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Post by tommydp on Jul 22, 2011 7:15:53 GMT
Hi again:-) Well, the symptoms were back again yesterday:-)
So, back to the vacuum leak theory. First of all, I have always found the PCV "mushroom" valve suspicious as oil still finds it way into it. There's been an occasional puff of blue smoke after rolling long hills with throttle closed too, on both heads even on the rebuilt engine. There's always a certaing amount of oil inside this valve after a drive, and that's not normal as far as I remember.
I've tried different valves but I've only got one diaphragm, which I suspect. It's a "modern production", most likely from the far east again, and seems thinner and less solid than the ones I had in earlier Landcrab days. As far as I understand, it's supposed to be closed at high vacuum, only opening when revving? It's not entirely closed at idle as far as I can see, listening to it it's sort of regularly pulsating and there's a corresponding blow of air from the small hole on the top cover of the valve.
So, I've now removed it and blocked the manifold connection off. The breather hose from the oil seperator runs out in the air, nothing suspicious about this either, no oil to be seen and a mild regular blow of air/ fumes.
So there must have been too much manifold suction applied to the crank ventilation as far as I can see, and I can't see any other reason than a failing diaphragm/ valve causing this on a reconditioned engine.
Referring to various MG sites this valve has for sure caused loads of unneccesary engine rebuilds, due to oil burning symptoms:-) At least my previous engine had bearing issues, rattles and low oil pressure so it's not all wasted:-)
Question is, will it be harmfull to the engine not connecting the breather pipe to a vacuum source, isn't this just a pollution device in some way? Will it provide sufficient breathing to have the pipe going directly to air from the oil separator? Lots of cars do, after all.. I imagine it will be worse to have oil sucked into the inlet manifold at higher vacuum? No doubt this could have caused what looked like oil carbon build up on the pistons, as the breather valve has always had some oil in it when checking..
Haven't had the time for a test drive after this, will report later on. Suppose the mixture has to be reset once again too...
Regards, Tommy:-)
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Post by tommydp on Jul 22, 2011 7:49:29 GMT
www.mgparts.co.nz/burning_oil.html"The pollution control valve on the manifold (where fitted - 18GA, 18GB, 18GD engines) can develop a leak which allows the crank case to be vented to the inlet manifold under vacuum rather than only under full-ish throttle conditions when the manifold pressure is much closer to atmospheric. The result is that the strong vacuum sucks furiously at the crankcase, scavenging neat oil as well as the intended fumes into the inlet system. Hence oil combustion and blue smoke! " Regards, Tommy:-)
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Post by dave1800 on Jul 22, 2011 8:43:46 GMT
Smoke on deceleration could also be worn valve guides. Definitely not a good idea to run without either of the two crankcase ventilation systems in place, did you ever see the white foamy sludge in the rocker box covers where the ventilation is not working? Here are a couple of sites if you've not seen them yet: mgaguru.com/mgtech/engine/cv102.htmThere's a really excellent article if you Google "MGB crankcase breather mgmanawatu" and select the PDF file on the www.mgmanawatu.com/ website. Unfortunately the url link doesn't work if I try and insert it here and if you just go to the website main page it can't find the article. The PDF downloads fine. I thought it was too good to be true yesterday! regards David Read more: landcrabs.proboards.com/index.cgi#ixzz1SozPnUyr |
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Post by tommydp on Jul 22, 2011 9:51:13 GMT
Smoke on deceleration could also be worn valve guides. Definitely not a good idea to run without either of the two crankcase ventilation systems in place, did you ever see the white foamy sludge in the rocker box covers where the ventilation is not working? Here are a couple of sites if you've not seen them yet: mgaguru.com/mgtech/engine/cv102.htmThere's a really excellent article if you Google "MGB crankcase breather mgmanawatu" and select the PDF file on the www.mgmanawatu.com/ website. Unfortunately the url link doesn't work if I try and insert it here and if you just go to the website main page it can't find the article. The PDF downloads fine. I thought it was too good to be true yesterday! regards David Read more: landcrabs.proboards.com/index.cgi#ixzz1SozPnUyrI found it to good to be true, too:-) I haven't got the carb with the vent pipe on now, so only option is the PCV valve, which lets oil in.. Took it for a drive with the breather's manifold connection blocked and hose from oil separator to air. Seems to be running better then, and the idle is smoother too. A far as I could see, there was no smoke on deceleration now. Had a look at the plugs again, and there were no traces of oil there. What gets me though, looking down at the piston tops is three of them are somewhat wet, from oil or petrol I dont know. One is dry, and the strange thing is this cylinder has an old Bosh W 7 DC plug now as I broke one when checking... The other cylinders have NGK BP6 E plugs. Could there be an issue with these plugs? Unfortunately I only have one of the old Bosch plugs. After a drive the bosch plug looks better too, in any cylinder. It has an even biscuit brown colour both on insulator and electrodes, while the others are somewhat red on the insulators. I suppose resistor plugs should be avoided? If it's important to have the breather hose connected to either the PCV valve or carb, I suppose I have to put another carb in again, or get a new diaphragm. There's never been any white sludge inside the rocker cover, nor in the PCV valve. In deed, the guides could be worn too, but I guess oil in the PCV valve is no good either. Regards, and thanks:-) Great links:-) Tommy:-) |
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Post by tommydp on Jul 22, 2011 10:18:28 GMT
The NGK BP6 E plugs, which I'm using, do not have a copper core it appears unlike the BP6 ES which is stated for the model. I couldn't get the BP6 ES plugs, the 6 E would be the same according to the shop. Who knows?
