73 Mopar 340 not pumping fuel

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MaxLegroom

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Ok so I can not get my 73 340 to pump any fuel. I put a new mechanical fuel pump on, new rubber fuel line, new fuel filter on the output of the pump, blew air through the metal fuel line, cleaned out the fuel pickup, cleaned the fuel pickup screen. And when I have the fuel line pulled off the carb there is no fuel coming out. Anyone have any other suggestions?
 
So it was working before and you just put on new fuel pump?
You have the pump arm below the cocentric?
 
I made sure that the lines were not reversed. And I put a new carb on and couldn't get it started so I pulled the line off and that's when I realized it wasn't pumping fuel. It was pumping fuel just fine before I pulled the old carb off. And Im pretty sure the arm on the pump is below because I pulled the new pump off and saw the marks on top of the arm and when I was putting the pump on it wanted to pull down so when I tightened the bolts it pulled the pump up into the right spot.
 
So the old pump was pumping fine. But when I put the new carb on it wasn't pumping. So that's when I replaced the pump.
 
Yea, when you push that pump arm in there, you can feel it push against the bottom of the round eccentric. You hold it in place and start a bolt
 
So i can't even pull fuel out of tank because after cranking for a long time with the fuel line disconnect from the carb I pulled the line off the inlet of the pump and it's bone dry.
 
Pull the fuel line from the tank off the pump and the feed the the carb.

Have someone crack the engine.

You should get some suction at the inlet.

It's a diaphragm and a one way valve in the pump. If the one-way valve is leaking there will be no suction.

If not pull the pump.
 
Put a vacuum gauge on the inlet of the pump and see if it has vacuum while turning the engine over. If it does hook it back up and do the same thing at the sending unit. I have seen many bad pumps from the chain stores.
 
MaxLegroom said:
So i can't even pull fuel out of tank because after cranking for a long time with the fuel line disconnect from the carb I pulled the line off the inlet of the pump and it's bone dry
Click to expand...
What else have you done to the car lately
 
I just started working on it and I put a new Edelbrock performer rpm intake on because someone had stripped out the carb stud threads. And I put a holly vacuum secondary on.
 
Did you make SURE your new pump is for a small block? The big block pump will fit but the arm will not reach the eccentric so it won't pump. Same with a small block or big block Chevy pump. They all have the same bolt pattern.
 
On one occasion my Dart had the same problem. Turned out that the keyway on the cam had worn off and the eccentric was just spinning freely.
 
These are the new and old pumps side by side the left one is the new one. Do you think that it is a big block one? It is a little shorter

16765013382375216178259694895082.jpg
 
No. The big block pump is short, like a Chevy pump. That arm sure is different, though.
 
Or a bad line going back that the pump cant suck through. Try new (or old) pump with inlet line to a gas can...
Both pumps look new to me...

Probably old pump is fine and like someone above said- just having the pump turn over by the starter isn't enough. Need to get them RPM's up.
 
"Ok so I can not get my 73 340 to pump any fuel. I put a new mechanical fuel pump on, new rubber fuel line, new fuel filter on the output of the pump, blew air through the metal fuel line, cleaned out the fuel pickup, cleaned the fuel pickup screen. And when I have the fuel line pulled off the carb there is no fuel coming out. Anyone have any other suggestions?"


"I made sure that the lines were not reversed. And I put a new carb on and couldn't get it started so I pulled the line off and that's when I realized it wasn't pumping fuel. It was pumping fuel just fine before I pulled the old carb off. And Im pretty sure the arm on the pump is below because I pulled the new pump off and saw the marks on top of the arm and when I was putting the pump on it wanted to pull down so when I tightened the bolts it pulled the pump up into the right spot."

"So the old pump was pumping fine. But when I put the new carb on it wasn't pumping. So that's when I replaced the pump."

"So i can't even pull fuel out of tank because after cranking for a long time with the fuel line disconnect from the carb I pulled the line off the inlet of the pump and it's bone dry."

"I just started working on it and I put a new Edelbrock performer rpm intake on because someone had stripped out the carb stud threads. And I put a holly vacuum secondary on."

"These are the new and old pumps side by side the left one is the new one. Do you think that it is a big block one? It is a little shorter"

"Ok so I pressurized the tank and had fuel gushing out of the outlet of the pump so maybe I have 2 bad pumps ."


So what you told us...

  1. It was pumping fuel just fine before I pulled the old carb off.
  2. So the old pump was pumping fine.
  3. But when I put the new carb on it wasn't pumping.
  4. Ok so I pressurized the tank and had fuel gushing out of the outlet of the pump


What we know...
  1. the line from inside the tank to and through the pump is clear.
  2. Everything worked till you replaced the carb and / or Intake
  3. old fuel pump stopped "Working" after the carb and/or intake change.

Have you...
  1. Blown air through the line from the fuel pump up to the carburetor with the carb disconnected? (my thinking is.. the new carb might have a stuck float. If it was stuck shut there would be no place to pump fuel and the pump, lines, and all would be dry.)
  2. Any chance you kinked the metal or rubber fuel lines from pump to carb
 
MaxLegroom said:
These are the new and old pumps side by side the left one is the new one. Do you think that it is a big block one? It is a little shorter
Click to expand...
Show us both pumps in full view. also the part numbers of the new pump
 
I havnt been trying to pump fuel with the carb hooked up because it won't even pump without it hooked up. And I have new rubber lines from the pump to the carb and blew air through the metal line and it's all clear.
 
when things like this happen I ask myself , What is different from before (when it worked) and after (when it does not)?
answer that and you might find the issue. Also just a note, don't use teflon on anything other than pipe threads and then use sparingly. To much and it can squeeze out and block the flow. Stock pumps are only producing about 3psi.
missing linc made a good point about the key way.
 
Welp 3rd times the charm I guess. I went and got another fuel pump and it's pumping like it should now. Kinda a weird situation how the old was was on it's last leg and the new one was just crap and didn't work. Thankyou all for your help. I really appreciate it
 
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