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Post by kelsham on Feb 6, 2012 8:59:24 GMT
You are living in the after glow. Once this has worn off your life will become empty of meaning, time will lengthen and you will find yourself dwelling on how you finally tamed the beast.
What you need is a second Landcrab to bring meaning back to your life, one that needs attention immediately would be best.
Seriously though, well done, long drives will help.
Regards Kels.
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Post by tommydp on Mar 25, 2012 16:33:52 GMT
Hi all!
I've not been very active lately, as I've been quite busy. When it comes to cars I've concentrated on fixing the Rover ti which is now back on the road and my daily transport. A marvellous car it is, I'm very happy with it:-) I've fixed the charging, brakes and exhaust and fitted new wheels and tyres. I've also fitted a new timing belt, to be sure:-)
I've also driven the crab quite a lot. As you may recall I was very happy it finally behaved well:-) Well, it couldn't last could it?
To make a long story short, exactly the same symptoms came back even after the cyliner head swap. It was fine for a week though:-) As before, it typically behaves ok for a week or so after it has been standing for a while.
It turns out the garage where my cousin works has a scope, so he has had a look at it. First of all he found the CO, unburnt fuel, to be sky high.. The meter goes to 8% and it just said error. Strange, as the carb has been double checked numerous times. Anyway, he fine tuned the carb and ignition/ dwell. The CO was then around 3, which is fine. According to the scope everything was in order. I'm not at all into scopes, but he said everything was fine.
He then performed a cylinder leak test and all cylinders were excellent, both valves and pistons/ rings. He tested it over and over again both on road and idling and found it performed very well in deed. So did I, for a week or so. It ran beautifully, both at idle and performed lively and smoothly on the road. We even took it for a 350 km journey and it was marvellous. On the way home I noticed some hesitation, and performance was down. As we were then driving through heavy, wet snowdrift straight against us I assumed it was just a matter of damp spark plug wires.
The following days, it gradually got worse, even though I checked for damp wires etc. Everything was dry again. I have not touched or adjusted anything on the car so it remains a mystery as always:-) It seems to me it's still struggling with unburnt fuel, it smells like it and the piston topss are wet, even after longer drives. I would have expected a soothy dry appearance. Firing ends on plugs are normal, but after it started misbehaving again I notice number one and two are leaner than 3 and 4. Strange, for sure. You would suspect the brake servo then, which is at the inlet port for 1 and 2, but it's fine and holds vacuum over night!
Other than this, I can't see anything obviously wrong. There is some oil finding its way into the PCV valve from the oil separator and it seems to me the pressure up the oil separator is somewhat high as the engine idles. Also the gearchange was silky smooth when it ran well, and the gears selected easily. Now that it's playing up again gearchange is hard. Too much pressure in crankcase?
Anyway, I've not touched or adjusted anything so it will be interesting to see what my cousin finds when he takes it back in again. I'm not doing anything more to it, as honestly I have no idea what to look for:-) Obviously there is some trouble with unburnt fuel but what else than a maladjusted carb and failing ignition, which were now fine, can cause this? Did I hear cam/ valve timing? :-) We'll see, still some time for the old car season up here, hope to have it sorted by May 1.
But hey, the suspension is excellent! No more stiffness and shake at low speed:-) Always look on the bright side of life:-)
Tommy:-)
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Post by Penguin45 on Mar 25, 2012 19:39:41 GMT
D@mn - I thought you had cracked it. I don't really know what to suggest. Main jet problem? It sounds like it enrichens itself.
Chris.