Getting som NOS Champion N 9 Y anyway.
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Post by dave1800 on Jul 23, 2011 2:12:23 GMT
Tommy, I found this quote and similar comments.
"....it is important to retain the crankcase ventilation system. Properly maintained, crankcase gases are drawn into the combustion chambers of the engine by the vacuum created by the fuel induction system, either through the intake manifold as in the 18GB through 18GF engines, or through the carburetors as in the later engines..... This permits the crankcase to function in a partial vacuum which causes oil mist inside the crankcase to be drawn upwards towards the camshaft and tappets. Without the partial vacuum provided by this system, the pressurized gases inside the crankcase of the B Series engine would cause oil to be blown past the pistons into the combustion chambers leading to carbon buildup and consequent preignition problems"
You should swab the pistons to see if the 3 are wet from fuel or oil.
I always used Champion N9Y plugs but tried NGK and Bosch as they worked well on my Saab but not so impressive on the 1800. If it is oil, with the crankcase vent disconnected it points strongly to valve guides /seals. If it is dry with the crankcase vent disconnected, but oils up when you reconnect the vent then back to the PCV etc. I assume you have cleaned out the whole system?
If it is fuel on the piston then sort out your spark plugs first and check again.
I would avoid plugs with inbuilt resistors unless you have high tech electronics on board as your ignition system is already stretched by the higher demands of modern fuel.
regards
David
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Post by tommydp on Jul 23, 2011 8:02:40 GMT
Tommy, I found this quote and similar comments. "....it is important to retain the crankcase ventilation system. Properly maintained, crankcase gases are drawn into the combustion chambers of the engine by the vacuum created by the fuel induction system, either through the intake manifold as in the 18GB through 18GF engines, or through the carburetors as in the later engines..... This permits the crankcase to function in a partial vacuum which causes oil mist inside the crankcase to be drawn upwards towards the camshaft and tappets. Without the partial vacuum provided by this system, the pressurized gases inside the crankcase of the B Series engine would cause oil to be blown past the pistons into the combustion chambers leading to carbon buildup and consequent preignition problems" You should swab the pistons to see if the 3 are wet from fuel or oil. I always used Champion N9Y plugs but tried NGK and Bosch as they worked well on my Saab but not so impressive on the 1800. If it is oil, with the crankcase vent disconnected it points strongly to valve guides /seals. If it is dry with the crankcase vent disconnected, but oils up when you reconnect the vent then back to the PCV etc. I assume you have cleaned out the whole system? If it is fuel on the piston then sort out your spark plugs first and check again. I would avoid plugs with inbuilt resistors unless you have high tech electronics on board as your ignition system is already stretched by the higher demands of modern fuel. regards David Thanks, David, for your invaluable help! Another great link. I'll absolutely have to provide one of the two engine breathing systems! Seems some people ignore this, I've seen lots of MGBs and others letting the fumes to air, and even through a filter which I suppose will eventually block.. Anyway, first of all, it's a tragic day here in Norway after the massive shootdown of more than 80 youths at a camp, as well as a bomb blast in the centre of the capital, killing about seven and injuring several. The work of a maniac. Horrible and unbelievable and the worst happening in this country since WW2. So, after watching the news all day getting sad, what better way to get away from the world's cruelty than having a look at the Crab inside the garage.. I've now changed the carb, which will enable me to try out both the breathing systems. I suspect the PCV valve or rather the diaphragm. There's massive suction at the oil filler cap with this arrangement, also the car struggles at idle. I believe it will be easier to inspect the operation of the carb operated breather. At least with the other carb installed it behaves like the Marina regarding the carb breather at idle, when removing the hose from the carb. There's also equal, mild suction at the oil filler hole at idle. Well, I'll take it for a run and report later on. Regards, Tommy |
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Post by dave1800 on Jul 23, 2011 9:42:06 GMT
So sorry to hear the dreadful news from Oslo. I'm sure everyone here feels the sadness and send their sympathy to the families.
