TR2/3/3A Periods of Intermittent Missing

[RedTR3]

Driving the TR3 today, It was running very well when all of a sudden it started missing badly during acceleration, the car "bucked" along the road with very low power although the engine never totally quit. I pulled over, let it idle, and after less than a minute it started running perfectly again. This happened about 3 or 4 times over a distance of about 3 miles.

I suspect this is not an internal mechanical problem since the car runs well most of the time. I checked the obvious looking for a loose ignition wire but they all seem to be attached properly.

Anyway, any ideas on where to start diagnosing what is wrong?

Thanks! Tim

 

[poolboy]

Do you have fuel filter that may need changing ?

 

[Jerry]

I am betting on the distributor rotor.
Jerry

 

[RedTR3]

I am betting on the distributor rotor.
Jerry

Good suggestions so far...

So Jerry, what can go wrong with the rotor to cause such a problem? I do have new one in my glove box that I can install/

 

[CJD]

I vote either a clogged fuel filter or vapor lock. Bucking is a good sign of a lack of fuel. Ignition normally is accompanied by exhaust backfires.

 

[toysrrus]

Hi Tim,

I had the same problem when I owned a "Bugeye". Driving fine for a "Questionable" period of time (Never knew for how long). Then bucking & ultimately would stall. Let her sit for a few minutes & Off we go with no problems but not knowing for how long.

Checked "Everything"!! Feul filter at Gas Tank & Carbs, Vacuum leaks, Elec, etc. etc. The final positive solution was I installed an "Elec. Feul Pump" & Problem was solved. The Mech. pump was left on the car & operational while the "Elec. Feul Pump" was doing its thing.

Russ

 

[Marvin Gruber]

When it does it again, pull the covers off the fuel bowls and see if they are full of gas. If one is dry then you know you have a fuel delivery problem.

Marv

 

[Vila]

Tim, first I am assuming you still have the mechanical fuel pump.

I have owned my 1933 Chevrolet for over 43 years and had the same problem with it approximately 20 years ago. It does not have a fuel filter and personally I don't feel it or the TR4 needs one, which I will talk about in a minute.

I checked the following items in the order listed.

1. Carburetor - absolutely no problems
2. Fuel pump bowl had a few rather large chunks of rust - removed bowl and mesh screen and cleaned both, but still had the problem.
3. Removed the fuel pump and gas tank ends of the fuel steel fuel line and blew at out with compressed air - bingo, all kinds of junk came out and was the cause.

Later I removed the gas tank then cleaned and sealed it with a Bill Hirsch gas tank sealing kit ( https://www.hirschauto.com/products.asp?dept=4 ). I have had no problems since.

Vaper Lock, yes that could be a problem, especially if you are using ethanol fuel. I am lucky and have a gas station nearby that still sells ethanol free gas. Ethanol is more prone to vapor lock on these older cars since the fuel system is not pressurized like modern cars. Also on modern cars the fuel that bypasses the pressure regulator returns to the gas tank which also eliminates vapor lock.

Some of my Chevrolet friends have used fuel filters and had some of the problems mentioned in the postings above.

Personally I have never used a filter on my cars that did not have them from the factory and I have never had a problem. Yes, modern fuel injected cars need fuel filters to filter the very small particles that may clog the fuel injectors. Did you even look at the size of the fuel passages on the triumph carburetors, they are huge and anything that gets part that screen mess in the fuel pump will not clog any part of the carburetor. Same with my 1933 Chevy.

The attached AC fuel pump photo looks similar to the TR4 fuel pump, but it is actually a spare I have for my 1933 Chevrolet and most of the parts are exactly the same. The main difference is the angle the bottom have is bolted to the top and the angle the outlet pipe comes out of the pump.

In my opinion, the filter screen along with the sediment bowl on the original Triumph fuel pump is more than sufficient to filter the fuel for the Triumph TR4 carburetors. If you need a new filter screen, glass bowl, or other individual pump parts, may of them are available from www.fillingstation.com

Vila
1933 Chevrolet
1962 Triumph TR4
1984 BMW 633 CSi

 

[RJS]

Absolutely my vote is the ignition rotor.

My cap and rotor served me well for 9 years and 9,000 miles. However, after a bit of research, I see that they were cheaper replacements. The cap used aluminum terminals and the rotor was "riveted" and used high carbon black plastic. Apparently, a known issue with these rotors is that the spark will follow the path of least resistance from the rivet, through the spring clip to the distributor shaft. Thus, the misfire. It becomes worse when hot and under load. Exactly my symptoms.

I replaced the cap and rotor with higher quality parts. Cap has brass terminals and the rotor is the red plastic option (not high carbon black plastic) and no rivet. $25 for both.

See post here: https://www.britishcarforum.com/bcf/showthread.php?90955-Fouling-Ignition-Rotor

Bob

 

[karls59tr]

The same thing happened on my tr3. It turned out to be the fuel filter was clogged with a yellow powder which I assume was from bad gas.

 

[BillyB62]

Tim,

Does it happen during engine load? I've had issues with my dashpots leaking and when the oil is gone the car start to buck going up hills. I've switched to a heavier oil and it ran all day yesterday (over 200 miles) without a single miss.

 

[TR3driver]

I'm not seeing how a failed rotor would recover after a resting period. Definitely they can carbon track between the moving contact and the center shaft; but I don't see how that could ever get better.

