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MG TD TF 1500 - Power Issues

Saturday was a really nice day so I finally took all my winter work for a test drive.

Winter work:
Replaced a 5.125 rear for a 4.55.
New axles.
New wire wheels.
New tires.
New springs and misc. hardware.
Replaced the Judson for the new Moss supercharger with new pulley, carb. and filter.
New Halogen headlights with relays.
Air horns.
Put all the smoke back in the harness.

The car seems to lack power at high speeds. In one direction on the hwy it would not go over 60mph.
Coming back it was responsive up to 70mph then hesitated. Tail wind?
Then later I was cruising along at about 60 in heavy traffic and I got one large backfire. (Good thing I brought along extra underwear.) The water temp. was never an issue. 80-85 ±.

I just checked the new pulley and the TDC is right on.
At idle of 800rpm I'm about 5 degrees BTDC and a 26 degree advance at 3,000rpm.

I'm getting about 6 pounds of boost at speed and on demand.

Any thoughts on why the hesitation at speed??????

(pertronix ignition, 5 speed tranny, oil cooler, spark plugs look healthy)
Mort Resnicoff (50 TD-Mobius)

Mort,
You didn't mess with the petronics,, or the plugs,,,
The 5.125 combined with the 5 speed might give the impression of lack of power,, but I would go back and check the settings on the new carb/supercharger,,,,, maybe go our again, and run it until you feel the lack of power,,, when this happens, SHUT THE IGNITION OFF! and coast to a safe stop,,, Then check the plugs,,, that might give you a clue as to what is happening t that speed,,,

You only have 62 days to figure this out !!!!!

SPW
STEVE WINCZE

Somethings not right. At your altitude it should pull right on up till you chicken out. Back fire was an indication of unburnt fuel loading up. You need to get a hand held volt meter you can hook up and read inside the cockpit. I've found the Pertronix will go to crap if the line voltage is much under 12 volts. Also as stated above..get a good reading on the plugs.
L E D LaVerne

Mort,
I suspect your issue is carburation. Check to see if the piston moves freely. Are you getting good airflow? Is the air cleaner restricted? Vaccume leak? It may have the wrong needle. I remember something about the carb with the Moss supercharger. Use the Moss tech support if the problem does not jump out at you.
Good luck,
David
D. Sander

Mort, my car is set up very similarly to yours. One thing I did was send my distributor to Advanced Distributors (Jeff Schlemmer) who reworked it and tweaked it to go with my blower, compression ratio, gearbox and axle ratio. It goes up to 80 mph (or more?)if I want it to but I don't care to push it like that. Hills are a different story unless I start shifting out of 5th.
It also has the pertronix ignition.
Jim Merz

Mort,
I second what Jim says. I don't think your distributer is the problem, but having Jeff rebuild, recurve and map it to your engine would make sense.
-David
D. Sander

If it was a backfire, that is, back through the intake, it's lean. If it was an after fire or out the exhaust, it's rich. Think of a backfire as air, looking for fuel and an after fire as fuel, looking for air.
J E Carroll

I'll stick with my first guess without more info. I'd guess the back fire was through the pop off valve. Check the casting around it..I'll bet its shows some black carbon. This is a been there done that moment for me. And the trouble was as I stated above.

Did you have those head lights one at the time?
L E D LaVerne

A misfire is usually caused by an ignition problem and may manifest as a back or afterfire. LaVerne points out that the Petronix ignition has issues at low voltage. Good luck troubleshooting it. It should be that you do all that work and it runs perfect but you'll find it.
J E Carroll

J E Carroll, wouldn't a sticking exhaust also give an after fire? a sticking intake valve a backfire?

Mort, was it a backfire (back through the intake/supercharger??? or an after fire out the exhaust?
it would be helpful if you are able to provide the results of data obtained from troubleshooting rather than describing symptoms. vacuum readings when running, differential compression test, fuel height at bridge, voltage at coil, etc., etc..
regards, tom
tom peterson

Tom,

You are indeed correct that the symptoms would be so and I suppose the winter layoff could contribute to some stickiness.

Since Mort just changed the intake system and is reporting lack of power, I suspect, from miles away, of course, that a possible lean condition exists. I think that LaVerne's suggestion the the electronic ignition module might be starving for a few volts may contribute to a misfire, especially if the new headlights might be more than the generator is capable of but it shouldn't manifest itself at speed when the gen output is at its best.

