Jump to content
  • When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

Mechanical Fuel Pump Pressure Adjustable?


John76

Recommended Posts

John and Tom,

I know at least on 76 year model cars fuel circuit was equipped with Valve13311259194 and non-return valve13311263522. Those parts were missing on my car and since I am original pursuit guy found them (thanks to a member) and I tell you I do not smell gas whatsoever around carburetor anymore and car restarts just fine in hot day after several hours driving even. 

Also no sleeve is needed with 6mm hose from fule pump output port to the valve.

(not my pictures)

 

5932b9999893e_FuelReturnValave5.thumb.jpg.2922b4493371738113fa6925cc32aac5.jpg5932b99b7052b_FuelReturnValave9.jpg.4ef1554d9c2efe40e508e967a6fc1cda.jpg

 

Edited by Buckeye
  • Like 1

76 2002 Sienabraun

2015 BMW F10

Link to comment
Share on other sites

Is the vacuum line on the fuel return valve connected to manifold or ported vacuum?

I can't tell from the original Solex connection diagram. The Solex has 3 vacuum ports, with one described as being "timed"....whatever that means. The original diagram shows the fuel return valve connected to the front port.

I connected the return valve to the manifold spigot on the #1 intake runner with the Weber card and it seems to be working.

Fuel pressure is steady at 3.75 psi at all rpms, so appears to not be influenced by the action of the fuel return valve.

Link to comment
Share on other sites

How does that valve work?

 

The emissions sticker on my 49 state '76 shows the diverter valve connected to the vacuum port on the stock carb.  Unfortunately, I do not own a solex, so I am not of much help.  

041.thumb.JPG.5e7df416a30b70afd8411e34bc3aae7b.JPG

 

My thoughts on the Jeep filter bypass fitting having a 3psi valve were silly, in hindsight.  Even if that had been true, it would not have meant that the carb would get 3psi.  (I heard a rumor that Da_ron knew this :ph34r:).

 

The filter is still helpful, even though it does not regulate pressure; because it does allow the pressure to drain off, after the engine is turned off.  I went to Rock Auto and pulled up tons of Jeep filters.  I think the triple-nipple version started in '74 or '75 and before that they do not show the bypass feature.  

 

I read the INFO on a bunch of them and only the Hastings filter mentioned this feature,

"Patented all metal, self-venting drain valve for unmatched durability."

It sounds like the filter is designed to bleed off the pressure after shut down.

 

This thread has led to rerouting fuel lines and trimming their lengths, as well as flipping hose clamps over, for a more pleasing presentation.  I ran the incoming fuel line through the air cleaner bracket and slid a piece of 5/8" heater hose over that leg for chafe protection.  

005.thumb.JPG.929e16a6cc4a3706b65727375014f094.JPG017.thumb.JPG.9ea7c2feea538bbb6f29bf7b21c76acd.JPG033.thumb.JPG.cce05021bcc4ce0bceade6c737ab9e36.JPG

Lots of little 1/4" pieces of hose around, from trying to get the lengths 'just right'.  Cheap fun.:)

 

  • Thanks 1

     DISCLAIMER 

I now disagree with some of the timing advice I have given in the past.  I misinterpreted the distributor curves in the Blue Book. 

I've switched from using ported-vacuum to manifold, with better results. 

I apologize for spreading misinformation.  

Link to comment
Share on other sites

If I had to guess, I'd say the vacuum line is just there to keep the return on the fuel line closed while the engine is running, then when the engine is off and vacuum is 0, the return opens and depressurizes the system.

 

Purely a guess though.

John Baas

1976 BMW 2002

2001 BMW M5

My Blog!

