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MG MGB Technical - New B owner



Greetings to a great resource, I originally posted this on the 'General' site but
suspect that it should be on the 'Technical' site. I have a 1979 MGB (with SU
twin carbs, type SU HIF, and a Lucas sport coil ... no emissions stuff)) that I've had for about a month.Everthing has been brilliant with it until last night: I filled up with premium (as I have done two or so tanks since owning) and started on my way ... just as I attempted to make a left turn the car hesitated, gurgled, and stopped running. I haven't been able to start it since. This is what I know:

Battery is fine
fuel pump is pumping fuel
small spark appears to be happening at plug tips
starter motor is turning her over

I just attempted to put some gasoline into the carb throat (type SU HIF), and
still nothing ... not even a pop. The distributor doesn't look that old, no marks, all cleaned and sprayed ... still nothing ... even tried a boost (the battery was
labouring after so many crank attempts) but nothing ... so it's towed and stowed in the garage ....

Any suggestions? I'm willing to fiddle on it myself ... on a mechanic scale of 1 to 10 ( 10 being you do it for a living) I'm about a 3 pushing toward four :))
I'm pretty sure it's a Lucas type 45DE4 with an electronic ignition module
(Lucas type as well) and a Lucas sport coil (gold colour) ... this is a little
overwhelming regarding troubleshooting ... so I appreciate any advice through
experience!
Thanks very much!
Lance
L Couri

The only time I had this happen with my 77 B, the rotor went out. But if you have a spark at the plugs, this could not be the case.
I'm out of ideas!
Greg Knodel

Okay, I just got it to fire with 'Quick Start' sprayed into both carburettors ... the fuel pump is working just fine ... what does this tell me?
L Couri

I know this sounds crazy, but are you sure you put gas in it. I had a friend with a Honda who recently had the smae thing happen got about 30 ft from station and died. He accidentaly put diesel in.
J Arthurs

Could it be running too hot? Also, my MGB has had problems with an intermitant fuel pump - eg. a loose wire or terminal could be a possibility and would explain that it now seems ok.

Regards,
Steven
Stveen

I just checked the receipt ... I put the proper fuel in it ... whew. I should clarify, the engine just fired up , it DIDN'T run for any time. My thought is that the ignition is okay since it detonated the 'Quick Start' fluid ... ?
L Couri

Since you appear to be getting spark, and fuel pump is running, I suspect fuel is not getting to the carbs. Look for a fuel filter that may be plugged. Take off the fuel line at the carb and put it in a coffee can or other suitable container, and switch on the ignition, but do not crank. See if fuel flows. If it does not flow, disconnect fuel line and blow out. If it does flow, check the inlet to the carb for obstructions. This may require disassembly of the front carb bowl to check the needle/seat valve.
Pete H 76B
Pete Haburt

You say a small spark. As suggested before you should be able to draw out the spark to about 1/2", sometime less sometimes more depending on coil.

Timing? Firing order 1342 anti-clockwise? I know is was running and now isn't but at some point you have to go back to first principles.

By blowing (with a MkI mouth) into the carb overflow pipe you should see fuel come up the jet. If not but you can blow air there is no fuel in the float chamber. If you can't even blow air something is blocked.
Paul Hunt

This may be grasping at straws, but...

It's interesting that your car stopped running right after a fillup. That it fires with QuickStart implies it's a fuel problem. Could it be that you got some water with your fuel on the last fillup?

To check, you could disconnect the fuel line at the carbs, put it into a jar and pump out a pint or so. Water and fuel don't mix, so you'll see bubbles of water at the bottom of the jar if you have both.

I've had water in the tank contaminate the fuel filter. The element got water soaked and kept the fuel from flowing through it. If you do have water, it's cheap insurance to replace your filter too.

Best wishes, and when you conquer your problem, please let us know what solved it.
Matt Kulka

If it runs on starting fluid I would say that it is probibally fuel related. As Pete suggested test the fuel filter, you can just replace it if there is a parts store near by as it is cheap. You might have some sedimane in the carbs too. If the car had sat before it was sold some of the old gas may have evaporated and turned into a nasty gunk. Sometimes when you fill up the tank sedimants are stired up and end up in the fuel line. First I would check for pressure at the carb, but disconnecting line and using a bowl. If none test before fuel filter. If none there the clog in in the line. If it is getting fuel to carbs, then I would guess the carbs them selves are gummed up. The SU's come off fairly simply, and you can remove the bottom cover to get to the bowl. As long as you do not mess with the float height, you can probibally clean them out with carb cleaner. By the way, if the system is working your bowl should fill up pretty quick.
J Arthurs

