Moved tank, now it runs bad - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Hudsonaj36 · 07-09-2015, 11:18 PM

I moved my fuel tank to the rear, put in a new mechanical fuel pump, and a new steel fuel line. Now it's running lean??? Tried another new fuel pump and no change. Tried new filter with no change. Any ideas?

Not using a return line and I do have the tank vented.

Mmorgan32 · 07-09-2015, 11:37 PM

Put in an in tank pump to push the fuel. I don't think a mechanical pump on the engine will work with your tank that far away maybe a pump with more psi?

**Already Gone** · 07-10-2015, 12:07 AM

I have an ECE stainless tank that I want to install in my 72 stock 350 engine longbox. I was talking with my insatller yesterday and asked if my mechanical pump on the engine block would be sufficient to suck the gas from the back of the truck and he said he has done a few of these and the stock fuel pump on the block has done the job. I'll be watching this thread for other comments, ideas.

Hudsonaj36 · 07-10-2015, 12:20 AM

Yeah I figured a lot of cars came with rear mounted tanks and the pump is a carter street and strip 6psi at 110gph. The tank is poly with a sump and the line comes out 90's up about 8 inches then 90's over about 8 inches then follows the frame to the pump.

Hudsonaj36 · 07-10-2015, 12:22 AM

I almost feel like it's a coincidence and I just happens to get a vacuum leak at the same time, but there were no issues prior to moving the tank.

Mmorgan32 · 07-10-2015, 12:23 AM

Maybe something obstructing the opening at one of your fittings? Like Teflon tape

Mmorgan32 · 07-10-2015, 12:24 AM

If the vacuum leak is on your carb that will make it run lean

cdowns · 07-10-2015, 05:00 AM

The good old mechanical pump worked just fine for the millions of suburbans on the roads for the past 50years or so

makes you think

**Already Gone** · 07-10-2015, 05:36 AM

Quote:

Originally Posted by cdowns

The good old mechanical pump worked just fine for the millions of suburbans on the roads for the past 50years or so

makes you think

Excellent point..

Hudsonaj36 · 07-10-2015, 11:01 AM

I'm going to run it out of a fuel can next to the pump and see if that changes anything.

cdowns · 07-10-2015, 01:27 PM

Quote:

Originally Posted by Hudsonaj36

I'm going to run it out of a fuel can next to the pump and see if that changes anything.

SURE IT WILL PROBALY RUN LIKE A TOP DUE TO PROPER VENTING OF THE fuel can

makes you think

Hudsonaj36 · 07-10-2015, 01:30 PM

The tank is also vented, I even removed the cap to verify but no change

70' · 07-10-2015, 01:46 PM

What process was used to ensure all the air was purged from the new fuel line? I would suspect an air bubble in the line between the tank and the pump. Probably in a bend, which would allow flow, but maybe not full flow to adequate feed the pump. If it were me, I would unhook from the pump, and purge the line with fuel backwards to the tank using a small hand pump, then reconnect and see what happens.

Hudsonaj36 · 07-10-2015, 01:58 PM

I sucked fuel through with a hand pump, even though a mech fuel pump is self priming

MARKDTN · 07-10-2015, 02:12 PM

Where is the filter? It may not work if you try to suck through a filter. The filter should be between the pump and the carb.

Hudsonaj36 · 07-10-2015, 02:34 PM

The filter is between the pump and carb

Redline novdog · 07-10-2015, 06:22 PM

can you put a pressure gauge on by the carb? Just jacking up a vehicle can slosh sediment from carb bowl into the jets.Filters don't catch everything !

autocross · 07-10-2015, 09:37 PM

What size fuel line did you install when you relocated the tank. It should be at least a 3/8 ID line if its got more HP then stock. A return line is good to eliminate vapor lock. It could also be something in one of your jets blocking fuel too. Pull the fuel line from the carb. have someone crank the motor over while you catch it in a measuring cup and see if your getting it there. If you are then it's filter or in the carb itself.

brad_man_72 · 07-12-2015, 11:31 AM

Put the original fuel pump back on. You may be pushing fuel past the float valve. Worth a shot for free.

clemsonteg · 07-12-2015, 05:58 PM

Have you checked all connections? A loose connection could cause the pump to suck air rather than fuel. Not enough fuel=running like crap. I had this issue yesterday when driving down the highway. When I got home I found a hose clamp on my pre pump filter had come loose. It didn't allow fuel to leak out, but it allowed the pump to suck air and not deliver enough fuel when the engine was under heavy load.

Hudsonaj36 · 07-12-2015, 06:08 PM

I'm going to do some work on it tomorrow

cplcorndog · 07-12-2015, 06:24 PM

Hi there,

So a lot of good information from the reply's, so I'll give you what I did and no issues since. I added an electric switched Holly pump. My guess is that your tank is to far away to get the proper amount of fuel, and your mechanical pump is most likely trying to suck fuel though a filter, almost like a straw. Even if you got it to work correctly, I'm certain that you'll over work your pump and burn it up.