I think if it was overly rich it would be smoking black. There's a much quicker falloff in performance when you go lean that when rich, at least in my experience.

You're right, a better description of the parameters and symptoms will help us armchair diagnosticians!

Jim
J E Carroll

We've run a Magnacharger for quite a few years in 2 TDs, and it has been a fun experience. Also have a Marshall on one now, also, but it is semiretired. (Also have a Shorrock and SCoT waiting in the wings).
Check plug color, but my guess is they'll probably be white. I installed an O2 sensor to keep an eye on air/fuel ratio and wouldn't run without it. It had issues where about 60mph, the gauge would drop out lean, then pop back up, but by 80, it spent most of its time disappearing lean (3:92 MGB gearing- 80mph only 4000rpm- 2 fuel pumps, too). I used Dave Braun's technique for adjusting fuel level with respect to the bridge, rather than the "upside down float...3/16" drill bit" method, and it has stayed just a touch rich ever since.
I notched the crank pulley to set timing- 25 degrees advance max. If your engine ran fine with the Judson, ignition probably isn't the issue.
The TDs are wifey's toys. She cruises at 80 and it'll hit 230F; just recently had radiator recored more efficient, so hopefully we'll see lower temps this summer. Since it ran so hot, and occassionally backfired out the blowoff, (only at that temp on the highway) I opened valve lash to 19thou. I was worried the valve train may have compromised the clearance while scorching hot.
Have invested in Len's roller lifter cam with street/supercharged grind for the original XPAG engine awaiting new life. Like to think reducing overlap may control the exhaust heat and fuel mileage a touch.
Plan to add a remote 1 1/2 gallon spin-on oil filter just in front of rear axle for an oil cooler!
I recently acquired an Eaton blower for $100 to install on one of our Honda CRXs, to convert it to a stroke. For an encore, how about converting another CRX to a two cylinder, using the two middle cylinders to supercharger the two outer cylinders? It is now April 2nd here, this isn't an April Fools joke.
They're all a work in progress!
JIM NORTHRUP SR

Damn Jim! that"s a big ass filter.

Mort could have could have any number off issues but considering he released some valuable smoke recently and along with my experience, I'd start with some voltage checks and then move on to other areas. With his drive train set up and his geography, the car should pull hard until it gets to twitchy to handle.
L E D LaVerne

Jim,

Do you 1 1/2 quart? I have 2 quart filters on a couple of trucks and they're pretty tall!

Jim
J E Carroll

Should proof better! It should say "do you mean 1 1/2 qt?"
J E Carroll

Gentlemen,
I appreciate the many very excellent responses to the power issue. I have had a delay in the troubleshooting. I messed up my fuel line (pump to carb) and am awaiting the arrival of a new one. I will resume and post after it arrives.
Mort
Mort Resnicoff (50 TD-Mobius)

One more consideration...fuel delivery. I recently had a problem with my MGA...it would run fine up to 50 mph but would bog down anything over that. Turned out to be ethanol jelly (or something like that) in the fuel line preventing full fuel flow. Replaced the fuel line and all is well. You could also have a partially clogged filter in the fuel pump or carb.
Gene Gillam

Dont forget the filter in the tank, this can cause serious trouble with power dropping due to no gas. Of course with anything Lucas, all fuel problems usually are electrical in nature.. LOL
Tom Maine

The starvation of fuel will definatly show up as a failure of the engine to rev beyond a given RPM, but the backfire (which we haven't been told where it came out of) is suspicious to me as having occured at the pop off valve. Trust me it will make you wonder if a rod just went into orbit. The cause in my case was low voltage caused by long running on the interstate with the lights, heater, wipers,gps and phone all drawing power and a generator that couldn't keep up with it all. Build up of fuel from non firing plugs and intermitnent BOOM through the pop off. Shut the head lights off and all was well. Later noticed that the engine wouldn't fire while spinning the starter but would immediatly fire when I released the starter. Diagnosis was the Pertronix will not work at a voltage that will still crank your engine. I'm not sure what the point is but I do know that there is a threshold where it will not work.
L E D LaVerne

Mort,

I have the Eaton blower with a 1.5in carb and had a similar problem. If you pull out the choke when you have the loss of power and it runs better than you have the wrong needle for the carb. Check with Joe Curto for a replacement.

