Fuel Vapourisation

Post by **Pikey** » Wed Sep 23, 2009 9:16 pm

Hi all
I realise that this has probably been discussed in length before, but is there any way I can stop the fuel vapourisation in the petrol pipe to the fuel pump.

Why? Well when I was queuing to get into tredegar house show in newport, last sunday after about 40 minutes of literally 2mph crawling traffic in really nice hot british weather, the pickup started to run fairly roughly (trying to stall but never actually did) and I could hear the fuel pump working hard to keep up even on tick over. The pump was working harder than it was travelling at 50-55mph on the bypass she had only just travelled on two minutes before. Also once the engine had cooled off and before my journey home she was running fine again, so I suspect the fuel pump was sucking vapour instead of fuel.

Does anyone have any experience of successfully sorting out fuel vapourisation. Also should I fit a shield the carb from the engine etc. I note that MGB's/midgets etc have a shield between the manifold and carbs does the mog need something similar perhaps.

Regards

Steve B

Post by **bmcecosse** » Wed Sep 23, 2009 10:53 pm

Some vehicles seem to be prone to this - possibly down to a weak fuel pump. The real answer is to mount the pump lower down - so it doesn't have to suck the fuel up so high. That's where the vapourisation happens - the pump will then have no problem pushing the fuel up to the carb - but they are not too good at the sucking!

Post by **Pikey** » Thu Sep 24, 2009 8:29 am

Ok thats for that.

I might try replacing my aftermarket in-line fuel filter by the petrol tank first, perhaps my filter is clogged and the pump cant lift fuel that easily and when she hot it just exasparates the issue.

Failing that I might invest on one of these nice higher capacity glass bowl types that Ive sometimes seen and mount it somewhere on the body/chassis under the rear wooden floors for easy access.

Does anyone know where I can find a nice external glass bowl type filter. Does SU Burlen sell them.

Regards

Steve B

Post by **bmcecosse** » Thu Sep 24, 2009 8:44 am

Why do you want a fuel filter ? The pump has one in it's base - just get rid of the on you have (in case it's blocked) and clean the one in the pump! It may very well be part of the problem.

Post by **mike.perry** » Thu Sep 24, 2009 10:05 am

Fuel vapourisation can be a problem in hot weather with the Series MM, particularly the lowlight model. This is because the fuel line runs very close to the exhaust manifold and also because the lowlight lacks the bakalite spacer between the carb and manifold which helps prevent heat transfere. The problem with the fuel line can be solved by re routing the pipe or insulating it inside a rubber pipe where it passes near the manifold.
A Series engines do not normally suffer from fuel vapourisation so I would agree that it is more likely to be a fuel delivery problem, either a weak pump or a blocked filter. Is it a proper Lucas fuel pump, not a foreign imitation? As it is useful to have a spare fuel pump anyway, I would suggest changing pumps and servicing the current pump.

Post by **bmcecosse** » Thu Sep 24, 2009 12:18 pm

Lucas fuel pump ?? Usually SU surely. The filter in the suction line will be making it even harder than usual for the pump to suck the fuel - take it out! It's nothing to do with bakelite spacer - the problem is before the pump - hence it's ticking like mad trying to suck up fuel.

Post by **MarkyB** » Thu Sep 24, 2009 5:40 pm

I think what Pikey is looking for is a filter king like this:http://www.minispeed.co.uk/classic/inde ... &id=fpr004

Post by **bmcecosse** » Thu Sep 24, 2009 7:30 pm

Never had a fuel filter on any of my cars in 45 years motoring - and never had the slightest suggestion of a dirty fuel problem! It's just not necessary.

Thu Sep 24, 2009 8:28 pm

like bmc never had a fuel filter..

i seem to recall the kit sold by grumpies consisted of two parts, one that shielded the carb bowl. The other piece shielded the pipe in the engine bay before it got to the fuel pump.. the bit i think mike is talking about covering with a rubber pipe

Post by **MarkyB** » Thu Sep 24, 2009 9:39 pm

I asked ESM about these kits a little while ago and I believe he was going to get a new batch made.

Post by **Pikey** » Thu Sep 24, 2009 10:41 pm

Many thanks to all whos replied.

Ive had my eye on those Filter Kings on the dreaded ebay. I like the look of them being of the oldie glass bowl type and wouldnt look too out of place and being of fairly large capacity I think wouldnt restrict the flow so much.

The reason Im using an in-line filter is that I know that my petrol tank isnt in that best condition inside and I tend to pick up quite a bit of rust and silt etc, so Ive fitted a filter just to stop contaminants getting to the rest of the system. I know I filth up a in-line filter annually anyway, and Id rather change that, than clean the pump, its filter and carb bowl etc.

My only concern about these Filter Kings is what is the pressure regulator part of it is all about, we dont have pressure in the mogs fuel line its a vacumn so does that matter.

Does anyone have a photo of the grumpy's kits it wouldnt be too hard to replicate one?

Im fairly sure my pump is in pretty good condition. Its been totally refurbished with new valves/diaphram and points etc, so there shouldnt be anything wrong with it.

Regards

Steve B

Post by **bmcecosse** » Thu Sep 24, 2009 11:02 pm

It's because you have the filter in the suction line that you are having the problem! If you really feel you want a filter - put it in the pressure line - after the pump!

Post by **mike.perry** » Thu Sep 24, 2009 11:30 pm

Lucas Fuel Pump. Silly me, must engage brain before hitting keyboard!

Post by **Chris Morley** » Fri Sep 25, 2009 12:11 am

It's because you have the filter in the suction line that you are having the problem! If you really feel you want a filter - put it in the pressure line - after the pump!

Of course if you do that it will always be clean, as any gunk will be caught by the filter in the pump. Having two filters is pointless, but feel free to have two if you want! A bit like people who want a rev counter - there is no point if your ears work!

Post by **bmcecosse** » Fri Sep 25, 2009 8:27 am

Filter in the feed line adds extra resistance to the pump's 'sucking' ability - which reduces the vapour pressure in the fuel travelling to the pump - which further encourages it to 'vapourise' - hence the problem is exacerbated!

Post by **MarkyB** » Fri Sep 25, 2009 7:28 pm

What if you mount the filter downhill from the pump?
Then gravity would be helping things along.

Post by **bmcecosse** » Sat Sep 26, 2009 9:50 pm

I really don't understand this fascination with filters! They aren't needed!!

Post by **aupickup** » Sat Sep 26, 2009 10:00 pm

never had one and dont want one

my mog runs quite happy thank you

Post by **MarkyB** » Sun Sep 27, 2009 8:08 am

It's handy being able to see that there is petrol getting through to the carb.
It doesn't do any harm either.

Post by **aupickup** » Sun Sep 27, 2009 9:47 am

you can not see the petrol when you are driving surely

a mate of mine put one on and had a few probs, so he took it off