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This issue keeps coming and going, runs good for a few days then has a couple of bad days then runs well again. Last few days have been bad. Usually at it's worst when the engine isn't up to running temp
Today I decided I would go back to base settings on the carby's and give them a tune again. All seemed good for a bit. I left it to cool down then it started stalling again on the next try, and idle was up and down again.
Pulled the plugs and found this.
Rear 3
Front 3
Going by that it tells me the rear carby is rich, but just being tuned today it shouldn't be. The only thing we haven't played with is the chokes so had a bit of a poke around there and found the the fast idle cam on the rear carby was sticking sometimes leaving the jet pushed down to the full rich position.
After a bit of playing around I discovered the cam on both chokes are slightly different, the rear one has a sharper lobe on it, the front one is more curved. Causing the rear carby cam to get caught on the stop screw when the cable was fully extended. Therefore the rear carby was running on full choke.
Rear cam
Front cam
I adjusted the stop screws further back so the cam isn't fouling, just means pulling choke further out to engage it.
I hope I'm onto something here, had a good test drive and will test again tomorrow.
See, that codger that came over at the servo to tell you your "left bank was running a bit rich" , he was onto to something :-) Look like to are going down the SU rabbit hole again. You will have sorted through a few current and potential bugs by the end of this, it should give you back some reliability reward points.
Not a good start this morning, didn't really want to run well at all. Pulled the plugs again and all looking on the lean side, (no photos's, camera battery was flat.)
Tweaked the mixture a bit, 1 & 1/2 turns richer on the rear carby and 1/2 a turn richer on the front carby. 40 km round trip she ran sweet so let's see how it goes from here.
The problem really is worst at total cold start in the morning, tomorrow will tell another story.
I think a couple of Paul's Cuban cigars and the duty free scotch would help. Not with the car , but life in general. Always good to take some time out and relax with mates.
Reading through this stuff about the SUs I am confuserated. I am really only familiar with HS2s so that may be why.
The mixture you are adjusting, I thought, was really just the idle mixture and doesnt do anything about mixture setting when the car is running. I thought that was down to the needle taper (I recall you had badly worn needles and replaced them) and free movement of the piston. If a piston is sticking and doesnt rise and fall down easily with a metallic click when you operate it by hand , the results do get a bit random.
Are the HIFs (?) more sophisticated in regard to running mixture control?
Still on the Rig or moving house, or just plain AWOL with the Jazz.
Clearly the V12 is behaving, must work on that sabotage plan we always have on the back burner.
Paul is settled in the new house, picked his XJS up from storage at his Dad's place and has returned to the high seas.
Originally Posted by yarpos
Reading through this stuff about the SUs I am confuserated. I am really only familiar with HS2s so that may be why.
The mixture you are adjusting, I thought, was really just the idle mixture and doesnt do anything about mixture setting when the car is running. I thought that was down to the needle taper (I recall you had badly worn needles and replaced them) and free movement of the piston. If a piston is sticking and doesnt rise and fall down easily with a metallic click when you operate it by hand , the results do get a bit random.
Are the HIFs (?) more sophisticated in regard to running mixture control?
They are HS8's Steve, from what I read you are correct. The biggest problem is at idle and mostly when not up to running temp. Usually when coming to a near stop then accelerating off again, if you stop for long enough like a red light it splutters and recovers itself before driving off.
Needles, Jets, floats, (and needle & seat) were replaced about 20k ago as were all the o-rings and gaskets.
Still dramas the last couple of days, so today I pulled the carby's off and took everything apart for a clean and see if there was anything not quite right. Everything seemed ok but replaced the o-rings, split pins and washers while I was at it.
Put it all back together and reset, mixture, idle and chokes again. Ran sweet. (as it has the last few times everything has been set at running temp) I will see how a cold start goes tomorrow.
Paul is settled in the new house, picked his XJS up from storage at his Dad's place and has returned to the high seas.
They are HS8's Steve, from what I read you are correct. The biggest problem is at idle and mostly when not up to running temp. Usually when coming to a near stop then accelerating off again, if you stop for long enough like a red light it splutters and recovers itself before driving off.
Needles, Jets, floats, (and needle & seat) were replaced about 20k ago as were all the o-rings and gaskets.
Ah, I misunderstood the problem. Thought you were chasing rich running rather than idle/stalling. The only other thought around idle maybe is wear in the butterfly valve shaft bushes, and sucking to much air at idle.
Next move is to put it on the gas analyser and check exactly what its doing. We can also give the ignition side of things a good check over. Good excuse to check out the beer fridge.
11-19-2017, 05:36 PM
