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Sun Nov 02, 2008 4:57 pm

Hi,
I need help regarding fuel issues for a 36hp.
Here is what i can confirm.
1. Fuel comes out of the metal line exiting from the pan.
2. Fuel filter is about 80 percent full at tranny location.
3. Gravity position of metal line from fuel pump to rear is set as best as i could. Metal line from pump to fuel filter is clear.

One question i have is does fuel need to drip out very strongly at the metal line before it enters the pump? I cant figure out whats going on but i dont any any fuel at that point. Its in the filter, but cant seem to make its way freely to the end of the metal line.

Should I rebuild my fuel pump or is it a plumbing problem/gravity issue between the hardlines?

Thank for looking appreciate any comments....
Kevin

Sun Nov 02, 2008 5:33 pm

Hi,

Your fuel system does not depend on gravity to work.
The only part that relies on gravity is the fuel inlet valve connected to the carb float and opens and closes as the fuel level drops and rises due to consumption and replenishment.

The fuel pump sucks fuel out of the tank and pushes it to the carb.

If you don't get fuel with it hooked up and the lines are not clogged, suspect your fuel pump.
The older fuel pumps have a built in filter screen on the top of it. If you unscrew a little cover you can access and clean it out. This screen plugged will prevent fuel from getting to the carb.

Dave

Sun Nov 02, 2008 9:55 pm

Dave,

thanks for your post, I was told that vapor lock might be an issue, but i pulled the cap off and seems to not help....I also tried to blow air from the metal tube "pump inlet" side and got air to go all the way to the tank, as i heard the bubbles from the air i was blowing. Now i know thats clear, should a good working fuel pump get the gas from the "tranny fuel filer" and deliver it to the pump.

Thanks for reading.

Kevin

Sun Nov 02, 2008 11:35 pm

I don't quite understand what you're saying but your pump should drip fuel out if you turn the engine over by hand, if you crank it over it'll be a slow stream. If it hasn't been rebuilt in a while I suggest buying a rebuild kit from Wolfsburgwest. (It's good quality) Take notice of how it does together and throw it back in, it's cheap reliability insurance!

Mon Nov 03, 2008 12:29 pm

I got a tip to jack up the car from the front and get the fuel dripping into the pump as I am hearing the 36 hp pumps are a little fickle...Im going to get a new pump as well. Hopefully this will work..

Thanks again,

Kevin

Mon Nov 03, 2008 1:20 pm

The pump may not be pumping for a few reasons-
the pump diaphragm may be torn, or the fuel in/fuel out valves may be damaged.

Rebuilding a pump is pretty simple- there is a preload required on the pump diaphragm- search rebuilding 36 hp fuel pumps- which will make the it last longer. The springs that control the fuel in/out valves can break from old age

Sat Nov 15, 2008 10:53 pm

here is the problem i am having with my 36hp fuel pump,
the car runs fine when it's cold but after it heats up and i drive it on the freeway it acts like it's running out of gas, the last time it happened i pulled over, took the top off of the carb and sure enough the float bowl was empty, i got off of the freeway and back on the the city streets and made it home, when i got home i pulled the top of the carb off and sure enough it was full.
i took the pump apart and every thing seems to be fine, i started it back up and let it run and gas was passing through the pump just fine when the motor got hot i noticed there was a bunch of bubbles coming through the fuel filter, i made sure to put all the tin back on the motor but it still doesn't help... when it's hot and i disconnect the fuel line i find the fuel line is pressurized... can anyone please let me what is causing this this to get vapor locked???
about the car it's a 1957 with a low mileage used 36er runs perfect in the streets all day long but not on the freeway... thanks
kombi kid!

Sun Nov 16, 2008 10:10 am

kombi kid wrote: here is the problem i am having with my 36hp fuel pump,
the car runs fine when it's cold but after it heats up and i drive it on the freeway it acts like it's running out of gas, the last time it happened i pulled over, took the top off of the carb and sure enough the float bowl was empty, i got off of the freeway and back on the the city streets and made it home, when i got home i pulled the top of the carb off and sure enough it was full.
i took the pump apart and every thing seems to be fine, i started it back up and let it run and gas was passing through the pump just fine when the motor got hot i noticed there was a bunch of bubbles coming through the fuel filter, i made sure to put all the tin back on the motor but it still doesn't help... when it's hot and i disconnect the fuel line i find the fuel line is pressurized... can anyone please let me what is causing this this to get vapor locked???
about the car it's a 1957 with a low mileage used 36er runs perfect in the streets all day long but not on the freeway... thanks
kombi kid!

First of all, where is your fuel filter? If it is in the engine bay, remove it and put it alongside the tranny where the metal line connects to the rubber one (but you don't really need a fuel filter, IMO) Engine bay fuel filters are the #1 cause of roadside VW barbecues.

"Vapor Lock" is often misunderstood, caused by 2 things, and I doubt you have either. Generically it refers to the gas turning to a "vapor" state in the fuel "fluid path" and causing things to stop working (liquid systems don't pump "air").

On problem is with non vented tanks, and is especially prevalent when the tank is very full. Liquids are far less compressible (or expanable) than gases. You create a vacuum in the small "air" space in your tank and the pump cannot pull gas from it. This usually happens after you shut down a full-tank car and they try to re-start.

