Hello everyone, I have a 69' 3/4 ton camper special w/ a 390. My problem seems to be lack of fuel under a load. At an idle the truck purs, but when I get under a load it is starving.

With that said I have a new holley 1850 series 650 cfm that ran great for about five miles. After I filled it with gas it started to run bad (this fuel starvation deal). I also have a new fuel pump and filter. Is there a possibility that the filter on the bottom of the fuel pump could be clogged? If so is there an easy way to remove this filter to check it?

As I stated earlier it did not start running poor until I filled it up with fuel. I may have been about to run out of fuel when I stopped to get gas. Do these fuel pumps have a hard time pumping the air out of the fuel lines? Sounds silly, but Im looking for any possibility. I thank you in advance for any info you are willing to pass on.

 

Does sound tank crud related. Is your tank behind the seat, or under the truck? My tank that is behind the seat has no filter. Just a tube sticking in it that draws fuel. I had lots of rust and varnish problems when I first got my 68. It had sat in a garage for over three years, and the tank was varnish city. Also lots of fine rust that gets carried through the system. I had to pull the tank and clean it. On mine, the line itself once got clogged underneath the drivers side door. There is a little rubber hose that connects the long line to the shorter tank line. Mine got clogged with chunks of rust. I blew it out, and has been fine since. On mine, I use three fuel filters. I have one before the fuel pump that is clear plastic. " I can see if I'm getting gas". Then I have the stock filter in the fuel pump itself. I've had to clean it once after the tank problem. Was loaded with rust powder. Then I have another one yet, right before the carb. I like clean fuel.
I bet your tank had a fine coating of rust that got washed down to the bottom when you filled up. It's now clogging something. MK

 

The crud in the tank is a definite possibility. Another is the carb, have you checked the float level in both bowls on the 1850? There is a plug on pass side of carb for each bowl, float level is adjustable from the outside. I have a 460 with a 600 Holley in an F250 that would basically run out of steam on a grade with a loaded trailer. In its younger days, I could pass anything up a grade loaded or unloaded. I finally traced it to a low float level in the secondary bowl. Just my 2 cents of experience.

Jwrboss302

72 F250 CS
85 F250 4x4

 

That filter just unscrews to check it. And like the above said install a clear filter it will make you life alot easier to diagnose problems now and later with your fuel system.

 

Thanks for the help guys. I replaces the filter at the pump and I get plenty of fuel now. It was the fine rust particles.

Now I have a new problem. It is with the carb, at low rpm it feels like a missing or popping, possible vacume leak but I can not find it.

 

Spray WD40 at all possible leak areas. If the RPMs rise, you have found your leak.