Fuel Delivery Components and Considerations

This is an ongoing compilation, started 2014, and is a Subpage to the SU Carburetters page.  Nov 2021 R. Kwas  (Comments Added)

CAUTION:  Fuel is Highly Flammable!  When working with fuel in the open, don't be complacent, but observe fire prevention practices, and have extinguishing options, like a suitable extinguisher and/or fire blanket on stand-by!  Work Safely!

Note:  The components shown here are only suitable for low pressure, carburetor systems (<5PSI), and not suitable for high pressure fuel systems (>20PSI), such as fitted on the Bosch D-Jetronic equipped cars. 

For D-Jet notes and discussions of fuel handling components, see:  http://www.sw-em.com/bosch_d-jetronic_injection.htm


Mechanical Fuel Pumps
    Bakelite Spacer
Electrical Fuel Pumps
Fuel Pressure Regulator/Filter

Fuel Filter


Mechanical Fuel Pumps: 


Glass Dome type:

Glass Dome FuPu by AC used to approx '64.  Shown without a hose-barb fitting. 
Gold Disc in glass bell is a cleanable screen.


Exploded assembly diagram of the AC Fuel Pump. 
Picture Source:  Skandix.de

AC, Metal Dome Type:

(PLACEHOLDER for info for metal domed AC fitted from '64 to '69)


Rebuild Kits including the Diaphragm and non-return valves are available for both AC pump styles.  (PLACEHOLDER for Source and PNs)

Not perfectly sealing non-return valves are what allow the weight of vertical column of fuel between FuPu and Carbs to drain back, when the engine is shut OFF (at a rate determined by how well they seal...or don't seal!)...but suggestions that this also drains the fuel bowls are simply impossible as the fuel falls into the bowls out of the Bowl-Valves, so there is no unbroken column of fuel which would allow it to siphon and empty bowls completely! 

Prolonged cranking after an extended parking time, to start, is more likely a result of the Fuel Bowls being vented to atmosphere and having dried out to some extent (leaving fuel remnants with all the octane and willingness to burn with that of Italian salad dressing) and needing to be refilled with fresh fuel...a good working, well adjusted Choke can't hurt either.  

See also:  Long Cranking during Starting Attempts after Extended Parking Times

Earlier cars (where a driver might actually open the hood and touch something) were equipped with Fuel Pump with priming lever.  This allowed a manual pre start-attempt priming of the fuel bowls after the car was parked for an extended time.  J G Coutts picture used with his kind permission. 

Glass-top Fuel Pump with priming lever.



Cover of the Pierburg pump is permanently swaged on,
making these pumps non-serviceable.


Bakelite Spacer for Mechanical Fuel Pumps:  

In order to limit the pressure and delivery of either type of mechanical FuPu, to a level which will not overwhelm the BowlValves, the Bakelite spacer must be installed between Housing and engine block.  This limits excursion of the actuating level by Camshaft lobe, and goes a long way to preventing turning your engine into a ECB18You have been Warned!!   

Tip:  Tighten the FuPu securing bolts evenly, and certainly with less Torque than when tightening a simple "stack-of-metal".  Bakelite is brittle!  See also:  Mechanical Fuel Pump Fasteners

Bakelite Fuel Pump Spacer.

See also:  Mechanical Fuel Pump Fasteners


Electrical Fuel Pumps:

I don't know why one would want to fit one, as the mechanical Fuel Pumps work well, are quite reliable, and put out the required low pressure necessary for carbs, but installing an electrical FuPu, it typically means selecting a low pressure type (instead of a 60PSI Bosch Fuel Injection type pump!), and still installing a quality low Pressure Fuel Pressure Regulator to assure carb fuel bowl valves are not overpowered.

When changing to an electric Fuel Pump for a carbureted system, (not a fuel injected system where a Crash Safety power shut-off functionality is built-in and part of the FI Electronic Control Unit * ), it is important to include an Inertial Crash Safety Switch, which will kill power to the pump in case of a crash, where fuel lines might be compromised...we wouldn't want the FuPu to continue pumping, possibly into the open!  In the CSS, a calibrated Mass in a non-self-resetting mechanism, controls electrical contacts. 

*  In fuel injection systems such as the D-Jetronic of the 1800E/ES and 140s, such a safety function is built-in...FuPu energization is controlled by the ECU which kills power to it, after "timing-out", if it does not sense pulses from Distributor indicating engine is running. 