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Post by tommydp on Mar 25, 2012 20:10:54 GMT
Thanks Chris! I thought it was solved myself this time.. I'm not that disappointed really as I've come to the conclusion it's best never to take it for granted it's solved when it comes to this car:-)
I must admit it's frustrating though.. I thought I knew these cars inside and out, and we're not exactly talking high tech here:-) It's just fuel, spark and compression after all.. It would be better if it just stopped. But it never does, it always starts and runs:-) I think carb issues can be ruled out, as I've tried different ones. Funny thing is it seems this ghost has been with me all the time, even on the previous engine, through different carbs, fuel pumps, distributors, cams etc and hours of adjusting.. That just leaves the fuel tank and the supply pipe from tank to pump! The only items I've had all the time:-)
I can't wait to find out what's really wrong with it, that is if I ever manage to figure it out:-)
Tommy
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Post by tommydp on Mar 26, 2012 22:02:04 GMT
Took the crab for a spin today, and it performed well again:-) I have not touched a thing on it. Had a look at the plugs when I got back and the readings were now correct. All biscuit brown, number 2 an3 a little richer than 1 and 4. Piston tops dry. Last time I drove it piston tops were wet and 1 and 2 were weaker than 3 and 4 and the car lacked power and hesitated:-)
My cousin will have a look at it after Easter, checking the CO again, as I haven't touched a thing on the engine. He will also check the duration and peak lift of the cam:-) Claims he can do it without dimantling anything. Looking forward to that:-) This bloke really knows his stuff and has all equipment, so I'm positive it will be solved eventually.
Could the brake servo play up things even though it holds vacuum well? I suspect it as its vacuum source is at inlet port for 1 and 2, which are weak when it misbehaves..
Regards, Tommy
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Post by Penguin45 on Mar 26, 2012 23:10:05 GMT
I've got three Girling Powerstop IIB servos, and none of them work........ Can't see it affecting the engine directly, even if the diaphragm fails. The mixture would weaken, sure, but it wouldn't flood petrol into the engine. If the diaphragm failed it would be a permanent condition, not intermittent or time related.
Chris.
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Post by kelsham on Mar 27, 2012 8:35:06 GMT
Could it be an intermittent ignition fault? condenser, rotor arm, plug lead orn distributor cap. The nature of the syptoms would seem to rule out camshaft.
What type of crankcase breathing system is fitted.
Regards Kels.
P.S. I had further trouble with my car misfiring went back through the recently fitted ignition components and to my amazement found the points had a loose nut holding the ignition supply wire???
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Post by dave1800 on Mar 27, 2012 11:55:35 GMT
Rotor arm / distributor cap. I have seen many reports of rotor arm failures recently. This could cause high CO readings and unburnt fuel in any cylinder(s).
I believe 3% CO is too lean (even though desirable from an emissions point of view) judging from MGB forums and that a figure of around 4.5-5% is needed to prevent misfiring.
Good luck again!
regards
David
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Post by threelitre on Mar 28, 2012 8:26:32 GMT
I have all my cars at a consistent 2.5-2.7% CO and they run just perfect - even the 1800 S can be adjusted to this level when appropriate care is taken on synchronisation. Lean the mixture out until you feel the performance starts to be affected and then back up 2 flats, if everything is in good working order I always achived fine running, good economy (in relative terms to the type of car) and above given CO figures. But I still use high octane fuel and not 95 RON standard unleaded.
The LHD servo is different from the UK servo! I have had two of these fail now. Due to the typical point of failure on the diaphragm, they'll not be leaking until the brake is actually pressed - resulting in a suddenly very hard brake pedal and an engine occasionally stalling when pressing the clutch. As the car had a 'modern' one way valve fitted inline with the vacuum line, I just turned it around and continued the holiday trip with no servo... So to take the servo out of the equation - if you think so, Tommy - just blank it off and use some good shoes for good braking force.
Is Tommy's misfire due to a flooding engine or is the wet spark plug caused by the misfire? I can't imagine a misfire caused by rotor arm or condenser to be concentrating onto a single cylinder? If it is the same cylinders sticking out all the time, I'd look at the ignition components of these particular cylinders.
