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MGB 1st MGB-1st Ride-1st Trouble

PRBrauer

Freshman Member
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I am an MGB newbie. Picked up my 1971 MGB tonight. Got almost home with it when it began choking out. Seemed to be running on only a couple of cylinders. Somehow managed to get it home. Sad after the excitement of fulfilling a 30 yr old dream. Anyway I have no experience but feel I am about to set on a new educational route. This forum looks like a good place to begin. Here's the best I can do with regard to explaining the symptoms. The car ran fine for several miles after picking it up (however it was not good at idling at all). Then it began to sputter, I guess it reminded me of my old days with fouled spark plugs on a 2-cycle motocycle engine. It got progressively worse. At one point it just died. I pulled on some of the spark plug leads to see if it was maybe bad connectors. Must have been stopped 5 min. I got it started and in fact it ran okay for about 50 feet and began to die again. Managed to get in the driveway. I pulled the plugs and discovered that plug 1 looked wet with fuel, plug 2 was not as bad, plugs 3&4 had a nice rust brown color and were dry. I know the car has a new fuel pump. Haven't had a chance to crawl under it yet but it's likely 3rd party. Inside the hood by the fuel line is a Purolator fuel regulator, set to #2 (whatever that means). Could the fuel pressure be too high and that's what's killing cylinders 1/2 since that carb is the first in fuel line?. Maybe it's as simple as changing the pressure setting (could that also cause the bad idling?). Have no idea if the high number on the regulator means more or less pressure. The car has SU-HS4 carbs. Since I am new to the forum I hope I haven't run on too long. Any suggestions for a rookie that is diving into the mgb tech jargon would be greatly appreciated. Hope to get some driving in before winter gets here.
Thanks to all.
 
I really want to help but there are so many equations here and the car has an unknown history. Can you tell if it's fuel on the spark plug or if it's oil or coolant? Fuel delivery could certainly be a culprit. Is the fuel filter clean? I'm not sure if a '71 is the same as an early car but if it's the same, check to make sure the heater valve, located above the distributor, isn't leaking into the distributor. If so then this is your problem. See if you can make the problem reoccur, and immediately remove the distributor cap. If there is any moisture then it's probably the heater valve. Keep us posted!
 
At this stage, the possibilites are many. I'd check resistance on all of the plug wires, particularlly #1 & #2, as those seem to be the problem cylinders. Check the cap for cracks and evidence of carbon tracking. Take that fuel pressure regulator and throw it as far into the night as you can, as those types are junk.
Either install new plugs, or thoroughly clean and dry the old ones, and try again.
Has the car been sitting for an extended period of time? Was the gas fresh?
Lots of things to think about at this stage.
Jeff
 
Wow! This is the place. I will give all the suggestions try. The car was not sitting. But the previous owner only had it a couple of months. He said he only put about 120 miles on it. I had test driven it about 10 days ago and other than the poor idling, it ran quite well (I had an experience MGB man with me to look it over too). I actually called the PO tonight to see if he had any such experience with the car and he said no and said he was sorry that it had happened. With regard to the reply to my post that the heater may be dribbling on the distributor-- it is in such a configuration where this could happen. In fact the PO pointed out that that had just happened to him with his other MGB. There is no evidence that that is the case here but I will give it a closer look tomorrow. I will also look closely at the plug wires. What was meant exactly by the term "carbon tracking"? Is this a black powdery residue on the plug wires at the distributor connections or somewhere else? Would that be an indication of a bad connection or distributor problem? Thanks
 
A note on the heater valve... if no drip is apparent it can still dump coolant all at once if you move the heat control. That's what happened to me once in my MGA. It was running great, and as soon as I moved the heat control the car died.

If your symptoms are related then it's probably ignition-related. Another thought, have you done a compression check? That can tell a lot about an engine.
 
Along with the other replies, I agree there are a host of elements to look at with the aftermarket fuel pump and such. Let me offer some items to look at from the viewpoint of someone that has had some As, Bs and Cs --- all with SUs.

First, check your dashpots on top of the carbs for oil. Even if they show oil in them, could be old and thick. Shoot 'em full of WD40. It might loosen them up. Don't run WD40 all the time in the dashpots, but it helps once in a while. Second, check that front carb mixture. Underneath the carb (should have a black plastic end on it pointing down) you'll find the adjustment. Good idea to spray the spring with WD40 and clean it up a bit. Rotate the 6 sided nut until it's snug to the spring and back it out 11 "flats". That's almost 2 full turns. That should be close. There are lots of other possible causes, but those are a couple to look at.

By the way, that nut on the carb is tough to work with. Haven't checked the catalogs these days, but still have an "SU wrench" in my tools. You'll note the thickness of the nut and how a normal open end wrench is tough to navigate in there.
 
