Home » Public Forums » GMCnet » Dual Carter Pumps
| Dual Carter Pumps [message #183130] |
Tue, 04 September 2012 21:03  |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Rounding up my parts I called the Carter Tech guy to get his thoughts. I told him I was planing on removing the socks and selector valve and using a Cadillac fuel filter in front of each tank P4070 pump and a check valve at each pump outlet(no mechanical pump). He said that would work but suggested a 404 501 HP regulator at the Carburetor with a return line to the tanks. I said but the pumps are already regulated at 5 lbs? He said if the pumps start to sense vapor in the fuel the pressure can rise and over power the carb float valve? A new one on me? He also said the pumps will run cooler with the bypass so I said won't the fuel temperature rise with all that circulating fuel he didn't comment. I also saw an article that suggested it was better to use a roll over switch from a ford crown Victoria rather then wire the pumps thru an oil pressure switch? Anybody want to comment on these thoughts. I don't want in tank pumps if I can get the external ones to work OK. Besides I have 3 P7o's
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: Dual Carter Pumps [message #183136 is a reply to message #183130] |
Tue, 04 September 2012 22:51  |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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| roy1 wrote on Tue, 04 September 2012 21:03 |
He said that would work but suggested a 404 501 HP regulator at the Carburetor with a return line to the tanks.
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???? According to Summit and Carter the 404 501 is a non-return regulator.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: Dual Carter Pumps [message #183138 is a reply to message #183130] |
Tue, 04 September 2012 23:00 |
bwevers
Messages: 597
Registered: October 2010
Location: San Jose
Karma: 5
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I like the P4070 Carter on my 1975. It seems to me that
a Carter on each tank output with a check valve would work fine.
-Bill
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
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| Re: [GMCnet] Dual Carter Pumps [message #183139 is a reply to message #183138] |
Tue, 04 September 2012 23:45 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Mine have for 6-8+ years.
Today was a letdown though. Y'All may remember my comments a few days ago
about HER aversion to giving out of gas. This weekend was my first trip
after dropping the tanks, refurbishing the level senders, and re-plumbing
and -wiring the fuel system. I left here last Friday with full tanks -- 51
gallons loaded. In the past, after initial fill, I've never put more than
40 gallons or so into "empty" tanks -- just wouldn't go. And the gauges
have been very erratic and unreliable. So my fuel management procedure has
been to run with the Main tank selected until the engine stumbled, switch
to the Aux, and proceed leisurely to a service station, secure in the
knowledge that the Aux tank, with all return from the EFI's forward 1 g.
surge tank going into it, had 6 gallons or so reserve. It's always worked
well and I haven't worried about traveling 30+ miles to a service station.
Today's return from Winder, GA, 164 miles away, was going well. 22 miles
from home, with 367 miles on the odometer since I departed, the engine
stumbled on the main tank, which sender had just hit "E", so I selected the
Aux tank and didn't worry about the fact that I'd just passed the last
service station before home. At 377 miles the engine stumbled again! And
Died! And Stayed Died! Sumpin' done happened to my 6 gallon Aux reserve!
Or the engine suddenly decided to drink gas a whole lot faster! At any
rate, I had to call HER (who came home by car yesterday) and beg her to go
to the shop, collect a couple of empty gas cans, go to the service station,
and bring me gas, 12 miles from home. :-((
One 5 gallon can got me home OK, but I'm baffled as to why the Aux tank no
longer contains my 6 g. reserve. All I can figure is that the pickup tube
somehow is no longer close enough to the bottom of the tank to get all
that's there. But I did nothing to account for any such change. I'm
really anxious to get to the service station tomorrow to find out what my
actual usable capacity is now -- I'm sure it's not 50+ g.; it may now be
<40 g. Which would be nice, in a way, 'cause I'd have gotten over 9 mpg on
this trip ... but I'm not THAT optimistic.
Ken H.
On Wed, Sep 5, 2012 at 12:00 AM, Bill Wevers wrote:
>
>
> I like the P4070 Carter on my 1975. It seems to me that
> a Carter on each tank output with a check valve would work fine.
