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MG TD TF 1500 - Where to start
|I re-built much of my 52 TD over the past 5 years and have an issue that I am not sure is typical of the MG or a real problem that I just can not resolve (obviously, this may be multiple problems). The engine will not run without full choke until it is pretty warmed-up. It takes 3 or 4 minutes on a nice California day to operate without choke. During that period it backfires and has no power. Once warm, it runs fine with good power, although it always smells like it is running rich. Distributor was rebuilt by Advanced Distributors, new plugs, new wires, rebuilt and smoothly operating carbs, timing set at TDC to idle and 36 degrees at 3000 RPM. Any ideas where I might start?|
Thanks in advance.
|Welcome aboard Dave(something about Dave's and T cars ?)|
These engines usually take a bit to warm up without the choke. That said they usually run fairly well with the choke. I'm wondering if perhaps you are only getting full choke on one carb. Check the linkage with the choke off. Then fully engage the choke and see that the jet tube is lowered equally on both carbs. Since the car runs fine when warmed up I wouldn't suspect any other carb or timing issues.
By the way...we are a visual bunch...we like pictures
|L E D LaVerne|
|LaVerne: I have been lurking and posting on-and-off for years. But thanks for the welcome back! It appears that the choke linkage is fine. To be clear, the engine won't run at all at 70 degrees unless the choke is engaged. With the choke, both jets lower the same. I did notice that #1 and #3 plugs show to be much "richer". A pic to show how the linkage is set is attached. The choke cable is disconnected in the photo.|
|Welcome back, Dave. Perhaps it's an optical illusion but, it appears to me that your float bowls aren't vertical. Yes --- your float bowls aren't right. I'll have to check some other images to pin it down. Bud|
|Bud - It is only slightly an optical illusion. They are in fact slightly out of vertical. That said, I don't see how there is any way to adjust them. And, the car should run fine on a slope ?|
Your float vent pipes should be large diameter down towards the lid, an aluminum washer under the bolt, and a segmented fiber washer between the banjo and the lid.
My car starts at any temperature above 65 without the choke, from cold.
Download my PDF on setting up the carburetors. It has some checks you can do. www.dbraun99.com
|Do you have timing problems? It sounds like you may.|
|This may be a too simplistic solution to your problem however I experienced a somewhat similar issue when I had low oil level in the dampers. Car would backfire thru the carbies until it was totally up to operating temperature.|
|Dave R. I hadn't noticed the vent banjo fittings until Dave B. mentioned it. If you don't have the segmented aluminum washer between the top of the float bowl lids and the bottom surface of the banjo fitting, the float bowls will not be vented as they should and could be a big part of the problem you are having. Also, if the float bowls are not sitting level, you could have the wrong bowls. I'll have to take a look at my Burlen Fuel System catalog and see what the correct bowls are. Cheer - Dave D. |
PS to LaVerne - "something about Dave's and T cars ?" I suspect that it is the age - go over to England and the same generation has a preponderance of Paul's.
|Err.. David, segmented FIBER washers. The aluminum is solid just under the banjo bolt.|
|Dave B. - You're right, I got the two mixed up.|
Dave R. Do your float bowls slope back from the vertical towards the engine? If they do, you probably have them on the wrong carburetor. The float bowls are designed such that, with the carburetors are sloped back towards the engine at about 20°, the float bowl will sit vertical. Cheers - Dave D.
|Should just need choke to crank, then just a bit for 30 seconds or so if really cold. Run fuel pump to fill float bowls. Remove the bowl tops to make sure both filled evenly and that the floats are floating. Or you can remove the pistons and measure the depth of fuel at the jet bridge. This has to be correct. A piece of trash can plug a jet also. Make sure the needles are correct, and that the pistons move freely. Find and watch John Twist's video on checking the pistons/suction chambers. Check for air leaks by spraying carb cleaner at manifold/head joint and carb/manifold joint while running. It will speed up if there is a leak. Watch pistons when gassing it, both should move up at the same speed. Interesting about the plugs. Many SU 'problems' turn out to be ignition- change rotor, check cap, make sure not plug wires burned off at the cap end, etc. Is timing TDC static or running? And always try new plugs if all else fails. George|
|I am heading out to the shop to check on the fiber washers and the position of the float bowls. |
|I have included two photos below. I plan to re-do David's procedure for setting the float height to see if I can get this puppy running correctly. Does anyone see anything wrong? The float bowls appear to be correct to me, they are vertical but they do slope somewhat when looked from the side of the car. The split washer was right, no leaks, rebuilt distributor, good wires. I do have a question on timing. Should the static timing be TDC or an 8 degree advance? This feels like a carb issue as the #1 and #3 plugs have more carbon on them. While the pistons move freely now, the rear-most carb piston seemed sticky when I dismantled it. Maybe I had the oil fill wrong???|
Thanks in advance
|Carb from top
I think I see the problem, if you look very carelully at the rear carb, you will that it is missing its dashpot.(weak joke but I couldn't resist)
Seriously, One thing to check which could cause your problem is that one or both jets are not centred, this will prevent the pistons from moving freely.
John 52 TD
|Looks fine to me. I think the initial picture on the thread is just distortion from being zoomed to wide angle. To check for sticky pistons, put the suction chamber back on, and remove the damper from the top. Lift the pistons up, drop them and they should drop straight down and click when they hit. There should be pretty much no drag lifting them up either without the damper, and even with the damper. is there a hole in the damper top? "This feels like a carb issue as the #1 and #3 plugs have more carbon on them" Have to disagree with that, if no air leaks or other problems, 2 and 4 would also be dirty. The only thing 1 and 3 have in common is they are next to each other in the firing order, so make sure the plug wires are in correct order and not swapped, and really look at the inside of the cap to check for short marks. Just because stuff is new doesn't mean it is good or correctly installed. Lastly, check the fuel level before you do anything else, all is dependent on that. George|
|PS- I left of ""with the damper and no oil".|
This thread was discussed between 24/06/2013 and 25/06/2013
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