MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - MGB ran when Parked (30 years ago). Won't start

After replacing the steering rack, reassembling the engine aciliaries, rebuilding the carbs, lapping the valves, replacing the battery, and the fuel pump, she will crank but wont start.

Compression tests revealed that cylinders 1,2, and 4 had only around 40-50 psi, whereas cylinder 3 had 80 psi. Wet compessin tests shoed an increase of 30 psi all accross the board.

On cranking it behaves similar to a timing problem. We have taken off the valve cove and checked to see that the timing marks on the front damper pulley match with the valve timing and set the spark timing as per John Twists instructions, but no luck. It has new plugs, a fresh oil change, gets plenty of oil pressure when it cranks. The best we've done is get it to fire on one cylindar.

Any Ideas?
S.A. Jones

Valves sticking open? Rings stuck? You don't mention going thru the ignition.

Sounds like stuck rings, not as bad on the one piston, but not good on any of them.

Have you soaked the tops of the pistons with penetrating oil or something like that? It's possible to improve the sticking rings this way, maybe wiggling the crank back and forth a few times a day. At least the engine's not frozen up.

I have heard of the valve springs taking a "set" after being compressed for years in the same position, making them weaker than they should be.

I guess you don't have much to lose by trying a few tricks. But after such a long layover, the engine should be disassembled and checked out completely for your peace of mind, if nothing else.
Tom

Don't know if a motor will run with such low compression.
Have you check to make sure you have spark at each cylinder?
Does the oil smell like gasoline?
Have the spark plugs been fouled with fuel or oil?
Kimberly

Did you set the ignition timing on the right side of the cam lobe. The Rotor arm goes ccw viewed from the top. However the compression seems very low and it's probably stuck rings. The penetrating oil advice is good.
Stan Best

I presume you are using fresh petrol?
Willem van der Veer

Are you really saying that the car has been sitting for 30 years and you are wondering why it won't start!

If that is the case it needs stripping down and most of the parts changing. I'm surprised it turned over at all if it hasn't run for that long.

Tony
Tony Oliver

Tony, maybe its a trick question?? Now what else would you expect after 30 years and with that sort of compression?? I would assume it was parked for the same reason it doesn't start now. I think an engine rebuild is in order. Barc
Barc Cunningham

Yep Barc, it got me sucked in. I really hope SA isn't serious. I get more compression than that in my bike tyres.

Tony
Tony Oliver

"MGB ran when Parked (30 years ago). Won't start"

Ho ho!
Paul Hunt

Well, a couple years ago I started a 1600 that hadn't run for 11 years and it ran and idled beautifully with 60# oil pressure at idle after 20 minutes. While it's unlikely, it's not inconceivable that an engine would run after 30 years.

If this engine is firing on one cylinder, it may be as simple as spark wires on the wrong plugs (wrong firing order).

At top dead center with both valves on #1 closed, the rotor will point to #1 on the distributor cap. Then, moving ANTI-clockwise around the cap, the order is 1-4-3-2.

I would follow all the above advice first. Since you've already spun the engine, you might keep soaking the piston tops with penetrating oil for a few days and then spin it frequently with the plugs out over the following few days. I take it that your wet compression readings are running something like 80-80-80-110 (although probably not in that order). Not good, but I would think it would probably run.

But, running the engine at this stage of the game is really little more than a few grins and a an exercise in diagnostics. Most likely, after running for a period of more than 30 minutes, you're going to discover marginal oil pressure, and oil-consumption/blow-by is/are going to show up at clinical levels. You may be able to postpone it briefly, but barring incredible luck, a full engine rebuild is on your not-too-distant horizon.

FWIW,
Allen
Allen Bachelder

There is spark at all 4 plugs, the engine smells like gas after cranking, we see 60 psi oil pressure when cranking. It was parked after an accident that did minor damage to the rear end. It was also rusted enough to warrent a restoration 30 years ago and the owner had it in pieces to do the restoration but did little to nothing on it. Itsat on blocks untill 5 years ago when he had to move and my dad bought it. We have been reassembling it and doing some bodywork ever since. It has fresh petrol btw. New brakes new brake fluid etc. We lapped the valves and put in new valve springs. The piston rings may well be sticking and need refreshing. We didnt think to mess with those.

My dad is convinced that such low compression shouldnt be a barrier because he "rebuilt" a model A ford engine in africa that was siezed up. He took a log and ounded each piston free with the head off and then patched the whole thing back together. It burned more oil than gasoline but it ran. I suspect that the MGB engine is not so forgiving as that.
S.A. Jones

Compression, ignition, fuel, is what is needed to make an engine run. Lubrication and cooling is what is needed to keep an engine running.

Get compression – by adding a little oil (5ml) through the spark plug and a short crank without plugs you can temporarily improve ring compression before start up.

Get ignition and check by removing and earth each plug – check for a spark while cranking the engine.

Ignition timing should not have moved by itself, even in 30 years.

Fuel is simple, when the above have checked out, pore about half an egg cup of fuel through each spark plug hole, quickly fit the plugs and wires (before the fuel can evaporate or disperse). Carburetors must be held fully open, ignition on and crank the engine. Keep cranking the engine while holding the carbs fully open. Within about 30 seconds the fuel in the engine will lean out, fire up (keep the carbs fully open) for about 5 seconds and die.

Proof - the engine works. You can do this until you get tired of it.

Next is to keep the engine running. This is another ball game. The fault is normally caused by fuel vapor not entering the combustion chamber, or in the correct amount, but the engine works.

Richard.
RH Davidson

Something that seems to be missing from this thread is welcome to MG ownership and congratulations on choosing the best ever MG IMHO and well done for putting in the effort to save a car that was abandoned by it's previous owner. The B series engine is not a sophisicated thing, and if the rings can be freed up this one has every chance to run fine for a long time to come.
Stan Best

S.A., your Dad sounds like a guy that will get the thing going again. The parts are available, so you shouldn't have to add more oil than gas. Have fun!
Tom

If it's any consolation, I had pretty much the same problem in the spring this year. I had bought an old engine (which had been standing for a couple of years in someone's garage) when mine needed to be rebored.

I swapped them over, so I knew that the carbs and distributor were working, but couldn't get it to fire. I had been putting Redex into the bores for a couple of days before trying to start, but was still getting very low compression. It took a few more days trying, using a battery booster for every attempt, and drying the plugs as well. It finally fired a few times and then started.

One thing to try is to scrape graphite from a pencil around the plug electrodes. Apparantly it gives a much bigger first spark, which may help getting the first firing stroke.

The compression came back to reasonable levels after some use, and starting has never been a problem since then.

I'm now nearly ready to swop back to the rebuilt one. Hope that starts alright!

Keep trying.

David.
D Balkwill

I WISH I COULD START LIKE I DID 30 YEARS AGO,
AT 54 I'VE GOT A JOB TO GET OUT OF BED IN THE MORN,
HA HA
da wright

Stan Best, Buckinghamshire, United Kingdom

Thanks for the welcome. I'll pass it on to my brother. This will be his car. The B is new to me but I've owned a 1971 MG midget for 8 years now and my father had it for about 13-14 years before that. There are some subtle differences that make it a bit challenging at times.

Tom
Yeah my Dad certainly brings some skills to the table, but I think in some ways I have surpassed him, though he still is way better at sorting electrical faults.

David.
Thanks, I will try the graphite.
S.A. Jones

Reasonably sure the compression is to low to run.
Bruce-C

The firing order is actually 1-3-4-2. I think Allen just made a typo on that.

Good luck
Jeff

This thread was discussed between 16/09/2008 and 18/09/2008

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.