TheSamba.com :: View topic

Sun Apr 13, 2014 9:16 am

Sorry folks. I searched for an hour and couldn't find the answer.

Is it possible to install an aftermarket fuel filter that is too big for the mechanical fuel pump to operate?

Back story.

I bought two glass fuel filters from cip1. They both broke apart from poor building quality after 4 months. After I gave cip1 a piece of my mind, they convince me to let them send a replacement. Well, due to work and the cold, the car sat for 2 months. I went to replace the fuel filter yesterday and those idiots fave me the wrong size filter (the nipples was too big). So I threw them away and not buying anything from them ever again. Went to a local auto shop and the guy got me two metal fuel filters that "will work. No issues". Well, I installed them, add 4 gallons of gas and no worky. The fuel pump isn't sucking the fuel through. I check for blockage, all okay. I have fuel. I even mouth suck fuel through the system to make sure it can get to the fuel pump. Today, I took out the fuel pump. The push rod is worn down 1mm from the 100m. The spring is working and I can hear air sucking and pushing while pushing on it. The spacer/guide slides up and down easily.

So this kind of means to me if you put a bigger then stock fuel filter on the car, the 3-5psi pump can not pull the fuel through.

True? False?

Sun Apr 13, 2014 9:38 am

Nah, I think you're problem is going to lie somewhere else...if you got the metal fuel filter that's about 1 1/4 inch diameter and 2 1/2 inches long you should be fine...start checking everything else

Sun Apr 13, 2014 10:15 am

Nope, ...ah... size doesn't matter. (Ok Samba Ladies, go right ahead & argue all ya like... but I'm talkin' fuel filters here. ;) ).

It doesn't matter if you put a fuel filter the size of a 55gal drum before the pump,(except that little bug fuel pump may take quite some time to draw enough fuel through it to finally feed the carb, but that's only a matter of time).
Once any size fuel filter is full enough, the pump will draw & feed the carb at it's designed rate of flow. ...that is as long as the pump can draw the fuel to itself. This is the catch with Bug Fuel Pumps.. and 'why' VW Bugs are "Gravity Fed Fuel Sys". They do not draw very well at all but are basically only designed to 'push fuel' far enough to the carb. (also another reason most original fuel filters were placed after the fuel pumps & not before them).

As long as the fuel lines are well sealed & not drawing air,(other than the tank itself which must displace the used fuel with air or it creates a vacuum that stops the fuel flow altogether), then the fuel will travel by gravity to the fuel pump & then pump it up to the carb, as it should.

"Vapor Lock" can be generally a hated problem w/ all cars, VW Bugs will simply "Park" your butt on the side of the road if this occurs. Any air coupled with certain temps causes vapor lock and will interrupt fuel flow.

If I'm not clear on something, just let me know. ;)

IHTH

Michael

P.S. Now if you're looking for a higher volume fuel pump, you could install and electric fuel pump near the tank as long as it's mostly below the mean gas tank fuel weight line. (Depending on the type of electric fuel pump you choose, some are mostly designed to 'push' giving good carb/fuel line pressures, and some are mostly designed to draw the fuel with a noticeably reduced out going carb/fuel line pressure.) There are some electric fuel pumps that both draw and push well with good pressures on the in & the out going sides of the pump, but they tend to cost a bit more.

It is a caution to not get too high a volume electric fuel pump in these bugs as the carbs can be effected in a 'not good' way. It's my understanding that 3-5 psi to the carb is desired in these aircooled bugs, depending on the year of the bug.
http://www.youtube.com/watch?v=7TYk5w_opXs
http://www.youtube.com/watch?v=R3bNQcY8P-g (Language caution.. this guy's got a mouth on him.. ;) )

Sun Apr 13, 2014 11:57 am

Micheal

Thanks for the reply.

I hooked up the bug to my honda battery (bug battery is right now) and cranked the car for a total of 5 mins with no luck. It was working fine with the small fuel filter. This one is 3x wider in volume then the stock small plastic ones.

Any other idea what is wrong then?

Sun Apr 13, 2014 12:04 pm

Did you remove the line to the carb and watch for flow,

or just imagine it would displace the air at some point?

Is there another filter under the car somewhere?
or a kink in a metal line would shut it off

Sun Apr 13, 2014 12:08 pm

I pulled the fuel line off the pump from the tank and got gas freely dripping from it (not full flow). Line from the pump to the carb is dry.

I pulled the pump and hear sucking noises from the bottom and blowing from the top by manually operating it.

Sun Apr 13, 2014 12:34 pm

Ok, I'm dealing w/ a similar situation att.. check out this thread & my last post for some you tubes that may address something you haven't looked at yet...

http://www.thesamba.com/vw/forum/viewtopic.php?t=590536

IHTH

Michael

Sun Apr 13, 2014 2:12 pm

When you have a full tank of gas, disconnect the suction line from the pump.... gas will gravity feed from the open fuel hose...change the gas tank outlet hose...it's most likely deteriorated internally, causing a restriction of gas flow. 8)

Sun Apr 13, 2014 3:54 pm

FIXED

.... The hoses was backwards.

All the information i read online said the bottom nipple is from the tank and the top to the carb. Well..... Mine is the other way around.... $40.00 lesson for 'trusting' the internet. Lol[/b][/u]

Tue Apr 15, 2014 8:35 pm

I've found this very same thing on a few fuel pumps, now I test them for flow & direction of flow 'before' I put 'em in. (that is, after looking ten different ways to see what else might be wrong)

Get one non-functioning, "new" fuel pump from the local parts shop & see just how much ya learn about air cooled VWs... LOL

:)

Michael