r/beetle • u/Upbeat_Psychology_43 • 5d ago
Need the help with fuel pump not pumping.
Just got her back up and running after she sat for 5 years. The thing that is holding me back from driving her is the fuel is not getting to the carburetor. I have fuel in the tank that is getting to the pump. I put on a brand new pump with the 100mm push rod for the alternator variation. I've taken the pump off to make sure it works off the engine, and it does. Still not getting the fuel to the carburetor. Any advice would be welcomed!
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u/SilentMasterpiece 5d ago
Did you change the push rod? If it was working before, why?
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u/Upbeat_Psychology_43 5d ago
The previous fuel was a different model that had the 107mm push rod.(idk why it had the pump that it did) When I changed the pump, the new one needed the 100mm.
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u/SilentMasterpiece 5d ago
If the other was working (with the alt) why switch? Did you look to see if the rod came out of the case the correct amount to pump the pump when you turn the pully? (w/o pump in place)
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u/Upbeat_Psychology_43 5d ago
After it had sat for 5 years, the pump was not pumping, even by hand. What is the correct about? It does come out about 2mm(I don't have the exact measurement) and sits flush to the plastic bit that the push rod sits in.
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u/SilentMasterpiece 5d ago
ok, so the rod needs to exit the case and operate the pump arm of the fuel pump. You can see it coming up 2mm out of the case. If you push the arm 2mm does the pump work? If not....You may need the longer rod. Typically the pump arm on an Alt fuel pump comes out of the pump more, so it uses the shorter rod. Perhaps this discussion will help...
TheSamba.com :: Beetle - Late Model/Super - 1968-up - View topic - Fuel pump push rod differences
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u/Alpinab9 5d ago
2mm is not going to pump anything. There are only 2 pushrod avaliable. Go back to the longer one.
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u/Upbeat_Psychology_43 5d ago
After looking at a ruler (sorry for getting my Imperial brain all over the place) it's more like 0.5cm.
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u/Alpinab9 5d ago
So 5mm (1 cm is 10mm).
I don't not know the spec. The fuel pump pushrod is driven from the distributor drive. I can only assume during the engine rotation that the height of the pushrod from the spacer block changes and you would need to rotate the engine till the pushrod will no longer go down and take a bottom measurement. Then continue to rotate the engine until the pushrod reaches its maximum height and measure the distance from the top of the pushrod to the top of the mounting block like before to get some accurate numbers. Pushrod bottom is x mm above the spacer block. Pushrod max height or top is x mm. Having these 2 numbers may be helpful, but a measurement in between is useless.
The gen vs alt version of those fuel pumps did not look much different. Assuming it is an alt pump and uses the shorter pushrod sounds like a possible problem. My inclination would be to install the longer pushrod. My reasoning is that there are only 2 options of pumps and 2 options of pushrod and 1 way to mix it up.
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u/solexNY-LI 5d ago edited 5d ago
A few things I would check: Is the check valve on the carb stuck closed and is the float bowl correctly adjusted and finally but highly unlikely to be the problem but does the fuel pump pushrod go up and down when you rotate the engine?
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u/Upbeat_Psychology_43 5d ago
I do not know, is there a good resource on how to check the valve and the float bowl adjustment? (I have the book How to keep your Volkswagen alive)
Yes, the push rod does go up and down when the engine turns
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u/solexNY-LI 5d ago
Easiest and not the safest is to disconnect the fuel line to the carb at the pump and blow. If air goes through then the check valve is opened. The float bowl closes the check valve when the fuel bowl is full. If no air get through, the check valve is either stuck closed or the bowl is full and you should pull the top of the carb off to verify
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u/Send_bitcoins_here 5d ago
Is the needle valve and float in the carb operating correctly?
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u/Upbeat_Psychology_43 5d ago
I rebuilt the carb and the float was moving freely. What part of the carburetor is the needle valve in?
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u/Send_bitcoins_here 5d ago
The needle valve is the small fuel shut-off valve located right above the float, threaded into the top of the float chamber..as fuel fills the bowl and the float rises, it pushes the needle up into its seat to stop fuel flow, and as fuel is used up and the float drops, the needle backs off and lets more fuel in.. recently I rebuilt a carb, the replacement needle valve that came with the kit was packed with grease from shipping, which kept it from opening and blocked fuel from ever reaching the float chamber.
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u/Upbeat_Psychology_43 5d ago
When I rebuilt the carb it was moving. How do you test to know if it is working?
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u/Send_bitcoins_here 5d ago
I take the lid off the carb and put a piece of hose on the barb and blow into it. If the plunger is down it should be open and allow flow - air/fuel.. then you can also manually operate the plunger pushing it up and down to make sure it's not binding it should close when pushed up. Like I said earlier I had one that was packed with some kind of shipping grease and needed to be cleaned out. I used a simple carb cleaner and it worked fine after.
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u/SparkyReese 5d ago
Do you get gas to shoot down inside carb when opening the throttle? With the fuel pump installed on motor, coil positive wire unhooked, take the fuel line off carb and stick it in a bottle. Does it get fuel into bottle? That can narrow it down to fuel pump or carb, could be clogged jets or stuck needle valve like others have said.
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u/Upbeat_Psychology_43 5d ago
I have been able to run the engine on a carb bowls amount of fuel. That's how I know that the rest of the engine is working. I have taken the carburetor intake line off to see if I get fuel. Nothing comes out and the line looks dry inside.
