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MG MGB Technical - Won't Start

This is my first question to the thread, although I have been using this as research for years. Archives are'nt helping.
Problem, 1970 B won't start. Getting good crank, but won't catch.
-electrical, new points and condenser.
Getting spark on all plugs.
Distrib was static timed, and then have tried moving it all over the place at fractions of movement at a time. Getting about 11 volts to the coil. Have tried different coils and condensers. Rotor has been set pointing to #1 at TDC so it is not 180 degrees out. Wires are in proper firing order. Rotor cleaned. Distrib has been closely inspected for proper wiring on post with good fiber washers. Point gap set at .015.
-Gas, carbs completely cleaned and jets set proper.
See gas in jet and have tried spraying with starter fluid but nothing changes. Choke works properly. Plugs are good visually and wet with gas.
-Compression weak, but should be good enough to start. Highest is 126. lowest is 98.
Any thoughts on what I am missing?
Bradley Dryden

Is it firing at all while cranking? If so with wet plugs it may be flooding due to faulty float bowl needles and seats. If it is not firing at all it would still appear to be electrical unless the timing chain has jumped teeth, this could also affect your compression readings
John H

OK. Lets go from basics here. Turn the engine over to TDC No1 firing stroke. Remove the rocker cover and move the crankshaft ensuring that rockers 1 & " dont move but that 7 & 8 "rock" If not, turn the engine one full revolution to achieve 7 & * rocking. Now turn the engine back half a turn and then forward to 10 degrees BTDC. It really doesnt matter about this setting as timing for starting is not critical and the engine will start anywhere between about TDC and 20 degrees BTDC but let's get it about right. Now slacken the distributor and and rotate it anti clock then turn on the ignition and rotate it clockwise until the points just spark on OPENING. Make sure that it is opening and not closing. Lock the distributor. Take the main coil lead and place it near to the cylinder head and if you open and close the points by hand you should get a fat blue spark between the lead and head which should extend to about 1/2".
The rotor should now point at the five/ten past position position when looking at the dist face on . Fit the cap and the lead at the position which the rotor is pointing to should go to cyl 1 with the remainder being 3, 4 & 2 in an anti clock direction round the cap. I should have said fit a new cap and new leads or ones from another running MG.

Fit new plugs gapped to .028" and pour about 1 teaspoonful of petrol into each cylinder !!

Pull the choke out fully and if the float chambers are full and the jets approx one turn down from flush with the bridge the engine will start.

Good luck
Iain MacKintosh

Thanks John and Iain. Did as you had suggested but other than the gas down the cylinder which scares me, still no start. Seems like it wants to catch, but won't. Can you think of anything else?
Bradley Dryden

Bradley. Should we call your Bradley or Brad? We are, for the most part, a very friendly group around here. A group who comes together because we like things MG and like to share what we have learned with others while learning from them at the same time.

I would refer you to my website, www.custompistols.com/ for some general information. The MG section has some good tech articles on it which may be of use to you. Iain has a good description of how to find top dead center, on the compression stroke, of number one cylinder--the one we use for timing purposes. I provide the same basic information that he has, but do it in a different manner. Often, something said one way does not make sense, but, said another way does. Re-read Iain's post and, please, read my article on ignition timing, then re-check to see that you are timing properly. If you have any questions, ask them here.

One area which has not been addressed is the spark plug wires. There is a tech article on how to test them on my site. When I lived in Germany, I went over to the house of one of my fellow officers to help him get his car started. He was not used to winter weather such as we had there. Having been transferred there from Wyoming, I was somewhat familiar with severe winter weather. Everyone who had helped him before thought the mere fact that you could get a small spark from the plug wires would be sufficient to allow the car to start. This is not true in my experience--you need a strong spark and modern wires will, over time, break down and show their worst when things get cold out. He replaced his spark plug wires and the car started with no problems. Therefore, please check your wires and let us know what you find.

One trick that was used, up in Wyoming, during the winters was to change to a slightly hotter plug for use in Winter. The NGK BP5ES is, I believe, one stage hotter than the BP6ES that most of us run. It might be worth considering. Also a good idea to take a good look at the plugs you already have. If they are carboned up they will not work well for starting and will cause the engine to run poorly. As Iain mentions, a new set of plugs, properly gapped, is always a good idea when there are starting problems.

I have no problem with removing all of the spark plugs, then using an eye-dropper full of gasoline squirted into the cylinders before installing the plugs and trying to start the engine. The worst that can happen is the engine will not start--I have not found any other dangers. I have also squirted raw fuel into the intake manifold before trying to start. If the car starts briefly, it is an indication of a fuel system problem.

