Classic Mini - Help diagnose my problems!

[Mini_Lund]

Hi PH,

I have posted my problems on the Classic mini’s section in my thread, but it’s a little inactive! http://www.pistonheads.com/gassing/topic.asp?h=0&a...

I have recently been having trouble with my Mini. It’s a 1979 British Leyland, Mk4 Mini City (850). She is reluctant to rev and runs rough, when driving there are lots of flat spots but then she'll pick up. It’s a standard engine, air filter and carb (HS4). The carb has recently been refurbished by myself with a new jet and float chamber needle. The standard needle still remains. The Mini seems to warm up quite fast, today she squirted water out of the overflow pipe all over my drive?

I drove the mini down to my friend’s workshop to be timed with a strobe light. I couldn’t manage to move the dizzy at all It had seized to the block somehow. Rockeze did the trick

Timed the dizzy to factory standard setting, and put the points back on. She doesn’t like the electronic ignition, as soon as you press the accelerator she doesn’t rev, just knocking noises from the block! So put the points back on.

Driving home, she is full of flat spots, wont go, it feels as if the engine is restricted, rocking back and forth. I am also rocking in my seat to, eager to go!

I decided the timing wasn’t correct and unbolted the distributer and tried timing it by ear. Whatever position the dizzy was put in, I still had the same problem. So now I'm thinking, it isn’t the timing at fault and I've just buggered my nicely timed dizzy.

From time to time she also has a misfire, running on 3 cylinders. I run her on minimum oil as she burns the oil if there is plenty in - blue smoke. I suspect the valve oil seals and head gasket. Oil is getting through somewhere.

I’m guessing quite a few of you will have had experience with minis in the past or even currently, so can anyone help me out?

Thanks in advance

Tom

[Mini_Lund]

Thanks for all of the feedback.

The spark plugs are set to 0.0025" thou with points on. HT leads are in good condition and engine note changes when each lead is taken off.

If we leave the Electronic Ignition out of the equation, I'll keep it on the points!

Plugs look normal colour, quite black but with copper deposits.

I also agree that its possbile that the distributer could be 180 degrees out, but it runs!?

Dashpot oil is topped up nicely.

As for the reluctant reving. I took the petrol lines off and hose connections and blew through them with a bicyle pump, also connected the petrol pump to the line and blew that out. I then forced air down the line and into the tank. It seems for that moment, she revved fine when all connected back up...

Crankcase breather is breather fine, I also suspected this and took the tube off the carb and blocked it with my finger. Engine then stalled, suggesting that it needs to breathe!

Also, I removed the vacuum advance line from the carb with the engine running, but it made no difference to the engine note what-so-ever, am I right in thinking the engine note should drop?

Many thanks so far guys, its a big help.

Tom

Edited by Mini_Lund on Wednesday 7th May 23:16

[Mini_Lund]

x 7usc said:

you say she warms up quick? does she run fine when cold or is it all the time, its just i had this on another make of car had a couple of mechanics stumped, turned out to be a faulty spark plug tracking to ground when warm.

She runs hot or cold, just not very well. However when she got hot, she wpuldnt rev, knocking noise could be heard from the engine and thats it, didnt sound healthy at all.

Unfortunately I dont have a compression tester so cannot complete a compression test, unless there is any other way of doing it?

[Mini_Lund]

Hooli said:

your comment on the breather sounds odd to me too, it shouldnt stall if you block that.

Hmm thats interesting. Okaym so when I remove the pipe from the carb, the car wants to stall, if i block it, it does stall.

The points are set to the correct gap with the feeler gauges.

Carb and dashpot all looks grand.

[Mini_Lund]

52classic said:

I'm a bit worried about the 'knocking noise' and we don't seem to have investigated it so far.

Top of engine or bottom? Could be pinking which AIRC can be cured by retarding the ignition and removing the vac advance temporarily.

Is there smoke to accompany the knocking noise? I'm thinking a sticky or weak valve.

There might be a sticky valve, as sometimes it runs on 3 cylinders...and with high revs it sometimes cures it. I've got a 998 unleaded head to fit, going to get it skimmed and then investigate when I fit it, got a genuine top end gasket set also. Knocking noises sound dreadful, sounds like its from the block, as if the pistons were bottoming out.

When the vacuum advance is removed, there is no difference in engine note.

Tom

Edited by Mini_Lund on Thursday 8th May 08:31

[Mini_Lund]

Elan159 said:

Mini_Lund said:

The carb has recently been refurbished by myself with a new jet and float chamber needle. The standard needle still remains.

Did the rough running coincide with your work on the carb? If so I'd concentrate here first - does the piston rise and fall easily? You may not have centered the needle correctly.

Yes it ran rough before work on the carb commenced, one thing i must point out is that the needle wiggles in the piston, its firmly in place and centred just it wiggles from side to side.

[Mini_Lund]

onomatopoeia said:

Mini_Lund said:

The spark plugs are set to 0.0025" thou with points on.

I'd open those out a bit. Less than three thousandths of an inch is way too small a gap. If it was a typo and you meant 25 thousandths then ignore me.

As others have suggested, work through stuff methodically. I start from the points gap then the static timing. Ensure that the dizzy will advance centrifugaly by attempting to rotate the rotor arm by hand - it should move a short way against its direction travel on the springs. If it doesn't and the shaft is solid then it will not run well. The vacuum advance can be ignored as that's just a touring economy device.