>
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: Dual Carter Pumps [message #183151 is a reply to message #183130] |
Wed, 05 September 2012 07:16 |
bobby5832708
Messages: 237
Registered: November 2006
Location: Winter Springs FL
Karma: 3
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Roy,
What you have described is almost exactly how my fuel supply system has been for the past 4-or-so years. It works great. I have no vapor lock issues, always starts quickly hot or cold, no burping, farting, or hesitations like so many here have reported.
I have found that the Carter P4070 can put out 8+ psi at times, this will overwhelm the Qjet. I am using a Magnaflow pressure regulator set to 4.5psi (don't remember which model) that is a non-bypassing type. In hindsight I should have bought the bypass type. I have made my own bypass out of a plumbing tee with one leg filled with solder and about a .025 hole drilled in it and returning fuel to the rear tank.The 73-74 models have a 3/8" hose fitting on the left side of the rear tank that was capped off from the factory. It appears GM had this fuel/vapor bypass planned --- if all of their air conditioned large cars of that time used a bypass then why didn't the GMC motorhome? I have found that even an external electric pump can vapor lock although nowhere near as bad as the engine-mounted mechanical pump. I put the bypass tee underneath the coach about 2 feet from the pumps. I'm not concerned about vaporized gas in the pressure line to the carb, the only thing that happens when idling in traffic for extended periods is the in-drive-aircon-running RPMs go from a normal 540 down to 520. Without a tach I would not notice the 20 rpm drop. I have idled for almost an hour in a traffic jam and then once past the accident the coach accelerated right up to 70 with no drama. Good enough for me.
For filtering I have removed the in-tank socks and use Wix 33033 metal 3/8" filters between the tanks and the pumps. My front tank was really dirty so I paralleled two filters for that one. It's been about two years since I last changed the filters, maybe that will be this weekends project, but the coach is running fine so maybe not. In the Qjet I used a marine-type mesh filter, not the paper one. I don't know why, I just did.
I ran another wire from the dash area and am using a standard DPDT-center-off toggle switch to put power to either pump. There is no tank selector valve so I used that wire for one of the pumps. I forgot where I got the one-way check valves, probably someone on Ebay. I've currently got no crash protection, key on and the pumps work, key off and the pumps stop. The Ford crash switch seems like a good idea but it's just another thing to go wrong. An oil pressure switch and relay would work fine too, yet another project.
That's all I can think of right now. Good luck with your fuel supply project!
Bob Heller
2017 Winnebago 29VE
Winter Springs FL
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| Re: Dual Carter Pumps [message #183182 is a reply to message #183151] |
Wed, 05 September 2012 11:25 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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| bobby5832708 wrote on Wed, 05 September 2012 05:16 |
Roy,
What you have described is almost exactly how my fuel supply system has been for the past 4-or-so years. It works great. I have no vapor lock issues, always starts quickly hot or cold, no burping, farting, or hesitations like so many here have reported.
I have found that the Carter P4070 can put out 8+ psi at times, this will overwhelm the Qjet. I am using a Magnaflow pressure regulator set to 4.5psi (don't remember which model) that is a non-bypassing type. In hindsight I should have bought the bypass type. I have made my own bypass out of a plumbing tee with one leg filled with solder and about a .025 hole drilled in it and returning fuel to the rear tank.The 73-74 models have a 3/8" hose fitting on the left side of the rear tank that was capped off from the factory. It appears GM had this fuel/vapor bypass planned --- if all of their air conditioned large cars of that time used a bypass then why didn't the GMC motorhome? I have found that even an external electric pump can vapor lock although nowhere near as bad as the engine-mounted mechanical pump. I put the bypass tee underneath the coach about 2 feet from the pumps. I'm not concerned about vaporized gas in the pressure line to the carb, the only thing that happens when idling in traffic for extended periods is the in-drive-aircon-running RPMs go from a normal 540 down to 520. Without a tach I would not notice the 20 rpm drop. I have idled for almost an hour in a traffic jam and then once past the accident the coach accelerated right up to 70 with no drama. Good enough for me.
For filtering I have removed the in-tank socks and use Wix 33033 metal 3/8" filters between the tanks and the pumps. My front tank was really dirty so I paralleled two filters for that one. It's been about two years since I last changed the filters, maybe that will be this weekends project, but the coach is running fine so maybe not. In the Qjet I used a marine-type mesh filter, not the paper one. I don't know why, I just did.
