Glass Bowl Fuel Pump Experience

[Stevie-Heathie]

Just sharing for the sake of completeness and to help others in the future, following on from my previous post asking about repair kits here viewtopic.php?f=40&t=52555.

In the end, after discussing with Max at MAX500 I decided to replace the glass bowl fuel pump with a new glass bowl pump, rather than use a repair kit. A bit more risky in terms of fit and quality but quicker.

As Max kindly advised, It IS possible to replace the pump from below working alone. Neither the carbs nor the air box need to come off. The oil filter and starter motor DO need to come off though.

Access is VERY tight, even by Elan standards. My car doesn’t have the footwell hole, which would have helped for sure. You need to improvise with sockets and think laterally to find a way to get the two bolts in. And stubby spanners are needed to connect the fuel lines. Dizzy cap needs to come off so you can thread your right arm in.

It took me 7 hours to do the whole change out, but but now I know the above it could be done in a couple of hours. Very satisfying in the end but my poor “office hands” took a beating . Lots of feeling in the dark and sharp chassis edges to contend with.

New pump with its clean filter is probably sending more fuel to the Webers than the old one, so another tune up might be required.

I’ll get a kit and repair the old pump to keep it on standby as a spare.

Hope this might help somebody down the road

Steve
67 S3 SE

[alan.barker]

Well done Stevie,
A useful thing i've found before trying to fit new pump. Turn the Engine by hand and make sure the Cam for the Fuel Pump is in lowest position. So the operating lever/foot needs the least depression while fitting the 2 setscrews. The spring action on the Pump lever/foot is quite heavy.
Have fun
Alan

[billwill]

The float valves in the carbs control the fuel, so increasing the pump efficiency should not affect the engine tuning.

(unless it pumps too hard & overcomes the float valves, which is why electric fuel pumps usually need a pressure regulator between pump & carbs.)

[Stevie-Heathie]

Thanks Bill - yes I stuck my finger in and the cam was at the bottom so made it that bit easier.

Yes Alan you are quite right, Max said the same - any minor change in fuel flow will be compensated for by the Webers.

Goodwood track day on Saturday - woohoo!

Best
Steve

[billwill]

Thanks Bill - yes I stuck my finger in and the cam was at the bottom so made it that bit easier.

Yes Alan you are quite right, Max said the same - any minor change in fuel flow will be compensated for by the Webers.

Goodwood track day on Saturday - woohoo!

Best
Steve

I think you got Bill & Alan the wrong way around there!

[Stevie-Heathie]

UPDATE;

The saga continues. Turns out the new fuel pump I fitted is over pressure (I should have rebuilt the old one). Anyway this is overcoming the float bowls in the Webers and they are running super rich and the car stutters on acceleration no matter what timing advance we set. Called master tuner Tom Airey and he says 1/3 of all the cars that come in have too much fuel pressure and need a pressure reducer fitting, and it needs to go downstream of the pump (tricky with mechanical pump as you know - no space).

Tom recommended the Malpessi type but they need to go horizontal and that would require a bracket on the rad or the carb and no time to sort that out. So I ordered a cheap little one from Amazon and it was delivered same day with Prime (amazing!).

A mate donated some hose and I made up a new assembly, complete with pressure reducer.

Now to fit that and - hopefully - all will be well and Goodwood track day day after tomorrow is a go.

Added bonus - the old hose inside the braids was deteriorating so new hose was needed anyway. When I have more time I’ll get some new braided E10 hose and fit a Malpessi somewhere nice.

Phew.

Is it like this with all classics or just Lotuses?

Steve
67 Elan SE DHC

[alan.barker]

Is the new Mechanical Pump ALL Metal.
If so all of the metal mechanical pumps i have seen produce too much pressure.
Like ypu say rebuild old glass pump is best solution.
Alan

[andywatts]

Noted that your fuel pipes were cracking up. I fitted braided hoses (from appearences the same type) thinking they would be high quality and a bit of extra protection in the case of a fire. But apparently the deterioration meant that quite a lot of my fuel ended up on the floor of Chris Foulds workshop when he was working on the car! Now replaced with standard - non braided- fuel hose. If it doesn't last any longer at least it can be inspected.

Re fuel pumps - interested to hear that mechanical pumps might overwhelm the Webers. I've stuck with a small electrical pump (from Webcon and stated to be compatible with DCOEs). No problems, but I've also decided to go back to the original pump when I next do work on the car. I guess some pressure measurement (or perhaps careful checking of fuel level by removing the jet cover and probing for the fuel surface) is a wise precaution.

[alanr]

The all metal mechanical pumps are long proven to deliver an unsuitable pressure for Webers.
Also there are now available from the usual suppliers 'new' repro non-genuine but similar to original glass bowl mechanical pumps (Chinese?)which I understand also are delivering too much pressure for Webers.

I would say it is best to stick with your original and genuine AC mechanical pump and rebuild it.

Alan

[Stevie-Heathie]

Confirm that the new pump is an unbranded glass bowl type and appears to be over-pressure.

With hindsight I should have rebuilt the original AC glass bowl pump and that would be my strong recommendation to others.

Best
Steve

[snowyelan]

While you shouldn't have to do it in the first place, a simple spring change is all that is required to change the pressure. I swapped in one from an old pump when I had the same problem.

[pharriso]

While you shouldn't have to do it in the first place, a simple spring change is all that is required to change the pressure. I swapped in one from an old pump when I had the same problem.

Why would you want to change the fuel pressure?

[snowyelan]

Several posts above noted that replacement pumps were being supplied with too much pressure.

[pharriso]

Several posts above noted that replacement pumps were being supplied with too much pressure.

Ah… so you want to swap the spring out to reduce the pressure back to spec?