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What did I do wrong?

Posted by Silex88

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Re: What did I do wrong? #41
BH Davis Thompson, CT, USA 1973 MG MGB	Posted: April 26, 2012 12:11PM Registered: 6 years ago Posts: 808

Given my experience as mentioned a few posts up I'd suggest retuning the carbs. Having solved my earlier poor running problem by finding a loose connection on the coil I was convinced a loose white wire (ignition) connection would solve the problem I was currently having. The ignition wire repairs.......while probably saving me trouble down the road...... didn't fix the problem. The car was running worse all the time.

When checking plugs, timing and valves yield an improvement there was nothing left but the SUs. I couldn't believe that was the problem because like you I was running great for a month and then first thing in the morning the car was running rough again.

However it WAS the carburetors. I didn't take them off........just tuned them again. When done the car immediately ran right. Makes no sense.......but then do these cars ever make a lot of sense devil smiley

. So I'd suggest you try the same. Start with the jets flush with the bridge and then lower them 2 turns (actually 3 turns works better on mine as a start point). That alone should show improvement if this is the problem. From there do a normal carb tuning.

Oh.... and as someone else may have mentioned........check the carburetor linkage. I too loose linkage cause a problem a few years ago.

Good luck...........hope that works.
BH

Edited 1 time(s). Last edit at 04/26/2012 12:15PM by BH Davis.

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Re: What did I do wrong? #42
Silex88 Randon W Ponce Inlet, Florida, USA 1972 MG MGB MkIII 1974 MG MGB MkIII	Posted: April 26, 2012 01:17PM Registered: 1 year ago Posts: 88

Just went through and reset the carbs. I set both to 3 turns below the bridge, loosened and adjusted the cinch bolts, double checked the dash pots. Problem is still there.

I took another video just after I reset the carbs. I tried using my finger as a gas pedal representation again. It's quite strange; I keep easing on to the gas and it doesn't want to go past 1K. The sputtering simply gets louder until it just shoots up past 2K all of a sudden. Above 2k the sputtering is still there, but the revs seem to be much more steady.

I really am having trouble figuring out what I even have left to test. I have yet to find anything that even seems to make a decent difference, let alone lead to a solution. However, I have faith in the old girl! Hopefully, I'll run across something simple, that magically cures everything, sometime soon. If you guys can keep helping me come up with ideas to test, I'll keep trying them until we find something that sticks! smiling smiley

Edited 1 time(s). Last edit at 04/26/2012 01:19PM by Silex88.

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Re: What did I do wrong? #43
trymes Tom Rymes Concord, NH, USA 1959 Riley 1.5 1969 MG MGC GT ~ For Sale ! ~ 1971 Jaguar XJ6 Series 1 1971 MG MGB GT 1972 Chevrolet C20	Posted: April 26, 2012 01:40PM Registered: 4 years ago Posts: 3,259

I haven't read the entire thread in a while, so may have already done all or some of these, but, I am not so certain:

Verified a good engine ground strap (tight connections, not insulated by rubber motor mount).
Tried another distributor cap.
Checked your points gap and cleanliness.
I don't think you have electronic ignition, but if you do, try points.
Made sure that your distributor shaft isn't wobbly.
Grounded removed plug to block while cranking and verfied that you have a nice, fat, strong spark.
Empty the fuel tank by running the fuel line to the carbs into a gas can and tried new gas. Unlikely, but who knows?

Tom

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Re: What did I do wrong? #44
Silex88 Randon W Ponce Inlet, Florida, USA 1972 MG MGB MkIII 1974 MG MGB MkIII	Posted: April 26, 2012 02:09PM Registered: 1 year ago Posts: 88

In reply to # 2051164 by trymes I haven't read the entire thread in a while, so may have already done all or some of these, but, I am not so certain:

Verified a good engine ground strap (tight connections, not insulated by rubber motor mount).
Tried another distributor cap.
Checked your points gap and cleanliness.
I don't think you have electronic ignition, but if you do, try points.
Made sure that your distributor shaft isn't wobbly.
Grounded removed plug to block while cranking and verfied that you have a nice, fat, strong spark.
Empty the fuel tank by running the fuel line to the carbs into a gas can and tried new gas. Unlikely, but who knows?

Tom

Ground strap looks to be in good shape with no frayed wires. (pic attached)
Heading to pick up a new cap shortly, but the old cap still looks good. (pics attached)
Cleaned and filed old points, then installed new points and condenser. No change from either.
Have points ignition.
Not very wobbly. Definitely no more so than when it was running perfectly.
Heading out to check this now.
Tried fresh gas from gas can, to no avail

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Re: What did I do wrong? #45
Silex88 Randon W Ponce Inlet, Florida, USA 1972 MG MGB MkIII 1974 MG MGB MkIII	Posted: April 26, 2012 02:11PM Registered: 1 year ago Posts: 88

Other side of the dizzy cap.