Hey L:

It sounds most likely like the fuel pump ain't pumping. Check that it buzzes when you turn the key. If you already have fuel in the system it should click once or twice every 20 seconds or so. Its common for the points (in the pump) to get cruddy, particularly after long lay-ups. Give it a smack or two (gently) to get it going again. Most of the time it works enough to get you home.
Luigi

it appears that I now own a museum piece ... well at least it looks good.
Here's the latest:

The fuel pump works great!
The carburettors work great (I disassembled them, then reassembled them with no leftover parts ... no blocks or stickiness.
Quick Start highly explosive fluid works great!
I tried the old Lucas coil and that changed nothing.
The ignition amplifier? I haven't the foggiest.
the distributor .... well all I can see is a spark in the plug gap (I'm not so exp[erienced to assess whether or not it's a good spark or a faint spark ... it's just a spark) ... my theory is this: Quick start works because it'll explode if you rub the can too much hence the faintest spark will ignite it ... but it won't continue combusting with gasoline ... which leaves the distributor ... apparently a Lucas 45DE4 (outlined on page 102 of the Haynes) but the Pick up has no adjusting screws and that's about it (for what I can adjust on it). the wires are all new ACCEL brand high performance ... nothing has changed since it ran last.


Thanks for taking the time to reply ... it makes me feel less alienated :))

L Couri

If your distributor is indeed a 45DE4, with the original type integral (not remote) amplifier, I would be suspicious of it. The amp is known to be troublesome. It's possible that you are getting a spark that's too weak to fire the mixture.
Kevin Kelleher

Lance, back to basics it can only be one of two things, either fuel or ignition.

If you have checked that fuel is getting to the carbs from the other posts and if it is the problem must be ignition related.

It's not unusual for the ignition points on the older cars or the solid state modules on the newer one to fail. I was driving through an intersection after driving for over 300 miles and the car, 74 MG just stopped,just like yours. No warning and it wouldn't start at all. Checked all the usual things and it turned out that the ignition points had burnt a high point on the contacts and the gap was too small to cause a spark. So first of all check to see if you have points or soid state ignition. If points, replace them and the condensor or just file the contacts smooth and regap them.

If solid state aprt from replacing with a Petronix system, which I did for about $100, I don't know how to check them.

Also check to see that the distributor is in the correct place and hasn't moved. If the distributor has moved somehow the timing will not be at the right position for the engine to fire.

Reset the timing in accordance with Haynes.

Good Luck and let us know how you do.

Andy
Andy Preston

Tomorrow I'll go and grab a Petronix e-ignition for the car ... but will it work for my model B? 1979, with that intergrated amp and electronic triggering distributor? Or is it meant for an older points type B?

I'll keep you posted, thanks!
L Couri

When you get your Petronix make sure you tell the supplier type and model of distributor there are different models for each.I have a 76B with the horrific 43DE dist which has an Allison/Crane electronic system installed --works fine but no vacuum advanve and incorrect curve for my modified twin SU engine--so I have gotten a 25D distributor and am putting in a Petronix Ignitor and coil to hopefully get a little better performance.
Good luck --hope this rectifies your problems.
Another enthusiastic B owner
Gil Price

Well it has come to this: I will push her out of the garage and have her towed to a mechanic to solve the problem. I will definitely report back to all of you who took the time to respond ... much thanks!
L.
L Couri

No, don't tow it yet... Andy brings up a good point - something happened. Lance, you keep saying "fuel pump is good" - what makes you say that? Strong spark or weak, you'd still get the thing to fire - maybe not run, but at least fire a bit... I'm thinking fuel some how. My B's favorite thing to do - granted, after it sits for a while - is for the float valves to stick closed. It just takes me the time to take them apart, wiggle all the bits free and spray it. I'd take a look to see if you have any fuel in the float chambers. I also like the timing theory, though. Did you check it? Maybe it's time to drop back and statically time it? Maybe something was loose and it got shook somehow. Even with bad timing, starting fluid would burn before genuine fuel. Just my two cents...

