9 replies to this topic

[Timmytimtim]

Hi,

I have a 1990 mini sidewalk 998 and have a problem with the throttle response. If I can keep the revs low in first gear I can get moving, but if I put my foot down or try higher revs or try getting into third, the engine just dies. If I leave it in neutral and press the accelerator it will rev briefly then just die.

I've tried a few things:

1 - Sprayed WD40 on the spark plus and dizzy to clear any water - no improvement
2 - Taken off the dizzy cap, cleaned, put back on and sealed with Vaseline. - no improvement
3 - Replaced HT leads as the connection to the ignition coil had broken - no improvement
4 - Run redex through the carb - no improvement

This is as far as my technical knowledge goes!

So, I rang the local VW restoration place (yes it's not a mini place but they do old beetles so I called for any advice I could get) and they suggested I need to replace the carburetor diaphragm. I asked my mate who is pretty good with minis and he thinks it could be a diaphragm in the fuel pump?

Any help and advice would be great, it's doing my head in!

Thanks

Tim

[Cosford Cowboy]

Sus don't have diaphragms, they do use oil in the dash pot though, get some engine oil or better SAE20 grade oil and fill the brass tube in the dashpot (undo the large black plastic cap)

If that doesn't cure it, then try removing the lid mthingy with the fuel pipe on it and see if the petrol is clear with no muck in the bottom, clean if it has.

I don't think it is the pump.

[R1minimagic]

check the choke isn't sticking on, how do the plugs look, brown, black etc

Also a good idea to get the ignition timing checked

[Timmytimtim]

Hi, thanks for the replies.

I'll have a go at cleaning the float chamber - how do I do this?

Thanks

[R1minimagic]

It is like a toilet valve, opens if empty, closes if full, just check it moves freely and should be ok

[Timmytimtim]

R1MIniMagic - I have checked the spark plugs and all look good - looks like could have been replaced few years back before I got the car, still shiny!

At the bottom of the float chamber there is what I can only describe as 'rusty sand'. Is this my imagination and its simply wear on the inside or is this something that has settled in there? I didn't want to stick my oily fingers in to find out!

[Timmytimtim]

So, someone over me trying my car after looking at the chamber and said it sounds like it's miss-firing. Either needs a new earth strap or ignition coil!

[dklawson]

Never start by replacing the coil. Work through all the other ignition components and adjustments first. Also, if your starter motor is turning the engine over freely... you do not need a new earth strap. Regardless, the earth strap will not be the cause of misfires.

Clean the grunge out of the bottom of the float chamber. (That's normal stuff, particularly if there is no fuel filter between the pump and carb). Use spray carb cleaner to flush the line from the bottom of the float bowl to the inside of the carb body. Remove the vacuum chamber from the top of the carb CAREFULLY and use the carb cleaner to remove any grunge from the needle that will be on the bottom of the piston. If you find a lot of deposits on the needle, spend time CAREFULLY with a pipe cleaner soaked in carb cleaner to clean the inside of the jet where the needle came out of. Make SURE the pipe cleaner has no sharp metal wire bits sticking out that could scratch the inside of the jet.

All that said (and assuming your distributor uses points) clean and set the points gap, replace the condenser. Make sure the spark plugs have not fouled, if the plug wires are old and have any cracks, replace them. And if those spark plugs really are several years old, fit new ones BUT make sure you gap them before installation. They do not come pre-gapped for the Mini.

[twrminisport]

Check your dashpot oil
Failing that clean out the carb with spray carb cleaner
Make sure fuel is getting into the cylinders properly at some pressure
Failing that work your way through the ignition system starting with the coil.

If there is sufficient fuel and a good consistent spark then it will go. Simple.

Jesus

[dklawson]

Failing that work your way through the ignition system starting with the coil.

Since coils seldom go bad, they are expensive, and not easily tested by the home mechanic... I suggest again what I said earlier (and in the OPs other thread) save coil replacement until after you have ruled out all the other ignition components.