The suggested circuit for retrofitting an electric FuPu with carbs, where no ECU handles the Crash Safety power shut-off function, is shown here:  


Inertia Switch, internal circuit.  A calibrated mass (M), working in concert with an accurate and repeatable (but not self-resetting) mechanism,
controls the contacts.  The Normally Closed (NC), and Common (C) contacts would be used to enable and power Fuel Pump by way of a Fuel
Pump Relay, as shown in circuit above.  The Normally Open (NO) contact is not used here, but may be used in other vehicle configurations, as
an input for crash safety related equipment (like air-bags, or passenger restraint pre-tensioners, or 911 on speed-dial, etc.).


See also YT video on this Ford CS/I switch:  Inertia Switch/Impact Sensor: Disassembled & Explained



Fuel Pressure Regulator/Filter

Even "Low-Pressure" Electric FuPus typically put out waaaay too much pressure so need a quality pressure Regulator like for example, the Malpassi Filter King Pressure Regulator/Filter combo, in order to not overwhelm the carb Bowl Valves (SU bowl Valves will not reliably shut, at a line pressure over 5PSI with potentially disastrous result!)..don't take a chance with overflowing Fuelbowls after installing an electric FuPu!     

Picture source: https://www.fuelpumpsonline.co.uk/malpassi-67mm-filter-king-with-glass-bowl-86-mm-unions-fpr004-34-p.asp

Beware:  The typical FPRegs which come up when simply searching, which look like this: 

...are label-engineered under a number of sellers, but they are all similar ultra-junk chinashit, which I strongly recommend against.  I have personally seen these leak, and when they are not leaking, it doesn't seem like they regulate very well either, or last longer than from 11:00 until noon...just look at the feedbacks on this one:  chinashit FPReg  My recommendation:  DON'T be tempted and taken in by the inexpensive price! 

...and the ones sold by Holley, are now also made in china, so no better!  You have been warned! 

Holley FPReg, now also by way of bejing...possibly slightly better than the above (but keep your receipt, and a Fire Extinguisher in the car!), a number of
the feedbacks complain of casting and machining faults...at least its "Shiny"...!  Link to Source


Fuel Filter: 

If a Filter / Fuel Pressure Regulator combo is not needed, I like this style for its inspectability, and cleanability.  Unscrew the metal endcaps which compress and seal against the thick glass envelope, and the plastic mesh element can be accessed and flushed clean, and any Foreign Object Debris (FOD) can be inspected and identified after removal.  As these are a bit too heavy to just let the fuel line support them, a holder is recommended and a good idea, to keep the glass envelope from hitting a nearby hard surface and breaking it! 

Glass envelope, serviceable Fuel Filter. 


Inexpensive Transparent Fuel Filter: 

I also like also these because they are inexpensive, still transparent, and available everywhere (including the lawn-mower isle of most every home supply store!).  These are so light, that they can be inserted without a holder, into a (low pressure fuel line) by simply inserting it into a section cut out of the line before the carbs! 

Plastic housing disposable fuel filter. 


Reference Information: 



External sources attributed when possible.  Otherwise this information is Copyright © 2014-2021 Ronald Kwas.  The terms Volvo, and other manufacturer and tradenames are used for reference only.  I have no affiliation with any of these companies than to try to keep their products working for me, help other enthusiasts do the same, and also present my highly opinionated results, including pointing out that china could f**k up a junkyard...many of their products are utter trash...and they are flooding the aftermarket with this rubbish!  Therefore: Know your suppliers and check the quality and suitability for service, of the components you get from them, and are installing into your car...you have been warned!!  The information presented comes from my own experience and carefully considered opinion, and can be used (or not!), or ridiculed and laughed at, or worshipped, at the readers discretion.  As with any recipe, your results may vary, and you are, and will always be, in charge of your own knuckles, and future!

You are welcome to use the information here in good health, and for your own non-commercial purposes, but if you reprint or otherwise republish this article, you must give credit to the author or link back to the SwEm site as the source.  If you donít, youíre just a lazy, scum sucking plagiarist, and the Boston Globe wants you!  As always, if you can supply corrections, or additional objective information or experience, I will always consider it, and consider working it into the next revision of this article...along with likely the odd metaphor, or analogy (see:  ABS!) and probably wise-a** comment. 


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