Link to comment
Share on other sites

here is list of discussions on the valve.

https://www.google.com/search?q=1976+bmw+2002+fuel+return+valve&rlz=1C1RUCY_enUS743US743&oq=fuel+retun+valve+1976+bmw+2002&aqs=chrome.1.69i57j0.4564j0j7&sourceid=chrome&ie=UTF-8#q=1976+bmw+2002+fuel+return+valve+site:www.bmw2002faq.com

 

Below quote from a member (copy and pasted)

what that does is allows fuel to bypass the carb when you don't really need it, it is vacuum actuated.  When you are doing a hard decelleration the engine is spinning really fast but not using any fuel to speak of, the pump is working pretty hard for nothing, the vacuum generated by a decelleration triggers the bypass valve to return gas to the tank.  Once gas is in the carb the only way it should exit is through the engine.

Here is snap shot 76 49 states with Weber carburetor part of Pdf file attached earlier;

5934485f71aea_197649states.PNG.6fd2f9cb24d837a2f8eaf4e3dd4b2b5c.PNG

 

 

  • Like 1

76 2002 Sienabraun

2015 BMW F10

Link to comment
Share on other sites

The diagram that comes with the Weber has always confused me. It shows the fuel return valve connected to manifold vacuum. With the stock configuration, it is connected to what appears to be a ported vacuum source on the Solex.

 If the return valve is open when vacuum is applied, it would return fuel to the tank at idle speed and deceleration, which makes sense (low fuel demand). However, if fuel is returning to the tank at idle, wouldn't this decrease the pump pressure to the carb?

I don't see that with mine...but then I may have a frozen return valve. I know the Pierburg pump has a non-return valve in it which keeps the fuel line pressurized...but I did not see what happens to the pressure after shut-off. Another thing to test!

The Weber diagram also shows manifold vacuum to the distributor advance (regulated by the black electro valve and coolant temp switch). And, the 49-state '76 does not have a vacuum retard.

I've tried it both ways, and the vacuum advance connected to ported vacuum (no retard) gives the best result.

 

Link to comment
Share on other sites

So I have followed and changed my vacume hoses to routing per diagram below

 

5936fa04c63b7_197649states.PNG.18e4d3ded5e86a818678c13c372d0e8d.PNG

 

but now not sure what need to do with port (F)? Should I cap it off or run hose from port F and tee to the hose coming from 4-way valve?

There is also vacume port below port F on the manifols. What should be done with it?

 

5936fa6f47f03_webercarb.PNG.30a33d28cc3181793752e7c00df7e63d.PNG

76 2002 Sienabraun

2015 BMW F10

Link to comment
Share on other sites

isn't port F ported vacuum, which you have run to your distributor's advance pod?

The manifold vacuum port below it should be plugged, if not in use.

 

can we see some photos of your setup?

     DISCLAIMER 

I now disagree with some of the timing advice I have given in the past.  I misinterpreted the distributor curves in the Blue Book. 

I've switched from using ported-vacuum to manifold, with better results. 

I apologize for spreading misinformation.  

Link to comment
Share on other sites

On ‎6‎/‎2‎/‎2017 at 7:50 PM, '76mintgrun'02 said:

I saw those too.  Mine was at the twelve o'clock position.

I have found a ton of listings for the filter I am using, but none of them supply any data about valving.

 

so, I'm trying to follow all this, since I have (I think) a flooding problem once I shut down, the ambient pressure does purge fuel down the carb into the intake, making warm, hot starts troublesome,

 

does that Jeep filter relieve the ambient fuel line pressure, once shut down, even at 4psi? or does nothing, unless 15 psi or higher?

Link to comment
Share on other sites

Without the Jeep filter, the fuel line stayed pressurized at 4 psi.

 

I put the gauge on with the jeep filter installed and the residual pressure (after shutting the engine off) slowly bleeds back to zero, in about three or four seconds.

 

Yesterday I installed a little fuel pressure regulator that I've had on hand, but never used/tested.  It reads about one psi low, so one psi is actually around 2 psi, but that is fine.  I documented what each setting read on the pressure gauge, so at least I know what the real numbers are.  

