Purge Pump.. alternatives?

This forum is specifically for engine and gearbox posts, please try to keep on topic in any thread to make things easy to find

Moderator: Board Moderators

Post Reply
Zaphod
Junior Poster
Posts: 60
Joined: Mon Aug 23, 2021 21:38
Model: Excel SE
Colour: Blue
Year: 1990
Location: Uffington

Purge Pump.. alternatives?

Post by Zaphod »

Me again! looking at the purge pump it was obvious that it had been opened up, it was also obvious that it was not working when 12v was applied to it. I took it apart and found an old MFA (Model Flight Accessories!) motor in it, loose and not really attached to much and a lot of black dust.. the motor does however work but it's unlikely the original and even less likely to do much as the shaft is way too small for the pump.. (the motor literally fell out when I got the unit open). So I guess it's as dead as the infamous parrot. While I know its not overly important I would like to put something else in its place to do the same job, has anyone found anything suitable?

On another subject, I have the breather 'valve' back on the block, and one end fits to a pipe to the air cleaner, and I have that, but I do not have the pipe that attached the crank case breather to the thermal valve at the back of the inlet manifold, what size pipe is this, it looks to be different diameters at each end?
Of all the things I have lost I think I miss my mind the most...

1952 MG TD
1959 Austin Healey Sprite
1975 MG Midget 1500
1990 Lotus Excel
2007 BMW E92 320d M Sport

User avatar
hodders
Senior Poster
Posts: 446
Joined: Mon Aug 28, 2006 22:13
Model: Excel Celebration
Colour: Calypso Red
Year: 1992
Location: Lambourn, West Berkshire
Contact:

Re: Purge Pump.. alternatives?

Post by hodders »

-- hodders

1992 Lotus Excel Celebration, Calypso Red
2016 BMW i3, Protonic Blue
2020 Jaguar I-Pace, Eiger Grey

Zaphod
Junior Poster
Posts: 60
Joined: Mon Aug 23, 2021 21:38
Model: Excel SE
Colour: Blue
Year: 1990
Location: Uffington

Re: Purge Pump.. alternatives?

Post by Zaphod »

Hi, I was reading that which was why I took a look at it, but I think the actual pump end is too far gone
Of all the things I have lost I think I miss my mind the most...

1952 MG TD
1959 Austin Healey Sprite
1975 MG Midget 1500
1990 Lotus Excel
2007 BMW E92 320d M Sport

Online
AndyC
Senior Poster
Posts: 2100
Joined: Tue Nov 01, 2005 20:01
Model: SE x2 + Celebration
Colour: Gold,blue and green
Year: 1987
Location: Norwich
Contact:

Re: Purge Pump.. alternatives?

Post by AndyC »

If you were to replace the whole pump then it would need to be something that is pretty much sealed from the electrical part to the part holding air/fuel mix. Perhaps not a perfect hermetically sealed arrangement but at least one that reduces the potential for an explosive mix where the motor may spark.

User avatar
bash
Senior Poster
Posts: 1561
Joined: Thu Nov 03, 2005 15:34
Model: Se, V8
Colour: white
Year: 1986
Location: Doncaster
Contact:

Re: Purge Pump.. alternatives?

Post by bash »

My older car never had one from new and I dont think I missed it either......add lightness and bin it.
Bash
You are only young once but you can be juvenile all your life !!

Online
AndyC
Senior Poster
Posts: 2100
Joined: Tue Nov 01, 2005 20:01
Model: SE x2 + Celebration
Colour: Gold,blue and green
Year: 1987
Location: Norwich
Contact:

Re: Purge Pump.. alternatives?

Post by AndyC »

They do make a noticeable difference in one situation. Warm engine left for the right/wrong (PoV thing) time.
If the engine is cold, then no need. If the engine is warm and left a long time, no need. If the engine is warm and only left a few mins, no need. it's that period of time where a lot of the petrol in the carbs has evaporated but stayed in the airbox / venturi, before dissipating further. Try and start the car then, and you get a too-rich mixture, especially if you allow the carbs to be completely refilled by the fuel pump. In those set of circumstances, the purge pump will have basically vented that rich mixture to atmosphere, and you'll be OK to start normally.

User avatar
Hawaiis0
Senior Poster
Posts: 3514
Joined: Sun Jun 30, 2013 18:39
Model: Excel SA No 3
Colour: BRG
Year: 1986
Location: West Oxfordshire

Re: Purge Pump.. alternatives?

Post by Hawaiis0 »

I did a repair to mine and got it working . I did notice a difference with the hot stars

User avatar
bash
Senior Poster
Posts: 1561
Joined: Thu Nov 03, 2005 15:34
Model: Se, V8
Colour: white
Year: 1986
Location: Doncaster
Contact:

Re: Purge Pump.. alternatives?

Post by bash »

Perhaps the later jets made a difference but I never had a problem hot or cold. When it was hot I held the throttle open slightly when cranking but it never failed to start or gave a hint that it wouldnt.
Bash
You are only young once but you can be juvenile all your life !!

