MaliceResistor
Active Member
Hello all,
I am writing about an issue of fuel starvation in my 1974 383 Challenger.
Background: The car had not been run in quite a while, as I spent the winter rebuilding the front suspension. I had a suspicion that the gas in the tank had gone bad, so I did a test start/run by connecting the fuel line from the pump to a 2 gallon can on the ground. It fired up, so far so good. The tank had been relined a few years ago, and I had installed a new sender with return line to help solve a vapor lock issue.
I next decided to flush out the tank by connecting an air powered diaphragm pump to the fuel line. It operated with extreme difficulty, and only produced a trickle of fuel. I think this was the first sign of something else wrong. I applied blow gun into the fuel line, and gas started to coming out. It was varnished up, and I chased it with a couple gallons of clean gas into the tank clean to flush it good.
At this point, I was not feeling good about the external diaphragm pump's struggles, so I did the following:
I disconnect the following three lines, and with my son's help, used the blow gun end to end to check for leaks:
1. Vapor Hose at Charcoal Canister, and the Vapor Port at Tank Collector, below:
2. Fuel Return line from Filter to Sender:
3. Fuel Line from Pump to Tank Sender. Please note that the bent rubber hose was replaced with a straight 3/8" piece.
With my son's help, we confirmed that each of the three lines held pressure with no leaks.
With that done, I thought would do some upgrades:
3/8" hose where there had been 5/16".
New Fuel pump and filter:My next
After all of this, the pump is unable to draw fuel from the tank. I tried priming the fuel hose between the 4160 and the new pump, but the engine only used that up.
My next test is to disconnect the fuel line at the tank, and see if the car can pump from a gas can on the ground. I will use a clear inline filter here.
This leaves the tank. The sending unit is stainless steel, and not that old. The tank does not leak, but I suspect there is a vacuum issue at play somewhere. It has a metal locking vented cap made by stant. I have removed this during my attempted tank flushing, and it did not help.
I suspect that the issue has something to do with the vapor collector, but I am not sure what that could be. I have discovered that these are surprisingly unobtainable, yet gas tanks are still made with four vapor ports to attach to them??
Any guidance is greatly appreciated.
I am writing about an issue of fuel starvation in my 1974 383 Challenger.
Background: The car had not been run in quite a while, as I spent the winter rebuilding the front suspension. I had a suspicion that the gas in the tank had gone bad, so I did a test start/run by connecting the fuel line from the pump to a 2 gallon can on the ground. It fired up, so far so good. The tank had been relined a few years ago, and I had installed a new sender with return line to help solve a vapor lock issue.
I next decided to flush out the tank by connecting an air powered diaphragm pump to the fuel line. It operated with extreme difficulty, and only produced a trickle of fuel. I think this was the first sign of something else wrong. I applied blow gun into the fuel line, and gas started to coming out. It was varnished up, and I chased it with a couple gallons of clean gas into the tank clean to flush it good.
At this point, I was not feeling good about the external diaphragm pump's struggles, so I did the following:
I disconnect the following three lines, and with my son's help, used the blow gun end to end to check for leaks:
1. Vapor Hose at Charcoal Canister, and the Vapor Port at Tank Collector, below:
2. Fuel Return line from Filter to Sender:
3. Fuel Line from Pump to Tank Sender. Please note that the bent rubber hose was replaced with a straight 3/8" piece.
With my son's help, we confirmed that each of the three lines held pressure with no leaks.
With that done, I thought would do some upgrades:
3/8" hose where there had been 5/16".
New Fuel pump and filter:My next
After all of this, the pump is unable to draw fuel from the tank. I tried priming the fuel hose between the 4160 and the new pump, but the engine only used that up.
My next test is to disconnect the fuel line at the tank, and see if the car can pump from a gas can on the ground. I will use a clear inline filter here.
This leaves the tank. The sending unit is stainless steel, and not that old. The tank does not leak, but I suspect there is a vacuum issue at play somewhere. It has a metal locking vented cap made by stant. I have removed this during my attempted tank flushing, and it did not help.
I suspect that the issue has something to do with the vapor collector, but I am not sure what that could be. I have discovered that these are surprisingly unobtainable, yet gas tanks are still made with four vapor ports to attach to them??
Any guidance is greatly appreciated.