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Post by Penguin45 on Jul 24, 2011 12:19:39 GMT
Appalling tragedy. Puts our little car problems into perspective.
Chris.
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Post by tommydp on Jul 24, 2011 19:47:58 GMT
Appalling tragedy. Puts our little car problems into perspective. Chris. In deed, in deed.. It really puts things into perspective. It's been a horrible weekend, still hard to believe it has really happened:-( Regards, Tommy |
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Post by tommydp on Jul 27, 2011 19:38:41 GMT
Well, I've spent lots of time again trying to solve the problem. I guess I just have to face it. I won't be able to fix this car. This has really become a nightmare.
No matter what I do, it's hesitating/ missing, especially at 70- 75 kmh, also going downhill with throttle closed. It's also missing under load. It's still hunting occasionally at idle, missing now and then, idle drops then catches up again. This also shows on the tachometer (Gunson Testune) Dwell angle is stable.
I don't believe there's a vacuum leak. Changed all gaskets between carb and manifold today, installed a heatshield from a Princess at the same time. Tried different carbs and needles again, float level is fine, using the complete float lid from the Marina now. I've checked the brake servo for leaks, can't find any.
I've tried two different other distributors too, no change. Different condensers, red rotor arms, different points, to no avail.
I even had a look down into the fuel tank, it's absolutely clean. The in tank filter looks clean too. I've centred the jet, the jet is new, there are no leaks. Tried both with spring loaded needle as well as the other.
It's still difficult to get steady behaviour using the lifting pin. Seems as if the mixture changes. I've tried over and over again adjusting the carb according to my SU manual. If I enter a slightly rich setting, the stalling will be even more obvious. To make it run as smoothly as possible I have to find a rather weak setting. Even then it will cut out irregularly.
Well, I'm more suspicious when it comes to the electrical system. All coils still get hot at idle, and it seems the problem starts as soon as the coil starts to heat up, which is about 5 minutes after starting. This is the only obvious clue I've got. But I can't see what causes this when everything has been checked over and over again..
Regarding oil smoke, there is none when revving adn there's no sign of oil on the plugs after driving. Inside the exhaust pipe there's only a light coat of completely dry sooth. There's an occasional puff of smoke after going down very long hills with throttle closed though. Happened withouth the breather attached too. I suppose there could be an valve guide issue then, but I find it hard to believe that causes the other problems.
Well, this has truly become a nightmare and I have ran out of ideas. It's a sad situation really, as the car is otherwise excellent and looks stunning. I just can't spend more time and money on it, however I won't rest until I solve this.. I'm awaiting a Sports coil (lucas). However I doubt it will improve things, after all the coils I've tried.
Regards, Tommy
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Post by dave1800 on Jul 28, 2011 3:38:06 GMT
While you're waiting for the sports coil to arrive, warm up the engine to the point the problems start then immediately swop coils to see if the coil heat is actually playing any part or not. Also rotate the distributor (advance I would suggest to start with) to see if another setting overcomes the problem. If it does double check again that the TDC pulley mark is corrrect and if not reassess the valve and ignition timing. Good luck regards David Well, I'm more suspicious when it comes to the electrical system. All coils still get hot at idle, and it seems the problem starts as soon as the coil starts to heat up, which is about 5 minutes after starting. This is the only obvious clue I've got. But I can't see what causes this when everything has been checked over and over again.. Regards, Tommy |
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Post by tommydp on Jul 28, 2011 23:06:21 GMT
Another day spent with the crab:-) I checked with a cool coil, when misfire started, no change.. Tried to advance the timing, no change..
