Gas sender unit

[JAM1777]

Hi,
I have a 1969 chevy C10 longbed. I have had a problem with the engine bogging down at freeway speeds and as soon as I get into the slow lane and speed drops to about 40mph the truck starts picking up speed again. I have put in a new chevy performance 290 crate, i have rebuilt the carb, I have installed a new fuel filter, and installed a new msd streetfire distributer. I'm running out of trouble shooting ideas and its driving me crazy. the one other thing I remember is when I bought the truck, the gas gauge was working most of the time and slowly stopped reading.....so my question is.......if the float on the sender unit went out, would that cause the filter sock to drop and stay at the bottom of the tank and get dirty enough so that at freeway speeds my truck would bog down and act like its not getting gas??? Does anyone have experience in this same issue?? any help would be very appreciated

[ray_mcavoy]

No, a failed float will only cause the gauge to read incorrectly. It won't affect engine performance.

In other words, you can think of the sending unit as 2 separate components. One is a pick-up tube that stays in a fixed position and normally places the "sock" near the bottom of the tank. The other is the variable resistance sender & it's float that only serves to operate the fuel gauge.

Now, that's not to say the sending unit isn't the source of your problems. The sock could still be dirty and restricting the fuel flow.

[JAM1777]

Ok, Yes i realized after I posted that the filter sock stays pretty much stationery at the bottom of the tank. Has anyone on this forum ever had a problem with the filter sock causing fuel flow problems causing the engine to bog down at freeway speeds??

[LockDoc]

Originally Posted by JAM1777

Ok, Yes i realized after I posted that the filter sock stays pretty much stationery at the bottom of the tank. Has anyone on this forum ever had a problem with the filter sock causing fuel flow problems causing the engine to bog down at freeway speeds??

Sure, if the sock is partially plugged it will restrict fuel flow. The more RPM's the engine is turning the more fuel it needs and the more a restriction will affect it. (freeway speeds) Also, if the sock is rotted or missing it could be picking up bigger chunks of debris in the pickup tube. They will drop back off of the tube when the engine is shut off.

If you are using a Q-jet be sure and replace the filter in the carb inlet. It will catch fine particles that will pass through an inline filter.

LockDoc

[jamie72]

was your truck a factory 6cyl. truck? they came with smaller fuel lines from tank.

[JAM1777]

Im not sure what a Q jet is? I have a holley 650 carb

[JAM1777]

Originally Posted by jamie72

was your truck a factory 6cyl. truck? they came with smaller fuel lines from tank.

I am not sure........will smaller fuel lines that were originally for a stock 6 make a difference when running a V-8? How do I know what size my fuel lines should be?

[Blakeman350]

I was having pretty much the same problem. I fixed, replaced or rebuilt everything I could think of before finally pulling the tank. I cleaned and coated the tank and replaced the sending unit. The sock was pretty much completely plugged and the tank was full of rust and junk and the float had a pin hole. Haven't had a problem since. Good luck

[LockDoc]

Originally Posted by JAM1777

Im not sure what a Q jet is? I have a holley 650 carb

GM Quadrajet carb.

LockDoc

[JAM1777]

Ok, is cleaning and sealing the gas tank an easy do it yourself type of thing?? Does any know how to do it? What products and cleaners to use?? Or would I need to have a someone do it?

[Blakeman350]

You have to take the tank out of the truck which is a bit of work if your by yourself. Napa sells a kit that has everything to clean and coat. It's really easy to do but takes alot of time between stages and dry time but in my opinion it was definitely worth it. Or u could just buy a new tank, their pretty inexpensive.