Lotus Elan

Vapor lock (I think)

PostPost by: JKING » Wed Aug 28, 2013 12:44 am

Meg, did you mount your pump in the spare tire well? Your choice of the Facet pump looks pretty good and I wonder if it will fit in there with an upstream filter.
Did you remove the mechanical pump?
I plan to add the electric pump in series with the mechanical pump and only use it for dry carburettor starting and in the event the vapor lock problem persists. I don't know if you can push fuel through the Facet pump as I don't know how it is constructed. Apparently fuel can be pushed through the mechanical pump if you are pressurising the fuel tank to prime the carbs. I plan to add by-pass tubes with check valves on each pump if fuel can't be pushed or drawn through.
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PostPost by: Quart Meg Miles » Thu Aug 29, 2013 12:07 pm

JKING wrote:Meg, did you mount your pump in the spare tire well? Your choice of the Facet pump looks pretty good and I wonder if it will fit in there with an upstream filter.
Sure did, and on Page 4 of lotus-carbs-f40/fitting-electric-fuel-pump-t26800-45.html you'll find pictures of both Alex Black's and (at the bottom) my installations with upstream filters. I fit a spare wheel, unlike Alex, and there's plenty of room and I could PM you a picture with the wheel in place if you ask.

JKING wrote:Did you remove the mechanical pump?
No, I pump through the mechanical pump but might remove it at a later date. The valves are very light and I used to blow through them easily to prime the carbs before fitting the Facet.

JKING wrote:I don't know if you can push fuel through the Facet pump as I don't know how it is constructed.
It will suck through the Facet as long as the vapourising problem is absent. I tested it a few hours ago, with less than half a tank of petrol, and ran five miles from cold without the Facet but after parking for half-an-hour I had to switch it on a mile after starting off as vapourisation occurred, and again after another half hour break. So best to have that switch in a handy place!

There are two Facet Posiflow pumps and I seem to remember you were talking about a high power engine so be careful which one you choose. I believe one had a higher flow rate and pressure. I intend moving my pressure regulator to follow the mechanical pump to reduce the pressure at the Webers which is probably too high at present.
Meg

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PostPost by: JKING » Thu Aug 29, 2013 9:23 pm

Thanks for the info Meg. The pressure drop across the Facet pump while running only the mechanical pump would exacerbate the vapor lock problem so I think I shall install the by-pass plumbing around the Facet pump. Your test indicates that there is a marginal problem.
No, my engine is the stock S1 engine and looking over the posts it seems that about 2 psi and about 10 to 15 GPH are the parameters to shoot for and there is a Facet pump that matches this. So maybe I won't need the pressure regulator. There also is a Carter pump with a filter that matches it and available at a locat auto parts store.
Looking at the pictures of the Facet cylindrical shaped pump I realize that I had one on my sailboat pumping diesel for 28 years with no problems. I believe it was then made by Bendix.
I looked at the picture of your very nice installation. I hope you don't mind if I just copy it.
John
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PostPost by: Quart Meg Miles » Thu Aug 29, 2013 10:19 pm

JKING wrote:I looked at the picture of your very nice installation. I hope you don't mind if I just copy it.
John
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I'm flattered!

Posiflow installation 105-496.JPG and

Be careful with the hoses at the bottom, it is quite tight down there as the top pipe loop has to stay below the boot floor panel. If you omit the regulator your routing will be different and take care not to strain the pipe to the engine too much.

Here's a photo of the pipework at the tank which also shows the rubber grommets reducing the pump vibration to the body panel. I'll replace the wingnuts with nylocs now it is proven. The tank has been cleaned and zinced!

Posiflow tank & delivery 105-498.JPG and
Meg

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PostPost by: billwill » Thu Aug 29, 2013 11:33 pm

JKING wrote:Thanks Meg
I have replaced the rotor with a red one from Advanced Distributors in MN. I'll see if that solves the problem although creating the problem is a bit hit and miss.
I had planned to add an electric booster pump in line with the mechanical pump primarily to make starting easier after a long (couple of weeks) idle time for the car. The float bowls apparently dry up and it takes lots of cranking to fill them. Rather than crank it so much, I remove the air box cover and shoot some starting fluid into the carbs. A booster pump would solve this problem as well as the one you describe.
John


Have you seen the messages on this forum about using a marine outboard motor fuel bulge pump in the boot?

A few squeezes on one off those will pump fuel up into the carbs for initial starting after evaporation. And its a lot less hassle than an electric pump, for which you really ought to fit an inertia cut-out switch to stop the pump if you should crash.
Bill Williams

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PostPost by: JKING » Fri Aug 30, 2013 1:12 am

Clever idea Bill. I looked for an aircraft "wobble" pump which would work but they all seem to be really expensive. The outboard primer would be a lot cheaper.
But I'm after not only the starting primer function but also a booster function in the event of a "vapor lock problem" which may actually be an ignition problem (see above). As to the cut-off switch, I plan to only use the booster pump for starting when needed and/or the vapor lock problem which goes away when cooled by open road running or sitting switched off.
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PostPost by: JKING » Thu Sep 26, 2013 4:28 pm

Hi Meg
I have obtained the Facet Posiflo pump which has a negative ground circuit. My Elan has a positive ground. Isolating the ground for the pump is no problem with the fibreglas body. I have looked up the electrical resistance of gasoline and it is pretty high so with neoprene hoses there should be no problem. But Facet says in the instructions not to use the pump with a positive ground car. Maybe they fear that an installation would not be isolated sufficiently.

Question: Does your car have positive ground?

I didn't find a Posiflo pump for positive ground but there are Facet "Cube" pumps available with positive ground but they are hard to find.

John
Last edited by JKING on Thu Sep 26, 2013 5:57 pm, edited 1 time in total.
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PostPost by: elancoupe » Thu Sep 26, 2013 5:32 pm

I have been using a Facet negative ground pump on my positive ground car for a very long time.............. :)
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PostPost by: JKING » Thu Sep 26, 2013 5:47 pm

Thanks Mike. I'm sure that with proper ground isolation it should be OK and I will proceed with my installation.

John
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PostPost by: Quart Meg Miles » Thu Sep 26, 2013 8:15 pm

JKING wrote:Hi Meg

Question: Does your car have positive ground?

John

Yes, and as they provide two insulated wires and a plastic body round the pump I can't think why Facet are concerned with polarity unless they are worried that people will ground the Black wire and attach the Red to the negative battery.

Provided you maintain Red to positive (chassis on most Elans) and Black to the ignition terminal all should be well.

For the record, I haven't had any problem with vaporisation all summer since fitting the pump.
Meg

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PostPost by: JKING » Thu Sep 26, 2013 9:36 pm

Thanks Meg. After posting that I noticed in the picture of your installation that the red wire appears to be connected to a mounting bolt which implies that your car has positive ground.

... and a plastic body round the pump ...


I checked the pump body with an ohm meter and found that the base is plastic but the cylindrical part is painted metal and connected to the black wire. So the pump body will be "hot". I may add some sort of cover around it.
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