Regards,
Alexander
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Post by dave1800 on Mar 29, 2012 0:36:58 GMT
Alexander It's interesting to note that you are achieving good running at a much lower CO content than some of the posters on the MGB forums. It suggests their problems probably lie with the the ignition and / or worn carbs and you have things just right! Tommy As cylinders 1,2 were affected they are next to each other in the firing order (1-3-4-2 =2-1 3-4) I have the following thoughts. (a) is there an air leak that affects two adjacent cylinders? The only two I can think of are the servo (see Alexander's comments) and the manifold / head joint. I have seen the manifold nuts work loose allowing air to leak past the gasket - both easy to check (b) ignition again two things to check. First the distributor cap for breakdown between adajacent terminals, a hairline crack maybe that is heat and moisture sensitive AND / OR I recall you said your electronic ignition trigger ring wasn't a tight fit originally. Maybe your fix has worked loose? I haven't seen this model but I assume you have to set the gap between the ring and the sensor and if the ring wobbles it could upset this setting maybe on adjacent cylinders. I had a Saab 900 which had a magnetic (hall) sensor in the distributor and the rotor arm / trigger vane was bonded to the distributor shaft to prevent any movement. I still think that a weak rotor arm could push any of the above "faults" to a misfiring situation, again easy to change. Regards David (b) I have all my cars at a consistent 2.5-2.7% CO and they run just perfect - even the 1800 S can be adjusted to this level when appropriate care is taken on synchronisation. Lean the mixture out until you feel the performance starts to be affected and then back up 2 flats, if everything is in good working order I always achived fine running, good economy (in relative terms to the type of car) and above given CO figures. But I still use high octane fuel and not 95 RON standard unleaded. The LHD servo is different from the UK servo! I have had two of these fail now. Due to the typical point of failure on the diaphragm, they'll not be leaking until the brake is actually pressed - resulting in a suddenly very hard brake pedal and an engine occasionally stalling when pressing the clutch. As the car had a 'modern' one way valve fitted inline with the vacuum line, I just turned it around and continued the holiday trip with no servo... So to take the servo out of the equation - if you think so, Tommy - just blank it off and use some good shoes for good braking force. Is Tommy's misfire due to a flooding engine or is the wet spark plug caused by the misfire? I can't imagine a misfire caused by rotor arm or condenser to be concentrating onto a single cylinder? If it is the same cylinders sticking out all the time, I'd look at the ignition components of these particular cylinders. Regards, Alexander |
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Post by dave1800 on Mar 30, 2012 3:55:51 GMT
Hi Tommy You may be interested in this article on engine breather systems www.106rallye.co.uk/members/dynofiend/breathersystems.pdfI was trying to ascertain whether unburned fuel finding its way into the sump could cause excess crankcase pressure, still not sure. I found that the gearchange smoothness depended a lot on smooth running of the engine, not too low an idle and ignition not over advanced. The throttle damper seemed to play an important role, but they took this off later UK models. What's the secret of the suspension cure? Regards David quote author=tommydp board=talk thread=263 post=2269 time=1332693232]Hi all! There is some oil finding its way into the PCV valve from the oil separator and it seems to me the pressure up the oil separator is somewhat high as the engine idles. Also the gearchange was silky smooth when it ran well, and the gears selected easily. Now that it's playing up again gearchange is hard. Too much pressure in crankcase? But hey, the suspension is excellent! No more stiffness and shake at low speed:-) Always look on the bright side of life:-) Tommy:-) [/quote] |
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Post by kelsham on Mar 30, 2012 7:33:40 GMT
The reason i asked about the crankcase ventilation is because I was wondering if you had mixed and matched components from different set ups.
I did this when I tried to fit the Mk1 valve to the later system without the oil separator the result was a smoking engine .
It occured to me that a fault on this could cause odd symptoms.
Regards Kels.
