• Hi Guest! Being a Paying Supporter is NOT a requirement to participate at BCF. However, subscribing will help ensure we can continue to serve the LBC community for years to come. If you enjoy BCF and find our forum a useful resource...Please consider supporting us by **Upgrading**
    (PS: Subscribers don't see this banner)

Type L SU fuel pump


Great Pumpkin
Just wondering if anyone here can advise, or point me to a troubleshooting source, for an SU fuel pump "issue".

Issue: no more steady tick/clicks - just a fast whirring fluttering sound.

Tom M.
Country flag
The SU fuel pump uses a reinforced rubber diaphragm activated by a solenoid body; i.e. it's essentially a piston, with one-way flapper valves to force the fuel in the proper directions. The most common failure is in the electrical switching mechanism, which is usually a set of contact points but modern versions use solid state switching. I can't imagine how one could make a whirring sound, but they can fibrillate (flutter). They aren't terribly difficult to repair, or you can buy new from the usual suspects. A third option is to send to an expert for a rebuild; Dave DuBois has fixed several for me, and he can install an optical switch which should outlast points: https://userwebs.donobi.net/sufuelpumps/ (NFI).

But, before you buy or repair, make sure the plumbing is in good nick. An air leak, esp. on the intake (tank) side can cause the pump to run rapidly, and reduce fuel flow.


Great Pumpkin
Bob - thanks for the advice.

It's certainly possible the diaphragm needs replacing. I'll need to remove it to see if it's the 3" long, or 2 3/8" long part.

Could you advise me how to remove the old one without breaking something? Do I just carefully lift the lip of the diaphragm, and grasp it and unscrew it? Or are there internal parts (bearings, springs, retainers, etc.) that might come flying out?

Here's what the current diaphragm looks like.


Tom M.
Country flag
Hoo boy ... that diaphragm is shot. My guess is ethanol got to it.

Yes, you can peel the edge of the diaphragm away from the pump body. The diaphragm has a shaft--as you say, 3" long, or 2 3/8" long (not sure which pump uses which)--that is screwed into a threaded trunnion on the points throwover mechanism. You can just rotate the diaphragm--counterclockwise--to unscrew it from the points, but you probably would have a bit of trouble getting the shaft and trunnion lined-up for the new diaphragm shaft. I think, given the poor shape of the diaphragm, you should pull the cap off the end of the body and have a look at the points; at the least, you'll probably want to file and adjust them. The adjustment process varies with models, and I only have the procedure for Big Healeys. Also, the quality of aftermarket points sets was suspect--China or Taiwan--last time I bought a set from the Usual Suspects, so you'd want to go to a source for genuine SU parts. There should be a paper gasket between the diaphragm and the pump head (where the valves are).


Darth Vader
Although I don't disagree with Randy on the cost benefit of purchasing a Facet pump over that of an SU, I have had my original SU pump running strong for the past 52 years with only minor issues. I am not sure that I agree with Bob and believe your diaphragm appears to show some contaminants from your fuel that may have caused the pump's valve to stick open. Fuel agitation as a result of the open valve could be the source of the whirring sound and could be blocking the tick and eliminating delivery.

I would clean out the pump and readjust for good flow. Additionally, if you have a points-triggered pump, I would clean the points and remove any electronic component connected to the points (SU placed diodes across the pump points to eliminate point flash but it didn't work all that well). I would then install a Transient-Voltage Suppression (TVS) Diode that will eliminate point flash and burn to make the points last almost forever.

As most are unaware, the SU pump depends upon a coil for operation. Many have not realized that this coil has the potential of raising voltage across the points to as much as 200 volts and is the primary cause of point flash and/or burn. A P6KE20CA TVS (manufactured by Vishay), at a cost of around $1.00 or so, will allow up to 27 volts to pass across the points and shunt to ground anything above. The 27 volts is sufficient to burn off point corrosion formed during long periods of inactivity and/or storage but well under that needed to cause point flash or burn. As a result, I have found no need to replace points or do any maintenance on my pump since installing

Yes, if you are going to replace your pump, the Facet pump is both reliable and much less expensive then a new points or electronic SU pump. However, I would first consider seeing if I could service the SU pump back to performance before a replacement.

Just my thoughts,
Last edited:


Jedi Trainee
Writing just to say that I found Randy Forbes' comments (and accompanying photo/website reference) on using a facet fuel pump to be a good alternative to the SU fuel pump, in the event of failure. There seems to be such a science built around fixing/servicing your old one (note Ray's (RAC68) explanation of the electronics), not to mention the various codes for the multitude of SU fuel pumps out there. Notwithstanding the general reliability of SU pumps, I quite agree that the simplicity and cost of the facet pump makes it a worthwhile consideration, particularly when electronics happens to be your Achilles heel, such as in my case.