Had a look at the carb again. For some reason I've managed to install a jet bearing meant for the spring loaded needles, ie not meant for centering the jet.. Actually I found out today there are two kinds of jet bearings. I can highly recommend the book "SU carburetters, tuning tips and techniques". So put in the correct bearing, centred very accurately the standard ZH needle. I'm using the correct jet. A set of Champion N9 YC plugs arrived today, so installed them too.
Adjusted the carb again and it actually ran somewhat smoother at idle, even when hot. It still seems to need a somewhat weak setting to run smoothly. When I obtain the "fastest, smooth idle and then richen it by one flat.." there's a noticable drob and it will miss at idle. It's very different from what I can remember from others, where you could turn several flats befor noticable difference. It seems to need a vary accurate setting, this one.. However, it's still hesitating and missing on the road as before. The engine runs sweetly and is powerful, but cuts occasionally as if starving for fuel, or spark. Rolling down hills with throttle closed, at light throttle and going up hill. I've tried to pull the choke when it occures, but there's no change. That's why I still suspect the ignition, or perhaps the alternator?
I'm now using a Lucas 16 ACR. The engine is very quiet at idle after installing the new rocker shaft, and no- the valves are not too tight:-) I seem to hear a rumbling noise from the alternator, which matches the miss at idle. Also, the voltmeter drops when this happens. But is it the engine causing the alternator to do this, or the other way around.
I've had some issues with the 16 ACR alternators on it. I wonder if something after the earth conversion makes them go bad? They all whine somewhat more than usual and one new one made the lights flash after a while. Took it for testing and they found it ok. I believe the wiring is correct, it's quite simple after all and I've converted other crabs before without problems.
The best alternator seems to be the 70 A Bosch unit. I's quiet and provides a relatively stable voltage. The ACRs seem to change all the time, from just above 12 when using headlights, heater, HRW etc, to 14,4 when revving. So I think I'll go back to the Bosch again, if it won't harm anything, as it puts out 70 A, compared to the ACR's 34 or so. I'm no expert on this so don't know..
Well, I have a feeling I'll crack the problem soon.. About b.... time, for sure:-) I'll never make up a car from bits and pieces again:-)
Regards, Tommy:-)
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Post by dave1800 on Jul 29, 2011 0:43:54 GMT
As you say these engines are usually very tolerant to the carburretor adjustment. Why is it so sensitive? Are you 110% certain that the jet is centred and the needle is straight so that turning one flat of the adjustment nut doesn't prevent the needle dropping?
If you suspect something strange from the alternator, try disconnecting it (the connection plug) briefly and see if there is any change. Not very likely, but running ot of ideas!
The fact that the voltage varies with load on the ACR is normal, as it's relatively low power whereas the Bosch delivers more current so isn't loaded so much, maintaining the voltage. I guess in your winter climate the Bosch is a better alternative.
I now feel I am as involved as you in trying to sort this out!!
regards
David
[quote author=tommydp board=general thread=189 post=1191
time=1311894381]
The best alternator seems to be the 70 A Bosch unit. I's quiet and provides a relatively stable voltage. The ACRs seem to change all the time, from just above 12 when using headlights, heater, HRW etc, to 14,4 when revving. So I think I'll go back to the Bosch again, if it won't harm anything, as it puts out 70 A, compared to the ACR's 34 or so. I'm no expert on this so don't know..
ieces again:-)
Regards, Tommy:-)[/quote]
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Post by dave1800 on Jul 29, 2011 5:52:49 GMT
Tommy this is starting to bug me! The problem must be staring us in the face but I just can't see it either! It sounds as though the engine is being choked at idle. If so that may point to the crank breather, can you blow backwards down the tube into the crankcase - try it with and without the filler cap in place? But, as you seem to have a bit of a mix and match carb are you sure you have the correct piston spring and not one from a twin carb set up which are only around half as strong? You will probably need to test it as the yellow colour is likely to have disappeared by now. If you have the wrong spring it will be impossible to tune properly. regards David Another day spent with the crab:-) It still seems to need a somewhat weak setting to run smoothly. When I obtain the "fastest, smooth idle and then richen it by one flat.." there's a noticable drob and it will miss at idle. It's very different from what I can remember from others, where you could turn several flats befor noticable difference. I Regards, Tommy:-) |
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