Regards,
Jim
Jim Neel 53TD28423

LaVerne...try driving when your #2 intake seizes in the guide and the rubber o-ring in the pop-off valve gets blown out when it backfired. FINALLY thought to pull the spark plug wire to #2 - and replaced the o-ring - ran fine then for the last mile.
Gene Gillam

Did you get one of the improved o-rings Gene. Terry sent me one couple of years back. Makes a big boom don't it?
L E D LaVerne

Yeah, got a couple...from Terry and Lange. In my tool box now.
Gene Gillam

Gentlemen, Thank you once again. I was on the path of troubleshooting the fuel issue when I messed up the fuel line. The new one is due in this evening. I will post the results this weekend after further tests.

Jim Neel, I will try that choke technique.

Tom Maine, The filters are all good. I replaced the one in the tank last year. My in line and pump filters are clean.

LaVerne, I saved all the smoke and put it back in through the valve in the harness. I'm going to pursue fuel starvation first.

News at 11

Mort
Mort Resnicoff (50 TD-Mobius)

Last evening, our TD (with Magnacharger) was bogging down on take off, and backfiring through the blowoff a few times at low speed. Quite odd, to say the least. Never happened before. No lights on and voltage was plenty high. New plugs barely have 100 miles. I knew it had gas since the low fuel light had just come on from the night before and we were only going on a ten mile excursion. My wife bugged me about the low gas so I grabbed a 2 gallon gas can and dumped the contents in just to make her happy. Along the way, wife kept asking why it smelled like gas, but it didn't smell like a gas leak. I had notice the wierd exhaust odor. Then it dawned on us, that familiar smell was much like that of our truck (without the vegetable oil).
My wife kept a 2 gallon red gas container by the mowers, with diesel fuel for her wiki lamps!!!!!!! Need I say more?

As for the oil filter, a picture is worth a thousand words. The spin-on filter is about 5" diameter and 10.5" long. Depending on the rpm, the oil may take a 2 minute trip slowly about 6' to/from and through the filter just in front of the rear axle. That ought to knock the temp down, and about double the oil capacity, for what that's worth. There are housings that accept 2 of those filters! I have a hydraulics business and don't put much faith in oil filters. I'll probably add a large neodymium magnet somewhere in the circuit to capture ferromagnetic fines, but my experience with oil pans, automatic transmission sumps and gas tanks, they don't really seem to draw the rust & fines out of circulation as well as one might hope. That may or may not be 2 cents worth.


JIM NORTHRUP SR

Jim,

I did the same thing to my wife. I needed some kerosine and had an empty red can in the back of the truck so I put it in there. She knows that diesel is in the blue cans and gasoline is in the red so...

She put it in a ZT mower and was a bit BS at me. It ran like crap and wouldn't shut off until she shut the fuel off. I was trying to figure out what to do with the mix that I drained and finally put it in an old John Deere 2 cylinder where it worked just fine!

Wouldn't it be a little more efficient to add an actually oil cooler rather than the extra remote filter or is it a case of using what you have on hand

Jim
J E Carroll

Gonna be an expensive oil change. I'd like to see the finished product Jim. I gave some thought to mounting my oil cooler back there. Might move it after I see how you go about it.
L E D LaVerne

I am really suspicious of the carburetor. Could be the wrong (lean) needle, an air filter restriction, sticking piston, wrong mixture adjustment, vacuum leak, etc.
Nothing changed in the ignition system, yet the air and fuel systems have been replaced.
-David
D. Sander

Mort,
I just had a thought. Can you put the carb from the Judson on and test drive it?
-David
D. Sander

Oil changes may be twice as expensive, but only half as often!

oil filter vs oil cooler?
Last summer, wife called and asked what that blinking red LED was for on the dash. I reminded her that it is the oil light. I ask "Is it running?" "Yes" she replies.
I reply, in a cool, calm scream, "SHUT IT OFF!!!!!!!!!!"
Big oil stream shows where she'd driven from.
Filled it with oil, but couldn't find any leak anywhere, until she started it... a stream of oil blasting out of the NEW wired braided tubing heading under the firewall to the oil pressure gauge. The ruptured tube was concealed under the wire braiding. The car was parked for a couple of hours until I could cut the line and clamp in an elbow with barb fittings.

For the filter circuit, my plans will include hoses, off the pump and into the block, that can be disconnected from the filter circuit, and connected together, in case of a bad leak. Don't like to be stranded. An oil cooler, especially down underneath in front, could be a touch vulnerable, like so many radiators I've had to redo.