User avatar
Lotus-e-Clan
Senior Poster
Posts: 4123
Joined: Thu Nov 30, 2006 13:25
Model: Excel SE - EWP/Waterless!
Colour: Not Blue or Green
Year: 1989
Location: Swaledale

Re: Purge Pump.. alternatives?

Post by Lotus-e-Clan »

The classic need for this device is to save face after filling-up with petrol (especially on a hot day -but not exclusively so). You return to the car after paying for petrol, and it won't start (airbox fumes = too rich as pointed-out previously) . And the bloke who was previously admiring your car from the neighbouring pump notices you churning the engine, turns to his partner, and says "Ha! LOTUS, Lots of trouble...".
If you're thick-skinned, you don't need it as Bash says. :wink:

You can replace the purge pump with an alternative, but I do recommend modifying the circuit so you can switch it off when you intend not to restart anytime soon. This is to save the purge pump motor from overheating when running-on too long.

Mine is an aftermarket in-line washer motor with the supply connected to the central locking circuit. The circuit is adapted to cut the supply to the pump when locking the doors (ie when you leave the car for long periods)

Unlike the Lotus OE pump, the aftermarket pumping section is already isolated from any sparks generated by the pump motor, so there is no issue with saftey (fume ignition). The OE Lotus pump was designed to fail because the method of isolation actually overheated the pump (no ventilation) - must have been designed on the back of a fag packet by a Drawing Office slave under pressure.

I replaced mine many years ago and it's proven 100% reliable.

If fact I filled up with petrol today in CattericK (E5 = £1.55!! :shock: ), and it restarted on the button.
Sooo glad, because I'm pretty sure that those Army lads and lassies filling-up their BMWs were willing it to somehow fail just so they could 'take the P' :wink: .
Peter K

User avatar
DavidOliver
Senior Poster
Posts: 580
Joined: Fri Nov 07, 2014 11:18
Model: Excel
Colour: Calypso Red
Year: 1985
Location: Malaga Spain

Re: Purge Pump.. alternatives?

Post by DavidOliver »

I am sure Colin Chapman would cringe at the thought of a purge pump, my 85 has no such thing and here in Malaga I have not had any starting hesitation.
Anyhow, flush the airbox with an open throttle, no pumping. I don´t like electrics around fuel systems.


Dave the cog.

User avatar
Tanz
Senior Poster
Posts: 1767
Joined: Thu May 03, 2007 22:05
Model: SE
Colour: Calypso Red
Year: 1988
Location: Wolverhampton

Re: Purge Pump.. alternatives?

Post by Tanz »

DavidOliver wrote:
Fri Nov 26, 2021 13:25
I am sure Colin Chapman would cringe at the thought of a purge pump, my 85 has no such thing and here in Malaga I have not had any starting hesitation.
Anyhow, flush the airbox with an open throttle, no pumping. I don´t like electrics around fuel systems.


Dave the cog.
Mine broke 24 hours after buying the car in 2007. Haven't bothered to replace it as it's such a small problem. As you say Dave - just put your foot to the floor and hold it there till it starts as if you had flooded the engine. Starts pretty quickly.
Cheers, Phil
Never take life seriously, nobody gets out alive anyway!

User avatar
Lotus-e-Clan
Senior Poster
Posts: 4123
Joined: Thu Nov 30, 2006 13:25
Model: Excel SE - EWP/Waterless!
Colour: Not Blue or Green
Year: 1989
Location: Swaledale

Re: Purge Pump.. alternatives?

Post by Lotus-e-Clan »

If I ever I get myself to a meeting one day (say a LITP), I'd organise a 'hot start competition'. ... a timed event.
It would go like this:
  • 1) Everyone warm their engine by idling until the fans cut-in.
    2) Switch-off and leave for 3 minutes.
    3) prepare to start as you would normally (open throttle or closed)
    4) One turn of the key to restart the engine ...and the key turn must last 1 second or less( ie one flip turn)
My guess is that the purge pump users will win because it will start on the button, like a modern.

Never gonna happen 'cos I don't go to car meetings. It would be a hoot though, especially after a pint or two in the car-park. :lol:

And I don't mind failing, all part of the fun! :mrgreen:
Peter K

User avatar
robertverhey
Senior Poster
Posts: 775
Joined: Tue Nov 01, 2005 10:54
Year: 0
Location: Sydney
Contact:

Re: Purge Pump.. alternatives?

Post by robertverhey »

Something like this would do the job I reckon

https://www.ebay.com.au/itm/High-Torque ... 635-2958-0
Robert Glacier Blue '87 SE

User avatar
DavidOliver
Senior Poster
Posts: 580
Joined: Fri Nov 07, 2014 11:18
Model: Excel
Colour: Calypso Red
Year: 1985
Location: Malaga Spain

Re: Purge Pump.. alternatives?

Post by DavidOliver »

Robert, if it´s not spark proof it might give you a surprise.

Dave the cog.

Post Reply