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MG MGB Technical - Another question (maybe old to you guy's)

Was messing with my MG again the one with the Webber 45 side draft carb. Last year I was able to get the car running for a short period of time. However it would never start again. So since the car had some wires loose I figured that might be the problem. So I went out and checked the wires for the starter, coil, tach, distributor and everything seems to be where is suppose to be. So my question is could my carb be the cause of all my problems. I tried towards the end of last year to adjust it (using tuning instruction that I had downloaded from the web.) with no additional success. Also last year the time I did get the car to work I pulled the carb off and took it all apart and cleaned every piece and put it back together and after an hour I got the car to crank. What do you people think I should try next? And paying someone to fix it will not fly the wife does not allow me to spend anything on this car and would prefer me to get rid of it.



The G

I think you need to start at the basics G,
Battery, enough power to crank till the cows come home.
Ignition and timing, if you do not have a healthy spark at the right time, its just heating the plugs, look up setting static timing and the distributor points gap on Pauls site. http://www.mgb-stuff.org.uk/

Finaly you can check what the carb is doing, if the plugs get wet then at least you are getting fuel else you need to set the jets and float level, first check the weber is getting fuel from the pump, by disconecting the feed pipe and putting it into a can then turning the ignition on. Let us know how you get on.
Tatty

What are the jets and choke sizes that you are using?

Have you made any other mods to the engine? Cam? High comp pistons?, etc.?

Fuel starvation? Is there fuel in the fuel bowl? Is fuel being squirted down the throats when
you open the throttle?

You may have checked the wires, but did you check to see whether if the spark plugs
are actually sparking? Hook up a timing light to each spark plug lead and look for a steady
series of flashes as you turn the engine.

How's the ignition timing? You might try advancing it 5-10 degrees before the stock setting.

Daniel Wong

Tatty, M, G,

I put in new plugs not to long ago however their are two new sets sitting in my garage that I will gap and replace just incase. I think new wires are needed when I was going over my wiring I noticed that one did not fit as good as it could so I’m sure that would help, and I will look into getting a timing light to check that. I had assumed that the timing was fine do to the car running that once. fuel pump is working and it is at least getting fuel to the bowl. Also what do you mean by jet settings? Thanks

Daniel Wong,

Not sure at the size of the jets (as I only have the one that where in the carb), I will pull them out this weekend when I have some time off. As for a choke this carb does not appear to have one. Not sure about the fuel squirting down the throats (although they are wet with gas). I will have to check the timing thing once I get a timing light. Thanks.
The G

Webers have idle and main jets, with a bit of fiddling, eg checking the butterfly valves are open, you should be able to open the idle jets to get the thing to start, there is no need to worry about the main jets till you have it started.
Tatty

G, sometimes it hard to know the skill level of the thread starter so trying hard not to offend ,you could start with the internal combustion triangle.
SPARK-remove the coil wire from the center of the dizzy[I've come to use that term as of late,not sure I like it or not] hold it by the insulated part about a half inch from a good ground [head bolt] have your lady turn the key to"start", neutral,clutch in , E-brake set. You should get a nice blue arc from the coil lead to the head bolt. If while makeing this test you get a jolt[you will know it when you feel it] you are holding the coil wire to close to the brass terminal or the wires need replacement.
No arc? look at the points and condenser first and the rest of Ignition next. Nice blue arc? Yes-

FUEL- turn the key, on listen for the pump[gentle thumping from behind the passenger seat] you can hear most pumps some of the new replacements are quiet.
No noise, turn off the key find the fuel filter up front, disconnect the carb side rubber hose point the filter nipple in a suitable container and have your lady turn the key on[not "start"] fuel should pump out nicely.No/Low fuel? take the filter out and flow test again from the tank side. Nice flow?Yes , turn off key,replace filter once you have good flow through the filter, reconnect fuel line. while you look down one of the carb. throats have your lady step down on the gas pedal[key off]did you see a nice healthy squirt of fuel?Yes

COMPRESSION-take the coil lead out again and ground it well to the head bolt with a vicegrip so it won't come off remove all four plugs, use your compression gauge to test compression in all four cyl.-100psi plus
and all about the same reading 10lbs +or- No gauge?
Useing your finger or some sort of rubber plug,plug up one spark plug hole at a time and have your lady turn the key to start[neutral, clutch in, E brake set]it should sharply pop your finger out the same on each cyl. no pop on one cyl? Bad valve. weak pop on all cyl? Timing chain

If you have good spark, good fuel and good compression
and you havn't fooled with any thing else ,put in a new set of plugs hold your foot to the floor and turn the key to start it should start when it starts don't let it over rev, in your joy of therush-RIC
G, let me add this, the above is by no means any where near a compleat test but its a good start for
the novice, if you are above this test you know it.
If you are not above it give it a try.
Ric

In a case like this, I sometimes try using starting fluid (a spray can of ether from the local parts store). It won't run the engine for long, but it helps to make clear whether the problem is ignition/mechanical or fuel. Give a squirt down the carb throat and then try to start; if it won't fire on ether, your ignition is dead (or your timing chain gone ...). If it will run for a bit and then die, the carb is the place to look.
Tom G

This thread was discussed between 07/03/2003 and 08/03/2003

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