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TR2/3/3A Troubleshooting Advice

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Skidude

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Was out for a drive today - everything running great. Got about 30 miles from home and the TR3A started missing, backfiring and sputtering. Finally stopped, checked all of the wiring and regapped the points (just to be safe). Didn't help -the more I pumped the throttle - the worse it got. Finally got it to calm down enough to limp back home as long as I didn't try to drive fast and kept the speed down to 35 or below.

I'm sure there are a number of possible solutions - but, at this point, I wonder if it is the fuel pump? Any of you more knowledgeable, mechanical types have some advice on what I should check/do?

Thanks for any and all advice.
 
I would first think fuel pump, or a clog (rust?) in the filter and/or fuel line.

Start the engine, fast idle for a couple minutes. Then rev the engine and hold at high rpm. See if problem returns.

We'll take it from there.
Tom M.
 
95% of all fuel problems are electrical. Likely a bad condenser, rotor or coil.

Lots of problems in the last few years with condensers and rotors. If rotor has a metal rivet they are notorious. Red rotors are best. IMO the yellow-wire condensers from the Distributor doctor in UK are most reliable.

When you've solved it, like to hear what the problem was.

DistDM6CondenserTop0620.jpg
 
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Do you have a filter between the tank and the fuel pump?

This is what my filter looked like after about 1000 miles. The tank was clean and the lines were new.

David

fuel filter resized.jpg
 
I would pull the spark plugs and look for a pattern for problem. They often foul out front to back.
steve
 
Okay - started car, let warm up then raised rpms to around 3500 - after about 30 seconds started sputtering again.

Going out to check plugs, replace the condenser and correctly regap the points now.

How do you check a coil to see if it's gone bad? I have a new coil (bought with the Petronix kit - just haven't installed yet). I want to get this problem straightened out before I install the Petronix.

Also - checked both Moss and TRF - didn't know distributor caps are no longer available. Anyone have a source for good, reliable distributor caps?
 
I have some coils around, so I just try a different one when trouble shooting; I suggest you get one. I bought one at the local auto parts store a while back. A tr3 has a resister coil. Your problem could easily be the coil. What do the plugs look like; I believe in reading the plugs for carbon or the lack of carbon that will tell a lot.

steve
 
Troubleshooting anything like this is simply a process or eliminating possibilities logically. Start by determining whether it is fuel or ignition. Ignition is easy to check--make sure you are getting a strong spark at each plug by removing each wire and making sure you can get a strong spark to ground. If you don't, start with the most likely culprits: replace the capacitor (AKA condenser), reset the points gap, since you probably got it wrong by messing with it beside the road, and since changing the points gap probably moved the timing, static time it to ~5 degrees. I'll bet that will do it. If not, it's time to look for a bad wire or coil. Again, hold the high-voltage wire from the coil close to the block, and see if you get a strong spark. If you don't get a strong spark and are sure you're using a known-good capacitor and set the points right, it's gotta be the coil.

If you have a good spark at all the plugs, it's not the ignition circuit, but it still might be the plugs. Check them for fouling. If they are OK, you can go on to fuel. Disconnect the fuel line at the carbs, aim the end into a container, and make sure you are getting a good squirt with each operation of the pump. If not, work backward to see where the line is plugged. remove the fuel filter, if you have one, and try again. If it's still plugged, disconnect the fuel line and blow it out backward with compressed air, if you have it. Tire pump if you don't. If that doesn't fix it, check the pump diaphragm. If all that checks out, it's time to look for problems with the carbs themselves. I won't get into that now, since I'll bet the above tests fix it.
 
While we're at it, take a look at this;

https://www.thesamba.com/vw/classifieds/detail.php?id=2241678

The guy has a conventional polypropylene capacitor potted in a nice package, with 1/4-inch spade connectors; a good solution to the trash-capacitor problem. It's $17.50, but if you were to buy the housing, cap, and potting compound, you'd be close to that.
 
Today’s update on my TR3A issues.