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Post by dave1800 on Mar 30, 2012 10:22:26 GMT
Hi Kels - that's a good point. As far as I understand the system, the cars with the PCV valve (with the rubber diaphragm) were fed from the crankcase breather that had the large vertical oil separator whereas the later cars had the separator inside the tappet cover and vented directly to a constant depression (ie vacuum) feed on the later carb. That is apparently a much better system - and simpler. Is that your understanding too? Regards David The reason i asked about the crankcase ventilation is because I was wondering if you had mixed and matched components from different set ups. I did this when I tried to fit the Mk1 valve to the later system without the oil separator the result was a smoking engine . It occured to me that a fault on this could cause odd symptoms. Regards Kels. |
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Post by kelsham on Mar 31, 2012 7:21:37 GMT
Yes david, thats how I understand it. I tried to run without the oil separator, using the valve when I rebuilt my engine.I am now running with the simpler later system. I was wondering if Tommy had a problem with the valve leaking.
Regards Kels.
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Post by tommydp on Mar 31, 2012 7:33:48 GMT
Hi all! Thanks a lot for many useful replies! I took it for a spin yesterday and it was still fine and I've still not touched anything. It's quite interesting, or rather annoying, how the car will be brilliant one day and then for no appearant reason play up the next. On the bright side, it has been improved. It is in deed good for longer periods compared to earlier.
The brake servo is the Girling Super Vac, and as Alexander points out these were only fitted to LHD cars. I've seen them on UK Maxis and early Marinas though. When the car plays up, the brake pedal seems a bit harder, but it's still servo assisted. So not sure if the servo causes a vacuum problem or is caused by a vacuum problem.. When the car starts to fail at idle it will not improve if i blank off the servo.
The same goes for the gear change, silky smooth when car behaves, stiff and needs more force when it's not. I don't have a throttle damper now as I have a Princess heat shield, not allowing room for it.
I now use the early type oil separator and PCV valve. I've also tried the other design, without mixing the two. I don't think this makes a difference to the engine. The PCV valve seems to work fine, diaphragm is good and the idle speed rises a bit when I open the oil filler cap and has a lumpier idle, as supposed to.
Since re- investigating the problem earlier this winter the car has had points again to make it more basic and easier to diagnose. I know I sound very certain when it comes to obvious items on fuel and ignition which could be failing, but honestly I can't believe anything being at fault here. I use a red rotor arm (distributor Doctor), Unipart/ Lucas points, condenser, cap. And I've tried changing all components more times than I care to remember, so.. well who knows:-) On the other hand I've had these cars running perfectly on 40 yrs old, more or less worn out components and my experience is if it breaks down due to ignition you'll notice, missing a cylinder or hard to start etc. It won't come and go, at least not on several distributors with different ignition components..
Anyway, I'm still optimistic! I have patience with children/ youths and British cars only as someone say jokingly:-) I'll use the crab regularly for a week now, until it's going back to my cousin the week after Easter for further investigation.
I'm happy it now works as it should, if not all the time. When fine, the piston tops are all dry and plugs are biscuit brown with number 2 and 3 slightly richer. So my conclusion is it boils down to an irregular condition of unburnt fuel which again affects the breathing of the engine playing up gear change, brake servo etc. The answer will lie in what causes the fuel to be unburnt and why will plug 1 and 2 become weaker when the problem sets in, while all piston tops show sign of unburnt fuel? I'm absolutely sure there is no air leak at the manifold/ gasket. Also, the problem seems more pronounced at high vacuum, as at idle and going downhill in gear. When it's good it will roll happily downhill in gear, keeping steady speed while on bad days it will hesitate and slow down going down the same hill at same speed, meaning I have to keep the throttle a bit open to keep up speed. When it's good there's no puff of smoke after downhill driving in gear, while there is some on a bad day. I am quite sure this smoke is from unburnt fuel rather than oil.
BTW, I also thought the CO of 3% to be too lean. However my cousin assured there was no danger and confirmed this by some information on lambda, air/ fuel ratio, percents etc.... all of which was well above my head:-/ Well, the plug readings are excellent, when it's ok, with no signs of too weak mixture or overheating and the temperature is rock steady normal and there are no signs of pinking, detonation etc and it will fly up a steep hill in fourth with loads of torque.
Regards, T
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