Daihatsu EF-CK engine / carb tuning
Discussion
I’m after a bit of assistance with a slightly unusual car / engine issue. I have a Japanese import 1998 Daihatsu Midget with a 660cc 3 cylinder petrol engine. It’s carburettor fed with automatic choke and automatic raising of revs as the engine warms up from cold.
It’s running rich (confirmed by MOT emissions test almost being off the scale, exhaust smell and it’s thirst for fuel!). The issue is I can’t seem to find any air / fuel mixture adjustment on the carb. What I have found adjustment for is idle speed hot and cold via seperate screws in the linkage and idle air adjustment. Other than that I have drawn a blank.
Does anyone know anything about the carb used on this engine or anything else I should be looking at? I have a new set of plugs ready to fit and will check out the HT leads and dizzy cap at the same time. Will also replace the fuel filter as I don’t know when it was last done but can’t see how that could make it run rich?
I have checked that the auto choke works properly - it’s fully open after about 5 mins of warming up and revs dropping to idle. All I can think of it that the carb possibly needs taking apart and the internals cleaning up as it’s probably never been done in 20 years of use.
Info on this engine and vehicle seems to be in short supply online so don’t think I can get a rebuild kit for the carb easily. I believe the engine also appears in import Hijet trucks but not much else.
Any help / info would be much appreciated. Also does anyone know of a carb or Japanese import specialist in greater Manchester area that may be able to help?
It’s running rich (confirmed by MOT emissions test almost being off the scale, exhaust smell and it’s thirst for fuel!). The issue is I can’t seem to find any air / fuel mixture adjustment on the carb. What I have found adjustment for is idle speed hot and cold via seperate screws in the linkage and idle air adjustment. Other than that I have drawn a blank.
Does anyone know anything about the carb used on this engine or anything else I should be looking at? I have a new set of plugs ready to fit and will check out the HT leads and dizzy cap at the same time. Will also replace the fuel filter as I don’t know when it was last done but can’t see how that could make it run rich?
I have checked that the auto choke works properly - it’s fully open after about 5 mins of warming up and revs dropping to idle. All I can think of it that the carb possibly needs taking apart and the internals cleaning up as it’s probably never been done in 20 years of use.
Info on this engine and vehicle seems to be in short supply online so don’t think I can get a rebuild kit for the carb easily. I believe the engine also appears in import Hijet trucks but not much else.
Any help / info would be much appreciated. Also does anyone know of a carb or Japanese import specialist in greater Manchester area that may be able to help?
Hopefully a photo of the failure readings should be below....... This was from 2016 before we figured out that readings were much improved if the engine was really hot.
It’s not a new issue unfortunately, it’s scraped through the last couple of MOT’s on the borderline after a good motorway run it’ll just about pass. It’s got a cat which seems to work properly but only when very hot. Possibly due to a rich mixture causing cat issues??
It’s definately rich when engine is warm, not sure about cold as it isles at about 2k until warm so it’s hard to tell how it’s running. When cold it starts fine but warm starts can be difficult. It’ll turn over for ages without starting, a tickle on the throttle will get it running with a low idle then a quick rev seems to clear it and everything settles down.
It does seem to run fairly normally, apart from difficult warm starts. it’s only 30 Bhp so it’s hard to tell if it’s meant to be as slow as it currently is!
Not sure if it’s related or not but there tends to be a petrol smell when you park and get out of the car. It’s definitely not leaking, I have double checked tank and all hoses.
There is a charcoal filter and vacuum operated purge valve that I think is responsible for the odour.
It’s not a new issue unfortunately, it’s scraped through the last couple of MOT’s on the borderline after a good motorway run it’ll just about pass. It’s got a cat which seems to work properly but only when very hot. Possibly due to a rich mixture causing cat issues??
It’s definately rich when engine is warm, not sure about cold as it isles at about 2k until warm so it’s hard to tell how it’s running. When cold it starts fine but warm starts can be difficult. It’ll turn over for ages without starting, a tickle on the throttle will get it running with a low idle then a quick rev seems to clear it and everything settles down.
It does seem to run fairly normally, apart from difficult warm starts. it’s only 30 Bhp so it’s hard to tell if it’s meant to be as slow as it currently is!
Not sure if it’s related or not but there tends to be a petrol smell when you park and get out of the car. It’s definitely not leaking, I have double checked tank and all hoses.
There is a charcoal filter and vacuum operated purge valve that I think is responsible for the odour.
