Mechanical Fuel Pump FAQ

[tjones02]

There are basically two different types of mechanical fuel pumps that were used on '02s. The '02 fuel pumps have 8mm inlet with 6mm outlet hose fittings, and one that has 8mm in and out hose fittings that is a performance upgrade......

#13 31 1 252 506 Pump is defined by its lever type operating mechanism that is below the mounting surface and the 8mm inlet and 6mm outlet hose fittings. This pump was used on single barrel and 2002 TI's before mid '72.

#13 31 1 265 192 The operating mechanism has a pin and coil spring that stick out of the mounting surface. This pump was used on 2 barrel '02s from mid '72 on.

#13 31 1 260 677 was used on the carbureted 6 cylinder M30 motors and is defined by the lever type operating mechanism, its ability to clear most side draft intake manifolds, AND its 8mm inlet AND outlet hose fittings, thus it has a greater volume capacity while having the perfect pressure for running many different types of carburetors on the M10 4cyl engines. M30 6cyl engines that used this pump had 170 to 190hp and dual carburetors. This is THE mechanical pump to use with side drafts on modified performance engines!

Picture of the two different operating mechanisms.

There are two different fuel pump push rods for 2002's. Early longer ones are for the "506" early pump and the "677" M30 engine types. This is the push rod for all the BMW mechanical fuel pumps that have the lever type operating mechanism that is below the mounting flange.

The two part #'s for the pushrods are...

#13 31 1 250 398 is 107mm long. Most of these have a narrow section in the middle of it. This is the push rod for all the BMW mechanical fuel pumps that have the lever type operating mechanism that is below the mounting flange. These longer pushrods are for the "506" early pump and the "677" M30 types.

#13 31 1 255 727 is 88mm long. This shorter pushrod is for the "192" and all the pumps which have the pin and coil spring mechanisms that stick out of the pump mounting flange.

#11 11 1 721 614 is the insulator block With gaskets on it.

#113 127 311 is a VW number for the gasket to reseal an old insulator block, you'll need two of them.

#13 31 0 075 752 is for the insulator bushings, use two (2).

To mount the pumps use two of the above bushings, two wave lock (not split lock!) washers and two 8x1.25 x 12mm wrench size nuts with a dab of blue loctite (13mm nuts don't work as nice in the tight space around the pump). Some try and use nyloc nuts but I find most of the time that the studs are not long enough to grab properly into the nylon. Try and not over torque the nuts as the bushings are fragile.

If your cylinder head doesn't have the provision for a mechanical fuel pump I suggest this Pierburg unit part# 7.21440.51.0 . They are specifically rated for the fuel pressure that our carburetors require, thus do not need an external fuel pressure regulator. And they are very quiet, especially when compared to a Facet pump. (SSF sells these Pierburg pumps as replacements for early carbureted Porsche 911's)

 

brandstofpomp_oldtimer_ombouw.pdf

 

In addition to this electric fuel pump I suggest wiring it with an RPM sensing relay like that from an early E21 320i fuel pump relay part# 12 63 1 277 245, or this VW relay that has a built in fuse holder (15A) part# 321 906 059C . All these relays need to work is a tach signal from the coil. Even Tii's can be wired with one of these relays to make them safer.

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[Son of Marty]

Thank you Tom, that's about as clear and concise a write up I've seen on m10 fuel pumps. 

Edited December 20, 2016 by Son of Marty

[zinz]

Thanks, Tom.  

 

I have successfully used a 90 degree Pierburg on my '71 with sidedraft Solexes for many years, without complaint.

 

Though your pictures show the un-rebuildable type, I'd like to add this note about rebuilding one of these pumps with a new kit designed for VWs.  I just performed this task for my '67 2000CS with Solex PHHs.  I found that the spring supplied in the VW kit was far too strong, resulting in the pump supplying way too much fuel pressure to my newly rebuilt Solexes.  I installed a fuel pressure regulator after the pump to isolate and solve the problem.  Unfortunately, before I could remove the Pierburg and replace the spring with the old one, the pump failed.  I believe the pump hammering away against the regulator caused the failure, but I haven't fully determined that, at the moment.

 

Here's a pic of the rebuilt pump and Solexes from last week.  