David DuBois has a couple of tech articles on the fuel system which he has allowed me to post for him. Dave has an article on the SU fuel pump which includes both fuel pressure and volume specifications. He also has an article on fuel system trouble shooting. Just seeming to see fuel in the jets may not be enough to allow the engine to start. Make sure you have sufficient pressure and volume to supply the proper amount of fuel. I remember, back when young, we would add "fuel line anti-freeze"--alcohol, to the gas tank at the beginning of winter to absorb any water which had collected over the year. Living in Michigan, which I remember as being somewhat humid (what is not compared to the desert I live in?) you may have collected some water in the gas tank and it may have frozen, blocking either the pick up tube in the tank or the line running from the tank to the pump or pump to the carbs.

With the information already provided, the information on my website and a fully charged battery (do put it on a charger for a while to make sure it is fully topped up) you should be able to either get the car started or to narrow the possible problem areas significantly. Let us know what you find (or, even better, that the car has started) and we will provide such support and ideas as we may be able to.

Les
Les Bengtson

Big vacuum leak somewhere in the intake
manifold?

Stuck carb dashpot pistons?

Just throwing out a couple of thoughts at 1:30 AM.
Daniel Wong

You say that the car is trying to start now and I've seen this before on a B and even one that had good compression. Your engine is in fairly poor shape and this will do nothing to ease starting. Just pour some fuel into each cylinder and I'm fairly confident that this will provide the help it needs to start up. As Les confirms there is no harm in doing this as the plugs are in and there is no risk of explosion. Make sure that the air cleaners are also fitted just in case there are burnt inlet valves and the engine tries to spit back through the carbs.

Good luck and keep us posted.
Iain MacKintosh

On a non-starter the first step should always be to check the HT, and this is best done by clipping on a inductive pickup type timing light to the coil lead and each plig lead and watch the flashes while cranking. No coil lead flash means go back to the ignition LT with a volt-meter or test-lamp, or it could be the coil. Flashing on the coil lead but not the plug leads indicates cap/rotor problems - none of the plug leads probably rotor, just one or two plug leads probably the cap. If they are OK point the light when on No.1 at the timing marks and make sure it is at about 8 to 10 degrees BTDC. If that's OK take out the plugs and inspect them. They should have a strong fuel smell after cranking a bit but not be wet, which means they are flooded. No fuel smell means no fuel is getting through ... did the pump chatter when you first switched on the ignition? If flooded crank with the choke pushed home and the throttle wide open, and it should fire, be ready to release the throttle and *half* pull the choke. Of course, if you have been fidling with the car since it ran last it could be anything, and plug lead order should be the first thing to check - 1 3 4 2 anti-clockwise ... assuming you know where No.1 lead goes in the cap!

A few days ago my Toyota wouldn't start, on a day that was just above freezing, everything soaked in condensation, after not having been run for almost a week. In that case it cranked normally, fired once, then cranked with an unusual noise. HT and fuel were OK but one of the compressions was right down, and the battery was only showing about 8v even though the cranking speed seemed normal. In the end putting the battery on charge for a bit upped the cranking speed and battery voltage, and it was obviously trying to fire every now and again. Kept at it and eventually it staggered into life, but roughly, sounded like an exhaust valve was sticking open. Eventually that cleared, and since then it has been fine as normal. Just goes to show that a combination of factors (weather, soft battery, sticking valve) can gang-up to make a non-starter whereas each on their own would probably not have done so.
Paul Hunt 2

Hey guys, just wanted to express my gratitude for your help. As usual, it was a very simple and of course, the last thing I tried. Spark plug replacement. Even though the old plugs looked just fine, replacement of them fixed the problem and it purrs once again. I would have never thought the old plugs were bad by a visual inspection. But that was what it was. Lesson learned. Again, thanks!!!!
Bradley Dryden

Let me also say, that what fooled me, was not only visually seeing what I thought was a good electrode, but also seeing what I thought was a good spark using both an in-line ignition spark checker as well as viewing the spark coming across the gap. Now I know to always start the analysis with new plugs. Just thought I had better clarify so you did't think I was a complete idiot
Bradley Dryden

Hi Bradley.

I'm glad that you have fixed the problem, and I'm quite certain that no-one thinks you are an idiot.
May I ask what plugs you were using ?.

I ask because it interests me to investigate what was actually wrong with the plugs. Assuming that a plug has a more-or-less correct gap and is reasonably clean, why should it nor work properly ?.

I know that a spark is more easily triggered if there is a sharp edge on the electrodes, but I can't believe that this will cause a non-start situation.

I guess that the resistor might go open circuit in a plug which includes one for interference suppression.

Do plugs go open circuit (hard to imagine how, for a non-resistor type anyway).

Does their insulation break down so that the spark energy is diverted away ?.

I really would like to know, not for any important reason other than curiousity !.

Don
Don

It is easier for a spark to jump the plug gap at atmospheric pressure than it is at the higher pressures inside the cylinder after the compression stroke. It is therefor very possible to see a good spark at the gap with the plug laying on the head and yet not get a spark with the plug installed in the head. Cheers - Dave
David DuBois

Bradley. Glad you got it started. When I had my first sports car, a 61 Sprite Mark II, I used the factory recommended Champion plugs in it. I had access to an auto hobby shop at the Air Base across the street from where we lived and would pull the plugs about every 3K miles, clean them in the plug cleaning machine, then, test them for spark under load on the same machine. Amazing how many of the plugs would not spark strongly, some not at all, under compression after less than 10K miles.

