Got the new Delphi pump, hand pumped it and it was very stiff but pumped. Installed pump and plumbed in all the way to the tank, there I dropped a hose in a gas can. This uses 100% of the factory fuel system but the tank. It did not prime in this configuration before. I primed the fuel bowl with a little 100LL and fired it up. By the time I could look, the fuel filter was full and everything peachy. Golden!

However, after further review the removed pump turns out to be a Carter, or it has a Carter p/n on it. Interestingly, the two pumps are not the same in a significant way, or at least I think it is.

Old "Carter" pump that would not prime....


New Delphi pump that primed like a SOB....


Notice the difference in the pump lever? The old one has a slight bend in it the new does not. This significantly changes the way the pump lever engages the pump cam. I'm not professing which is right, all I know is the Delphi worked for at least 20 minutes so far and was able to pull prime through the whole fuel system in a blink. I cannot find anything obviously wrong with the Carter pump, but it didn't work very well.

I have hacked, bent, tweaked and otherwise modified the wrong fuel sender and pickup for one that should work. I also got some rubber patches that will replace the factory insulators between the tank and the frame and mounting straps.

I hope once all this is back together I can put to rest a claim of vapor lock and the rabbit hole the PO of this truck went, when it was mainly wrong(pickup tube and sender) and bad parts(pump). Moving on....

 

Good to hear you got the fuel flowing now
I wonder if you mounted the "bad" pump upside down so it was riding on the other side of the cam lobe if it would work then?
IIRC the 70's trucks runs the pump upside down and wonder if you got a early 300 pump and why I say mount upside down.
Dave ----

 

So an update to the update is that I have the full fuel system assembled finally, the sending unit o-ring was a hold up for a while. I put exactly 1 gal of gas in a completely empty tank and turned the key. Took about 15 seconds and fired off. The gas gauge reads "E" or slightly below. Happy that all my Rube Goldberg sending unit modifications for both the fuel level and the ability to pick up down to at least 1 gallon were successful. I'm moving on...

Next up... Waiting for gear marking compound to arrive to verify my rear gear setup. For those wondering; Cortizone 10 does work as a gear marking compound, but not good enough to go on just that.

 

So with 1 gallon in the tank did the gauge move any? It is nice the pump was able to pick up fuel that low.
I know both my tanks when empty the needle is below the line. I added 5 gallons and the needle came up to the line.
I run the front tank down (I use this first) to the line and then flip to the rear and depending what I am using the truck for or where I am going I will run the rear tank down to the line also.

White grease is what I use, brush it on just like the marking compound and turn the pinion a few times forward & back and see what you got as a pattern.
Dave ----

 

When I modified the sending unit I had, I set it up so that the float would just touch the bottom of the tank(there was A LOT of dorking around to get this to happen). I previously verified the sender does register "E" when allowed full droop. The actual fuel pickup I also had to modify to actually reach the bottom of the tank, but I went one better and positioned it in the deepest part of the tank and about 3/8 from bottom to the pickup tube.

It all works. But.... I do not understand why the sender will send the gauge buried to right when it is at the full level. It ohms out correctly and does indicate empty perfectly. But full, it goes off the charts. I can live with this, because few care when the tank is full, but when that sucker gets toward the bottom an accurate gauge nice, and that part works. In my case when the needle hits "E" you better be pulling into a gas station because it ain't playin!

 

only around 800 rpm

 

I think going beyond the full mark is a feature. Mine read way past the full mark in 1986 when it rolled off the truck from the factory.

 

I am also ok with that but I don’t think I would want the float sitting on the bottom of the tank when empty. That couple gallons of “reserve” would be better than actually being out of gas.

 

When acquiring a new vehicle or working on the sender it's a good idea to see how close to E you can go. Take a jerry can of fuel with you and see where the guage is when the engine coughs. E stands for Excercise.

 

My truck has two tanks so I checked the gauge accuracy/ how far I could go with a “spare” full tank.

 

My truck with 9 gallons in it reads empty, reads full when full, new tank and sender. Haven't had
a chance to run the fuel out as I still cannot get it out of the yard. I need a fuel pressure gauge
and adjustable regulator, to diagnose the current issue ,google is all over the place, any suggestions?

 

As I said in a email just get a fuel PSI gauge to check the output of the pump as it should not need a regulator.
Pump should not put out more than 7 PSI if it is more than that there is something wrong with the pump.
I am not running a regulator on my 300 motor and it has a motor driven fuel pump.
Dave ----

 

Thank you