From your description, the first thing I would check are the two small wires inside the distributor, especially the one from the points to the terminal on the side. Disconnect one end, and use a DMM to check resistance while tugging gently on the wire. The point lead is forced to flex every time the vacuum advance moves, and although it is a special extra-flexible wire, it can fail inside the jacket. The ground wire can fail, too.

Then I would check the resistance of each plug wire and the coil wire, from the cap terminal to the other end. A bad connection here can cause the spark to jump to strange places some of the time.

If that all looks good, my next step would be a fuel pressure test, when the problem is happening. Then I'd change the coil & condenser. If still no joy, next I'd try to confirm that the coil is getting a steady 12v when the problem happens. (For example, run a temporary wire from the coil hot terminal into the cabin, where you can have a meter connected while driving.)

 

[RedTR3]

Thanks Randall, those are very good ideas which I will work on first thing in the morning. I did notice that the wire from the points to the side has some frayed wire strands sticking out...possible these could be shorting to ground inside the distributor? I will trim off the frayed bits for now and apply some insulating tape (until I can replace the wire).

 

[TRWisco]

Have an issue like this as well, except its like the car is running out of gas. Only happens on long drives So I'm thinking it might be some kind of heat soak problem?
I have no idea really. This is my first old car (aside from a 78 Jeep CJ-5. But that thing would run no matter what happened to it.)

 

[TR3driver]

Some more details might help; like which car you have, what mods it has installed and why you think it's running out of gas. Also how long it takes to recover, and what things you've tried.

Heat can certainly cause fuel problems, but generally "heat soak" refers to what happens after you turn the key off. (Things get really hot then, because the engine is still full of heat but the cooling system isn't working.)

One thing worth trying would be to pop the fuel cap open immediately after the problem appears. If you hear a "whoosh" of air, then the tank vent may be clogged or pinched shut. Air seeps in slowly through the cap or whatever, but under sustained driving, the pump pulls a vacuum inside the tank until it can't suck fuel any more.

IMO TR3s are simple, rugged and reliable. But they can have strange failures after 50-60 years of indifferent maintenance, etc. I drove one for many years before I ever even saw the maintenance schedule in the owner's manual, which seems to call for an incredible amount of maintenance by modern standards.

 

[TRWisco]

The part about the vent being blocked might be the answer. The car is a 57 TR3, it has an aftermarket exhaust, maybe corsa? I know the motor is built, but what exactly was done to it i have no idea? All I've ever heard was that its a "race-spec" motor. But the issue happened after about 20 mins of driving, with the last 15 mins of that being on a straight 55MPH road. It would just bog down like it had no power, let off the gas and it would be fine for another 2-3 mins before re-appearing. And then it did that 2 more times and then be fine.

I only get to drive the car a handful of times a year like that so I don't really have much more info. Its not my car but I get to use it every now and then. Its the same car as the engine noise thread on this forum. I need to find out more info about the car before he doesn't remember it anymore.

 

[tomshobby]

Hi Tim,

I had the same problem when I owned a "Bugeye". Driving fine for a "Questionable" period of time (Never knew for how long). Then bucking & ultimately would stall. Let her sit for a few minutes & Off we go with no problems but not knowing for how long.

Checked "Everything"!! Feul filter at Gas Tank & Carbs, Vacuum leaks, Elec, etc. etc. The final positive solution was I installed an "Elec. Feul Pump" & Problem was solved. The Mech. pump was left on the car & operational while the "Elec. Feul Pump" was doing its thing.

Russ

I had the same problem with my TR6. The first time it happened was a couple miles from Ft Knox while on trip. Turned out that if I held the accelerator to the floor whatever was happening would clear up. We continued on our trip and over the next few years traveled coast to coast through 28 States and Western Canada. All that time the problem would reappear randomly and after holding the accelerator down it would clear up. I checked everything including having the carbs rebuilt and installing a fuel pressure regulator. I did compression checks and did a few complete tune-ups replacing the cap, rotor, wires, and plugs. The result was a very nice running car that would randomly lose power until I would hold the accelerator down to clear it. This might happen several times in a mile or two or might not happen for a couple hundred miles.

I finally replaced the fuel pump even though when I checked it there was good flow and pressure. Haven't had the problem since. I have been working on cars for a lot of years and never even heard of anything like it.

 

[RedTR3]

Deleted

 

[TR3driver]

Deleted

So, did you find a solution?

 

[RedTR3]

So, did you find a solution?

Hi Randall,

Well, I was going to post my frustration. Here is what I have done:

1. Replaced points, condenser, internal distributor wires
2. Replaced coil
3. Installed new wires from ignition switch to coil
4. Checked dist cap and wires
5. Replaced fuel filter

After all this the car still has "episodes"...now to me it feels like perhaps I have a blown head gasket although there is no coolant loss. During the "episode" the car feels like it is running on 2 cylinders, can't go more than 15 mph. No white smoke from exhaust but it does have noticeable black smoke. Fuel level in carb float bowls looks normal. Usually if I let the car idle for a while the episode goes away and the car then runs normally, but not last night, it never "cleared up". I am stumped and losing confidence in this car, its let me down a lot I hate to say. I appreciate your help though in trying to figure this out