fuel leaking from Weber front and rear trumpets

[alan.barker]

FDB6923F-6891-493C-80E2-9067452E57DE.jpeg (94.08 KiB) Viewed 578 times

NWElan,
have the Back Plates been modded The hole stops Carbs dribbling.
Alan

[TBG]

Alan - what is the theory behind the hole?

[alan.barker]

I think when you stop the car without a hole in the Plate there is a small vacuum. This sucks Fuel into the place behind the Plate then dribbles out making you think you have a Fuel level problem.
It's a mod that was done on later Webers and if you buy new Gaskets for the Plate they all have the hole now. Have a look at the new Gaskets on the "Webcon" or "Eurocarb" web sites.
Many people don't know about this including so called experts
Alan
Info Eurocarb cover plate 52135.024
gasket 41640.021

[TBG]

Alan - thanks - yooom a werry clever chap!!

[Andy8421]

I added a fuel pressure regulator and tried pressure at 2 psi and 1.5 psi but doesn't solve the problem.

There is tremendous fuel blow back out of the carb throats when running. A film of fuel quickly coats the engine bay opposite the carburetors. More so at higher rpm.

I just finished re-installing the engine after replacing the water pump. The distributor advance is set to 10 deg BTC checked with a timing light. The engine starts up easily and idles but roughly.

What would be the symptoms if I re-installed the timing chain one tooth off?

John

'Standoff' is a well known phenomenon. Complex standing waves develop at certain revs in the inlet tracts with air/fuel flowing both in and out the carb.

Have a look at the following video from 1:08 onward.

https://www.youtube.com/watch?v=RSSYcVTUrT8

As mentioned above, a very good reason to keep the airbox.

[Craven]

If you are running a standard engine, that is with a Lotus camshaft the amount of fuel rejection is not of the order you are experiencing. Inlet cam mistiming is definitely worth checking; make sure you have fitted the correct cam sprocket to the inlet camshaft. Sprockets look the same but the Exhaust is marked by a roughly inscribed EX on the back.

[NWElan]

I just pulled the spark plugs. The plugs from cylinders 2 and 3 are typical dark grey. The plugs from cylinders 1 and 4 look like never fired and dry. The plugs are new, properly gaped and have strong spark.

I took photos of the cam shaft sprockets with the engine set at TDC before dis-assembly and then after re-assembly. Re-examination of the photos confirms the locations of the timing marks on the sprockets look the same. The engine did start and run before dis-assembly for water pump replacement.

How can fuel not get to cylinders 1 and 4 and is blown out of the carburetors while cylinders 2 and 3 run with out blow back?

John

[nmauduit]

I just pulled the spark plugs. The plugs from cylinders 2 and 3 are typical dark grey. The plugs from cylinders 1 and 4 look like never fired and dry. The plugs are new, properly gaped and have strong spark.

I took photos of the cam shaft sprockets with the engine set at TDC before dis-assembly and then after re-assembly. Re-examination of the photos confirms the locations of the timing marks on the sprockets look the same. The engine did start and run before dis-assembly for water pump replacement.

How can fuel not get to cylinders 1 and 4 and is blown out of the carburetors while cylinders 2 and 3 run with out blow back?

John

just in case, the corresponding two ignition wires would not have been swapped at the dizzy head by any chance ?

[NWElan]

Checked ignition wire order at distributor (1,3,4,2) and it is correct.

Thank you for the suggestion.

[RichardHawkins]

Sprintsoft

Thanks for the advice, have ordered some EZ Turn 40 Euros.

Sorry I got the name wrong,

Richard Hawkins

[nmauduit]

Checked ignition wire order at distributor (1,3,4,2) and it is correct.

Thank you for the suggestion.

then I suppose you already have had a good look at the jets of the carbs, esp. idle circuit for 1 and 4 ... is the car running on 2 cylinders or actually all 4 (starting cold, checking all 4 exhaust outlets temperature with a gloved hand while the engine warms up may help making sure)?

[alan.barker]

HI NWElan John,
Have you got the holes in the Back Plates.
Please let me know
Cheers
Alan

[NWElan]

Clearly cylinders 2 & 3 fire and not 1 & 4. I can keep my fingers on 1 & 4 exhaust while 2 &3 are much too hot to touch. Fuel literally spray out of 1 & 4 trumpets when throttle is applied.

My carbs do have holes in the backing plates.

[SENC]

Is it possible the accelerator pump jets are in backwards? Does it spray out if you pump the accelerator with the engine off? The jets are shouldered so they should only go in 1 way, but maybe worth a look.

[MarkDa]

Very strange.
Fuel is getting into venturies of 1 & 4 but not into engine.
Are the throttles opening?