For all practical purposes, a long oil filter circuit, with a generous oil supply, will dump the heat as well as a typical cooler. That filter also has probably 10-20 times the paper filter area of a typical car filter, and the oil will flow through so slowly, it'll be a far more efficient filtration system, especially since I'll be replacing just a gob of felt! As I said, I'm not really all that worried about oil filters; the first Detroit engine block to incorporate a filter was the '55 small block Chevy V8.
JIM NORTHRUP SR

So the reason I was out playing bumper cars yesterday was to test a few of the suggestions, made here, about my loss of power. This is my up to date report.

First tested for fuel starvation. I put a fuel pressure gauge in line using a "T". Just between the superchargers carb and the fuel pump. Since I have never had to use it before I forgot to mention it earlier but I have a second facet pump mounted under the rear deck. It turns out it is twice as strong as the MG pump.
When I turn the key with the MG pump on, the pressure goes to 2 psi. When I start and run the car it drops to about 1-1/4 to 1-1/2 psi. Using the facet pump it goes to 4 psi and when running it drops to about 3-1/4 psi.
With either pump I don't notice any further drop off at speed. Even with the stronger pump it still hesitates at 60-70 mph.
I will static test the pump for volume (8 oz. in 30 secs)and then submerge the end of the fuel line in a container of gas and check for air bubbles.

I also turned the key off at speed and pulled the plugs. I did get a single backfire or (afterfire???) when I turned it off. The plugs looked ok. See photo.

I also hooked up an old analog voltmeter to the generator. Both at start-up and running at speed it stayed at 14-15 volts. No drop off during hesitation at speed. I put the lights on bright and got maybe a volt drop.

As suggested I also tried pulling the choke out a bit when it would hesitate without much change in performance.

Suggestions for the next round of troubleshooting would be welcomed.
Mort


Mort Resnicoff (50 TD-Mobius)

Couldn't see the ceramics on the plugs to evaluate mixture.

Check out Dave Braun's SU site dave@dbraun99.com
particularly steps 6 & 7 for setting fuel level. Just undo the dome and pull the piston out... have fun.
JIM NORTHRUP SR

Sounds like the voltage possibility has been eliminated. But to be sure I'd switch to a set of points and check it again. With the two pumps running there is a possibility you are pushing fuel past the float.
L E D LaVerne

LaVern,
I have the two pumps on a toggle switch. It's either off or on one of the pumps so I can never run both at the same time.
Mort
Mort Resnicoff (50 TD-Mobius)

Mort,

I had a similar problem but with my stock '53 TD. Couldn't figure it out even tho Jeff had rebuilt the distributor. I talked to Jeff about my problem and he suggested closing the point gap to about 0.012inches from the recommended 0.015 that he had set the gap for at the time of the rebuild. Ran great after that. Also had another similar problem with the car cutting out and no power. The lead from the coil to the distributer would ground out at high rpm. Took a while to find that one. These might not be your problems but at least they are a couple more ideas.

Sorry about your car!

Mark
Mark Strang

Mark,
I've got a Petronix ignition.
Mort
Mort Resnicoff (50 TD-Mobius)

Suggestions: the only fuel that matters is what is in the bowl/jet, and how deep. Try running hard to the point it bogs, then shut down (key off, clutch in), coast to a safe spot, and take the float bowl lid off and verify that the fuel level is correct ( and not nearly dry or overfilled). Just because pump pressure and volume are fine does not mean the bowl is correctly filled (dirty/clogged inlet filter or needle valve, and/or vibration could effect.) Make sure the float is not filling with gas and partly sunken. Voltage: That is nice that voltage good at the generator, but is not where you should measure. Check at the battery (downstream of the regulator), and at the hot side of the coil (or Petronix, depending on the wiring- I don't have diagram handy). That is where you need 12V+. Also, just because the carb is new, don't assume it has the correct jet and/or needle. Trash could also be in the get. Old 2 stroke dirt bike trick: Take air cleaner off, rev it up, then stick palm over the intake w/ throttle open. Sometimes this would pull trash through the restriction. Could just be a piece of trash in the bowl to jet passageway, etc., etc. Check for stupid things I have spent hours chasing down like the coil wire being burned off in the center of the distributor cap, etc. Do you have a red dizzy rotor? Lots of rotor failures also w/ various symptoms. Good luck ! George
George Butz

This thread was discussed between 31/03/2013 and 11/04/2013

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