free hit
SU Fuel pumps - Fuel System/Carbs - The Lotus Forums - Lotus Community Partner #ForTheOwners Jump to content


SU Fuel pumps

catty s2

Recommended Posts

I think my pumps dead. R.I.P

It's got the ticking ok but there's no fuel getting to the carbs. The pumps not that old having only pumped a couple of thousand miles of fuel. Having read some other threads i see that these can be prone to failure quite early and they only come with a years warranty which is nice :lol: Im a bit pissed because she was booked in for an MOT today now ive got to fork out about seventy sheets just to get her there!

Link to comment
Share on other sites

Upgrade today to remove Google ads and support TLF.
  • Replies 8
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Normal SU fuel pump failure mode is due to the internal contacts...then it stops ticking and delivers no fuel. As Mat says, if they're ticking they should be fast does it tick? To start with, they should tick quickly, sort of BRRRRR sound which slows down and finally stops when the pressure has built up. You can get an electronic switch as a direct replacement for the contact even has the same ticking sound built in!!

Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

Link to comment
Share on other sites

If there's a blockage it will tick quickly and then slow to a stop as the pressure builds.

If you have no fuel reaching the carbs, but the pump runs continuously I'd be very scared as the pressure is not building up in the system. If petrol is not reaching the carbs it's got to be going somewhere!

You do of course have petrol in the car don't you? (many apologies but it's always useful to check the obvious first?)

Incidentally this is completely out of left field but I had similiar symptoms on an Exel. Turned out the atmosphere vent pipe on the fuel tank had become pinched and then blocked. This mean't that as the fuel pump pumped petrol out of the tank it created a vacuum in the tank as no air could flow back in to replace the petrol. As the vacuum pressure increased steadily in the tank it reached the point where the pump couldn't overcome it and voila, no more petrol to the carbs.

Only way I sussed it was one day trying to fill up the petrol cap wouldn't come off, and when I eventually got it to release there was a large sucking noise as the vacuum released.

As I said left field but you never know?




Link to comment
Share on other sites

The S3 SU pump packed in while unused for a year or so, no ticking, so I tried the usual universal tool (smallish hammer on the outside casing) it then started moving, but not as it should, so I blocked off the pipes, removed the motor side (leaving the pipes and diaphragm sections).

I lubricated the motor slide section slightly, and cleaned the contacts one had to be tightened as the rivet had become loose), all's well.

It's worth pulling the SU pumps off and checking them through, there's nothing that complex about them, the actuation arm moves as it reaches the maximum displacement it breaks the circuit and the arm returns fully the other direction.

Take the pump off (seal off 2 petrol lines and catch the fuel in a bucket) and check it works, but don't run it empty for more than about 20 seconds continuously.


Link to comment
Share on other sites

SU pumps have pulled me up twice - in the most embarrassing places, at traffic lights in the city.

I now have the upgraded 'hall effect' SU pump - with no contacts. The pump still taps away with the main solenoid action, but no chance of rusty contacts etc. A good upgrade.

I have found that the pumps give the impression of working when they are on their way out, and can also effect the tune of the engine. It is common to suspect the pump, then do nothing, then end up replacing the pump at the side of the road in a few days time!

Many a sad story like this...


Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Upgrade today to remove Google ads and support TLF.

  • Create New...