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MG TD TF 1500 - Surging

I hadn't had the TD (25009) out since November but the temperature just touched 60 F this afternoon and cabin fever pushed me over the edge(I don't want to hear from you guys in Minnesota, Colorado and points in the northeast - it really does get cold down here sometimes). She started right up and after running on partial choke for 30 seconds or so held idle well so off I went. The exhaust note was sweet and smooth but when cruising at about 50 mph I felt what seemed to be just a bit of engine surging. The carbs were recently refurbished by Dave and the distributor recently rebuilt by Jeff so I believe that they are good. Head reconditioned, new plugs and fresh oil at the same time. I tried to follow Dave's carburetor tuning directions as best I could but probably don't have then exactly right. Would too rich or too lean or not exactly balanced cause surging? I don't think the engine is missing and I can't hear any change in the exhaust note but it's just a feeling in the seat.

Given how well she ran (pulling hills and navigating twisty roads), maybe I'm just wanting a 62 year old car to feel like my wife's new Toyota but any thoughts will be appreciated.

Thanks.

Jud
J K Chapin

Make sure that you have the proper amount of oil in the dashpots. I also have found that periodically the needle seat does not come up all the way on one carb when pushing the choke in. They can stick sometime, even with a new rebuild. Take your finger and press up on the jet to make sure that they are seated all the way. Always try the easy stuff first
...CR
C.R. Tyrell

So I've learned (or I should say, am learning) - KISS is the word. I used a very light weight oil in the dashpots. I've read here that regular 30wt (or 20W-50)oil is appropriate so I'll try that and pushing up on the enrichening shaft. I did pull the choke knob all the way out to get it started after its two month sit. Thanks. Jud
J K Chapin

Jud - you are opening a can of worms here! pertronix vs points, oil brand and viscosity, etc. etc. There are almost as many opinions are there are T-series cars!

I do use Marvel Mystery Oil to good effect. Moss sells official SU oil that is about 20 weight, which is what I sometimes use when I can't find my Marvel Mystery Oil. Straight 30 weight might be too stiff. 3-in-1 oil is often used, but is closer to a 10-weight, as is sewing-machine oil.

I use Marvel Mystery Oil for so many things around the shop, so that it is probably my first choice. I buy a lot of orphan T-series cars that arrive frozen from long years of sitting, and I find Marvel Mystery Oil great for that.

If nothing else, the range of oils people use may well indicate that there really isn't that much of an effect, whether you use 10-wt. sewing machine oil, some multi-grade or 30-wt. straight. Relatively few street cars are tuned to a razor's edge like a race car, so perhaps it's no great matter.

Tom Lange
MGT Repair

t lange

Thanks Tom. I checked the dash pots (the oil currently in them is 20wt air compressor oil) and they are full and offer considerable resistance to pushing the plunger back down. You are probably right about the tuning so, given how it's running, I'm going to consider it "ain't broke." I may try to tweak the mixture and balance this spring when it's nicer to work in an unheated garage. Jud
J K Chapin

60 degrees? Thats warmer than my house. My dogs have put in a request to move to your house.


MG LaVerne

Can Smiley tolerate four cats?
J K Chapin

Deals off...he don't like cats...maybe it's cause they are bigger than he is.
MG LaVerne

Like the rest of us, you probably had spells of abnormally low temps. If your tank was low on gas, you can condense moisture on the inside of the tank and it can run down to the botom where it gets trapped. More heating and cooling cycles will reintroduce a bit more air and a bit more moisture. It isn't impossible you experienced small slugs of water running through the carbs creating momentary missing.
I find water in the lawn mower gas tanks and carbs every spring, and in the gas cans, too.
Up here in MI, we've experience some sub-zero nights. Due to NUMEROUS emergency runs to the ER recently (92 year old Dad, wife & brother), our van ran nearly empty one night, so I added an extra gallon from a gas can, to pacify my honey. I had the can in the warm van interior in case of emergency, and any moisture in it had a chance to melt! A few minutes later, the van refused to start. Gas line freeze up. My wife had to pull her TD out of the garage and we pushed the van in. Blowing warm air from the house melted the snow on the van making a mess in the garage, but the van was still frozen through and through. I heated up about 5 gallons of gas in 2 gas cans to approximately body temp in the laundry tub and dumped it in, along with some dry-gas. "On the road again..."
I liked it in the winter when we had maybe 10% alcohol (didn't like it in the summer though), but I don't see any alcohol labels on the pumps up here. I thought about picking up some E85.
I should get around to adding a few gallons of gas (mixed with a touch of waste hydraulic oil for injector pump lube) to my diesel truck, as there is probably a trace of vegetable oil still in solution. Vegetable oil in cold weather is about as bad as gas line freeze up! We could use some No. 1 diesel up here. Not sure biodiesel is sold around here anymore.
JRN JIM