Curt
Curt

Hey Curt, the fuel pump is good because it shoots a good stream when disconnected. I took apart the SU HIF and found the float valve to be working fine, fuel in the chamber and the needle was cool ... so I can only assume that fuel is making it's way to cylinder ... I tried a prtronix to replace the Lucas electronic ignition in the distributor and that's not cutting it ... I have no spark now and the ignition harness is pretty intimidating to me at this stage .... I'm just not sure what else to do ... I can't believe that something so mechanically complex would happen 'all of a sudden' !
L Couri

L-
You have checked a variety of things, but you have not verified if the fuel problem is really OK. My point is this: several times here in Michigan folks have had "bad gas". They have filled up, driven a few feet and stalled out not to drive again. Usually this happens to a number of people the same day. Check with the gas station and find out if this has indeed happened. The station will have to drain your tank, dispose of the fuel and give you a fill-up if this has happened. While this is rare, I know of three instances in the past four years, in my area. Most often water is in the gas.
In either case, you are at least getting a new ignition system, which will help your car run better.

Good luck and keep us posted, we all learn from these experiences.

Tom
Thomas Lennon

Lance,

if you've fitted the Petronix ignition system, you will need to reset the timing. The Petronix will require you to rotate the distributor by about 20 degrees but I forget in which dirdection. Set the timing statically to 10 degrees before TDC to get in close. If it fires use the dynamic timing at 1500 rpm with the distributor vacuum advance removed.

Good Luck, Andy
Andy Preston

Thanks Andy, I was under the impression that providing the distributor shaft was not removed, the timing would remain intact ... as for the vacuum, I didn't remove anything associated with this ... there still exist a thin metal strip with a hole punched through it at one end which leads out of the distributor and into the 'trumpet' looking bit (this strip is located under the base plate). This could be adding to my difficulty.
pertronix, installing in 15 minutes ... how amusing.

L.
L Couri

Lance,

For your car, you should have the LU-141 model of the Pertronix. If you're not getting anywhere with it, revert to the old pick-up that goes to your integrated ignition for now.

Just to mention one other thing to check, have you topped off the dashpots?.
Tom Young

Just a basic point, but if you are spinning the engine and it's not starting, pull a plug out. It should be wet and smell heavily of gas.
J Arthurs

It's not spark. A little bit of gas in the carb throat fires those two cylinders. I have solid gas flow from the pump, but as J arthurs mentioned I DO NOT have wet/smelly plugs! The carbs have functioning float valves and there is fuel in the chamber but it is not aspirating into the cylinder (compression is about 130lbs) the fuel vapor is just not getting into the cylinder. In a two carb system, if one is blocked, would the other fail to fire it's two cylinders? (this car did just stop in the middle of the road after many miles with no problem (('cept some small amount of run on))) Is this some sort of failsafe mechanism so you don't drive on two cylinders? What would cause there to be no vacuum or depression? Or is it just a carb blockage? I have no ASU or FASD visible on the carbs. I'm stuck with just a Haynes SU book (and an MGB) and a Chilton's MGB manual for reference .....
L Couri

There has been some suggestions about water in the gas; I'd like to add to that aspect. Purchase some water remover or methyl-hydrate from Canadian Tire or some other supplier, and throw it in your gas tank. Wait half an hour, and then try starting it. At least once a year, I have to do this procedure on my boat. It will run beautifully for the longest time, then all of a sudden it will just die. A bottle of the water remover, and life is good again. If this isn't your problem, you'll only have invested $2-$4, and won't have hurt or adjusted anything. It's worth a try.
SteveO

Hi
Just to add to the mix.
About 2 months after I got my '67 B I began to have similar problems except that it would start every once and a while and drive pretty good while it ran. I'd cut the engine then it might not start for another couple of days or staight away, the was no pattern to it. A friend eventually tracked it down to an old surpressor fitted years ago. Pulled it off and away she went. I won't say it's been plain sailing ever since but I did learn to not always look at the obvious. I've kept it as a reminder.

