Welcome to our resource for MG Car Information.
MG TD TF 1500 - Makin' me crazy!
|I'm getting very frustrated with the fact that my '52 XPAG runs rich no matter what I do.|
Timing is fine, points,etc all fine...Idle is good, starting , no problem...Runs great....No smoke.
Problem is with the plugs....Even at the leanest position on the carbs,(adjusting nut at the top, choke fully open), "Rocky" leaves the plugs covered in soot....No oil,no wet fuel, just soot.
I even replaced the new ES needles with new AP needles.(helped a little).
My jets are new, as are virtually all the carb parts.
Jets are centered, pistons fall properly, etc...
Floats are set at 7/16ths...
Using the Unisyn tool kit, I checked the rising and falling of the pistons, and they are the same.
I have used DB's step-by-step tuning procedures, with no change.
Car seems to run great, but this is the kind of thing that is "makin' me crazy"!
|For what it's worth, my #3 & #4 have the same symptoms. Is this what your's look like?|
I just replaced the points today (see prior post) and it runs a lot smoother and seems more powerful. Maybe the soot will go away also? If not, I wouldn't doubt it's rings? I'm just living with it for now. I'm sure the experts will chime in.
Have you removed the jet stack and checked all the points I mentioned a long time back? It's the only thing left and the first thing to check.
Not sure what "Even at the leanest position on the carbs,(adjusting nut at the top, choke fully open)" means. Is the Jet adusting nut full up as tight as it goes? The choke lever should be fully closed, with the jet heads up against the adjusting nut. You didn't crack the jet adjusting nuts trying to tighten them, did you?
What size drill bit can you let down into the jet? A 0.090 orifice should not accept a 3/32 drill bit. It has been know that some carbs have 0.100 jets and that of course would run rich.
Another thought, can you tell me how high the fuel is in the bridge with the floats set at 7/16 down?
|If your only worry is black plugs, forget it and drive. If it does not smoke, foul the plugs, and runs fine, just ignore the color.|
Just a thought.
I bought my TD from a PO who hadn't driven the car out of his subdivision for 23 years.
The plugs were covered in soot and it emitted black smoke.
I changed the plugs, checked the points, timing, piston fall, etc.
No major issues there.
I regularly take it on long, 3000-rpm drives and have had no issues since.
As kids, we justified fast driving by saying that we were "blowing the carbon out".
Maybe we knew something?
Best regards, Steve
This is a fun test. Grab your spark plug socket and take a ride. Pick a place where you can safely leave the road. Drive at least 10 miles, 25 is better, at 3000 RPM plus. As you approach the spot you picked kill the ignition while your foot is still on the gas, Depress the clutch and coast off the road. Pull the plugs and examine. I bet they will be tan or brown indicating a good mixture. Let us know.
|J. M. Haskins|
|Hi Ed et al,|
I just found this thread, and I agree fully with Jim H., I was going to ask just how/when you pulled the plugs before I saw his note. What he says is the only way to judge plugs, unless you want to judge them at idle conditions.
|A W Parker|
|Thanks for all the input....|
Re: the adjusting nuts...They are tight, but not damaged.
Choke levers tight against the nuts...I even put the nuts in the lathe , and took a few thou off the bottom, hoping that would help.
Re: the plugs...They are covered in loose soot (like chimney soot), not burned oil...Most will brush off, but it's still quite frustrating.
The jets were new less than 2000 miles, and a year ago...
Surely they were correct from the supplier?????
I will try the 3/32 bit, and see if that's the culprit.
Will also check the depth of fuel, after the pump stops.
I drove the car at high speed for 30 miles, but I didn't coast to a stop...Maybe I didn't do it right. Will try again, after installing my new pertronix (YAY!...No more points!)
That image shows rich running, alright (powdery black residue)...Not oil burning...Oil fowled plugs can't be mistaken...They are wet, and grungy looking..Frequently, liquid oil is also present.
I will report back ASAP , with more observations.
|Non related engine, but symptoms are the same. I have a 25 hp Kohler engine in one of the mowers which constantly fouled plugs. I put in 1 step hotter plugs and the problem went away. But, it still sounds to me that you have a fuel mixture problem. JMHO. PJ|
There's no doubt that it's a fuel-mixture problem...The question is what to do about it?....
Anyway, I'm moving forward with the Pertronix install, and maybe there will be some improvement.
