Lotus Elan

New WEBER Fuel Lines, Inline Fuel Filter Position

PostPost by: rcourtney » Fri Sep 26, 2014 9:53 am

Morning all,

My '68 plus 2 has had an electric fuel pump fitted by a previous owner. It sits in the lower boot space, just under the tank. Despite the elec pump, the car struggles to start on the first/second turn (always starts after throttle pumped and car turned over - it feels like the Carbs are initially starved. Once running the car stumbles, until warm, on tight left turns. When warm it runs well.

The fuel lines in the engine bay, into the WEBERs, with a 'home made setup' (6mm Lines) - see picture. They also put in a disposable inline fuel filter just before the T that splits the line off to each carb.

I have just bought a new fuel line from QED (http://qedmotorsport.co.uk/qed-shop/lot ... ious-types). And plan fit it this weekend - commitments allowing. I'm hoping that a correctly fitted (not sitting on top of the carbs!) fabricated fuel line will help these issues.

So ... to my question .. The inline fuel filter that has been placed in the engine bay just before the Carbs. Should i replace, re position or remove altogether (new tank and theres never any build up in the filter). I think it might be part of the reason I'm not getting enough fuel through initally. Space etc allowing I assume that i should place it just before the pump .. not after and obvisouly not in the engine bay.

All thoughts / advise much appriciated. I'm no mechanic (as my wife likes to remind me!)
Ralph
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Weber Fuel Line.jpg and
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PostPost by: Pistacchio sprint 72 » Fri Sep 26, 2014 11:57 am

I can confirm you that the fuel filter should be before the fuel pump and not just before the carbs.

Also, if it can help you to sleep better, your weber carbs have small fuel filter integrated... :mrgreen:
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PostPost by: Spyder fan » Fri Sep 26, 2014 12:56 pm

When you pump the accelerator the accelerator pump jets in the carbs spray a mist of fuel into manifold, this will aid starting a cold engine. Others on here much more expert on carburettors can explain it better, but I'm pretty sure that your pump will get the fuel to the carbs and that they will fill to the float level that's been set. The fact that there is quite distance from the carbs to the combustion chamber means that extra fuel is needed to encourage the engine to start and that it probably wont start on the idle settings without lots of cranking.

You should have a filter between the tank and the electric pump. Your problems on left hand bends and when cold sound like jet and float level issues.
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PostPost by: Pistacchio sprint 72 » Fri Sep 26, 2014 1:15 pm

also, now that I am looking at your engine bay... You have KN style air filters on your carb.
(I do have the same on my Caterham but the filters stick out of the bonnet!)

They re sucking hot air from the engine bay = not good.

You should have a carb air box + trunking and catching cold air from the front grill of the car in order to acheive better results.
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PostPost by: rcourtney » Fri Sep 26, 2014 1:46 pm

Thanks for the replies,

I had no idea that the Weber 40 contained a small Fuel screen (Weber Part number 37022.010). Is it worth replacing the internal fuel filter/screen? Looks like a simple job - unscrew the large nut by the Banjo, whip the internal fuel filter out, replace with new, add new gasket (Part number 41530.024) and tighten back up.

All in for 2x Filter and 2x Gasket .... 4.70 (ex VAT) - has to be worth it. I assume its not been done for years.

If still stummling post new fuel lines / removal of filter then will investigate further - although float issue sounds like it might get time consuming ..

Thanks again
Ralph
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PostPost by: rcourtney » Fri Sep 26, 2014 1:52 pm

Great advise re Air Blocks vs Air Box - car does get 'excited' when really hot under the bonnet .... that might be a contributing factor

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PostPost by: EPA » Fri Sep 26, 2014 3:23 pm

If your electric pump is starting when you turn on the ignition it should fill up the carbs to the level set by the floats. Try waiting a few seconds before trying to start the car i.e. leave the ignition on for a few seconds before attempting to start . This would be true even if the fuel pressure was a bit low due to a blocked filter or low pump pressure.
I would check if the pump is starting,the fuel pressure and the float setting in the carbs

Having said that I have had similar symptoms to this when the plugs have become a little fouled and cleaning or replacing the plugs fixes it.


