Lotus Elan

S4 starting

PostPost by: nickspeed » Mon Jan 18, 2021 1:13 pm

Hi. Bought an S4 back in the summer. On Strombergs. Difficult to start when left for more than a couple of weeks. Eventually fires on 2 cylinders, then 3, then 4. Completely crisp from then on. Spark looks ok. I'm thinking that the first carb fills first, and the delay on the second accounts for the misfire?? All advice appreciated. Am thinking an electric pump with a switch, just for starting, may be an idea? Many thanks
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PostPost by: ericbushby » Mon Jan 18, 2021 2:21 pm

Hi Nick, yes that is the way to go.
My Webers take about 8 seconds on the priming pump to fill after not being used.
A push button or spring return toggle switch is all you need.
I fixed the switch on a bracket off the back of the dashboard fixing screw as I was not prepared to drill the dash.
Something like this is what you need. I chose this switch because they are noisy so I could hear when it slowed.
Eric in Burnley
1967 S3SE DHC
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PostPost by: nickspeed » Mon Jan 18, 2021 2:40 pm

That's great. Thanks Eric. Reassured that's the problem. So you use the pump just for priming the carbs and then switch off?
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PostPost by: ericbushby » Mon Jan 18, 2021 2:57 pm

Nick, yes, it is a double pole spring return toggle switch under the dash, and I just let go when I hear the pump slow down.
I expect any pump would do. That one is a cheapo copy of a Facet type, about £14.00 on ebay.
Cheers
Eric
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PostPost by: oldelanman » Mon Jan 18, 2021 3:08 pm

The fuel inlets on Strombergs are teed together so they should fill simultaneously, unless one of the float levels is incorrectly set or the needle valve sticking, in that case you might expect poor running as well as difficult starting which you say you don't have. My Strombergs always need some choke to start from cold so I would check that both your chokes are working and the linkage adjusted correctly before you do anything else. The single loop-through cable arrangement can be tricky to adjust and if you don't get all the slack out between the two choke levers the rear carb choke may not work at all.
Roger
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PostPost by: ericbushby » Mon Jan 18, 2021 4:46 pm

OK, so accepting what Roger says and noting that I know nothing about Strombergs, you may be able to do a test. Do your carburettors have a cover which you can remove and top up the fuel manually. If the engine then starts OK then it is fuel shortage and a priming pump should help. If it is still slow then look elsewhere.
Best of luck
Eric in Burnley
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PostPost by: ericbushby » Mon Jan 18, 2021 5:10 pm

I think I am wrong there and I have been thinking about the Dellorto and Weber configuration. That might not work on yours.
Best of luck
Eric
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PostPost by: nickspeed » Mon Jan 18, 2021 5:22 pm

Thanks Eric. Good thought. Am not with the car at the moment, but will have a look in the morning. Will let you know
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PostPost by: miked » Mon Jan 18, 2021 9:50 pm

Hi Nick,
I built an S4 Stromber SE Elan and ran it for quite a lot of years and miles. It made book horse power on a dyno after i sold it. I had this problem. Electric fuel pump did not cure it. Chokes did not cure it. I had extra conductors in the earth to give better cranking volts and speed. I had a ballasted coil system to ensure good sparking under cranking volts. The car ran perfect and could do several hundred miles in a day. However if left for more than 2 weeks, it would not start. I had to pull the plugs out and squirt a small syringe of fuel into the cylinders. Upon doing this it would start straight away and off we would go.
Annoyed ths sh*t out of me. Before anybody says anything about engine condition, it was spot on. Fully rebuilt and went like stink. No air leaks.
My view which is maybe wrong is that this is a flaw in the design. Not based upon any great knowledge but gut feel. The length of inlet tract from the carburettor to the cylinder seems long. Is it possible that oil drains from around the rings and lowers the compression and consequently the ability to draw/suck fuel. The bit in the syringe makes it fire a starts to draw fuel.

I would be interested in any other opinions.
The other weird scenario which also occurs on bike carbs (they have heaters) is the icing. I had this on 4 occasions, 3 going over Shap on the M6. In April on a wet 3 degree day. Cause the butterflies to stick, not funny when overtaking a wagon and accelerating to 100 before killing the ignition.
I believe that is to do with air velocity and temperature flowing through the inlet tract length.
Cheers Mike
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PostPost by: 69S4 » Mon Jan 18, 2021 10:11 pm

The electric fuel pump on my Stromberg S4 takes some time to fill the float chambers when the car hasn’t been used for some time - you can hear it clicking away like crazy until it slows down as the chambers fill. That suggests the chambers are partially empty, but they’re not leaking. My working theory is that over time the fuel in them evaporates - or at least the most volatile parts do, leaving behind a fraction that doesn’t atomise - when cold anyway. Topping up via the pump only dilutes this stuff so it’s still only marginally combustible- and that’s what’s coming through the choke.

I get a lot of the same problem with my motorcycles although it does depend on carburettor design. The answer, and one that works every time with them, is to drain and refill the float bowls before trying to start the engine but the Strombergs don’t have drain screws. Some neat fuel straight into the cylinders will bypass the issue for a few seconds and often the extra vacuum is enough to pull the ‘heavy’ fuel through the carb.
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PostPost by: nickspeed » Mon Jan 18, 2021 10:38 pm

Thanks Mike et al. Sounds maybe a deeper rooted problem than I thought. Will check the choke is working properley on both carbs in the morning, and maybe then leave for a couple of weeks, hook up an electric pump and temporary fuel supply to see if that helps. Thanks again, Nick
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PostPost by: SENC » Tue Jan 19, 2021 12:46 am

I don't suspect it will be a choke issue - I've only ever had one carb choke hooked up and have not really had a problem, but it is rarely that cold here, either. I do have an electric pump that I allow to fill the bowls before turning over... once full and with some choke, I don't have much starting issue. It is rough at turnover, but can pretty immediately go to half choke, where I'll leave it to warm for 30-60 seconds.
Henry
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PostPost by: oldelanman » Tue Jan 19, 2021 9:27 am

Something else that people may not be aware of with Stromberg carbs.. when cold starting you need to keep your foot off the accelerator until the engine fires. Open the throttle while cranking and the choke has no effect.
Driver's handbook has this ....
PXL_20210119_085858320.jpg and

Might help maybe.
Roger
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PostPost by: nickspeed » Tue Jan 19, 2021 9:55 am

Ah. Thanks for that. Did not appreciate that if you use the throttle it cancels the effect of the choke. Will look at all later today.
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PostPost by: oldelanman » Tue Jan 19, 2021 12:03 pm

Another thought....
The choke lever travel is limited by a stop pin on each carb which has summer and winter settings .. presumably to reduce the risk of flooding in the summer. If left in the summer position it may inhibit cold starting in winter. Unlikely probably but might still be worth checking what yours are set to if you haven't already.
PXL_20210119_111517471.jpg and
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