If you get an electric pump place it as close to the tank as possible and then place a filter between the electric pump and carb (like said earlier). Electric pumps are made to push fuel not pull it. Then place your regulator somewhere in the engine bay so it's easy to adjust the psi on it. If you don't have a psi valve, you should get one. I hope this helps in some way.

racerface · 07-12-2015, 08:00 PM

Cdowns hit it right on the head. The mechanical pump will work fine. Electrical pump just covers up the problem. Use 3/8's line and double check the system from tank to carb. Happy hunting.

SierraMtns · 07-13-2015, 02:48 AM

Do you still have the in cab tank installed? You could switch it back and see if it fixes the problem.

07-09-2015, 11:18 PM	#1
Hudsonaj36 Registered User Join Date: Dec 2013 Location: Chico ca Posts: 69	Moved tank, now it runs bad I moved my fuel tank to the rear, put in a new mechanical fuel pump, and a new steel fuel line. Now it's running lean??? Tried another new fuel pump and no change. Tried new filter with no change. Any ideas? Not using a return line and I do have the tank vented.

07-09-2015, 11:37 PM	#2
Mmorgan32 Registered User Join Date: Jul 2013 Location: Fresno, ca Posts: 303	Re: Moved tank, now it runs bad Put in an in tank pump to push the fuel. I don't think a mechanical pump on the engine will work with your tank that far away maybe a pump with more psi? __________________ 1972 gmc c15 short bed... Sold 1970 chevy custom camper patina daily driver

07-10-2015, 12:07 AM	#3
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,104	Re: Moved tank, now it runs bad I have an ECE stainless tank that I want to install in my 72 stock 350 engine longbox. I was talking with my insatller yesterday and asked if my mechanical pump on the engine block would be sufficient to suck the gas from the back of the truck and he said he has done a few of these and the stock fuel pump on the block has done the job. I'll be watching this thread for other comments, ideas. __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " Circumsatances Do Not Change Responsibility " " The Sky is not the Limit, Your Mind is." Marilyn Monroe .. RIP Charlie Watts 1941 - 2021

07-10-2015, 12:20 AM	#4
Hudsonaj36 Registered User Join Date: Dec 2013 Location: Chico ca Posts: 69	Re: Moved tank, now it runs bad Yeah I figured a lot of cars came with rear mounted tanks and the pump is a carter street and strip 6psi at 110gph. The tank is poly with a sump and the line comes out 90's up about 8 inches then 90's over about 8 inches then follows the frame to the pump.

07-10-2015, 12:22 AM	#5
Hudsonaj36 Registered User Join Date: Dec 2013 Location: Chico ca Posts: 69	Re: Moved tank, now it runs bad I almost feel like it's a coincidence and I just happens to get a vacuum leak at the same time, but there were no issues prior to moving the tank.

07-10-2015, 12:23 AM	#6
Mmorgan32 Registered User Join Date: Jul 2013 Location: Fresno, ca Posts: 303	Re: Moved tank, now it runs bad Maybe something obstructing the opening at one of your fittings? Like Teflon tape __________________ 1972 gmc c15 short bed... Sold 1970 chevy custom camper patina daily driver

07-10-2015, 12:24 AM	#7
Mmorgan32 Registered User Join Date: Jul 2013 Location: Fresno, ca Posts: 303	Re: Moved tank, now it runs bad If the vacuum leak is on your carb that will make it run lean __________________ 1972 gmc c15 short bed... Sold 1970 chevy custom camper patina daily driver

07-10-2015, 05:00 AM	#8
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: Moved tank, now it runs bad The good old mechanical pump worked just fine for the millions of suburbans on the roads for the past 50years or so makes you think __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

07-10-2015, 11:01 AM	#10
Hudsonaj36 Registered User Join Date: Dec 2013 Location: Chico ca Posts: 69	Re: Moved tank, now it runs bad I'm going to run it out of a fuel can next to the pump and see if that changes anything.

07-10-2015, 01:30 PM	#12
Hudsonaj36 Registered User Join Date: Dec 2013 Location: Chico ca Posts: 69	Re: Moved tank, now it runs bad The tank is also vented, I even removed the cap to verify but no change

07-10-2015, 01:46 PM	#13
70' Registered User Join Date: Nov 2014 Location: Dickinson, ND Posts: 197	Re: Moved tank, now it runs bad What process was used to ensure all the air was purged from the new fuel line? I would suspect an air bubble in the line between the tank and the pump. Probably in a bend, which would allow flow, but maybe not full flow to adequate feed the pump. If it were me, I would unhook from the pump, and purge the line with fuel backwards to the tank using a small hand pump, then reconnect and see what happens.

