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MG MGB Technical - Help how big of a hole to bury a B

Compression test results dry only are as follows #1. 105 #2. 100 #3.105 #4.100 test was done with all plugs out and pedal to the floor. Car was warm to cold. Problems have been hard cold starts but running fine when warm with 70lbs pressure when driving and 60lbs at idle. Now the car will not stay running and fouls the plugs black. If I clean the plugs and try again the car will start but the oil pressure is relevant to rpms. Then the car dies slowly looses rpms and the car dies.
The car is a 77-mgb 92000 miles 20 % of wich are tow miles. I do want to fix it the bury bit was just a joke:))

Thanks for the Help
Gerry
Gerry

Gerry:

Since you live in arizona, I assume the car has no rust. Since it is rumored that heaven is in Canada, and all good (non rusty) MGs deserve to go to heaven, I could drop by and collect it at your convenience. No need to hurt your back digging with a shovel!
:-)

Pete


OR call Bob at Britt-Tek; they (There are two Bobs running the place) seem to be on top of the engine re-build kit list as far as I am concerned. If you have a crank, a block and a head casting, Bob has a comprehensive kit to put it back together at whatever cost and power level you desire. If you are comfortable with doing business overseas, call Chris at Octarine. MOSS and VIC are great at what they do, but they are not really suited to the uninitiaded because of the lack of continuity with advice and/or product support. Just my 2$worth

Pete
Pete

Sounds like a carb problem... too rich. Compression is likely OK, although a bit low, but it should be re-checked when at full temp. The important thing is that they are well matched. If it ran OK before, I'd look to the carb - it is still the ZS carb in there?

Dave
Dave Whitehead

Dave
The car is stock with a single zienth.But a month ago the carb was running lean ???what do you thing about the oil pressure and rpms at idle

Gerry
Gerry

The oil pressure's fine, even on the high side, and is usually related to rpm.

The compressions are nice and even, it would be worth trying another guage in case that one's low. The numbers are lowish if it's a low comp engine (130), or knackered if it's high comp (170). Try the comp test again with a teaspoon of oil down the plug holes and see if it improves. If so it may be bore wear, if not it may just need a valve job.

All or not much of this, may be to do with how it's running. If it is knackered you are desribing oil fouling of the plugs. If it's not then it's too rich, the spark's weak (points/condenser/coil/leads/caps) or the timing's retarded. Rich.
Rich

I agree with Rich -if you are going to keep her anyway - start by replacing ALL the electrics; coil, leads, dizzy cap rotor - reset the ignition timing/fuel mixture. if that produces a satisfactory result then plan to change the timing chain - in the foreseeable future.

Approaching 30 years - the old girl probably needs a new head gasket - and that might be a good time to regrind the valves.

If you have to probe further (which I wouldn't expect)-rebore is not without risk. Re-hone with new pistons and rings or just rings is another medium term, much cheaper solution.

RW

RMW

Gerry,

It really sounds like a carb or fuel pump or ignition problem and I would check all of these first. Nothing that you mentioned would indicate to me that there is any internal engine problems. The compression numbers do sound a bit low, but this could possibly indicate that the carb is flooding and washing down the bores and spoiling the compression at the rings. At only 93,000 miles I would be surprised if the problem is anything internal.

Good luck,

Cliff

Cliff Maddox

Update
One thing that is rather odd is I checked the oil level and the dipstick has no defining reading or level line. It is just covered with oil. I checked the coolant and coolant level and it is exactly were it was three months ago when I topped it of in the over flow tank and appears to be clear (Light green) without oil deposits in it. Checked the oil level two weeks ago and topped it off to max. Added about a ¼ quart. ?????

Gerry
Gerry

Gerry: Sounds like your carb is causeing all your problems don't take youur motor apart until you check your carb Ric
R E L Lloyd

Update
My oil level is twice as high as it should and is very thin that is why I couldn’t see a level befor. I smelled it and it smells like Gas. :( ???????

