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Author Topic: Can't Hold a Tune  (Read 1569 times)
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LanciaNut69
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« on: May 16, 2013, 01:26:18 PM »

Duplicate posting as not sure what the problem is!!  Fuel/Ignition or other!

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
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WestonE
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« Reply #1 on: May 29, 2013, 07:00:46 PM »

Darren

In a word Rings those compression figures are low for a standard 2000 and the oil pass by would soot the plugs. if you have changed /checked the inlet manifold gasket and changed the carb for a known working item it is down to low compression.

Cheers

Eric
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LanciaNut69
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« Reply #2 on: May 29, 2013, 10:19:30 PM »

Hi chap, 

Not changed the inlet manifold gasket as yet - going to do the rerun of the compression tests and then make a decision - hopefully tomorrow!

Cheers

Darren
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LanciaNut69
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« Reply #3 on: May 30, 2013, 07:14:04 PM »

Chaps,

Just to keep you updated on this and for the sake of completeness, compression test redone this afternoon after getting the car fully warmed up.  Carb was checked again first, and started without issue and ran as before, getting rougher as she warmed up.  At full temps, some black smoke was evident on revving and plugs were found to be sorted up on removal.

Dry compression test yielded following results

1 - 162
2 - 164
3 - 171
4 - 169

Wet compression test with 2 x tsp oil in each bore prior to test

1 - 205
2 - 197
3 - 202
4 - 199

So that looks like the rings are the issue!
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