Country flag
From the online patent drawings, both the cylinder and box Facet pumps have no diaphragms so should be most reliable. The one Randy uses is for >150hp. The gold box for <150hp.

Since I've never run an SU, am not captivated by the "romance" of them.

My car came with a plastic German aftermarket pump which performed erratically.


Healey Nut

Luke Skywalker
Country flag
Unless you're building up your car for concours showing__or you're a masochist__why bother with an original fuel pump at all
Just buy a solid state SU install it and be done with it . Find something else more worthwhile to tinker with .
Similar threads
Thread starter Title Forum Replies Date
B E-Type fuel pump speks? Jaguar 2
B Series 1 E-Type fuel pump question Jaguar 2
D location of fuel pump fuse on 1967 e-type Jaguar 3
TRopic6 TR6 TR-6 Fuel Pump Diaphragm Failure [Red-type] Triumph 2
K TR4/4A TR4 Fuel Gauge'"light bulb socket" type? Triumph 11
Martinld123 H Type Carburetors BN2 M version Leaking Fuel At Jet Bearing Area Austin Healey 18
Basil E-Type fuel tank mounting bolts [$&^##$%*!!] Jaguar 16
Basil About to re-install my fuel tank Series I E-Type Jaguar 6
S banjo type fuel lines--vacuum advance Triumph 0
Kleykamp TR2/3/3A TR3 fuel filter location and type Triumph 7
nevets fuel filter type? Austin Healey 3
nevets Fuel filter type? Austin Healey 3
K McLaren: Fiat/Mini Type Fuel Saver? Triumph 1
F S3 E-type Fuel Filter Jaguar 1
Gearhead what type of fuel? Spridgets 9
R TR6 Clutch Master Cylinder Hydraulic Line (Thread / Flare Type) Triumph 4
S TR2/3/3A 187 NOS sleeved type thermostat Triumph 16
M Series 3 E-Type Bonnet Jaguar Classifieds 0
Basil The new Kia E-Type? Jaguar 6
H TR4/4A A-type overdrive pump Triumph 4
Got_All_4 TR6 Refurbishing gearbox with A type overdrive Triumph 7
P Wanted E type spare tire bracket Jaguar Classifieds 2
P Wanted 62 E Type spare tire bracket Other British Classifieds 1
Got_All_4 TR6 Routing Speedo cable for a J type tranny in my TR250 Triumph 4
Got_All_4 TR5/TR250 Trying to figure out rear transmission mount with a J type tranny Triumph 9
I GT6 A type OD vs D type - engagement speed? Triumph 3
J For Sale Jaguar E Type and MK2 spares Jaguar Classifieds 0
VooDooDaddy63 Basic E-Type Question: Fasteners - Metric or SAE or ...? Jaguar 15
D TR2/3/3A Type A overdrive not engaging Triumph 0
D TR2/3/3A Type A overdrive not engaging Triumph 16
S For Sale Lotus Elan Factory Workshop Manual on CD/ROM - Type 26 - 1963 - 1965 Other British Classifieds 0
B Resistor type vs non-resistor type spark plugs for 100-6 Austin Healey 17
AH67 Heat Shield finish 66 Type Jaguar 5
AUSMHLY Grease type for zerk fittings Austin Healey 7
M TR4/4A A type Overdrive Oil Leak Fix Triumph 3
M 5-speed, 1968, 4.2, E-Type, OTS Jaguar 3
M e-type siries 1.5 shock abosorbers Jaguar 3
B TR2/3/3A 'A' type Front calipers, TR3 vendor??? Triumph 7
M E Type 4.2 engine rebuild Jaguar 4
D E-Type steering wheel Jaguar 6
DrEntropy E-Type windshield FYI: Jaguar 1
TRclassic3 TR4/4A A type OD working in 3rd but not in 4th Triumph 5
Graham H TR2/3/3A A type overdrive Triumph 6
H Post-War Other Wiper Motor [Early type DR2] Issue Triumph 7
M E-type series 1 plastic dash vents Jaguar 1
M TR2/3/3A SU H Type Carberator Float Lever Adjustment Triumph 10
KVH General TR Type A Laycock Overdrive Questions Triumph 8
Talon TR2/3/3A Float lever issue on SU type H carbs Triumph 1
D '69 E-Type sputters, coughs & dies Jaguar 20
Boink Left-hand Drive E-type at Windsor Jaguar 5

Similar threads