068.thumb.JPG.1273c5d937d5cce2a8291c184c7fed1d.JPG

 

 

I made two trips to the hardware store yesterday, looking for a brass adapter, to connect the pressure regulator to the Weber fuel inlet; but could not find what I needed.  The threads on the Weber inlet are 10mm x 1.0 (extra fine) and the threads into my pressure regulator are 3/8-24.  I have 9/16" hexagonal brass rod stock and the 3/8" die, but not the 10mm die.  The hardware store had the tap but not the die.  To my door, online shopping, $6... then I can make my fitting.

 

 

     DISCLAIMER 

I now disagree with some of the timing advice I have given in the past.  I misinterpreted the distributor curves in the Blue Book. 

I've switched from using ported-vacuum to manifold, with better results. 

I apologize for spreading misinformation.  

Link to comment
Share on other sites

Here is my set-up per 1976 49 States diagram above with less connection to carb ported port and manifold vac port. If pictures not clear I can take more pictures. I should be able to drive the car in next couple of days when starter motor installed. I should mention that had the 4-way valve connect to vac port on intake runner #1 and drove 1,000 mile with no issue what so ever. But know I want to try something different and find out.

IMG_2865.thumb.JPG.af47012777cb3e9dac9549d33ae43deb.JPGIMG_2860.thumb.JPG.07f098e8d8584b867f6cf2136720eb03.JPGIMG_2861.thumb.JPG.4917e27d9327d0dd991d0abe1ca9407c.JPGIMG_2864.thumb.JPG.5ef0578aecccd5441a38b6cb16610a12.JPGIMG_2863.thumb.JPG.4b323ac3a1d22a9ae55ff21786857510.JPG

 

Can somone tell me where is EGR port located? Weber document shows it here and I am thinking that is same prot as prevoius picture attched (port F). Thanks

59373f0e25486_Webersideview.PNG.e46544aa1af050870e010d90c0988f5f.PNG

 

  • Like 1

76 2002 Sienabraun

2015 BMW F10

Link to comment
Share on other sites

Thanks for the photos Buckeye.

Are you using an idle cut off solenoid, without providing power to it?

Did you nip the pin, or something?

593789b30ce1c_Buckeysfuelpump.JPG.5b2c1ff598f2eca30572ba004b3906ea.JPG

 

     DISCLAIMER 

I now disagree with some of the timing advice I have given in the past.  I misinterpreted the distributor curves in the Blue Book. 

I've switched from using ported-vacuum to manifold, with better results. 

I apologize for spreading misinformation.  

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • BMW Neue Klasse - a birth of a Sports Sedan

    BMW Neue Klasse - a birth of a Sports Sedan

    Unveiling of the Neue Klasse Unveiled in 1961, BMW 1500 sedan was a revolutionary concept at the outset of the '60s. No tail fins or chrome fountains. Instead, what you got was understated and elegant, in a modern sense, exciting to drive as nearly any sports car, and yet still comfortable for four.   The elegant little sedan was an instant sensation. In the 1500, BMW not only found the long-term solution to its dire business straits but, more importantly, created an entirely new
    History of the BMW 2002 and the 02 Series

    History of the BMW 2002 and the 02 Series

    In 1966, BMW was practically unknown in the US unless you were a touring motorcycle enthusiast or had seen an Isetta given away on a quiz show.  BMW’s sales in the US that year were just 1253 cars.  Then BMW 1600-2 came to America’s shores, tripling US sales to 4564 the following year, boosted by favorable articles in the Buff Books. Car and Driver called it “the best $2500 sedan anywhere.”  Road & Track’s road test was equally enthusiastic.  Then, BMW took a cue from American manufacturers,
    The BMW 2002 Production Run

    The BMW 2002 Production Run

    BMW 02 series are like the original Volkswagen Beetles in one way (besides both being German classic cars)—throughout their long production, they all essentially look alike—at least to the uninitiated:  small, boxy, rear-wheel drive, two-door sedan.  Aficionados know better.   Not only were there three other body styles—none, unfortunately, exported to the US—but there were some significant visual and mechanical changes over their eleven-year production run.   I’ve extracted t

  • Upcoming Events

  • Supporting Vendors

×
×
  • Create New...