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Re: What did I do wrong? #46
BH Davis Thompson, CT, USA 1973 MG MGB	Posted: April 26, 2012 02:58PM Registered: 6 years ago Posts: 808

Do you know how to tune the carbs? If so try going through the whole process. 2 or 3 turns below the bridge is only a starting point.

Just remembered another thing that caused me problems a few years ago.........loose needle in one of the carb pistons. Pull the dash pots and then check the needles in the pistons. Should be spring loaded and move up/down about 1/8" to 1/4". Should not "fall out" like one of mine did. I still think it's something with the carbs..........but I'm usually wrong about most things smileys with beer

BH

Edited 1 time(s). Last edit at 04/26/2012 03:02PM by BH Davis.

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Re: What did I do wrong? #47
myklos Michael LoSapio Endwell, NY, USA 1962 MG MGA MkII 1965 MG MGB 1973 MG MGB MkII	Posted: April 26, 2012 03:46PM Registered: 2 years ago Posts: 218

"I am now completely baffled. Picked up a new coil and wires, and at first just replaced the coil. Same exact problem. Make note, however, that the new coil did work on the first try, and the old problem was still there, with zero change.

I put on the new wires (now we have a new coil, and new wires) and she almost wouldn't crank at all. I could only get her to sputter at 5 - 700 RPM's with full throttle."

The problem got worse when you changed the wires. Make sure you have the right firing order 1342 counter clockwise. Jus a thought.

Mike

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Re: What did I do wrong? #48
Silex88 Randon W Ponce Inlet, Florida, USA 1972 MG MGB MkIII 1974 MG MGB MkIII	Posted: April 26, 2012 03:50PM Registered: 1 year ago Posts: 88

I actually did finally figure out how to tune the carbs when it was last running well. I learned a LOT when I couldn't get them tuned before I learned how important undoing the cinch bolts can be lol.

However, I played with the cap and that may be it! I ordered a new one that will hopefully be in by morning. However, I decided to sand down the tiny black spots on the cap (visible on the contacts in the previous pictures) to see if it did anything. The problem is definitely still there, but it seems as soon as the advance starts to kick in it jumps up the range (the skipping between 1K and 2K sharply, as seen in the previous video) and starts running much better. It only started doing this AFTER I sanded a lot of the little black bits off.

Also, I checked the rotor, and it has an odd rough edge on it. It's not bad, and I only noticed this upon further inspection after I thought that the black bits may have had something to do with the problem. What exactly causes the black bits in the cap, and possibly the rough edge on the rotor? Hopefully the new cap will cure this whole thing! smiling smiley

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Re: What did I do wrong? #49
timfred Tim Frederick Berkeley, CA, USA 1971 MG MGB GT	Posted: April 26, 2012 04:30PM Registered: 1 year ago Posts: 271

Kinda guessing here, but have you checked your alternator?

I don't know if this is possible, but your symptoms are similar to what I would expect out of an almost but not completely dead alternator/battery combo...when revs drop below a certain point, there's not enough power to make good spark and the tachometer goes crazy.

I had forgotten to reconnect the alternator after putting in a new engine and there was enough battery juice to crank and start the car with a lot of choke/throttle, but not enough to consistently spark and idle. Seemed counterintuitive ... if there's enough juice to crank, I would have expected it to be able to spark, but that's what it was.

Also check the connections on the back of the tachometer if you have an "RVI" current sensing model.

-Tim

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Re: What did I do wrong? #50
BumbleB74 William Milholen Tidewater VA, USA	Posted: April 27, 2012 09:00AM Registered: 7 years ago Posts: 4,686

The black on the distributor posts is from the spark jumping from the rotor to the post as it swings by. Pretty normal.

If the edge of the rotor were REALLY rough (which is unlikely), it could cause the spark to jump early or late, and foul up timing. AGAIN, a very slim possibility.

1974-1/2 Roadster, "Bumble Bee", Corvette Yellow - in shambles, wire wheels
1976 Roadster, un-named, Sandglow - "driver" condition (stock + 32/36 Weber DGEV, cast iron header, 25D distributor), bolt on wheels

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Re: What did I do wrong? #51
BH Davis Thompson, CT, USA 1973 MG MGB	Posted: April 27, 2012 10:36AM Registered: 6 years ago Posts: 808

My latest and most successful method to for check for spark it to take a spare plug and lay it in the hollow between the valve cover and one of the head bolts. It sits there pretty comfortably and grounds itself. Hook up #1 plug wire to it and start the car. You'll see if there is a spark. Repeat for each plug wire. If you have spark on all 4 wires it's probably not ignition related........other than timing and firing order at least.