 

And the pump I rebuilt for the '71, some years ago... that was rebuilt with an NOS kit and a proper spring.  No problems at all in about 20,000 miles.  

 

 

Thanks again for the 411 on Pierburgs.

 

Ed

Edited December 21, 2016 by zinz

[dlhoovler]

Ed, thanks for the tip on the VW kit spring being too stiff--good to know that the original should be reused.

 

Do you recall which VW pump rebuild kit matches up with the 2002 units? I've looked into them before from different suppliers and noted different numbers for the different displacements of VW engines, with no accompanying photos to eyeball it.

 

-Dave

[zinz]

I knew I forgot to add something to my reply...

 

I bought this one http://www2.cip1.com/ProductDetails.asp?ProductCode=VWC-111-198-553

 

 

The diaphragm matches up as does the rest of the hardware.  I think if you use your old coil spring, the pump would work just fine.  

 

Here's a nice write up on how to rebuild... it's super easy.  http://www.wolfsburgwest.com/wired/wired_12_99/wired_12_99.htm

 

Ed

[dlhoovler]

Thanks, Ed.

 

-Dave

[hynrgee]

A very useful piece for those of us dealing with fuel system issues. Thank you Mr. Jones! This will save others the time researching the differences in the pumps and the other parts that are recommended. A month ago I had to replace my fuel pump and decided to replace the hoses and fuel filter while I was at it. I'm glad I did as I learned that someone had installed the fuel filter backwards. The filter clearly has the word "out" marked on it so someone was in a rush. 

Ed had a post on a check valve near the fuel tank that I added to my order to address a similar problem. Putting the check valve in along with a better cap on the fuel tank's return seems to have stopped the fumes in the trunk as well. Along the way I had to replace the filler pipe since it had a slight puncture. The car is running much better than before as a result. I added a fuel regulator after the fuel pump to see if it made a difference and it did not so I took it off.

I still have a high idle problem as well as cold crank challenges, but the problems with uneven sputtering starts from stop are gone. 

 

 

 

[jrhone]

Great post!  I have a silly question...at what point should someone be looking to upgrade to the bigger fuel pump?  I have a weber 38 and a 292 cam and headers etc...I wonder if the bigger fuel pump will have any effect on performance.

[Simeon]

It won't effect performance unless you are getting fuel starvation at high speed. It's job is to keep the float bowl topped up and that's the same size as a 32/36. You will be flowing slightly more air and hence fuel but only marginally so. 

[zinz]

Absolutely don't need a bigger fuel pump, in most cases you will need a fuel pressure regulator because of too much fuel flow.  Webers only need about 3 psi, and Solexes need even less...

 

Ed

 

PS... thanks for the kind words above.  I do try to help, when I can.  I've found that check valve really helped a 32/36 on a hot restart, especially when using an electric pump (otherwise fuel drains back in to the tank, leaving most of the fuel line empty.  In today's gotta-have-it-now world, no one likes waiting for the system to reprime)  

 

The check valve is Amazon part # DFD018

 

[Kingryan86]

What are these pumps worth? I have 3 i am gonna list, Im not sure which ones they are until I look tomorrow. But would like to list for a fair price..

What do you think is fair for each of them?

[Simeon]

New ones are about $80 so somewhere between $0 and $50. 

[NickVyse]

Top nerdy work Mr Jones!

[nele-alpina]

 

Hello everyone. I have seen this pattern to put electric fuel pump.  I wanted to ask which model of pump, pressure regulating valve and the gas bubble separators i must buy. I bmw 1802, and I have two twin-choke Weber carburetors DCOE 40. I would like to do well this fuel system.

Edited February 6, 2017 by nele-alpina

[goodhobbes]

 Pierburg 13-31-1-260-677 Fuel Pump  just installed.   I have twin side-draught webers and based on your article, it would seem that this pump is the right one.  Similar in appearance to the old one, but unlike the new one, the old one did not have removable access to the diaphragm, but a press-fit cover.  The push rod is about 107 mm. and does not appear to have the depth of thrust necessary to operate the new pump. In addition the new pump requires much more thrust pressure to operate. 

Have I got the wrong pump?  Is my insulator block between cylinder head and pump flange too thick?

All thoughts appreciated. thanks.

Martin