I ran another wire from the dash area and am using a standard DPDT-center-off toggle switch to put power to either pump. There is no tank selector valve so I used that wire for one of the pumps. I forgot where I got the one-way check valves, probably someone on Ebay. I've currently got no crash protection, key on and the pumps work, key off and the pumps stop. The Ford crash switch seems like a good idea but it's just another thing to go wrong. An oil pressure switch and relay would work fine too, yet another project.
That's all I can think of right now. Good luck with your fuel supply project!
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Thanks for the report Bob your observation goes along with what the Tech suggested. He also mentioned a 404 500 HP regulator maybe that one has the by pass.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: Dual Carter Pumps [message #183184 is a reply to message #183182] |
Wed, 05 September 2012 11:52 |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
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My Ford Focus (2001) had a tumble sensing switch in the left rear quater of the trunk, that was designed to remove electricity from the in-tank fuel pump. Service tech indicated, if the car was even tapped hard, as in bumper tag, it would shut down the fuel pump. He showed me where the reset button was located. Perhaps this switch could also be used for an emergency shut down of the fuel pumps. Lots of Focus donor cars out there.
But I do like the no oil pressure shut-off system. With my luck, it is more likely that I'll lose the engine, than roll the GMC.
Tom, MS II
2012 Phoenix Cruiser model 2552
KA4CSG
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| Re: [GMCnet] Dual Carter Pumps [message #183188 is a reply to message #183183] |
Wed, 05 September 2012 12:32 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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| Michael Morton wrote on Wed, 05 September 2012 09:41 |
Sounds like your selector valve might have failed. Check the wiring and check the valve. Ask me how I know.
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Nope had that problem years ago. I'm just reducing my vapor lock issues hot weather,thin air & California formulated gas = vapor lock.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Dual Carter Pumps [message #183192 is a reply to message #183184] |
Wed, 05 September 2012 12:52 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Ford Rangers also use this switch. It is located in them on the passenger side in the upper footwell behnd a little metal guard. If you carelessly toss a gun case into the right seat it is possible to bump it hard enough to trigger the switch. If you've owned the truck for maybe three days, you maty not be aware this is why it doesn't start. Ask me how I learned this one rainy night in Georgia.
The switch is a lot easier to get at in the Ranger.
--johnny
From: Thomas Phipps <tph1pp5@yahoo.com>
To: gmclist@temp.gmcnet.org
Sent: Wednesday, September 5, 2012 12:52 PM
Subject: Re: [GMCnet] Dual Carter Pumps
My Ford Focus (2001) had a tumble sensing switch in the left rear quater of the trunk, that was designed to remove electricity from the in-tank fuel pump. Service tech indicated, if the car was even tapped hard, as in bumper tag, it would shut down the fuel pump. He showed me where the reset button was located. Perhaps this switch could also be used for an emergency shut down of the fuel pumps. Lots of Focus donor cars out there.
But I do like the no oil pressure shut-off system. With my luck, it is more likely that I'll lose the engine, than roll the GMC.
Tom, MS II
--
1975 GMC Avion, under forever re-construction
Vicksburg, MS. 3.7 miles from I-20
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Dual Carter Pumps [message #183195 is a reply to message #183192] |
Wed, 05 September 2012 13:36 |
GMC Cruse
Messages: 606
Registered: June 2009
Location: SE Michigan
Karma: 3
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| Johnny Bridges wrote on Wed, 05 September 2012 13:52 |
Ford Rangers also use this switch. It is located in them on the passenger side in the upper footwell behnd a little metal guard. If you carelessly toss a gun case into the right seat it is possible to bump it hard enough to trigger the switch. If you've owned the truck for maybe three days, you maty not be aware this is why it doesn't start. Ask me how I learned this one rainy night in Georgia.
The switch is a lot easier to get at in the Ranger.
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I have one from an '89 Cougar. They are located in the trunk behind the panel on the left side between the wheel well and the taillight. Very easy to get at, just remove that left side panel and it's right there. Not sure yet if I'll use it on my GMC or one of my other Hot Rods.
Mike K.
'75 PB
Southeast Michigan
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| Re: [GMCnet] Dual Carter Pumps [message #183199 is a reply to message #183139] |
Wed, 05 September 2012 14:03 |
LYNN L
Messages: 140
Registered: March 2005
Location: Pearland TX.