BH

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Re: What did I do wrong? #52
78mgb White Wonder 78mgb apple valley, Minnesota, USA 1978 MG MGB	Posted: April 27, 2012 10:12PM Registered: 7 years ago Posts: 1,398

Please do not take offense but after listening to your motor it sounds to me that maybe your spark plug wires have been crossed. I had my son cross the spark plugs wires on a car and it ran terribly. My son and his mechanic friend spent two days trying various things. When I suggested that the wires were crossed, he said that they had both looked and did not see anything wrong with the wiring. I finally drew a diagram and went and checked the car myself and found that the wires were crossed. Wired the spark plug wires correctly and the car ran fine.

Maybe your original problem was caused by bad gas (water in the gas) and when you tried to fix it you inadvertently crossed the spark plug wires.

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Re: What did I do wrong? #53
Derek70mgb Derek Gale Victoria bc, Canada 1970 MG MGB	Posted: April 27, 2012 10:50PM Registered: 6 years ago Posts: 555

seems like you have tried everything except a fresh set of new plugs. That would be my next move. Not an old set of used plugs.
Also check that the choke is not stuck .

good luck

.

my restoration video

next project

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Re: What did I do wrong? #54
spikemichael Michael Caputo Athol, MA, USA 1973 MG MGB 1973 MG MGB "Freebie" 1976 MG MGB "B-4" 1979 MG MGB "MegaBeanie" 1989 Suzuki Intruder 800 → more	Posted: April 28, 2012 03:24PM Registered: 4 years ago Posts: 6,934

I am still saying it is the distributor cap and rotor.

First off the rotor shouldn't be rough and it should be clean and shiny.

Second the carbon marks on the cap terminals are all on the far edge, I would think your timing
A is to far retarded.
B mechanical advance return spring is shot
C you are getting too much vacuum advance
or
D you have a heck of a vacuum leak.

Third, if you "sand" the terminals too much you are increasing the distance between the rotor and the cap and weakening the spark sent to the plugs. You should be able to just 'snick' off the carbon withthe tip of a small screw driver but CHANGE THE CAP AND ROTOR AS A SET.

Send the walnut brownies priority mail parcel post and they get moldy...

Michael J. Caputo
'79 RBB and '73 CBB owner with extensive experience in 12v Audio System design and installation.
Vendor of Regalia and Promotional Products. Forum Member with a warped sense of humor.

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Re: What did I do wrong? #55
eightyb G G oh, USA	Posted: April 28, 2012 08:29PM Registered: 2 years ago Posts: 48

My rotor looked like new but it was bad, can't go by looks...

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Re: What did I do wrong? #56
BH Davis Thompson, CT, USA 1973 MG MGB	Posted: April 29, 2012 04:35AM Registered: 6 years ago Posts: 808

So.........have you solved the problem yet?
BH

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Re: What did I do wrong? #57
Silex88 Randon W Ponce Inlet, Florida, USA 1972 MG MGB MkIII 1974 MG MGB MkIII	Posted: April 29, 2012 09:04AM Registered: 1 year ago Posts: 88

SUCCESS!!!

It finally started to run right, almost out of nowhere. So, I took the opportunity to retune the carbs. Then, It was idling near perfect, right at 1K. However, I went to rev it and it would just sputter and then started backfiring like crazy whenever I tried to keep the revs up.

Exhausted from literally bending over the fender through nearly all of the hottest part of the day (bad idea), I took a break and went to return the coil I purchased, as I suspected it was the wrong one. Sure enough, it was, and the good one had JUST come in on the shipment that morning! Due to the mix-up, they let me make an even swap, even though the new one was more expensive.

Back at the house, I proceeded to install the new coil. No more backfiring! However, it still was running like crap. I sat for a second before I realized that I had leaned the carbs out too far while trying to stop the backfiring. I reset the carbs and fired her up, and we have ignition!!! grinning smiley

I really need to find some overly dramatic name for this car, because it seems EVERYTHING that has gone wrong with it has refused to just die in a relatively normal fashion. It all seems to be going out in the most spectacularly dramatic ways imaginable lol.

Once again, thank you all for your time and effort in helping me with these issues. If it were not for you, this journey would be unfathomably more difficult, and frustrating!

Now I just need to sort out the carbs....again! eye rolling smiley

Randon

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Re: What did I do wrong? #58
BH Davis Thompson, CT, USA 1973 MG MGB	Posted: April 29, 2012 05:44PM Registered: 6 years ago Posts: 808

Outstanding! Congrats.
BH

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Re: What did I do wrong? #59
melbaver Chris Howells Broadwater NSW, Australia 1968 MG MGB "Moneypit" 1996 Jeep Cherokee "Shopping Trolley"	Posted: April 29, 2012 07:54PM Registered: 5 years ago Posts: 5,087

In reply to # 2053494 by Silex88
I really need to find some overly dramatic name for this car, because it seems EVERYTHING that has gone wrong with it has refused to just die in a relatively normal fashion.

Opera Diva!!!

Chris Howells

1968 MGB Purchased already dis-assembled which is why I'm often ignorant about what some parts are, and even more ignorant of where they go.

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