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

shrtbx · 12-12-2007, 08:46 PM

i have noticed on a few occasions that when the tank gets down to around half full or a little less, the engine starts to idle bad at stops. As soon as i step on the gas it runs fine though. When i fill it back up the bad idling goes away. Could that be a fuel sending unit problem. Im also having problems with the accuracy of the gauge as well as a stated in another post.

**old Rusty C10** · 12-12-2007, 09:23 PM

any chance that the tank is really empty or almost empty at half on the guage?

shrtbx · 12-12-2007, 09:25 PM

well filled it up before a trip this weekend to get a better idea of whats going on in the tank and i see the same thing happening. After i burn about 8 gallons it starts to idle bad, some im pretty sure there is a good amount of gas in the tank.

**old Rusty C10** · 12-12-2007, 09:52 PM

hmm thats a wierd one .. either the float or possibly something in the tank that makes contact with the pickup once you get to half a tank and the gas stops moving when you stop at a light?
this thing is EFI or carbed?

shrtbx · 12-13-2007, 12:33 AM

its carbed. Edelbrock carb and manifold. I just filled up the tank and its running fine now. A buddy of mine said i might have water in the tank. I think the tank is dirty, but its been filled and refilled a few times. I just started driving it consistently a few weeks ago. i bougt it 10 months ago. i just noticed it after the new (rebuilt) carb. When i bought the truck it had a 305 that took a dive. So i replaced it with a 350 i had.

Eyegore · 12-13-2007, 07:05 AM

As a suggestion you may want to replace your gas cap. There is a certain amount of pressure to maintain and when the tank is full the less room for air, when half a tank more room and more air in the lines and rough idle.

Just a thought.

**old Rusty C10** · 12-13-2007, 09:15 AM

well a can of dry gas wont hurt it if you think its water but i think prolly dirt orsomething else.. the gas cap is also an idea but im not sure he is right either... its a six dollar fix there so why not try it i think id drop the tanks and have it boiled out and make sure all the hoses /float assy are good and all

Eyegore · 12-13-2007, 10:13 AM

The more I think of this that it might have to do with your rebuilt carb, that when you said you started to ntice the problem. I would install a see through fuel filter just before the carb to see if your fuel has bubbles in it, this sounds more like vapor lock than anything else. Installing a see through filter will let you know what the fuel is doing.

shrtbx · 12-13-2007, 01:34 PM

Well i filled it up and found that im still getting the weird sound at idle. Its more of like small booming sounds coming from the engine. WHen the tank is full the sound is faint, but as the fuel level drops the sound is more dominate and the truck kind of gets a shake in it. Im gonna try the fuel cap though..its a start. I already have a see through filter before the carb so i will check that out today too.

12-12-2007, 08:46 PM	#1
shrtbx Registered User Join Date: Feb 2007 Location: los angeles Posts: 202	More fuel issues i have noticed on a few occasions that when the tank gets down to around half full or a little less, the engine starts to idle bad at stops. As soon as i step on the gas it runs fine though. When i fill it back up the bad idling goes away. Could that be a fuel sending unit problem. Im also having problems with the accuracy of the gauge as well as a stated in another post.

12-12-2007, 09:23 PM	#2
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,310	Re: More fuel issues any chance that the tank is really empty or almost empty at half on the guage? __________________ Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!!

12-12-2007, 09:25 PM	#3
shrtbx Registered User Join Date: Feb 2007 Location: los angeles Posts: 202	Re: More fuel issues well filled it up before a trip this weekend to get a better idea of whats going on in the tank and i see the same thing happening. After i burn about 8 gallons it starts to idle bad, some im pretty sure there is a good amount of gas in the tank. Last edited by shrtbx; 12-12-2007 at 09:26 PM.

12-12-2007, 09:52 PM	#4
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,310	Re: More fuel issues hmm thats a wierd one .. either the float or possibly something in the tank that makes contact with the pickup once you get to half a tank and the gas stops moving when you stop at a light? this thing is EFI or carbed? __________________ Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!!

12-13-2007, 12:33 AM	#5
shrtbx Registered User Join Date: Feb 2007 Location: los angeles Posts: 202	Re: More fuel issues its carbed. Edelbrock carb and manifold. I just filled up the tank and its running fine now. A buddy of mine said i might have water in the tank. I think the tank is dirty, but its been filled and refilled a few times. I just started driving it consistently a few weeks ago. i bougt it 10 months ago. i just noticed it after the new (rebuilt) carb. When i bought the truck it had a 305 that took a dive. So i replaced it with a 350 i had. Last edited by shrtbx; 12-13-2007 at 12:38 AM.

12-13-2007, 07:05 AM	#6
Eyegore What Hump? Join Date: Apr 2003 Location: New River AZ Posts: 2,009	Re: More fuel issues As a suggestion you may want to replace your gas cap. There is a certain amount of pressure to maintain and when the tank is full the less room for air, when half a tank more room and more air in the lines and rough idle. Just a thought. __________________ Lil red 86 c-10 99 Sub 78 Camper Special w/ 454

12-13-2007, 09:15 AM	#7
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,310	Re: More fuel issues well a can of dry gas wont hurt it if you think its water but i think prolly dirt orsomething else.. the gas cap is also an idea but im not sure he is right either... its a six dollar fix there so why not try it i think id drop the tanks and have it boiled out and make sure all the hoses /float assy are good and all __________________ Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!! Last edited by old Rusty C10; 12-13-2007 at 09:16 AM.

12-13-2007, 10:13 AM	#8
Eyegore What Hump? Join Date: Apr 2003 Location: New River AZ Posts: 2,009	Re: More fuel issues The more I think of this that it might have to do with your rebuilt carb, that when you said you started to ntice the problem. I would install a see through fuel filter just before the carb to see if your fuel has bubbles in it, this sounds more like vapor lock than anything else. Installing a see through filter will let you know what the fuel is doing. __________________ Lil red 86 c-10 99 Sub 78 Camper Special w/ 454

12-13-2007, 01:34 PM	#9
shrtbx Registered User Join Date: Feb 2007 Location: los angeles Posts: 202	Re: More fuel issues Well i filled it up and found that im still getting the weird sound at idle. Its more of like small booming sounds coming from the engine. WHen the tank is full the sound is faint, but as the fuel level drops the sound is more dominate and the truck kind of gets a shake in it. Im gonna try the fuel cap though..its a start. I already have a see through filter before the carb so i will check that out today too.



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