Problem with slow idle circuit- I think

[robb4100]

Driving home today my elan sputtered (as though I shut off my electronic fuel pump) when I lifted off the throttle. It stalled a couple of times but I could get it restarted and running if I could keep the throttle wide open. That eventually did not work so had to tow it home.

I have cleaned all of the jets, refitted them and still the same story. It runs strong with throttle wide open and stalls instantly when the revs drop.

Electronic fuel pump - no regulator. Electronic ignition


any ideas?

Robb
Dumb current owner

[1964 S1]

I check the easiest things first. Battery connections. If they're tight, I'd remove a fuel line and test fuel flow at the engine, if that's good it's probably an ignition problem. I've got points so I'm no help with new distributor gizmoes.

[robb4100]

I know that I have fuel because the engine will run at full throttle.
Would electronic problems explain a difference at idle and at full throttle?

robb

[paddy]

I'd check the timing if you've got a strobe.

Paddy

[neilsjuke]

Check that the Electronic ignition is not discharging add hop turn the ign on with a spare coil lead giving a gap to earth .

[rgh0]

It could be due to the carbs flooding due to excessive fuel pressure or leaking needle valves this could occur at idel and with high fuel flow at full throttle go away.

How long have you had the electric fuel pump fitted and what is its discharge pressure?

regards
Rohan

[robb4100]

Rohan,

I have had the fuel pump since last year. The pressure is rated at 4.5 psi but did not cause a problem last year.


the other thing is that the car has been in storage since November. It ran fine for about 60 miles (over a couple of trips) when this started to happen.

Robb

[neilsjuke]

As you have a ele/ pump is it still pumping when the engine is still ? if so needle valves not shutting

[rgh0]

4.5 psi is a little to high - needs to be closer to 2.5 psi i think. Maybe some build up on the needle valves preventing them closing off fully also.

i would take out and clean or replace the needle valves or and then try of reduced pressure fuel pressure supply if the problem does not go away.

cheers
Rohan

[ill_will]

Might be able to test the flooding-at-idle theory by disconnecting a wire from the pump. Webers should run ok for a short while at idle until the fuel in the bowl is used up, right? So if it runs badly to start, then is ok for a bit, then coughs and dies, I read it as being too full-> about right -> empty. Worth a shot; it's an easy check.

2.5 psi is the figure I have in memory too, per Rohan.

will

[ill_will]

PS the old saying of "90% of carburettor problems are ignition problems" might be worth bearing in mind if the overfilling diagnosis can be checked out ok...

good luck!

[ecamiel]

Just remove the jet cover and measure the fuel level with a strip of paper.

Eric
64 S1 Hart

[prezoom]

I built a sight gauge as described by Keith Franck several years ago. It has to be the best method of setting the float level I have ever used. Mikuni used to sell the same sort of gauge, no longer available, but didn't try one until I followed Keith's advice. After some testing, with a friend who prepares vintage race cars, he also swears by the guage and method. Also used his formula for factoring the air corrector jet to the main jet and eliminated the dreaded flat spot. One of these days, I'll mess around with the one way valve jet in the bottom of the float bowl and try for some better mileage. Just another item on the very long list.

Rob Walker
26-4889

[gjz30075]

Rob, any pics of said sight gauge? Also, what formula do you use to factor the air to main jet?

Greg Z