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PostPost by: mbell » Fri Sep 26, 2014 7:56 pm

I'd be interested to see a photo of your pump location.

I think the baisc checks you should do have been covered by Ed. But I'd did a bit of a write on on the +2 fuel system at:
www.lotuselan.net/forums/lotus-carbs-f4 ... 30305.html
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PostPost by: rcourtney » Sun Sep 28, 2014 5:00 pm

As requested ...

Appoligied for the poor perspective of the shoot

The pump sits below the 'floor' of the boot just below the tank, on the left of the battery (as you look at it). The battery sits in the red plastic box on the right of the photo.

I've very new to this but seem to have a very small pump (in the fuel line) that's not attached to anything !! And another device that's large, attached and appears plumbed! Filter?!? Any thoughts welcome ...

Ralph
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PostPost by: oldchieft » Sun Sep 28, 2014 6:17 pm

That pump looks like a SU double pump, with half of it removed.

This is what it should look like.
SU pump copy.jpg and
AZX 1501 SU pump


It is a bodge possibly from the days when you could not get cheap pumps.

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PostPost by: Pistacchio sprint 72 » Sun Sep 28, 2014 7:55 pm

It looks as if some taliban had set up a bomb under your car.
Don ?t get close to any military base with your elan or you might get into trouble at the first checkpoint! :mrgreen:
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PostPost by: mbell » Sun Sep 28, 2014 9:54 pm

Hi Ralph,

Looking at the photo the small cylinder on the right of the photo appear to be a inline filter or pressure regulator. I think I'd want to identify that unit and figure out the plumbing, if it is a filter I'd probably change it out just so you know its in good order.

Before messing too much with this I'd want to check if there is an actual problem so I find a pressure gauge and see if there is ~2-3PSI at the carbs. This would be good indication the fuel system is probably working ok and I'd move on to the carbs and things like the fuel level in the carbs.

Cheers,

Mark
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PostPost by: rgh0 » Sun Sep 28, 2014 10:05 pm

The smaller unit if it has a wire going to it could be an electric fuel cut off valve? but if its not earthed it will not be working !

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PostPost by: oldchieft » Mon Sep 29, 2014 6:17 am

The yellow wire is the feed to the pump, the black is the earth for the pump.

Old SU pumps are well engineered, I have one in series with my engine driven pump I use it via a sprung switch for a few seconds to prime the webers, but mine is a LP fitted under the bonnet.

If it works I would say sort out the mess that is the wiring and plumbing and keep the pump.

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PostPost by: rcourtney » Mon Sep 29, 2014 9:38 am

Hi All,

Many Thanks for your replies! This all makes a lot of sense - I feel like i'm getting somewhere.

Looks like I need to work out how these pumps are plumbed / wired. I'm assuming that the inline pump (if thats what it is (I believe it is) is inoperative, either that or its very quiet! Further investigation is needed.

I believe the old SU pump supplies the Carbs. Upon turning the ignition, the ignition light comes on and an audiable clicking can be heard from the back ... after pumping the accelerator for a while the clicking stops. From what I have read this is normal with an old SU setup .. they start pumping once vacum has been created and will click until pressure has been built up. This takes me full circle and would seem to explain why the car never starts on the first crack / until the accelerator has been pumped.

Now add this to the mix - Having spoken to previous / previous previous owners ... I know the car use to have fog lights and a fuel pump switch where the ash tray is located. These seem to have been removed and the ash tray replaced. I removed the ash try to find some yellow / black wires labelled 'fog lights'. I can see that the fogs are wired with blue wires .. I'm thinking that these maybe for the inline pump? - previously used to 'prime' before the SU takes up the job. Just putting it out there - maybe well off the mark but would seem to make sense ?!?

I'm very tempted to replace the whole setup with a facet posi-flow / regulator setup. Simplify everything and get fuel to the carbs from the get go without having to mess around while my wife tuts and shakes her head as i 'struggle' to start it (ie have to pump the accelerator and crack it 3 times).

Thanks again for all the advise - some investigation required!
Ralph
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