Karma: 0
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Ken. I don"t know how your system is plumbed. Did you spend a lot of time going downhill coming home? Maybe you transfered the rear into the front tank on the downhill side. Since I have never suffered from vapor lock in over 10 years, I never put my idea of running 2 carter electric pumps in parallel with check valves in front of both and putting a tee in the front to tie them together. Since both will run into your accumulator and the carb.will pull the gas off the bottom you could run a vent line from the top of the accumulator back into the the fuel filler vent and the fuel return line back to the tanks behind the pumps. This would eliminate the fuel selector valve and the switch could be used for the pumps. The check valves should eliminate the fuel transfer problem. What do you think? Hey, Report that Station to the weights and measures Department. Ain"t no way to get 50 into 40 even on empty. That gas station probably appreciates that extra 40 bucks you gave them.
Lynn L
76 Eleganza Cad.500
Pearland TX.
[Updated on: Wed, 05 September 2012 14:11] Report message to a moderator |
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| Re: [GMCnet] Dual Carter Pumps [message #183208 is a reply to message #183199] |
Wed, 05 September 2012 15:12 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Lynn,
My Main and Aux tanks each have a Carter 4070 whose output goes through a
filter to a check valve. The output of those tee'd check valves feeds the
1 g. accumulator tank beneath the driver's side cockpit floor. A return
from that tank feeds into the Aux tank drain plug. A bottom outlet from
the accumulator feeds another filter and the EFI's high pressure pump. The
throttle body return line goes into the accumulator. No selector valve and
no return into the fill tube.
The only mystery right now is why the Aux tank + accumulator only carried
me 10 miles after I selected the Aux. The terrain was basically level for
the final 100 miles of the trip, and since all return fuel goes into the
Aux tank, it should have held about 6 gallons upon selection. The only
change of any significance to the plumbing during this exercise was that I
found the fuel fill tube rotated so that the Aux nipple sloped slightly
upward toward the tank. I made it level, but that should not have affected
the reserve capacity by even one gallon.
The only possibility I've been able to think of is that BOTH boost pumps
were running while Main was selected; that would allow both tanks to empty
simultaneously. When I change the tank selector switch (with Prime
depressed), I can hear a change in pump sound. One pump is louder than the
other -- maybe because it's TWO running? I didn't intentionally change any
wiring, but... I'll find out tomorrow.
Ken H.
On Wed, Sep 5, 2012 at 3:03 PM, LYNN LAYCOCK wrote:
>
>
> Ken. I don"t know how your system is plumbed. Did you spend a lot of time
> going downhill coming home? Maybe you transfered the rear into the front
> tank on the downhill side. Since I have never suffered from vapor lock in
> over 10 years, I never put my idea of running 2 carter electric pumps in
> parallel with check valves in front of both and putting a tee in the front
> to tie them together. Since both will run into your accumulator and pull
> the gas off the bottom you could run a vent line from the top of the
> accumulator back into the the fuel filler vent and the fuel return line
> back to the tank behind the pumps. This would eliminate the fuel selector
> valve and the switch could be used for the pumps. The check valves should
> eliminate the fuel transfer problem. What do you think?
> --
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Dual Carter Pumps [message #183231 is a reply to message #183208] |
Wed, 05 September 2012 19:01 |
LYNN L
Messages: 140
Registered: March 2005
Location: Pearland TX.
Karma: 0
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Senior Member |
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Ken, that looks like a good setup. I wonder if you have a leaking check valve on the main tank side and when both pumps are on there is a loop to send fuel back into the main tank when the accumulator is full? That still won"t explain how 6 gallons being held for the generator left town. When I had a fuel injection setup, I used one high pressure pump ahead of the selector and a marine water and fuel filter seperator right into the accumulator with the regulated return going back in the filler pipe. It worked ok except gas fumes could be smelled on hot days when the gas cap vented and gas could still move between tanks in the hill country. There is an answer for every question and I"m sure you will find it with that inquizative mind of yours!! Besides that, as Hal said, we can always blame the Pilot..
Lynn L
76 Eleganza Cad.500
Pearland TX.
[Updated on: Wed, 05 September 2012 19:02] Report message to a moderator |
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