GreenV8S said:
Have you been able to look all round the carb? It wouldn't be unusual for mixture adjustment screws to be covered by a plug to discourage flddling. I also wonder how that cold start enrichment works and whether the mechanism may be failing to fully remove the enrichment.
Agreed. Japanese carbs used to have a barrel shaped cover on the idle mixture screw, a kind of anti tamper thing. The cover had a slot in the end and you needed a small collection of screwdrivers with different shaped blades which pushed through the slot and turned the screw. I’d be surprised if there was no way of altering the mixture on a carb. Are you sure the choke flap is going all the way off? If it’s anything but vertical when the engine is warm it will affect the mixture. Another thing to check is the float height but this means taking the carb apart and if you can’t get gaskets for it you could be stuck.
The old grey matter is working overtime now! Nissan Micras used to have problem with fuel pump seals failing and leaking fuel into the head casting-it ran off the camshaft. This meant the engine breather on the rocker cover could draw fuel straight into the manifold sending the mixture through the roof. Played havoc with the fuel consumption too. A quick sniff of the oil should tell you if you’ve got a similar fault.
Hi everyone, that’s for the help so far. I thought I’d had a good look round the carb but will definitely check again tomorrow. I’m pretty sure I must be missing the adjustment somewhere. I thought I’d hit the jackpot when I found a screw covering what looked like an adjustment screw underneath but it turned out to be the top of one of the jets.
There’s some decent pics of the engine in this link. https://minitrucktalk.com/threads/daihatsu-midget-...
The jet I found is under the flat head screw in the pic with the top off the float bowl. The white headed adjuster is the idle air screw and the one with large metal head on the right in the first engine pic is warm idle speed. The actuator next to it controls fast idle speed while cold.
I’m reasonably sure the choke mechanism fully disengages, I’ll double check it tomorrow too.
I’m wary of diving too far into the carb incase I wreck a gasket or something I can’t replace. Some parts are available still but have to be shipped from Japan so want to try and avoid that if I can.
Just in case anyone is wondering what a Daihatsu Midget looks like then this is the answer:
There’s some decent pics of the engine in this link. https://minitrucktalk.com/threads/daihatsu-midget-...
The jet I found is under the flat head screw in the pic with the top off the float bowl. The white headed adjuster is the idle air screw and the one with large metal head on the right in the first engine pic is warm idle speed. The actuator next to it controls fast idle speed while cold.
I’m reasonably sure the choke mechanism fully disengages, I’ll double check it tomorrow too.
I’m wary of diving too far into the carb incase I wreck a gasket or something I can’t replace. Some parts are available still but have to be shipped from Japan so want to try and avoid that if I can.
Just in case anyone is wondering what a Daihatsu Midget looks like then this is the answer:
Oops, missed the post about the leaking fuel pump before I replied. Will check that too and report back. I did an oil change a couple of months back and didn’t notice a fuel smell too it but wasn’t really looking for it at the time.
There is a fuel smell outside the van when you stop the engine, not sure if that could be related? I’d put it down to the vapour purge system.
There is a fuel smell outside the van when you stop the engine, not sure if that could be related? I’d put it down to the vapour purge system.
The last thing I'd be changing small pipes to is silicone. Use good quality rubber hose.
Although unlikely that is the problem. Would really need to see the carb itself to see. Trying to diagnose that from afar with so many pipes etc....almost impossible.
But clearly is is running mega rich. Whether that's from too much fuel, or too little air...harder to say. Ignition/health side of things cant be too bad as hydrocarbons are still pretty low.
Of course....might also be worth getting another test done elsewhere in case their equipment isnt correct. With numbers almost as high as 10% CO, your spark plugs must be black as your boot. Are they ?
Although unlikely that is the problem. Would really need to see the carb itself to see. Trying to diagnose that from afar with so many pipes etc....almost impossible.
But clearly is is running mega rich. Whether that's from too much fuel, or too little air...harder to say. Ignition/health side of things cant be too bad as hydrocarbons are still pretty low.
Of course....might also be worth getting another test done elsewhere in case their equipment isnt correct. With numbers almost as high as 10% CO, your spark plugs must be black as your boot. Are they ?
Edited by stevieturbo on Tuesday 5th December 09:34
I’ve got a set of plugs waiting to go in. Will be weekend before I get chance to do it so will report back after that but I’m expecting them to look like they’ve been down the pit!
Going to do some more digging round the carb at the same time. Will take pipes, etc out of the way and have a better look for tamper covered screws. Will double check choke linkages, etc at same time.
Going to do some more digging round the carb at the same time. Will take pipes, etc out of the way and have a better look for tamper covered screws. Will double check choke linkages, etc at same time.
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