Fuel pump not pumping

[nodoi]

My car was working fine and then it wasn't. It sat for a while and wouldn't fire up. I tried pouring gas into the carb and it fired off right away, but died. I think my pump dried up and now it isn't pulling gas from the tank. When I pulled the hose off at the carb and cranked the ignition, there was zero pressure or pulsing on the line. I tried removing the hose from the inlet side of the pump and primed the line by vacuuming fuel up until I could see it in the clear filter that I have inline. Then I pulled the line off at the carb and poured fuel into it to try to prime the pump. Still not starting. Do I need to pull my pump next? Any other thoughts?
 

[John76]

Couple of things to check before blaming the mechanical fuel pump. These are very reliable and long lasting.

1) Remove the sending unit from the tank and clean the pick-up screen.

2) Check the hose connection on the sender unit. There is a plastic sleeve that fits over the 6mm hose barb that transitions to the 8mm fuel line. If this leaks, the pump will suck air instead of fuel.

3) If you still suspect the pump, an easy check is to put the inlet hose into a jar of gas and crank the engine to see if it fills the fuel bowl.

 

 

[nodoi]

Thanks John! I’ll pull the sending unit and have a look. 

[nodoi]

Ok, pulled the unit out of the tank. Is the screen cleanable? I’m not sure how to remove it. It looks like there are gaps between the screen and the bottom of the unit. Maybe not a big deal? In the fuel line I see a plastic liner inside. I tried to get behind it with a pick to see if I could pull it out, but it doesn’t seem to have a shoulder in there. Is this just the same plastic line that appears later in the run with a sleeve on it? Maybe I am missing a spacer. 
 

Also, on the sender I have a brown and a brown with yellow stripe, can you confirm which goes to which? I’m assuming this it the fuel level, and mines never worked. 

[Sam_in_VA]

In your pics, I see several places where the rubber looks like it could be old and hardened, and air could get in causing the pump to suck air instead of fuel.  While it's apart, I'd go ahead and replace all of the fuel hoses.  You will need to carefully cut the white plastic "adapter" out of your existing fuel hose where it goes into the tank.  I used a bit of 1/4" fuel line at the pickup and a 1/4" to 5/16" brass adapter.  Since you were able to pull gas to the fuel pump inlet with a vacuum pump, though, your problem could be elsewhere.  As John recommended, disconnect line from carb and see if you can pump gas into a jar (if you have asimple  vacuum/fuel pump gauge, you can also test pump outlet pressure, IIRC ~2.5-3.5 psi).  While you've got the carb inlet open, connect a length of fuel line and make sure you can blow air into the carb.  With the carb's bowl empty, the float should be all the way down and you should be able to blow air past the needle (it's a small hole, so there will be some restriction).  If it seems blocked, the problem could be the carb.  When you pour gas into the bowl, you are bypassing the needle/seat.

[Son of Marty]

The solid brown wire goes to the uninsulated terminal (the lower one in your pic) solid brown in German cars is always ground, yellow and brown to the top one. Yes you need to replace all your rubber fuel hoses with ones that are alcohol rated, that cloth covered hose is most likely original to the car so it's probably 50 years old. You can cut that plastic spacer out of the old hose or just cut a inch of the plastic line that runs through the car. Hose clamps on every junction and  move your plastic filter to the pressure side of the pump.

Edited October 8, 2023 by Son of Marty

[nodoi]

Great advice, thank you!
Blew air through the carb inlet and it seems fine to me. I got a section of new 8mm hose and as I was pulling the old hose out, found out that the outlet from the fuel pump is 6mm. Inlet to the carb is 8. I ordered a couple 6mm to 8mm adapters from Amazon, should be here tomorrow. I'm also aware that my return line is not in use, not sure if this is a concern or not?

Son of Marty- I have heard from others to switch that filter position, but never heard why. I was thinking that keeping tank gunk out of the fuel pump was a good thing. Is the pump sensitive to the filter resistance?

Also any tips on cleaning the fuel level screen? Does it pry off of the end? I don't want to damage it.

[nodoi]

here's a shot of the different sized ends

 

[jimk]

8 minutes ago, nodoi said:

Does it pry off of the end?

nt  Different type of screen on the sender bottom from oe.  May have been replaced along the way.

Edited October 8, 2023 by jimk

[Son of Marty]

10 minutes ago, nodoi said:

Son of Marty- I have heard from others to switch that filter position, but never heard why. I was thinking that keeping tank gunk out of the fuel pump was a good thing. Is the pump sensitive to the filter resistance?

There's nothing that can go through the tank screen that will hurt the pump. Yes the filter before the pump does cause resistance and even more as it becomes clogged, but it's worse offence is it provides a air pocket on the suction side that reduces the effective stroke of the pump. 

[JQ02]

Don't underestimate the comment on the dry hoses. Any air getting anywhere into your fuel line ahead of the carb will eventually give you problems. Carbs would rather suck air than fuel if they can. I resolved my issues by replacing one of the old cloth lines - temporarily(!) only to realize that I missed one. Replacing that one and moving my fuel filter after the pump resolved my issues.

I just had the same problem - again(!) on my '36 Ford hotrod - air getting into the glass fuel filter, now replaced.

Edited October 9, 2023 by JQ02

[Stevenc22]

Make sure the pump its self isn't coming apart. I just helped a friend with the same problem and a similar pump and the main bolt in the pump was loose and the pump was sucking air from its self. 

[nodoi]

After patiently waiting a couple more days, my parts arrived and I replaced all the old cloth-covered fuel line. I moved the filter ahead of the pump and tried turning it over. Nothing. I tried pulling fuel up through the hose, using suction but wasn't having much luck with the small plunger that I have. So I also tried putting fuel down the hose to add some to the pump, thinking that it might be dry and having a struggle, but no change. 
So now I can rule out lines and filter, I guess next step is to pull the pump, yeah?

I'll do some searching for threads on manual fuel pump rebuilding, if y'all have any recommendations, please feel free to chime in.

[Son of Marty]

Just one more thing before replacing the pump, try filling the float bowl a bitt through the vent it's hard for the pump to pull enough vacuum at cranking speed.

[nodoi]

I'll give that a try in the morning. Just to be sure, this is the vent right?