Engine Question - LPG / Petrol - Van not running well, HELP pls

RAW

Full Member
Dear All
If there are any motor mechanics about I have a question.
Sylvia, old Talbot, 2 litre Petrol engine with Carburettor had an LPG conversion beginning of August.
Engine runs sweet on LPG.
If I swap to petrol though the engine runs poorly, less torque and feeling like the air/fuel mix is not quite right

Approx 1 month ago I got the engine Water Pump changed as it was leaking.
Gas engineer advised that after this was done then the Van should be run on Petrol until the new coolant etc had all flowed round engine. To do this I dropped Van at Garage running on Petrol, engine seemed fine
When I picked Van up she ran like a poorly dog on petrol, cough, splutter, no power.
Took it back to garage, mechanic tweaked the Carb fuel mix screw and she ran fine again on Petrol

So since then I have been running her on LPG, now probably 400 miles later I have again switched to Petrol and again running like a dog. I tweaked Carb screw 1/4 of turn but still did not help much

I need to run on Petrol now as in FAR NORTH of Scotland and might not have enough LPG to return to next LPG filling point.
Has anyone got any ideas ?? What to do ?

TIA
Robert
 

SquirrellCook

Full Member
Not much hep, but on most carburettors the idle mixture screw is just that. It will have next to no affect on the rest of the range. Without knowing the type of carb I can’t offer any help.
 

RAW

Full Member
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It was screw 3 that the mechanic adjusted and that I also adjusted a quarter turn, I think, maybe I should have adjusted screw 2 ? @SquirrellCook
THANKS
 

RAW

Full Member
Not much hep, but on most carburettors the idle mixture screw is just that. It will have next to no affect on the rest of the range. Without knowing the type of carb I can’t offer any help.
Full manual, I got the picture above from page 76 of the Russek Petrol Engine Manual PDF
For Full Manual it is here https://ra-w.uk/TALBOT

TIA
 

SquirrellCook

Full Member
So life is easier as it looks like a conventional carburettor. Just have a good look around to see if any little rubber pipe fittings have been split with rough handling. If all looks good pop the top of the carb, looks like six screws. What you don’t want to see is dirt or debris in the bottom. If it’s clean it suggests that something simple has happened and probably hard to find. This is working on the theory that all was well before it was subjected to finger trouble. I expect the idle mixture is messed up now and is best corrected with a gas analyser Rough running at idle can be put up with until you can get it to a garage with an old mechanic.
 

RAW

Full Member
Thanks very much
I expect the idle mixture is messed up now and is best corrected with a gas analyser Rough running at idle can be put up with until you can get it to a garage with an old mechanic.
Just to clarify when on Petrol and engine is hot then idle is fine. What is not fine is when under power and acceleration in that the engine has far less power than when on LPG like the fuel / air ratio is wrong or not enough fuel is getting to carburetor? Any other ideas please ? Thanks for the help so far.
 

wildebus

Full Member
Thanks very much

Just to clarify when on Petrol and engine is hot then idle is fine. What is not fine is when under power and acceleration in that the engine has far less power than when on LPG like the fuel / air ratio is wrong or not enough fuel is getting to carburetor? Any other ideas please ? Thanks for the help so far.
I can't give you any practical advice how to fix it, but I know of a couple of old-school garages who are both into traditional rally-cars and know loads about sorting out old engines. Both these are just about en-route to your highlands adventure, so if you don't get it sorted before then, you could go to one of those maybe?
One of them is a camper conversion company as well as it happens and might be able to sort any other niggles in Sylvia while you are there?
 
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harrow

Full Member
What is not fine is when under power and acceleration in that the engine has far less power than when on LPG like the fuel
So when the engine requires the most fuel it struggles ?
Then look at the main jet inside the carb looking for any blockages
 
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trevskoda

Full Member
Main jet semi blocked.
Screws 2 & 3 are for idle mixture control,one air the other fuel,dont fiddle if you cannot tune engines but get a old timer who knows the engines.
 

SquirrellCook

Full Member
Thanks very much

Just to clarify when on Petrol and engine is hot then idle is fine. What is not fine is when under power and acceleration in that the engine has far less power than when on LPG like the fuel / air ratio is wrong or not enough fuel is getting to carburetor? Any other ideas please ? Thanks for the help so far.
That's good then, more than likely there is dirt in the carb. Much easier to clean with compressed air.
If it worked before tampering and not after, blame someone's fingers. Also clever stuff hardly ever goes wrong, normally it's to simple to see.
 

RAW

Full Member
Just to add has that carb got a manual choke control, if it has add that when the engine struggles to confirm my diagnosis.
Yes there is a manual choke
Need to use it to start on LPG
Have not tried the choke when driving at 30mph in 4th on Petrol. That will be next step. Thanks
 

RAW

Full Member
I can't give you any practical advice how to fix it, but I know of a couple of old-school garages who are both into traditional rally-cars and know loads about sorting out old engines. Both these are just about en-route to your highlands adventure, so if you don't get it sorted before then, you could go to one of those maybe?
One of them is a camper conversion company as well as it happens and might be able to sort any other niggles in Sylvia while you are there?
Dear @wildebus
Could you send me the Garage locations / Names as i have no idea. At the minute we are parked up in Wick. Cheers
 
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