Spent the morning checking the carb floats, fuel pump, filters, put in new plugs, condenser and points (properly gapped). Old plugs were totally black with carbon. Don’t know it that was from driving the car 30 miles back home with the car sputtering and backfiring most of the way – or, is a sign of something else going on.

Car started up and ran like a top. Drove about 20 miles (at speed as much as possible since this where I had my problem). Had a couple of very slight burbles that I probably wouldn’t have noticed if I weren’t so paranoid in listening to how the engine was running – but overall ran fine.

Hopefully, fixed the problem. Will try to take a longer drive in the next few days to see if the problem comes back – or, the car is still running fine.

Thanks to everyone for all the advice.
 
Skidude said:
Today’s update on my TR3A issues.

Spent the morning checking the carb floats, fuel pump, filters, put in new plugs, condenser and points (properly gapped). Old plugs were totally black with carbon. Don’t know it that was from driving the car 30 miles back home with the car sputtering and backfiring most of the way – or, is a sign of something else going on.

Car started up and ran like a top. Drove about 20 miles (at speed as much as possible since this where I had my problem). Had a couple of very slight burbles that I probably wouldn’t have noticed if I weren’t so paranoid in listening to how the engine was running – but overall ran fine.

Hopefully, fixed the problem. Will try to take a longer drive in the next few days to see if the problem comes back – or, the car is still running fine.

Thanks to everyone for all the advice.
Click to expand...

What was the problem?
 
Since I changed the plugs, points and condenser at the same time - not sure if any one of those solved the problem - but, the combination of the 3 seems to have fixed the problem. Now, all I have to do is figure out what caused the problem in the first place (guessing it was the condenser that had/was going bad).
 
I would suggest that you carry that extra coil on your next ride and have wires to temporarily install it in case the problem occurs again.
 
20-20 looking back and the fix comes to you so elect. did you cover up the problem. I carry an extra coil to cap wire it does the work to all plugs. A weak fuel pump will cause the car to do the same as it can not keep up with RPM. As to finding a new cap look UK also British Parts Norwest in Oregon. and I know a friend that closed his British shop that my have one maybe in the box too. I will call him, Madflyer
 
Make sure your choke is fully shutting off by either looking at the jet or putting your finger on the jet and trying to push the jet back to its stop position. The choke on a SU is counterintuitive to other chokes because it does not shut off the air; it enriches the fuel. If the choke sticks open just a little, the plugs will foul. After I have driven my car for a while, and do a restart warm I hold the gas pedal way down to the floor. This lets in a lot of air, but not much or any fuel. That keeps back some fouling problems plus IMHO helps a lot with a hot start.

Try some NGK plugs or some split-fire if you can find them. You might just have a rich fuel mixture. I like what Steve G suggested by pulling the domes of carbs and looking at the positon of the jet in relation to the housing. The jet should be about 1.5mm down in the assembly which is not much.

Just curious do you need a full choke if the outside temp is say 60 degrees out and the car has not been started? Another thing I do on a cold start at about 60 is pull the choke out and let the choke back in right away. This lets a little gas in, but does not let raw gas keep coming in which contributes to fouling. These cars ran on 101 leaded auctain fuel when new, so we are always correcting that .
 
I use full choke to start TR6 and once started, I immediately push and turn choke to halfway position until I'm well under way. Then all the way off. Hot start? Never. Starts instantly when warm.
 
Perhaps I was not clear. I am suggesting when starting a tr3 when engine is fully warm is to push the gas pedal down. There is no accelerator pump and the open throttle lets more air into the engine. Did you think I said choke a hot engine?
steve
 
As two the Dis. cap there are two I do not know how to tell but the DM-2 is harder to find they are also to different sizes. And to starting LBC's with no accelerator pump. Always start not in gear clutch out full choke start half run off ASAP smoothed out. Starting with out the clutch in takes the load off thrust bearings in motor and trans that may have less oil at start. Madflyer
 
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