Gerry
Gerry

OK the carb is flooding. Fix the carb & change the oil and you will likely see the compression come up within minutes. Your compression readings are still balanced so you've not have cracked any rings (yet)....good chance you can correct this and be good to go with no damage.

Cliff
Cliff Maddox

Yes, agreed with Cliff, and don't even turn it over again til you correct the oil level Gerry, drain it asap, as you risk all kinds of problems inc leaks and hydraulic lock-up.
Rich

Ok
Should I turn the needle on the cab as lean as it goes and work down from there. Or at least one full turn from total lean. Also how can I know if any damage has been done as of now? My other thought was why is it so rich could the float bowl be messed up or maybe a problem with the charcoal canister.
Also all this happen after I cleaned the carb with carb cleaner I sprayed with nozel down the needle inlet and in the hole just behind the needle inlet toward the manifold. And changed my charcoal canister.Befor that my carb was running lean so lean I could not make it rich and I had the needle all the way to enrichen. Is it possable that I blew out dirt and now the carb has a good fuel outlet.

Gerry
Gerry

Gerry, I suggested that you contact Early Automotive Services at 480-474-4027 to have them put you car on their engine analyzer and exaust gas analyzer to see what is really happening. Have you contacted them??? There were several needles used with your Z-S carb over the years. You need to find out what needle you have, what needle you need for best performance and what needle you need to have to pass the Arizona Emissions Testing. These may not be the same needles. Thus, you may have one needle for emissions testing and another needle for driving. You need professional help in diagnosing your problem, as I have told you in the past, and, without it, you will not be able to solve the problem in an effective manner. Les
Les Bengtson

Oil level twice as high as normal? Thats a LOT of gasoline in the oil. Could the carb cleaner have eaten a hole in the fuel chamber float? Is there any other way for fuel to be sucked into the innards (Southern-speak <grin>) WITHOUT it going through the manifold. Damn Z-S's anyway - - Alec
Alec Darnall

Sounds like the carb is flooding...nothing to do with running rich or lean or needle choice. Almost certainly some defect in the float or metering valve letting raw gas por down the carb and into the bores, past the rings and into the sump. I'm not familiar with the later carbs but can you look to see if the float is still floating? Floats on early SUs can fail and sink to the bottom of the float chamber and produce just this problem.

Best of luck.

Cliff
Cliff Maddox

All the info is in Haynes but you need some special tools for a complete strip. If you want to try yourself check for a holed float and the float height and for the needle valve leaking. It could be a VERY rich mixture - if it's possible to set that rich - but my best guess would be automatic choke stuck on. That would pour unburnt fuel down the bores. There'll be a fundamental problem to fix and a tune up to do following. As Les says this could be a good job for an expert in these carbs, don't waste your time with anyone not familiar. Rich.
Rich

Les thanks for your help. I haven’t brought the car to them because I am concerned that they are not an mg specialist and have 0 Parts on hand to fix the problem nor do they understand Zenith carbs. When I called them to help with my lean problem they didn’t even have a proper carb adjustment tool. And admitted they don’t know much about the carb. I know they could do all other work fine with the Haynes manual that I would have to provide. But I do believe this is out of their league. And yes it is way out of my league. But I am hoping I can check the obvious first. Rich I converted to a manual choke about 6 months ago and I haven’t touched it. Visually it looks to be off from the front of the housing. Is it still possible that it is on? or slipped

Thanks Gerry
Gerry

Gerry. You may remember that I have recommended both Bob and Gil Schaulin, who both have tuned Z-S carbs and have the tools and manuals necessary. I have also mentioned that Ernie's Brit Cars, in Tucson, does excellent work and have the necessary tool and manual. You felt that Phoenix, a 45 minute drive, and Tucson, a two hour drive were too far away.

The Earlys have worked on a number of MGs over the past few years. They do not have the special Z-S adjustment tool simply because very few people, especially when emissions testing time come around, decide to keep the original carb. The Earlys have demonstrated the ability to tune SU carbs, very similar to the Z-S and to get the owner's cars through emissions testing. They have a fully equipped shop, including lifts, a five gas exhaust analyzer and an engine analyzer.