Well, I might as well throw my 2 cents in. My personal experience with the heater valve dripping was that it didn't just effect 2 cylinders, it filled the distributor cap with moisture and the whole thing quit and wouldn't start.
While I agree that plug wires could cause a problem like this, when was the last time any of you had two right next to each other go at exactly the same time? Unless the insulation broke down and they were arcing between each other.
It sounds to me like the carburator that feeds these two cylinders has a problem. Set too rich, float going bad and slowly filling up with gas or set wrong. You can remove the float and shake it while listening to see if there is any gas in it then reset the heighth. If the float is the foam type and not brass, take it out and "throw it as far as you can into the night."
The suggestion on the fuel pressure is also one to look into. If there is an aftermarket fuel pump on there maybe there was a reason for the regulator and the fuel pump puts out too much pressure. 2 lbs should be OK. If that regulator on there is trash, maybe you should check the pressure without it to see if you need a regulator and maybe Jeff can tell you which kind is best. Or go back to a stock pump. I did that after trying an aftermarket pump that only lasted 2 weeks. The original is still on there after rebuilding it and running great.
Bob
 
Bob, I have found that the Holley low pressure regulators are the way to go. You set them, tighten the locknut on the set screw, and you're done. They also have an extra port, so you can run a gauge, individual lines to the carbs, or whatever. About 30 bucks, and well worth it. Another plus is that they are rebuildable.
I have either had, or seen, those dial types come apart and spray fuel everywhere, or the dial will move, throwing the fuel pressure out. Junk, in my estimation.
But, both carbs feed all 4 cylinders, not front/front 2, back/back 2. That is the function of the balance tube on the manifold. Look at the firing order, and the valve timing.
Somewhere here I have an article that addresses this common misconception, and explains what really happens. I'll try and dig it out, and quote the relevant passage.
As far as the plug wires go, I would say it would be a rare occurence to have two adjacent wires fail simultaneously, but if the cap is carbon tracked on the inside, or if there is a short between the two wires, it would cause the symptoms described.

Jeff
 
This may not be everyones method but when I buy a car new to me which is not acting exactly proper, I replace the plugs, plug wires, points, distributor cap, condensor, fuel filter(s) oil, oil filter, check the timing, fuel is new and clean, air filter(s) etc.

Now I know where I stand with the car.

Bruce
 
Thanks, Jeff, I would really like to see that article. I didn't even think about the cross over tube. So you are saying that even if one of the carbs was way out an flooding the engine, it would effect all cylinders the same?
OK, on the carbon tracks in the cap. Yes, that could conceivably cause that. I know electricals can cause some weired probablems and replaceing everything electrical would eliminate all that but I guess I spent too long troubleshooting electronic circuits and I have this basic need to know what exactly caused the problem. Just me I guess plus I don't like to spend any more money than is necessary to fix the problem.
Bob
 
spark plugs wet on two cylinders next to each other....sounds like it might be a blown head gasket to me and the wet is coolant.
 
[ QUOTE ]
... I replace the plugs, plug wires, points, distributor cap, condensor, fuel filter(s) oil, oil filter, check the timing, fuel is new and clean, air filter(s) etc.

Now I know where I stand with the car....


[/ QUOTE ]
I agree with Bruce on this one & would do most or all of these things regardless of how the car is running. The problem(s) you have can be caused by any number of things but most common causes can be eliminated by an afternoon performing basic maintenance.
 
The discription of poor running and failing could be a number of things. However, plugs 1 & 2 wet and plugs 3 & 4 dry indicate that the problem is with the front carb. If the float is sticking open it will flood the car out. Since the car had been sitting for a while, I would order a rebuild kit for both carbs and rebuild them both. Check to see if it has a fuel filter in the system anywhere and replace it also. This is a simple diy job that could be done on a weekend day. It is not a bad idea to replace the plugs, points/condensor, rotor, dist cap and wires. Change the oil and filter and finish by flushing the cooling system. Adjust everything and you should be set for at least a year. Put the top down, take a drive and have a cold one.
 
I want to thank everyone with the suggestions. My acting on some of them will depend on how quick I can get in all the parts in (ie., rotor, points, plug leads, etc) to replace on my "B" to as some suggest "know the history". Since I really haven't had oily gasy hands since college, I don't even have a oil collection pan. Unfortunately I will be out of town for several days and will not likely get all this stuff installed before the current driving season is shot. For new newbies, everything takes longer. Heck it was a trying experience to get the air filters back on--Geez what were they thinking in '71.

I did notice that a spring leading to the heat shield to the front carburetor choke linkage was missing (was there on the rear carb) and that the throttle spring on the front carb was a bit stretched looking. The rear carb throttle springs look good and all in all the return on the linkage seemed to return the carb to its baseline position well. Have no idea if that would make any difference. Had the floats out and they did not slush so I don't think they are leaking. Move the float up and down too to open close the needle. Restarted the car after. Seemed to be running on all cylinders but still not sounding right (don't have a basis to compare-- my first MGB). However, its hard to tell as the exhaust seal is shot and I hear a lot of blow by-- and get a lot of exhaust smell. In fact I still smell that way. Again I need some parts and tools, don't even have a jack and stands yet much less know where to place them. I know it will all come together eventually--- after all I got all winter and a great forum group. Cheers everyone. /ubbthreads/images/graemlins/yesnod.gif
 
OK, good luck on th troubleshooting. We will be glad to help all we can and would like to know what the problem was once you get time to find it.
Bob
 
Hi,

If you wish to check the state of the ignition wires then check their resisitance with an ohm meter less than 50,000 ohms is considered satisfactory. I would replace all the spark plugs without question. For the carbon tracking, this is funny black ridges you see inside the dist. cap. Also hold this up to a bright light and examine for hairline cracks - replace if seen. Normally such would cause general rough running.
 
Hi, Sorry I forgot to add if coolant is being sucked into the engine you would quite know, as there would be a huge cloud of white smoke from the exhaust and a sweet odour. I suspect that the problem is in your ignition. One real possibility is a failing points and condenser.

Cheers.
 
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