I'm trying to salvage this nasty fuel sender from my 1976 Chinook project. I've got everything cleaned up but I'm concerned about this thing above my fuel pump. Can anyone tell me what it is? Maybe a pressure regulator? I can blow straight through it, and with one side plugged no air comes out the side vent.

 

Maybe a check valve that keeps the fuel in the line from draining back into the tank?

 

Here you go…
https://www.yotatech.com/forums/f114...cement-316723/

 

I don' see how mine can be a check valve, I can look straight through it.

 

You’re correct, it’s a relief valve.

 

Thanks for pointing to my post on this.

 

I may have to start a new thread , but I am trying to help a friend with a 77 Chinook, determine if his fuel pump is bad or the fuel relay is not providing the power to it.. I have tested the resistor on the pax fender well and it is 1.4 ohms, have not checked it under high heat , but I know from your previous posts which had great photos and advice, I need to find the fuel pump relay. Have searched the underdash, which is occupied by the a/c unit for the relay but have found nothing that even looks like the photo of an older relay you posted back in March 2020. Do you or anyone else reading this thread have any suggestions on where to looked next.. The black / yelow wire from the resistor is supposed to lead back to the relay, but that disappears into the wrapped wiring harness that is close to the resistor. We are not getting fuel at the carb or the small inline filter located just above the fuel line where it come out and up frome the frame on its way to the carb.. Thanks for your advice and comments.. JR in auburn, NY

 

I may have to start a new thread , but I am trying to help a friend with a 77 Chinook, determine if his fuel pump is bad or the fuel relay is not providing the power to it.. I have tested the resistor on the pax fender well and it is 1.4 ohms, have not checked it under high heat , but I know from your previous posts which had great photos and advice, I need to find the fuel pump relay. Have searched the underdash, which is occupied by the a/c unit for the relay but have found nothing that even looks like the photo of an older relay you posted back in March 2020. Do you or anyone else reading this thread have any suggestions on where to looked next.. The black / yelow wire from the resistor is supposed to lead back to the relay, but that disappears into the wrapped wiring harness that is close to the resistor. We are not getting fuel at the carb or the small inline filter located just above the fuel line where it come out and up frome the frame on its way to the carb.. Thanks for your advice and comments.. JR in auburn, NY

 

On most '75 to '78 pickups, the fuel pump relay should be located inside the cab, under the dash in/around the center section, to the passenger side of the A/C-Heater fan box On some Chinooks or other brand motorhome frames that have the dual rear wheel axles, it may be located somewhere around the steering column. The original style relay has a metal tab on it for a bolt to go thru to attach it to the underdash. Given the age of our trucks we never know what any previous owners have done, so it's possible that it may not be bolted up to the dash frame. Someone may have been in there previously & just tucked it up into the dash instead, so you're going to need a good rummaging search to find it. Or you may even find the unconnected 5 wire socket for the relay, as the relay may be missing entirely. OEM relays are expensive or hard to find & people often "borrow" them if they can.

If you can at least find the fuel pump socket & the relay is missing, you can still test the fuel pump for functionality. All you'd need is a short jumper wire to temporarily replace the relay for testing purposes (** see important note below**), going from the Black/White terminal (from Ignition Switch START) to the Black/Red terminal (power wire to fuel pump). With this setup & if the fuel pump is working, you should get fuel flow to the carb after a few seconds of engine cranking, as long as your fuel feed line is clear, fuel filter isn't clogged, pump sock filter isn't clogged & you have fuel in the tank.
** IMPORTANT NOTE ** ONLY DO THE ABOVE TO TEST FOR FUEL PUMP FUNCTIONALITY. DO NOT TRY TO RUN THE ENGINE FOR ANY LENGTH OF TIME IN THIS MANNER. IT ISN'T SAFE TO DRIVE THE VEHICLE THIS WAY & IF THE FUEL PUMP IS WORKING, YOU COULD KILL THE PUMP IN JUST A FEW MINUTES. THIS TEST PROCEEDURE SENDS FULL BATTERY VOLTAGE TO THE PUMP, & THE PUMP WAS NOT DESIGNED TO RUN CONTINOUSLY ON FULL BATTERY VOLTAGE.

If I can help with any other info I might have just ask.

 

thanks, I will search again!