Vapor lock (I think)

[JKING]

I'm driving my S1 in downtown on a hot day and it starts missing and running very erratically and finally quits altogether. I let it cool for 30 minutes and it fires back up again. The radiator core is old and I'm not sure of the temp guage calibration. So I get a new radiator core and send the Bordon tube type temp guage away for refurbishment. All seems ok. the temp runs about 70 deg C which seems a bit low but no problem. Another hot day and the same erratic behavior happens. I suspect a vapor lock somewhere.
So I want to back up the stock mechanical fuel pump with an electric in-line pump mounted back with the tank. I'll rig it as a booster to the mechanical pump by adding by-pass lines around both pumps with check valves. I'd like not to have the electric pump running continuously.
My question:
What GPH do I need. I'm guessing that at 100 mph I might get 4 mpg which would require about 25 GPH.
What pressure head do I need. The head rise is about 14 to 18 inches but I don't know what the line losses might be. Would 7 psi be enough?
Anyone have a recommendation for a particular pump?
Thanks
John

[elancoupe]

Webers have a recommended pressure of 2-3 lbs.

I have a relatively high pressure facet pump, but use a regulator near the carbs.

A large number of Elan fuel/carb problems are actually ignition problems...

[Jon.ford]

I would check out your ignition system first I had similar problem, engine started missing then stopped I let everything cool down then it would run again, changed distributer cap and fitted a red rotor arm all runs okay now.
The majority of fuel problems are an electrical issue in my opinion.
Good luck hunting down your problem
Jon

[Andy8421]

I also spent ages tracing a similar fuel problem that turned out to be a distributor cap. There seems to be a batch of caps that become conductive with increasing temp. I went through 3 or 4 caps that all exhibited the same fault before I found one that worked.

[Elanintheforest]

I totally agree with Andy and John....check out the ignition. I've had this so many times with classics, usually due to rubbish ignition components breaking down, especially when the engine bay gets very hot. The problem is that the aftermarket condensers, coils, distributor caps and rotor arms are not constructed to original specification, and can fail very quickly.

The is a company in the UK that has had a lot of stuff re-made to original spec, and it seems to work. Check him out...

http://www.distributordoctor.com/

Mark

[gino1]

Thanks for the link Mark
Just contacted them for a quote as I've had some of the recent ignition problems mentioned.

Gino
Milano
italy

[JKING]

Thanks a lot guys.
I'll check out that site Mark. I replaced the points and condensor with a "Pertronix Ignitor" 12 or 13 years ago and have had no trouble with it, that is unless this problem can be blamed on it. My coil is the factory original but the distributor and cap are not.
Thanks again.
John

[richardcox_lotus]

Coil failure was my culprit of those symptoms a few years ago.

[ericbushby]

Mine was just a dodgy rotor arm. The car would start easily and drive well for 20 miles or so and then start to misfire and die. Once recovered and brought back home, it would start on the trailor for driving off and into the garage.
Under a lens I could see some bubbles on the (bakelite?) inside the rotor arm and with an insulation tester got a reading from the internal spring to the brass arm. Isn`t it easy after you have found it.
Eric in Burnley
1967 S3SE DHC (still running well)

[JKING]

Thanks for the replies Eric & Richard
I'm busy removing the distributor to see what model it is and for inspection. I'll see if I can detect any signs of arcing in the rotor and the cap. Then I will possibly contact the Distributor Dr. that Mark suggested to buy a red rotor and a new cap.
John

[RichardHawkins]

John,

As you are in the States you might find side draught central a helpful group. Although they are mainly about carburation there is also help about distributors so that your carburettors have a better chance of working correctly.

Regards,

Richard Hawkins

[JKING]

Thanks Richard. I'll check it out.

[Quart Meg Miles]

Your problem sounds like mine, fuel vapourisation, and I cured it with a Facet Posiflow pump, the basic model. There are a number of threads about this problem, really was a fuel problem as the fuel pump emptied, so use the search facility for Facet and any other links you find there. You really need to know if your fuel did vapourise so look at the bowl of the fuel pump when it stops.

[JKING]

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

[Quart Meg Miles]

Thanks Meg,
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..... A booster pump would solve this problem as well as the one you describe.
John

That was my second reason for fitting one, though I blew down the petrol filler hole (with an adaptor) to push the fuel through rather than squirt noxious fluids into my inlets. As it happens I haven't had a long absence since fitting the pump but I can report back in a month or two; it certainly solved the burgeoning problem on short runs and I haven't had any problems in this abnormal British summer.