Just a side note, I installed the Moss rotor "upgrade", and did have a noticeable improvement in the way the engine runs.
|Here is a good test...Does it start and run when cold without the choke pulled out? I am always suspicious of the jet seals. If they were replaced, were they replaced with origional type oil impreganated cork seals? Some of the generic rebuild kits had tiny pieces of rubber hose instead. Has the car sat for a long time since the carbs were rebuilt and the seals possibley dried out? If the jet seals are bad, fuel gets sucked right past the jets and no amount of adjusting will help. I know that some folks seem to like teflon seals, but I always use the SU oem stuff...can be gotten from Joe Curto.|
As Jim said above,,,, did you " Drive at least 10 miles, 25 is better, at 3000 RPM plus As you approach the spot you picked kill the ignition while your foot is still on the gas, Depress the clutch and coast off the road. Pull the plugs and examine."????
Try this FIRST before you install the Petronix,,, as you have not proved that it is really running rich!!
|I drove to a friend's house today, mostly at about 55+,|
Then tried the idea about the shut down....
There did seem to be an improvement in the appearance of the plugs...Still dark, but no soot...
The Pertronix was installed, and that may have played a part, but maybe I'm looking for a problem that I really don't have.
I did notice more tendency for the exhaust to "pop pop", on long down-hills, when I backed off the gas...
It has done it before, but not this much....Don't know if this has anything to do with still running rich, or I could use a change in timing.
|what is the fuel level at the bridge??? where is the needle's shoulder in relation to the face of the piston?? |
if the fuel level is too high none of what you are doing to correct this issue will help. regards, tom
|Can anyone find and reactivate the original thread on this?|
As far as I know, this is the original thread. (I have two threads going currently)...One on carbs, one on Pertronix).
The AP (lean ) needles (shoulders) are flush with the
I am going to check fuel level tomorrow (again), but it actually seemed too low, the last time I checked...
It's hard to measure exactly...
I'm also going to double-check the jet diameter...
No. (this archive is a major PITA!)
Here's one, this board, 21 Aug 2011:
"Having a difficult time getting sorted out.,,Help!"
And the one referenced, on the MGB Tech board:
"How to adjust height of the bottom-jet bearing?" 24 August 2011
The cumulative upshot of all this is that several people have mentioned that IF the jets are the correct size as you say they are marked; "A" = .090", and the needles are correctly located, as you have confirmed, and the float levels are correct, then there is no way the car will run with the jet nuts fully upwards. The fact that it does run, and rich to boot means that there IS fuel leakage around the jet stack, which is what I've been trying to tell you all along.
You have repeatedly stated that the PO rebuilt the carbs, and you have no knowledge of how he did so or what parts he used internally. You have said you will take the carbs all apart this winter.
I have been trying to tell you from the start that removing the jet stack on a TD is a ten minute job, not even taking the carbs off, and it is all you need to do to solve this conundrum.
By now you have spent many ten minuteses, and parts you don't need, and far more time typing than it takes to find and fix it. You need a carb gasket set (maybe) and a good diagram of the carb jet stack assembly, a pair of pliers, and a 7/16W for the big nut that holds it all together. BTW, is that big nut tight?
I am more than willing to help, by phone if necessary, but please quit pissing around with this.
Might take and post a a pic of the carbs close on, straight down the throat before dismantling.
And then all the pieces you take out, laid out in order.
It came to me that you may be able to actually see if fuel is bypassing the jet assembly. With a strong light, and magnification if necessary, run the engine at fast enough speed to raise the pistons about 1/2", and look down the carb throats. You will see the fuel spray coming out of the jets. NO fuel should be coming out around the jet bearings; that would indicate that fuel is bypassing the jet around the outside of the bearing - missing or loose parts. It is still possible the fuel is bypassing the jet and coming out around the jet but inside the bearing. That would be due to a missing or broken upper gland seal, but the spray might be obscured by the flow from the jet.
I could never get my carbs to lean out after trying many many things. When I pulled the engine due to the broken crank shaft and looked at the cam lobes, the #1 and #4 exhaust lobes were nearly flat. Thus, the exhaust charge would never fully leave the chamber. I'll be up and running again in about 2 weeks. I'm looking forward to seeing the difference.
This thread was discussed between 27/09/2011 and 29/09/2011
MG TD TF 1500 index
This thread is from the archive. The Live MG TD TF 1500 BBS is active now.