Home > Personal, VW > Fuel system reorganization in progress

Fuel system reorganization in progress

May 7, 2006

UPDATE- I have consolidated this post and all the other fuel and carburetion related posts into one: 34PICT-3 Carburetor Final.  As new information comes in it will be added to that post.

Diagnosing the fuel system problems in my classic VW have been like an episode of House with high drama, imminent death of the patient, and the last-minute brilliant insight.  Namely: “there was no gasohol in 1967 in this country, and gasohol boils”. 

The most noticeable effect is something called “vapor-lock” in which fuel ceases to reach the carburetor but under some conditions (namely, if boiling occurs in the pressure-side of the fuel system between the pump and needle valve) the fuel pressure can jump, overwhelming the needle valve and dumping fuel down the manifold…

Back in the ‘70’s, I had a ‘67 type 1 that never had any fuel problems.  Aside from ‘no alcohol’, why was that?  I tried to remember/visualize its engine.  Fuel line, mechanical fuel pump (prone to pressure spikes and vapor lock) and a glass-jar fuel filter with a bronze filter element and… an integrated pressure regulator!  No wonder!  With the regulator in place, the fuel pressure would never have exceeded 3 lbs even when the engine was hot.  (Man, that was a good engine)

I couldn’t find an old-style integrated filter/regulator, so I got an electric pump and a separate pressure regulator.  After some experimentation, I am reorganizing the fuel system so that fuel filter will be under the gas tank, where it’s nice and cool (and where aircooled.net recommends you put it anyway).  Then I’m going to put the electric fuel pump and the fuel pressure regulator in the transmission well (where it’s nice and cool) instead of in the engine compartment (where it’s very hot).  Inside the engine compartment, there’ll only be the fuel line itself, insulated from heat by a fiberglass sleeve.

I know electric fuel pumps deliver very steady pressure but the regulator is just an added precaution.

Since another friend of mine is having very similar problems with his Ghia, I assume this may in fact be a very common syndrome with carbureted, air-cooled engine cars.  So I’m documenting this thoroughly and will post the results here.

Update, 10 May:  for various reasons, the current arrangement is tank, filter #1, line to transmission well, pump, filter #2, line to engine compartment, regulator, and carburetor.  The main reason for this arrangement is that I need to calibrate the regulator as it is delivering 1.8 lbs while set to 0.5 lbs.  Once calibrated, I plan to set it to 1.5 lbs, the minimum recommended pressure for the Solex design carb.

The car is running pretty well, but I’m not celebrating yet.  And I’m always going to carry a spare needle valve!

Categories: Personal, VW
  1. May 11, 2006 at 18:13 | #1

    Make it so!  Sounds like you’re on the right path.

  2. David
    August 14, 2006 at 17:56 | #2

    I own a 356 Porsche with similar fuel problems.  What fuel regulator did you use as I have been looking for one that can be set at 1-2 lbs?
    Does the regulator accomplish your objective?
    Where did you find/buy the regulator?

  3. August 14, 2006 at 21:06 | #3

    Since writing this post I have learned a few things about regulators and will put it here for reference and to share with other boxer engine fans.  It is a work in progress.

    First, I will never again use a mechanical fuel pump.  Just the advantage of being able to fill the carb without cranking the engine is enough to switch.  I put a cover plate where the mech fuel pump was, and never looked back.

    I have a boxy-looking little universal electric fuel pump that is rather noisy, so I will be switching to a low-pressure rotary electric fuel pump that I happen to have.

    Second, even the low-pressure electrical pump overwhelmed the needle valve, (just like the mechanical one did) so you definitely need the regulator.  Use a fuel pressure gauge, do not depend on any markings on the regulator.  The gauge will cost you about 8 bucks and you’ll only use it a few times while tweaking/troubleshooting your fuel system.

    Third, the regulator solved the fuel problem.  Car’s been running like a champ since I installed it – smooth, even idle, more reliable starts (probably because the manifold isn’t full of spilled gas)  It made a huge difference. Until…

    regulator-crappy.png align=right …the cheap fuel pressure regulator I got at the local auto-parts store failed and slobbered gas all over the place.  It was a frightening experience and my car would probably be a smoking wreck now if not for the homeless guy who yelled at me at a traffic light; “Hey!  Your car’s leakin’ somethin’ real bad!”  (I gave him twenty bucks – it seemed appropriate) I bypassed the regulator and drove home 2 miles, then parked.  Damn.

    OK, so now what regulator? regulator-holly.png align=right I now have in my posession a lovely low-pressure Holley regulator with one input, two outputs (so if I ever go dual carbs I am ready).  (It comes in both a low-pressure and a high-pressure model – I got it from Allstate Carburetor on eBay) It is supposed to be adjustable from 1 to 4 psi and I have read several good comments about this regulator online, though none specific to boxer engines.  So my current plan is to install the Holly regulator with the rotary pump.

    Both will be installed in the transmission well.  The only fuel component in the engine compartment besides the carburetor will be the insulated fuel line. This is for both safety and esthetic reasons.

    Aircooled.net specializes in the aircooled boxer engines we love, and they have all this stuff and a lot more.  Their site is search-only – just use their search tool for “pump” or “regulator” and then thumb through the options.  Intriguing to me is the one that is made for alcohol fuels.  That may become more important as ethanol takes up more of our fuel mix.  Maybe I’ll end up with an E85 Beetle someday!

    Hope that helps.  I’ll post here how the Holley regulator works after I get it installed.

  4. May 6, 2008 at 08:34 | #4

    Well it’s frightening when our car is leaking fuel like that. Thank God nothing happen to your VW.

  5. June 16, 2008 at 00:23 | #5

    Good thing that you make it. During my first time, i needed some help to get it fixed.

  6. August 4, 2008 at 12:04 | #6

    I see my VW combi station has a problem in its fuel system. I have replaced i for several times but seems no solution. It’s hardly to find original parts, It’s why i sold my VW eventhough I still love it.

  7. October 15, 2008 at 11:50 | #7

    Love your analogy!  I love classic cars, especially classic muscle cars.  But, because some of there stuff isn’t so reliable I had to go with a new age muscle car.  But, if you like working on your car, I’m all for it.  It just sounds like too much work for me, I give you props man!

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