07-10-2015, 01:58 PM	#14
Hudsonaj36 Registered User Join Date: Dec 2013 Location: Chico ca Posts: 69	Re: Moved tank, now it runs bad I sucked fuel through with a hand pump, even though a mech fuel pump is self priming

07-10-2015, 02:12 PM	#15
MARKDTN Registered User Join Date: Jan 2011 Location: Chattanooga, TN Posts: 2,141	Re: Moved tank, now it runs bad Where is the filter? It may not work if you try to suck through a filter. The filter should be between the pump and the carb. __________________ '83 K20-TPI '73 C10 '79 C10-ex-diesel(SOLD) '07 Tahoe(Son driving) '14 Suburban-DD '71 C10-current project

07-10-2015, 02:34 PM	#16
Hudsonaj36 Registered User Join Date: Dec 2013 Location: Chico ca Posts: 69	Re: Moved tank, now it runs bad The filter is between the pump and carb

07-10-2015, 06:22 PM	#17
Redline novdog Registered User Join Date: Jan 2012 Location: Washington,Il Posts: 632	Re: Moved tank, now it runs bad can you put a pressure gauge on by the carb? Just jacking up a vehicle can slosh sediment from carb bowl into the jets.Filters don't catch everything ! __________________ It builds on my intelligence when I make a mistake, Boy am I building on it! '67 C-10,'70 Nova SS



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07-10-2015, 09:37 PM	#18
autocross Registered User Join Date: May 2015 Location: RED BLUFF Posts: 23	Re: Moved tank, now it runs bad What size fuel line did you install when you relocated the tank. It should be at least a 3/8 ID line if its got more HP then stock. A return line is good to eliminate vapor lock. It could also be something in one of your jets blocking fuel too. Pull the fuel line from the carb. have someone crank the motor over while you catch it in a measuring cup and see if your getting it there. If you are then it's filter or in the carb itself.

07-12-2015, 11:31 AM	#19
brad_man_72 the boat guy Join Date: Jul 2007 Location: springfield mo Posts: 2,339	Re: Moved tank, now it runs bad Put the original fuel pump back on. You may be pushing fuel past the float valve. Worth a shot for free. __________________ 67, swb, fleet, tach, throttle, 5.3, 4l60e, 3.73's, fuel cell, 5 lug, p.d.b., 4-6 drop. great little truck 66, stevens drag/ski 18' silouette, 350, 2.02 doublehump heads. comp extreme marine 278 cam, vette 7 fin valve covers, old polished edelbrock intake, velvetdrive, casale v-drive, adj cavitation plate. 28, model a rpu project,

07-12-2015, 05:58 PM	#20
clemsonteg Registered User Join Date: Jul 2012 Location: Anderson,SC Posts: 953	Re: Moved tank, now it runs bad Have you checked all connections? A loose connection could cause the pump to suck air rather than fuel. Not enough fuel=running like crap. I had this issue yesterday when driving down the highway. When I got home I found a hose clamp on my pre pump filter had come loose. It didn't allow fuel to leak out, but it allowed the pump to suck air and not deliver enough fuel when the engine was under heavy load.

07-12-2015, 06:08 PM	#21
Hudsonaj36 Registered User Join Date: Dec 2013 Location: Chico ca Posts: 69	Re: Moved tank, now it runs bad I'm going to do some work on it tomorrow

07-12-2015, 06:24 PM	#22
cplcorndog Registered User Join Date: Jun 2015 Location: Tracy, CA Posts: 18	Re: Moved tank, now it runs bad Hi there, So a lot of good information from the reply's, so I'll give you what I did and no issues since. I added an electric switched Holly pump. My guess is that your tank is to far away to get the proper amount of fuel, and your mechanical pump is most likely trying to suck fuel though a filter, almost like a straw. Even if you got it to work correctly, I'm certain that you'll over work your pump and burn it up. If you get an electric pump place it as close to the tank as possible and then place a filter between the electric pump and carb (like said earlier). Electric pumps are made to push fuel not pull it. Then place your regulator somewhere in the engine bay so it's easy to adjust the psi on it. If you don't have a psi valve, you should get one. I hope this helps in some way.

07-12-2015, 08:00 PM	#23
racerface Registered User Join Date: Dec 2008 Location: wellington ohio Posts: 55	Re: Moved tank, now it runs bad Cdowns hit it right on the head. The mechanical pump will work fine. Electrical pump just covers up the problem. Use 3/8's line and double check the system from tank to carb. Happy hunting. __________________ Racerface Wellington, Ohio Freedom Isn't Free! GO BUCKEYES!!! Toys: 68 C-30 327-400turbo 68 C-30 Open Road Camper 327-400turbo 81 GMC Sierra 1500 250-350turbo Long Bed 83 K-10 4X4 Scottsdale

07-13-2015, 02:48 AM	#24
SierraMtns Registered User Join Date: Jun 2014 Location: Shingle Springs, CA Posts: 869	Re: Moved tank, now it runs bad Do you still have the in cab tank installed? You could switch it back and see if it fixes the problem.

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