I'm curious about the "surging". This could be interpreted as either like a burst of additional power or the engine momentarily racing with no increase in speed. Missing on the other hand is surely almost the opposite, an intermittent loss of power. Moisture could certainly cause the latter. My DD is a 1991 Toyota Cressida which has a button marked Extra Power which I guess just shoves more fuel into the carby if needed when trying to accelerate up hills & the like. This seems to cause the old girl to accelerate or "surge" if that's the right word. Cats, dogs & worms aside :), can anyone enlighten me on exactly what this phenomenon is & what causes it? Like Jud I'm curious. Cheers
Peter TD 5801
P Hehir

I agree with Peter,, I still don't know what is meant by surging,, and increase (or surge)in engine speed would make a change in exhaust note, but there isn't any. Even if the "surging" feeling in the movement of the car was caused by a slipping clutch, it still would give a different exhaust note,,,

SPW

Steve Wincze

Back in the day we always called it galloping, which was caused by unburned fuel. This usually goes away in a stock engine with a stock cam when it warms up and vaporizing the fuel more efficiently. Adjusting fuel mixture will usually help. If it does it spasmodically when the engine is warmed up and driving, I would say it's a carb problem. PJ
Paul S Jennings

I just remembered a problem we had once with an engine that would do the same thing and it was a broken spring in the distributor advance mechanism. Forgot about that, probably because it wasn't an MG, it was an old Dodge, but there's another possibility. PJ
Paul S Jennings

PJ,
But wouldn't the "surging" that you are describing result in a different exhaust note as it surges?? Especially in an MG that has bit more tone to the exhaust than other cars??
SPW
Steve Wincze

Yes it more than likely would Steve, but while driving, it would probably take a little concentration to recognize it, of course a normally loud exhaust would be easier to pick up the change in tone. My TF with it's Falcon exhaust is very quiet and would make it a little harder.
Paul S Jennings

I probably used the wrong word. Although the change in the feel of the engine pulling is very slight I'd describe it as more of a loss of power than a surge of power I'll try to be more careful with my word selection in the future.

I think Jim in MI may have put his finger on it. Until day before yesterday I hadn't driven the TD since late November. In the interim we had a spell of very cold (for here) days with highs around 35 F (1.5 - 2 C) and I had about 7 gallons in the tank. I suspect that I accumulated some condensation that settled to the bottom and was being pushed into the carbs causing the slight (what's the opposite of surging)hesitation. My exhaust is on the long list of replacement items and is pretty loud (sort of like a glaspak with the filling blown out) so I should be able to hear small changes in the exhaust note - I don't. The hesitation seems to be more prevalent at steady speeds on level roads. Under load (accelerating in 4th from 40 to 50 mph or going up a hill) the hesitation is undetectable.

Jud
J K Chapin

"I liked it in the winter when we had maybe 10% alcohol (didn't like it in the summer though), but I don't see any alcohol labels on the pumps up here. I thought about picking up some E85."

Jim, I read your post to imply that 10% ethanol will help in preventing condensate from fouling the gasoline (alcohol absorbs water). Is that right? I run 87 octane non-ethanol in my TD. Would you recommend that I run an occasional tank of 10% ethanol to remove any build-up of water from condensation? Thanks.

Jud
J K Chapin

My experience with water is that it causes sputtering rather than surging or sluggishness.

None the less it clears out and then the problem should go away. Since the water sinks to the bottom its not mixed in the tank always present.
Christopher Couper

This thread was discussed between 20/01/2015 and 22/01/2015

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