Lotus Elan

S4 No Fuel

PostPost by: Temmck » Wed May 04, 2022 4:08 am

With the engine cranking over now I am faced with a new problem.
With starter fluid, the engine lights and runs great. As soon as the starter fluid burns out the engine stops.
I have rebuild both carbs and the fuel pump - new gaskets, seals, diaphragm, and a complete tear down and cleaning of all passages. New diaphragm and valves in the fuel pump.
I pulled the front carb and the bowl is full of fuel. The float valve opens and closes as it should and float level set per the manual.
Idle trim screws are fully closed.
The carb pistons are moving up and down during cranking. No oil in the dash pots yet.
I have tried with and without choke.
Engine is original configuration with active crossover pipes and secondary butterflies.
Any other ideas before I pull the carbs back off and tear them down?
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PostPost by: ncm » Wed May 04, 2022 7:58 pm

"The carb pistons are moving up and down during cranking. No oil in the dash pots yet."

You need to add oil to the dashpots as these act as a damper to the pistons. Without oil you are likely to be pulling little ( if any) fuel through the carb..
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PostPost by: Temmck » Wed May 04, 2022 11:35 pm

Added oil - no joy. It cranks and cranks without even a sputter. Shoot a little starter fluid in there and she jumps to life. Looks like the carbs have to come off again.
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PostPost by: SENC » Wed May 04, 2022 11:50 pm

If the bowl is full of fuel, then it is getting that far... the only fuel path from there to the engine is the jet and manifold. The only thing that should impede the jet flow is the needle. New jets and/or needles?
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PostPost by: Temmck » Thu May 05, 2022 12:13 am

Same original jets. These are the non adjustable variety so i did not remove them when rebuilding the carb, just cleaned them up and made sure that they moved smoothly in the bore and that the pistons dropped slow and steady.
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PostPost by: h20hamelan » Thu May 05, 2022 12:26 am

Can you blow some compressed air from the tank filler, have an assistant crank or at least look
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PostPost by: Temmck » Thu May 05, 2022 12:31 am

What am I looking for? fuel in the carb? If so, I could probably do that easier by blowing into a hose on the fuel inlet to the carbs since I don't have a fuel sender in the tank yet, just tape over the hole.
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PostPost by: Temmck » Thu May 05, 2022 12:33 am

But since the carbs are full of fuel, the needle valves will be closed preventing the air pressure from pushing the fuel into the carb.
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PostPost by: SENC » Thu May 05, 2022 2:47 am

Ok, so fuel is getting to the bowl and you have the same jets and needles as previous... the other variable is the air flow to pull the fuel through the jet... is the vacuum port on the manifold connected to the front chassis section or lights (or, better yet for this purpose, just plugged)?
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PostPost by: SENC » Thu May 05, 2022 2:50 am

Just saw your comment about taping over the hole - is that the filler hole? Possibly creating a vacuum in the tank that is eventually causing fuel to stop flowing sufficiently?
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PostPost by: Temmck » Thu May 05, 2022 3:28 am

Tape is over the fuel sender hole. Filler cap on the filler neck.

I'll take a closer look at the vacuum ports tomorrow and plug them. Hoses are all original so even If the hoses are connected, they are probably leaking badly.
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PostPost by: alaric » Thu May 05, 2022 11:44 am

Hi. If you have fuel in the carbs then I'd expect it to at least sputter :). How old is the fuel? If old, then try some new fuel directly into the float chambers.

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PostPost by: SENC » Thu May 05, 2022 12:23 pm

Grab a picture of your overall setup to post, too. It struck me I made an assumption you have Strombergs based on various other comments, not because you said so. Seeing your carbs, how they are mounted, etc. might spark more ideas.
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PostPost by: Temmck » Thu May 05, 2022 11:23 pm

Sorry! Yes, this car is fitter with Strombergs.
Fuel is new.
I plugged the vacuum lines in the front and rear of the intake manifold - No joy.
Squirted a little fuel in the carb and engine jumped to life...briefly.
I have attempted to add a picture. I hope it comes through, seems necessarily complicated.

S4 Carburetors.jpg and
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PostPost by: oldelanman » Fri May 06, 2022 6:28 am

Missing nut .. possible source of air leak ?

S4 Carburetors.jpg
S4 Carburetors.jpg (143.38 KiB) Viewed 235 times
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