Apologies, that was a spelling error! 0.025" thou are the spark plug gaps. The rotor arm rotates by hand, springs and bobbings move freely and the shaft is in good condition.

Surely the enine note should change if the vacuum advance is taken off?

When the crankcase breather is disconnected from the carb, the engine stalls. Should it do this? If not, without taking it off, could I run an airline into the tube and pressurise air inside, to free things up abit?

[Mini_Lund]

Sorry to have to bump the thread

[Mini_Lund]

freddytin said:

Have you a spare carb, and or coil to substitute ?

I have a spare carb but its an early HS2 (1.1/4), whereas mines a HS4(1.5). I tried the coil off my old mans land rover series 111 and still had the same problems. The series 111 coil could be dodgy also, but would be a coincidence!

I pushed the piston up with my finger, it moves up slowly and fall slowly, but smoothly.

Here's what we're working with by the way:



Not the best of pics, need some decent weekend weather to spray the bonnet vermillion:

Edited by Mini_Lund on Thursday 8th May 22:34

[Mini_Lund]

freddytin said:

OK , remove the oil filler cap, pull the breather tube off at the carb end, then blow into the breather as hard as you can. You should be able to hear air coming out of the rocker cover, if not the breather is blocked.

I'll attatch an air line from a bike pump to the end of the crankcase breather and listen for bubbles. It might not bubble much as I have her running on minumum oil. I just reminded myself. I need to watch that closely. Will give it a go tomorrow.

[Mini_Lund]

pat_y said:

Bit left field but dont suppose you could have a blocked exhaust (collasped silencer), this will make it run like a total bucket guaranteed.

Its a straight through system rc40, less than 6 months old, I think its fine

52classic said:

It's encouraging that the engine bay looks just right - and the car generally a credit to you Tom - Clearly the motor is not freshly cleaned and there is no sign that oil or water being chucked anywhere therefore chances are that the engine is serviceable.

Not sure about the 180 degrees out theory, I have heard of this happening but never experienced it.

Thank you, Im unsure about the 180 degrees out too. Its running ok for now belive it or not. Sounds a bit tappety but will sort that out when I fit the unleaded head. Theres no difference in engine note between the choke halfway out and fully in, suggestin that its running lean. Need to weaken it off.

Edited by Mini_Lund on Friday 9th May 10:53

[Mini_Lund]

pat_y said:

Mini_Lund said:

pat_y said:

Bit left field but dont suppose you could have a blocked exhaust (collasped silencer), this will make it run like a total bucket guaranteed.

Its a straight through system rc40, less than 6 months old, I think its fine

Fair comment, i'll get back in my corner then.

Its good that were ruling out possible causes, thanks

[Mini_Lund]

freddytin said:

OK , remove the oil filler cap, pull the breather tube off at the carb end, then blow into the breather as hard as you can. You should be able to hear air coming out of the rocker cover, if not the breather is blocked.

I can hear air through the breather, nice and easy to push air through. Im unsure if my carburettor is adjusted properly, as mentioned before the piston moves up and down freely, but if I push it up too far it sticks at the top and doesnt fall down. lubricate the hollow shaft it slides on?

Unsure if the mixture is set correctly, I know its an 850, but I seem to have a lack of power when i need it the most... what should I adjust?

I have also noticed that there is no difference between the choke all the way in and the choke half-way out. Although the idle speed seems normal to me.

Thanks once again, all of you helping me at PH!

Edited by Mini_Lund on Friday 9th May 17:21

Edited by Mini_Lund on Friday 9th May 17:24

[Mini_Lund]

aw51 121565 said:

In the 'dashpot' (top of the carb), the hollow tube will lubricate itself as oil 'spills' from the inside of the hollow tube and down its outside. So that looks after itself .

Have you had the dashpot apart and cleaned everything (I mean everything, including the inside of the chamber and outside of the piston) up inside there with white spirit and kitchen paper? It often makes a difference to a poorly running car as a lot of 'sticky crud' can build up and cause the piston to stick.

But don't use any kind of polish, as that messes up the clearances between the piston and chamber and the carb will never ever work again...

Failing this, when did the problem start? Does it go as far back as when you swapped carbs (presuming I am reading that the engine has a non-original carb)? If this last is irrelevant, ignore it .

Nice looking Mini btw - and it has a registration number local to me.

Yehr cleaned it all, the whole carb was cleaned in petrol. The carb on the car is the original carb, the head is also the original head. Its basically untouched...until recently Since it was the last of the 850's produced by British Leyland, it has a HS4 carb and a Cam 4810 head. (998 head)

What area is the plate from?

Edited by Mini_Lund on Friday 9th May 18:03

[Mini_Lund]

Will do this all in time and get back to you

I know what nbeeds doing, just need to do it now!

[Mini_Lund]

freddytin said:

Did you receive the article through your e mail on carb set up and adjustments ?

Don't worry too much about black plugs or smoke at this stage , probably just a consequence of a poorly tuned engine.

I certainly did, I replied.

[Mini_Lund]

freddytin said:

Looks like you're better at checking your e mail than me.

Its one of the tabs I keep open in firefox; you'd be surprised at how many emails I've had off PH members. Really good to know I'm well looked after at the tender age of 18. I have a vast knowledge of Mini's but still learning, gaining much experience! I'm more hot on Land Rovers to be honest with you, but there has it! ooo just received an email from Tesco...