I'm helping my friend fix his 70 bug that is a real pile, and were having some trouble. After fixing everything else to make it roadworthy, the last problem was the fuel pump (mechanical). After going through tens of different length pushrods and pumps from a local vw shop they were sure would work, nothing did. So we decided to do an electric pump conversion.
To preface all this; the thing would run fine with starting fluid or if the carb bowl was filled manually and a light blow through the fuel lines resulted in me on the other end getting unceremoniously sprayed in the face by gas.
The electric conversion is still an exceedingly simple system, 2 wires, 2 lines, and the pump which is mounted below the tank. But, Its not freakin' working! Or at least it isn't now, at first install I started it up and the car ran perfect for about 2 minutes then I turned it off satisfied in my success. few days later my friend tries to move it for the first time in 5 years and it starts for 10 seconds then dies, then wont start. The pump is on ignition signal and its still ticking away but its just not moving fluids, not a drop when I unplugged the line from the carb, is it a dud? no leaks no clogs. How could such a simple little thing break after just sitting dormant for 2 days?
To recap the pump is mounted right under the tank as instructed by the makers of the pump, there is fuel right up to the inlet side just from gravity, and pump is still ticking and sounds no different now then it did 2 days ago when it worked.
p.s. I hate bugs, not trying to be mean but this one is ticking me off. At least they are easy to work on
Is there dirt in the tank from sitting plugging up the pump?
Does it have a non vented gas cap or a plugged cap vent causing it to try and draw against vacuum it's creating?
Tank is full of junk, and he's sucked a bunch of crap onto the screen in the tank.
The tank is easy to remove, pull it out and clean it.
Quick confirmation is to blow a little compressed air back into the tank.it will flow again at least for a while.
Response to everyone: cleaning out the tank was one of the things we have already done, sorry should have mentioned that
Patrick (Forum Supporter) said:
Does it have a non vented gas cap or a plugged cap vent causing it to try and draw against vacuum it's creating?
I liked Patrick’s idea here... I’d be curious to see if removing the cap is enough to free the system up. If that does it, the fuel filler vent might be suspect.
If taking the cap out of the equation doesn’t work, the next thing I’d try is to hook a short hose up to the outlet of the pump, and see if you can transfer gas from the bugs tank to a gas can or bucket. That way you can at least confirm the pump is working.
If that goes well, time to take a closer look at the factory fuel line through the pan and on to the carb....
Jerrysarcastic hit it.
The reason the stock pump didn't work is the same reason the electric one won't work. It needs a new fuel line from the tank to the carb.
In reply to Purple Frog (Forum Supporter) :
To add a little more to this, I have seen several of these failures where the outside of the hard pipe looked perfect, but the inside had corroded closed. When removing the hard pipe it would crumble and collapse at the failure.
I mean the easy test would be to pull the hose off the carb and see if you can suck fuel thru it, but I suspect as others have mentioned the hard line in the tunnel is your culprit... or a clogged in tank strainer, although I'd check the cap suggestion as well. Does it have another filter inline?
I recently went thru the same thing with mechanical pumps and pushrods too though. Ruined 2 new Brosal pumps before I discovered my 73 somehow had a long fuel pump pushrod in it... even though it was a short base, angled pump. Bought a new 100mm rod and Empi alternator pump, and good to go.
NOHOME
MegaDork
7/24/20 9:32 a.m.
Saw where a tank that had been coated had a failure of the coating and a flap of the material positioned itself just perfectly so as to act as a flapper valve. It would gravity drain the entire tank and not shut off, but put a pump on the end of the hose and it would suck the flap over the pickup aperture. Drove the owner nuts by the time he figured it out.
The same flap-valve phenom can happen inside of any line caused by rust or a deteriorated inner rubber surface that has been exposed to modern fuels.
I found some interesting things* in a VW fuel line once. Same issue. Full tank. Vented. New pump. What you got here is blockage.
* it was a bee! And some foliage.
In my case the fuel line to the pan seemed fine, and would pass the “compressed air” test but was still more constricted than I realized due to corrosion .
The engine would idle fine and run for a while, but when you drove the car around (i.e. put the engine under load) fuel would not fill the carb bowl fast enough and it’d eventually run dry. What a pain that was to find!
I think if you work methodical and narrow down to what part of the system is having trouble, the fix will present itself. Good luck!
Pressurize the tank with compresses air with line at the engine disconnected and aimed into a container.
Use a blow gun and a rag at the filler.
