Can't get a tune!

[LanciaNut69]

Chaps and chappesses,

I hope someone out there can help or at least give me some other options to pursue. The patient is a Series 2 Montecarlo. 2 Litre 8 valve engine, on standard 34 DATR carb and manifold. Exhaust manifold is standard, as is the exhaust system with the exception of the rear box. Cams are standard. Jetting in carb is as per the tech manual.
Compression test when engine to full temp 1 - 4 as follows - 157, 153, 155, 154 PSI
Tappet clearances all within tolerance
Valve timing correct
Ignition timing timed off No.4 @ 10 BTDC

Plugs - NGK BPR6ES - New - 0.8mm Gaps
Leads - new
distributor cap - new
Hall sensor - new
Ignition Amplifier - new
Coil - original, but appears to be ok.
Fuel pump (mechanical) - new
Fuel supply and return hoses - with inline filter - new

Vacuum port on inlet manifold for heater controls temporarily plugged as hose is showing signs of age

Car was delivered to me with all of the above in place - with the exception of new fuel lines and filter, and ignition timing - as a non-runner. After checking and resetting timing, the car started but ran extremely roughly and lots of smoke from the exhaust (rich) No adjustment to the idle mixture, cleaning and blowing jets and emulsion tubes made any difference, and tickover was not less than 1100 rpm.

Noted that fuel was running into the chokes, so needle valve was checked, along with float level and all appeared ok. A fuel pressure regulator was fitted, which solved the problem of excess fuel, and cleaned jets allowed some adjustment to be made, but tickover remained high, albeit at a slightly lower level of 1000 rpm.

Revs are gradually increasing and falling over a period of 10 - 20 seconds. Gaskets between manifold and spacer, and spacer and carb have been renewed. Spray of carb cleaner around joints has no immediate effect of increasing revs, but I think there must be a leak somewhere.

A pair of colourtunes in No 1 and No 3 showed a proper mixture and yet the plugs were sooty on removal.

Does anyone have any ideas or pointers? Any help gratefully received!

Darren

[gengis]

I take it that it's running well now, apart from inconsistent idling.  Sounds like a worn carb to me, check for any play in the butterfly spindle.  Time for a replacement carb, or service kit on original.

[LanciaNut69]

Hi Gengis,

Thanks for coming back to me - would agree with you to a certain extent, but have changed carbs and problem is still the same.  Carb fitted has had an overhaul kit fitted.

Cheers

Darren

[gengis]

Geez...I feel for you on this one.  Does any electrical load applied (heater fan motor, lights, etc) make any difference to the running?

[peteracs]

Hi

When you say you checked the timing, did you check the cam timing relative to the crank as well?

Not sure if the symptom would be the same, but worth checking on unknown engine. Certainly sounds like rich running so would suspect leak/flooding is the issue, but why on refurb carb, hard to see how.

Peter

[LanciaNut69]

Geez...I feel for you on this one.  Does any electrical load applied (heater fan motor, lights, etc) make any difference to the running?

Hi Gengis,

Slight drop in revs when cooling fan cuts in, but no more than normal.  It is a bit of a bugger!!

Cheers

Darren

[LanciaNut69]

Hi

When you say you checked the timing, did you check the cam timing relative to the crank as well?

Not sure if the symptom would be the same, but worth checking on unknown engine. Certainly sounds like rich running so would suspect leak/flooding is the issue, but why on refurb carb, hard to see how.

Peter

Hi Peter,

Yes, cam timing relative to crank checked - I'm in agreement - definitely think it's a leak or rich running - just need to find out where!!

Cheers

Darren

[MattNoVAT]

I noticed that the inlet manifold gasket is not on the list of being replaced.... long shot I know but maybe thats the source of the leak.

Also, I thought maybe the valve stem oil seals are worn hence the soot on the plugs?

Do the revs rise and fall identically i.e. always over the 20 second period, and when the revs do drop is it sudden or gradual?

[LanciaNut69]

Hi Matt,

Good to hear from you chap!  I had thought inlet manifold gasket - was changed about 4 years ago when the head and head gasket were fitted.  The head came from Mr Weston, so I think that the valve seats and seals should be ok.  I'm going to do another set of compression tests, dry and oiled to see if there is a difference, which would suggest rings/bores.

Hope to get back to work on it tomorrow, so I'll keep you posted.

Cheers

Darren

ps - change in revs happens over a period of say 1-2 seconds, reasonably regularly - thought it was cooling fan cutting in to start with, but isolated that. 

[peteracs]

If it is hunting that quickly, still sounds like over lean/over rich running, would not have thought the compression would have had that effect.

Peter

[LanciaNut69]

Hi Peter,

Yes, I think you're right and it is a mixture issue, I just need to sort out the cause!  Update to follow

Cheers

Darren