If you are unwilling to take your car into one of the professional shops willing to work on MGs, you will have a significant problem in dealing with your carb problem. There are no hobbyists, that I am familiar with, who are knowledgable on the set up and tuning of the Z-S carb in our local area. Most of them take their cars to Bob and Gil's to have the carb set up properly.

Since, over a series of months, you have not been able to get your car sorted via the internet, I would suggest professional help might be necessary. Les
Les Bengtson

The oil level sounds like water in the sump. You might not see it on the dipstick or notice the loss but if you top up the expansion tank and then squeeze the top hose you will hear whether it blows bubbles and sucks in fresh water. If that it the case - don't start her whatever you do.

let us know the results

Roger
RMW

Update
I drained the oil and measured it at 5 quarts I know I put in 3 and ¾ quarts to fill at max last oil change So that means I have 1 ¼ quart of something what I believe is Gas. The smell of the oil is gas and thin. There is no water oil droplets in the drained oil. So I filled her with new oil and filter. Put everything back and will take the car to a shop on Monday a.m. I will let you know.
I would love to try to fix her on my own. But am tapped of knowledge. On a better note. I just finished total redo of interior and the Vic Brit seats kits are the balm. Looks like she just drove of the lot in 1977.


Gerry
Gerry

Gerry,

This is a problem I see on 1500 midgets - do you still have and electric fuel pump or has someone fitted a mechanical one on the side of the block?

In the Midget the diaphragm splits and lets neat fuel into the sump!
Chris at Octarine Services

Chris
electric fuel pump

Gerry
Gerry

<<I converted to a manual choke about 6 months ago and I haven’t touched it. Visually it looks to be off from the front of the housing. Is it still possible that it is on? or slipped >>

Yes, get someone to work the control and see if it's moving correctly against the fitting instructions for the choke kit.
Are there any signs of flooding/leaks or smell of petrol outside the carb?
Excess fuel is the problem but it could be the fuel supply that is too great or a restriction that causes a lowering of pressure and hence too much fuel to be drawn from an otherwise OK carb.
Hence check for dirty/blocked/wet air filer element and any obstruction in the air intake such as a damaged air temp control valve.
Rich.

Rich

I had a similar problem where the car suddenly ran very rich and would stall out. Turned out to be a tear in the diafragm on the Z-S carb. I didn't have any extra fluid in the sump though...

Did you take the top off to spray in the carb cleaner? Possibly when you put it back on it split, or it did not seat correctly.

- Phil
Philip Coburn

Gerry,
I had the same problem, however with min. gas in the oil, it was a combination of a tear in the diafram and debris in the needle or float bowl. I had rebuilt the carb. only 6 months prior, however the ZS carbs are so particular they will stop for any reason. I tried everything, then rebuilt in again and it worked perfect. I don't think I will have that problem again however, I just got a Weber Carb. new intake and exhaust manafold. By By ZS!
Neel
N Choate

Well the car is home and running good.
Had the carb cleaned float level adjusted new needle and seat Valves set and timing.
By a specialist. The car now starts from dead cold first turn of the key. And no longer coughs from the carb. Freeway speeds of 65mph with room to go. Idle is better but not perfect.
Well worth the money spent.

Thanks to all
Gerry

Gerry

Gerry. It is far easier to keep a car running well than to have to sort all of the problems yourself. Particularly when you are just learning. You showed a rare form of wisdom by getting the car professionally repaired so that, now, you can learn how it should be tuned, then learn how to do the work yourself. Glad you got it up and can drive it again. Les
Les Bengtson

Les thanks for your encouraging words. Lets get together soon I would love to show you my new seat kits I installed.

Gerry
Gerry

Gerry. And I should love to see them. Am just having that job done on my daughter's 77. Give me a call at your convenience. Les
Les Bengtson

This thread was discussed between 19/03/2005 and 27/03/2005

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