter 4070 in a race
> car with carbs (because the output pressure from the 4070 could directly
> feed those carbs with no pressure regulator). The 4070 quit running after
> not much use. As it appeared to be "dead" but it was passing current, I took
> it apart by "uncrimping" the motor part from the pump part. A couple of
> surprises !!!!. The motor is cooled by the fuel as the motor runs wet. I
> guess a permanent magnet brush type motor can't spark when it is full of
> gasoline!!! LOL. 2) the magnets had come unglued from the housing, glue was
> meled by the "race" fuel.
> I reglued the magents with expoxy and put it back together and it works,
> After that episode, I decided to use the low pressure Holley(I forget if the
> blue or the red was the low pressure pump) that isn't wet and play with
> pressure relief springs until I got the desired pressure.
> I wouldn't depend on the Carter without carrying a known GOOD spare(who
> knows what the ethanol is doing to that glue!!!)
>
>
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| Re: [GMCnet] Electric fuel pump and Carbs don't mix [message #79949 is a reply to message #79943] |
Fri, 09 April 2010 20:58 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
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Senior Member |
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Since we're talking fuel pumps, I might as well tell about my day:
Ever since I got the Cad 500 installed, I've been snake-bit: I've had
several roadside stoppages, including one which lasted 3 days. I've had a
couple of ignition module failures, apparently caused by a bad coil. I've
had several just plain quit running events wherein I'd pull off the road and
after scratching my bald head a little, crank back up and proceed -- maybe
50 feet, maybe a mile, maybe 5 miles.
Finally a couple of days ago I watched in fascination as the fuel pressure
gauge on my Howell EFI suddenly dropped to zero. When I'd turn the ignition
on, the pressure would come back up; after the engine ran for a minute or
two, the pressure would suddenly drop to zero again.
Today I finally got around to troubleshooting it. I won't go into all the
details of fuel pressure gauges, etc. A test lamp Gorilla taped to the
windshield to monitor the under-hood fuel pump relay for my two Carter
4070's finally told me the problem: That relay provides power to the
selected Main or Aux tank pump when the ignition is on and one of these
conditions exists: 1. The prime switch is depressed. 2. The starter
solenoid is "hot". 3. There's engine oil pressure. 3. was not occurring
so naturally the engine couldn't run very long after a start, right? Wrong.
Here's the interesting part: I have a homemade surge tank, installed along
with the EFI. It holds about 1 gallon of fuel. At the top of the end cap
on the horizontal 8" OD aluminum tube there's a return line to the bottom of
the Aux tank. An inch or so below that there's a return line from the
throttle body. A couple of inches below that there's the supply line from
whichever of the two 4070's is active. On the very bottom of the cylinder
is the supply line to the EFI's high pressure pump. This whole affair is
intended to ensure that the EFI pump always has a supply of fuel.
My analysis of my weird problems is this: Because I've had so many ignition
problems, I haven't been surprised to sometimes need the starter for several
seconds rather than the very brief period EFI normally requires. During
those long start attempts, the surge tank has filled with its 1 gallon or so
of fuel -- enough to carry me quite a ways, thus the long good running
intervals.
When I've gotten quick light-offs, the 4070 has not had enough time to put
much fuel into the surge tank, so I might only get 50'.
When, as has happened a couple of times, I've made a hard turn and the
engine's died, it was because the surge tank was low on fuel and sloshed off
of the supply tube for the EFI pump -- merely accelerating the
about-to-happen shutdown.
I've got a new Vega oil pressure switch ordered for delivery tomorrow
morning.
Incidentally, Gene, if you read this: The pressure switch listed on the
Carter diagram on your site is available from several internet sources --
for about $25. The ACDelco G1809 and Standard PS64 are basically the same
and sell for $8-13 at Rock Auto, Autozone, OReilly's, Advance Auto, NAPA,
etc. Just ask for a 76 Vega oil pressure switch with 3 terminals. Carrying
a spare is not a bad idea -- I've had two fail before this incident and no
one had one in stock today.
Ken H.
Americus, GA
'76 X-Birchaven
www.gmcwipersetc.com
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| Re: [GMCnet] Electric fuel pump and Carbs don't mix [message #79957 is a reply to message #79949] |
Fri, 09 April 2010 21:53 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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got it, thanks
http://www.gmcmotorhome.info/engine.html#pump
liked the jackpad, how have to make one of those also
gene
> Incidentally, Gene, if you read this: The pressure switch listed on the
> Carter diagram on your site is available from several internet sources --
> for about $25. The ACDelco G1809 and Standard PS64 are basically the same
> and sell for $8-13 at Rock Auto, Autozone, OReilly's, Advance Auto, NAPA,
> etc. Just ask for a 76 Vega oil pressure switch with 3 terminals.
> Carrying
> a spare is not a bad idea -- I've had two fail before this incident and no
> one had one in stock today.
>
> Ken H.
> Americus, GA
> '76 X-Birchaven
> www.gmcwipersetc.com
> _______________________________________________
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--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
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| Re: [GMCnet] Electric fuel pump and Carbs don't mix [message #80012 is a reply to message #80004] |
Sat, 10 April 2010 11:22 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
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Senior Member |
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Matt,
I've done so many dumb things like that, they hardly disturb me any more --
I just scratch my head, trying to figure out how it can be so dense, & move
on. It is really frustrating though, to think how long it took me to figure
it out, and the fact that the temporary fix could be just a sliver of metal
to joint two Fast-On connectors. :-)
Ken H.
On Sat, Apr 10, 2010 at 10:42 AM, Matt Colie <mcolie@chartermi.net> wrote:
>
>
> Please read (or reread if you did and don't remember:
> GMCWiperMan (Ken Emeritus of Fri, 09 April 2010 21:58
>
> Question for Ken:
>
> When you finally found the root cause,
> Did you throw something heavy,
> Or
> Go pour a stiff drink?
>
> Matt
> --
> Matt & Mary Colie
> '73 Glacier 23 Chaumiere (say show-me-air)
> SE Michigan - DTW 3.2/4R
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