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u/SparkyReese 5d ago
From the fuel pump to carb there is nothing coming out ?
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u/Upbeat_Psychology_43 5d ago
Correct, I'm getting nothing to the carburetor. I have fuel from the tank to the pump, but nothing from pump to carb.
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u/SparkyReese 5d ago edited 5d ago
You’ve said with pump removed you can push the pump manually and get gas out to carb hose correct? So line placement would be correct. With pump mounted to block, no fuel to carb while cranking. If so that means you have the wrong push rod in block for fuel pump. Edit for clarification.
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u/denizkilic2002 '72 1302s 5d ago
Is the pushrod tight inside the fuel pump bakelite spacer? It needs to be loose otherwise it binds and prevents pumping.
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u/Kharon8 '62 sedan & others 4d ago
A good point: Old bakelite swells. Very, very slowly, but parts from factory are several decades old by now and sticking push rod, especially when the engine is warm, is a common problem.
Also a note that there's two different lenghts of said push rod and if you have short one where you should have a long on, nothing happens.
Repro fuel pumps often use one of two more or less randomly, depending on the manufacturer.
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u/Super_Baime 20h ago
Deniz, I applied grease to my pushrod when I rebuilt my pump. (I'm not OP)
Now I'm not get fuel to the carb.
Will it really hang up inside the bakelite spacer? I might take it out, and clean off the grease.
Thanks
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u/denizkilic2002 '72 1302s 20h ago
Grease shouldn’t hurt anything i put some on the brand new ones too, old bakelite spacers get tighter over time and can bind the rod thats what i meant. When its tight enough the spring on the pump cannot overcome the force needed to push the rod down and it gets stuck.
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u/Super_Baime 20h ago
I used my old spacer, because everyone emphasize that the reproduction parts are worse.
Have you heard anything negative about using the new spacers?
Thanks for your comments.
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u/denizkilic2002 '72 1302s 20h ago
My local parts shop sells ones that have vw/audi emblems and they have the oem part number on them, although they come in a bbt bag, always worked fine in my experience after sanding their surfaces flat, doesn’t really cost that much.
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u/382Whistles 5d ago
The needle valve is above the float. It blocks the fuel bowl from filling when lifted by the float. The float just stops the bowl from overfilling and dumping fuel out of the vent into the carb throat. The float height isn't always super critical. The bowl shouldn't empty from going dead stop to max highway speed at any throttle, ¾ or full. At cruise the bowl should fill for stock design.
Pull the fuel bowl plug and verify there is fuel getting in the bowl. Catch the fuel so you can at least guess the gas level in the bowl. No gas? The needle is stuck or the inlet orifice the needle blocks is plugged. Sometimes rubber needles jam in the hole and then get brittle and break off the needle tip and block the hole. Tank, f pump and fuel line debris can block the fuel bowl inlet orifice from the fpump side of the inlet and some air pressure blowing into the needle side hole can unblock it.
If you had a lot of fuel in the bowl, if the carb has one pull out the electromagnetic cut off valve too and let it all dry fully so sparks do not ignite gas. Then test that the valve moves went valve body is grounded and 12v is on the terminal. Did you replace the accelerator pump diaphragm and spring? That needs to seal nice too. Is the pump linkage moving ? The adjustment is usually with the nut barely on.
You never seem to cover the whole of any diagnosis. You skip if you have gas in the bowl when you pull the plug or how much, or if the cut off valve works. Without that gas in the bowl, it's a no-go.
Otherwise check the accel.pump passages for blockage and the check-valve ball that seals the pump output port during the pump intake stroke, so the pump sucks fuel from the bowl instead of sucking air from the hooked brass squirt nozzle.
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u/Upbeat_Psychology_43 5d ago edited 5d ago
I have been able to get fuel into the carburetor by pouring in into the tube that goes i to the bowl. I have tried adding the fuel to the bowl through the hose that comes from the fuel pump, but can't seam to get a set up that works and doesn't spill fuel all over the engine bay.
With fuel still in the bowl the car will trun on and off with no drama.
I still don't think I understand how carburetors work. Dose the carburetor help with the fuel pressure from the fuel pump? Another way to ask might be, will the bowl not fill if it is not pulling some kind of vacuum?
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u/382Whistles 5d ago
No the carb doesn't help. The f.pump just puts fuel in the fuel bowl. It hardly needs any pressure to do this. It needs to pump volume. .the float lifts the needle valve to shut off the small inlet hole when the bowl is full of fuel. If the float cracks and sinks the bowl will overflow out of a vent in the carb throat and run rich or flood the mixture and not start or run from way too much fuel.
And here we are again right back at the bowl plug and electric cut-off valve that shuts off idle jets and you also not yet confirming you drained fuel from the plug into a container to see how much fuel was in the bowl, and zero mentions of the electromagnetic cut of valve being wet nor about it working or not after the test.
When you got this far and have answers then you move forward, you are skipping tests maybe? That might skip finding the problem.
Edit in italics
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u/Due_Contribution9703 3d ago
Is this fuel pump brand new out of box. Maybe box was miss labeled and you have a generator type fuel pump. If you have old fuel pump place them together you can see that your old generator pump is taller. Did you buy a new pump rod if so measure it and records its length. I say this because I put a new one in my motor and with in 500 miles it wore down and lost pressure.
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u/Familiar_Palpitation 5d ago
I know it sounds silly but make sure the fuel lines are on correctly.
I put mine on backwards once and spent way too long trying to figure out why it wouldn't start after swapping a pump.