5 replies to this topic

[CGilmour]

Evening peeps!

Another Sunday passed Another mini problem.

My 1982 Mini Austin HLE running a Metro A+ 998 (Un-sure on year) SU Carb using Ducellier Ignition. Has developed a Idle running problem.

It seems to be only running on 3 cylinders on idle. When you take HT lead number 2 off it doesnt seem to drop in engine tone. As when 1, 3 and 4 are removed (individually of course) the engine tone drops dramatically.

I have ran through checks:
. Replaced all 4 spark plugs (Electrode gap set correctly)
. Swapped Plugs around incase a plug is faulty
. Replaced HT leads (also checked they are in the correct order)
. Re-set points gap correctly
. Checked for cam wear on distributor
. New distributor cap
. New rotar arm
. Done a compression test (All equal at 10 bar)
. Timing is correct and checked
. Valve gaps are correct

After all of those checks, start her up, still idles wrong. Pull off HT lead number 2 again... seems to make no difference. However when the engine is under load it seems to run fine no backfire or lumpy running.
When I remove HT lead number 2 and then put the engine under load it makes a diffrence to the running (runs lumpy as you would expect it too)

So why is it only on idle does the car seem to run on 3 cylinders but under load it seems to be fine and run on all 4?

I would of thought if it was an air leak from the inlet gasket it would affect cylinder 1 and 2 not just 2?

Very confussed!

I would love your help on this as I have spent all day puzzeld!

Thanks in advance!

Chris.

[JonnyBMX]

Oh Chrissy! Shudda rang me I was about all day yesterday!!!! Checked the manifold gasket? Also have you pulled the plug on idle to actually check its got a proper spark on idle at cylinder 2?

Strange that its just 1 and only on idle? Have you asked josh?

[KSTANDSTEVE]

Agree with comment - check for spark on suspect cylinder to elliminate this.

Just sorted a start up problem on mine by stripping down and cleaning the carb/jets. Like you I checked all electrics first but to no avail.

[CGilmour]

Oh Chrissy! Shudda rang me I was about all day yesterday!!!! Checked the manifold gasket? Also have you pulled the plug on idle to actually check its got a proper spark on idle at cylinder 2?

Strange that its just 1 and only on idle? Have you asked josh?

Graham popped round as I was doing it, we are both confussed. No I havent asked Josh yet.

If it was the Manifold gasket wouldnt it affect both 1 and 2 cylinders not just 2? As 1 & 2 share an inlet as does 3 & 4...

If you pull the HT lead off 2 and hold it to a cylinder head nut it gives a good spark. I also attached the HT lead number 2 to a spare spark plug and ran the engine, the plug gave a nice heathy blue spark. Wether its a good spark under compression im not sure.

It is very confussing. Its now making me think its an air leak or a head gasket problem... Really not too sure. If you take spark plug 2 out and shine a light in the hole looking into bore 2 you can see its wet with fuel. So its getting fuel in there okay.

Its stange it only seems to affect the idle tho, not the drive under load.

Yes KSANDSTEVE I allways check the electrics 1st as 9/10 it seems to be the problem haha. The fact its only affecting one cylinder doesnt lead me to think its the carb tho.

Hmmm Going to keep on thinking about this one, If anyone has any other ideas while I try a few more of these ideas do share!

Thanks again, Chris.

[JonnyBMX]

yeah chris the manifold gasket are all separate for each port so the on mine 4 inlet ports with 3 exzaust ports if one of those is blowing could cause some weirdness....

as for the headgasket what makes u think that if the compression is good and at the same level across all 4 bores?

[CGilmour]

I will replace the Manifold gasket soon when I fix my tappet chest oil seal leak & see if it solves the problem :) Got a gasket ready to go on!

Thats a good point, who knows! Im just not very lucky with engines at the moment it seems

As long as the engine keeps on going till its time for the conversion!