Donal
Donal

I haven't added to this yet and am not a technowiz but I've had the problem. Mine turned out to be the points. They closed by themselves. Some homeless guy walked by and said he had one that used to do that. I checked and he was right. I know this is not the problem with yours but it had to be told.
Have you checked the intake area? Maybe, possibly, the intake is allowing too much air. A loose spacer between carbs and intake, cracked intake, vacuum line split or disconnected? Just another place to look.
kids1

If *none* of the plugs are wet after much cranking, particularly with some choke, then fuel isn't getting through *either* carb. An engine should start and run, albeit badly, on just two cylinders.
Paul Hunt

Kids1 -

That's what happened to me a few weeks ago and it did turn out to be the points. I had posted it on another thread. My problem was/is being so used to the new cars going for 100k between tuneups. I had forgotten that 6-8k on a set of points isn't unreasonable.
Greg Smela

Okay. So just to recap: 'driving along in a car that is mechanically sound and all of a sudden the engine dies ... won't restart for over a week. The diagnostics found that I had a spark, fuel was flowing into the carbs, but still no combustion .... no fuel was wetting the cylinders ... blocked carb? What are the odds of two carbs kakking at the same time when being fed with high quality fuel purchased from Esso? Possible, but unlikely. Hoses were all accounted for and the engine has decent compression. so why no vroom vroom?
After all of your suggestions, which I pursued keenly, I had to resign to calling for a tow to brit garage.

The problem?
The frost plug.
Mine fell out.
The engines breathing dynamics are comprimised and thus will not start.

Hopefully my experience will save someone spending money for this problem.

Thanks again all who helped!
Lance
L Couri

After all these years of attempts to add my two cents when I could in hopes of finding the cause of someone's problems, I may have actually had the answer? Mark this day on the callendar! So, the problem was too much air? I take suggestions/info from this forum and take and take. It felt good to think I may have given back with my guess, even if I was off by a bit (spacer/hose/manifold area = frost plug).
O.k. to get back down from the clouds, I have to admit, I probably would have let a mechanic find the plug that fell out after searching all the things that were cover here too.
But, now that you've spent some real quality time under the hood, doesn't it feel good to be behind the wheel with a more complete understanding of the workings of your B?
kids1

your absolutely right ... I have begun to bond with this vehicle (and the Haynes people) and found a new light in shedding the intimidation of mechanical workings. I will have to ask/find out a couple of things though:
1)what caused this plug to pop in the middle of one of the hottest July's in recent years and 2) how this part relates to the manifold pressure? and finally I must have lost all of my coolant, no? None of my reference material discusses this part or it's location ....

I'll keep you all posted!
L Couri

L, I would have to assume it's not a 'frost' plug per se, but a 'Welch' plug, found at either end of the twin carb manifold. If it were a frost plug, you would indeed have lost your coolant, but the car would still have run. With a manifold welch plug gone, the engine can suck in huge amounts of air, rendering the mixture too lean to burn, if indeed it sucked any gas at all through the carbs.
Probable cause of plug blowing out: a backfire up through the carbs putting more pressure on the plug from the inside than its press fit could withstand.
Ken Lessig

Just a note. The proper name for these plugs are Casting Plugs but they are called frost plugs because when your coolent freezes and expands they pop out. When a block or manifold is made they use a casting method with a mold and use sand.These holes which are later plugged are used to get the sand out of the mold. That's why we use the term Cast Iron and the plugs are called casting plugs. I really learned a lot from this thread and know now that is my B quits I can find the problem for sure

Cec
Cec Fry

Frost/freeze/welch/casting plugs are in blocks, not inlet manifolds. Inlet manifolds have blanking plugs in unused vacuum take-off points.
Paul Hunt

Congrats, Lance. Also, thanks to all that participated in such a wonderful and useful thread. I just love happy endings!

Curt

Curt

Paul - What happened to me, and what I believe happened here was the losing of one of the steel plugs, one each at the ends of the otherwise aluminum intake manifold.

I've heard them called "welch" plugs, and I took it to mean any press fit cap or plug in a casting. As in "all frost or freeze plugs are welch plugs, but not all welch plugs are freeze plugs". "L" may have been incorrect in calling it a frost plug, but that's what welch plugs are most commonly associated with. As these are not unused vacuum take offs, I suspect that the welch plug terminology may be correct in this case.
John Z

And Moss' catalog calls them "end plugs" (in this case for the intake manifold).

Wayne
Wayne Pearson

I rate myself as a bit of a bush mechanic and I never would have picked that, at least I wouldn't have if it was the rear one. I guess the mechanic removed the inlet manifold & carb assembly and hey presto there it was! My points close up by themselves and all sorts of other odd stuff. My daily drive is a BMW M3 so I value the "manual therapy" offered my the B, currently undergoing the final stages of a bare metal rebuild
Chris Stansfield

Yes of course the inlet manifold does have end plugs, I suddenly remembered after posting.
Paul Hunt

This thread was discussed between 25/07/2002 and 01/08/2002

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