The other problem (heat related) is when the gas line (anywhere) gets hot enough to BOIL the gas inside it, turning it to vapor, and you have the liquid devices pumping air thing again. Bubbles in a fuel filter is perfectly normal. I have seen them in every filter in every car I had (when I used to run filters) and if the gas was truly hot enough to boil near there, you would have a melted filter, cooked rubber lines and all sorts of other (major) issues.

Sounds like a fuel delivery problem to me. The fact that your bowl went empty on a hot high way run says that. Try another fuel pump if possible. While I have never done it, I guess you can get cheap electric ones and just temp wire them up in there and run them from the gen hot lead (in line fuse!!!) as a test.

Sticking carb float might also be an issue, have you replaced the float valve? Have a new carb you can try?

Look close at the disc valves in your pump. If they are the rubber variety, get rid of them and get a rebuild kit with the brown fiber ones. Also, yank the tap out from the bottom of the tank, and clean it out good (or replace it). I have experienced and see many flow related problems with those. Agreed should not have anything to do with heat though.

See the "Fuel Path" article at my website thebugshop.org and please post back here when you find the problem. Fuel problems are frustrating, but all are fixable. You just have to zero in on the right area.

Sun Nov 16, 2008 12:36 pm

johnshenry wrote: kombi kid wrote: here is the problem i am having with my 36hp fuel pump,
the car runs fine when it's cold but after it heats up and i drive it on the freeway it acts like it's running out of gas, the last time it happened i pulled over, took the top off of the carb and sure enough the float bowl was empty, i got off of the freeway and back on the the city streets and made it home, when i got home i pulled the top of the carb off and sure enough it was full.
i took the pump apart and every thing seems to be fine, i started it back up and let it run and gas was passing through the pump just fine when the motor got hot i noticed there was a bunch of bubbles coming through the fuel filter, i made sure to put all the tin back on the motor but it still doesn't help... when it's hot and i disconnect the fuel line i find the fuel line is pressurized... can anyone please let me what is causing this this to get vapor locked???
about the car it's a 1957 with a low mileage used 36er runs perfect in the streets all day long but not on the freeway... thanks
kombi kid!

First of all, where is your fuel filter? If it is in the engine bay, remove it and put it alongside the tranny where the metal line connects to the rubber one (but you don't really need a fuel filter, IMO) Engine bay fuel filters are the #1 cause of roadside VW barbecues.

"Vapor Lock" is often misunderstood, caused by 2 things, and I doubt you have either. Generically it refers to the gas turning to a "vapor" state in the fuel "fluid path" and causing things to stop working (liquid systems don't pump "air").

On problem is with non vented tanks, and is especially prevalent when the tank is very full. Liquids are far less compressible (or expanable) than gases. You create a vacuum in the small "air" space in your tank and the pump cannot pull gas from it. This usually happens after you shut down a full-tank car and they try to re-start.

The other problem (heat related) is when the gas line (anywhere) gets hot enough to BOIL the gas inside it, turning it to vapor, and you have the liquid devices pumping air thing again. Bubbles in a fuel filter is perfectly normal. I have seen them in every filter in every car I had (when I used to run filters) and if the gas was truly hot enough to boil near there, you would have a melted filter, cooked rubber lines and all sorts of other (major) issues.

Sounds like a fuel delivery problem to me. The fact that your bowl went empty on a hot high way run says that. Try another fuel pump if possible. While I have never done it, I guess you can get cheap electric ones and just temp wire them up in there and run them from the gen hot lead (in line fuse!!!) as a test.

Sticking carb float might also be an issue, have you replaced the float valve? Have a new carb you can try?

Look close at the disc valves in your pump. If they are the rubber variety, get rid of them and get a rebuild kit with the brown fiber ones. Also, yank the tap out from the bottom of the tank, and clean it out good (or replace it). I have experienced and see many flow related problems with those. Agreed should not have anything to do with heat though.

See the "Fuel Path" article at my website thebugshop.org and please post back here when you find the problem. Fuel problems are frustrating, but all are fixable. You just have to zero in on the right area.

john,
thanks for all the helpful info, i have read all your posts about the fuel delivery, i have owned about 45 vw's in my short 50 year lifespan never had this problem before, i have owned a few 36er but never had this type pf problem before, tank is clean petcock is new, i've tried 3 carbs (1 being new in the box) took my pump apart ( disc are metal!) i bought all the tin for under the pump and rear breast plate. i have not taken it out for a run since my last bit of checks but i will try to remove my fuel filter and re route my fuel lines and take it out for a spin today... i'll let everyone know what happens, thanks, kombi kid!

Sun Nov 30, 2008 1:37 pm

ok fuel delivery problem has been solved. i replaced the needle and seat and it didn't help, still ran out gas on the freeway, i bought a NOS fuel pump for my 36er and when removed the old pump i noticed the the return spring tat pushes the lever against the fuel pump rod was broken and had fallen off, i put the NOS pump on it and problem solved, i just too it on a ten mile drive on the freeway and it ran perfect, thanks to all that left comments and helped me pin point the problem... kombi kid!

Sun Nov 30, 2008 2:02 pm

Excellent!!

Something cool about fixing a problem like that and then driving anxiety-less afterward....

Sun Nov 30, 2008 3:32 pm

That's great!
Thanks for letting us know what you found. =D>
So many of these questions get a lot of suggestions made by readers but it is somewhat infrequent that people come back after the problem is fixed and let everyone know what was wrong.

Dave