The NGK BP6ES is the preferred spark plug of many of us. Roger Parker, back when he frequented here and before becoming the chief of tech services for MGOC, recommended them to me and I have used them, exclusively, since. Last tuned up my 79LE two years ago before emissions testing. Just had it rechecked last Friday. Very low emissions numbers indicating that it is still well in tune. If you are not using NGK plugs, you might consider them in the future.

Again, glad you got it started.

Les
Les Bengtson

Les, David and Don, they were your BP6ES NGK's. They are about 2 years old. But of courrse, on only about 2K miles. But, as soon as I put new Champion RN9YC in it started right up. Now, they were pretty wet with the attempts which may have caused fowling somehow. I tried wiping them I recall. But bad they were anyway. So, at least I have a number one thing to check. Guess I will buy new plugs first instead of the new coil I bought first, if it happens again. Regards.
Bradley Dryden

In the early 60s, my father had a 1930's Ford sidevalve that would never start from cold for anyone else. I got him to show me the trick. He took out the plugs and held the business end in a blowlamp flame till it was really hot. If he replaced them quickly enough the engine would catch and run and once hot would be no problem to restart. He claimed to have learned to do this with his Bren Gun carrier when fighting in sub zero weather in the Ardennes.
Perhaps not to be combined with the petrol down the bores tip.
Vic
V Todman

Vic,
Good story! As the weather went down into single digits during the Bulge, I would think necessity was indeed the Mother of Invention....keeping the rifle operating was of the utmost importance!
Robert Dougherty

Robert. Actually, a "Bren Gun Carrier" was a type of vehicle. As I remember the photos, it was an early form of what we would call an "armored personnel carrier". It had a BREN gun (an automatic rifle/light machine gun similar to the US Browning Automatic Rifle or BAR) mounted on it to provide covering fire for the people on board when they had to exit or get into the vehicle while under fire. Thus, highly desirable that a Bren carrier start and run properly. Saved you a lot of walking and increased your odds of survival due to the the armor on it and its ability to provide surpressive fire.

In Korea, where there was also a small war a few years later, the vehicles had to be started and run every few hours if the petroleum oil, of single weight, was not to get too cold, cause a drag on the rotating components and keep the engine from spinning fast enought to start. (Sometimes, the cold could keep the engine from turning at all.) In such cases, heaters, when available, were placed under the engine to try and warm it up enough to get it started. In an emergency, a camp fire was built under the engine compartment in hopes of getting the engines started.

Cold weather is not your friend and I am still in the habit of doing a tune-up/inspection in the fall before the start of cold weather. (Although, this year there has been very little cold weather here in the desert.)

Les
Les Bengtson

This seems absolutely ridiculous, but if it were mine, I might be so curious as to put the NGK's back in now that it's running. Nah, I'm too lazy, but the curiosity is killing me.

I'm glad you got it running! Plugs are cheap, ignore my wierdness.
Tom

Tom,

Like you I'd be curious. I once had a problem that sounds similar. I tried for hours to be methodical but was getting nowhere! In the end I did what you shouldn't really do and replaced the lot. Plugs, leads, condensor, points, rotor arm and cap. The car started first time!!! I thought I really must start switching all the old stuff back in to find the problem, but decided my time was more valuable than identifying the fault, binned the old stuff, and went for a drive!

Iain
I D Cameron

Hi all.

Off topic, but since we have drifted into nostalgia..

A friend of mine used to drive petrol tankers in WW2.
He told me of a device that was used to keep an engine running when it was suffering severe plug fouling.
It was effectively a spacer that screwed into the plug hole and plug screwed into it, so keeping the tip of the plug outside the combustion chamber.
I would guess that it did horrible things to the engine characteristics, but when push comes to shove..

Don
Don

There was another WWII device called a Scrutton Supercharger or some such which was in effect a stack of insulated washers which created multiple but very small additional air gaps. Reputedly originally developed for petrol motors in small Naval craft it was still kicking around in the 60s, and I've seen something which looked similar being demonstrated at classic car shows in recent years. It caused the HT voltage to rise further before it jumped the plug gap which allowed it to fire fouled plugs. Although I never got one in my impecunious youth I do remember not being able to start my Mini occasionally on cold and very damp days so eased the coil lead a little way out of the coil while my wife cranked it - it always fired up straight away like that.
Paul Hunt 2

I've seen a button used in a lead to create a spark gap. Seemed to work
Iain MacKintosh

Now you say that so have I - with a copper-cored cable and a four-hole shirt-button. Most shirts come with a spare ...
Paul Hunt 2

This thread was discussed between 16/01/2006 and 24/01/2006

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