fuel problem - The 1947 - Present Chevrolet & GMC Truck Message Board Network

PMS · 07-31-2011, 06:13 PM

I haven't been here in a long, long time. Finally got my 72 long bed together and running but I am having fuel problems. I put a fuel tank from a newer suburban behind the rear axle. Replaced the 1/4 return line on the sender with a 1/2" line for a pick tube for the electric pump. I removed the in tank pump and used the stock 3/8" line as a return line from the regulator mounted in the engine compartment. The truck has been lowered 5/6 so the pump could not be mounted below the tank. The pump is mounted flush with the top of the tank. The inlet to the pump is about 20" in length total. 1/2" lines run to the regulator. When you first start the truck it will maintain 7psi but after driving for about 10-15 minutes the pressure drops to 3psi. I have checked the pressure with a different gauge and it is not the gauge. The electric pump is a carter vane style pump. Do I need a bigger / higher psi pump or will I have to have a custom tank built with a sump system? Have any on you had this problem?

cdowns · 07-31-2011, 08:16 PM

do you have a working vent for your tank?

chevytruckluver · 07-31-2011, 08:17 PM

The pump should be able to pull from the tank. So it sounds like your problem is where you are trying to pull fuel from, the original size 1/4 inch, you will always have a 1/4 inch line even if you attach a 1/2 to it. Also are you sure that 1/4 in line inside the tank is picking up fuel all the way at the bottom of the tank? Why are you wanting to use such a large line? with that pump 3/8 should work fine. got any more info on the motor? why are you using a regulator with a return line? are you running a fuel filter?

PMS · 08-01-2011, 02:01 PM

A 1/2" od line was placed through the top of the sending unit and into the tank as a pickup tube. I am using the original 3/8" line as a return for my regulator. I had a filter before the pump but with this problem I removed the filter element to see if it was a restriction. Yes the tank is vented with a roll over valve and a vented cap. I set the fuel system up for the next engine in line - blown or big/big block.

07-31-2011, 06:13 PM	#1
PMS Registered User Join Date: Aug 2004 Location: Overland Park, KS Posts: 79	fuel problem I haven't been here in a long, long time. Finally got my 72 long bed together and running but I am having fuel problems. I put a fuel tank from a newer suburban behind the rear axle. Replaced the 1/4 return line on the sender with a 1/2" line for a pick tube for the electric pump. I removed the in tank pump and used the stock 3/8" line as a return line from the regulator mounted in the engine compartment. The truck has been lowered 5/6 so the pump could not be mounted below the tank. The pump is mounted flush with the top of the tank. The inlet to the pump is about 20" in length total. 1/2" lines run to the regulator. When you first start the truck it will maintain 7psi but after driving for about 10-15 minutes the pressure drops to 3psi. I have checked the pressure with a different gauge and it is not the gauge. The electric pump is a carter vane style pump. Do I need a bigger / higher psi pump or will I have to have a custom tank built with a sump system? Have any on you had this problem?

07-31-2011, 08:16 PM	#2
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: fuel problem do you have a working vent for your tank? __________________ 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

07-31-2011, 08:17 PM	#3
chevytruckluver Eat, Sleep, Drive a Chevy Join Date: Apr 2010 Location: the town of the cow, Texas Posts: 1,152	Re: fuel problem The pump should be able to pull from the tank. So it sounds like your problem is where you are trying to pull fuel from, the original size 1/4 inch, you will always have a 1/4 inch line even if you attach a 1/2 to it. Also are you sure that 1/4 in line inside the tank is picking up fuel all the way at the bottom of the tank? Why are you wanting to use such a large line? with that pump 3/8 should work fine. got any more info on the motor? why are you using a regulator with a return line? are you running a fuel filter? __________________ Trey Silence may be Golden, but Duct Tape is Silver! 72 Short Step 57 "big window" short step

08-01-2011, 02:01 PM	#4
PMS Registered User Join Date: Aug 2004 Location: Overland Park, KS Posts: 79	Re: fuel problem A 1/2" od line was placed through the top of the sending unit and into the tank as a pickup tube. I am using the original 3/8" line as a return for my regulator. I had a filter before the pump but with this problem I removed the filter element to see if it was a restriction. Yes the tank is vented with a roll over valve and a vented cap. I set the fuel system up for the next engine in line - blown or big/big block.



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