TR6 new TR6 owner looking for advice

[sirrahtap]

I'm a new Triumph (74 TR6) owner, looking for some advice on a problem. I'll try and be thorough with my explanation and with what I've done so far.

My dad was the previous owner of the car, and he drove it very rarely for the last 5 or so years. For the last few years, he said that whenever he'd go out for a short drive (<10 miles), it'd end up running rough, and sometimes even die. After letting it set for about 30 minutes, he'd start it back up and be able to make it back home.

When I got the car, I took it for a quick spin, and basically had the same issue. At first it ran great at any speed, any gear, any revs, any throttle. After 5 miles, it started to run rough, and eventually died. I'd try to start it, and it absolutely wouldn't fire. I saw it was getting spark, so figured it might be a fuel issue. Eventually, after numerous times trying to start it, it just fired right up. I drove it a few miles back home and it ran fine the whole way.

Since then, I've done a little work...
New Battery
Pertronix igntion (I was planning to do this conversion regardless of the issue). Timing was checked, and remained same
New coil (according to recommendation to match the new ignition system)
New Spark plugs (old plugs seemed to be fine...they didn't point to any obvious issues)
New fuel filter
New fuel pump
Disconnected vacuum retard on distributor
Checked carbs by opening air piston and gauging the reaction...both seemed to be good.

Tonight, I took it for another spin. It started up great, and ran great again for the first 5 miles. It might've even been running a tiny bit smoother than before, unless I just imagined that. After about 5 miles though, it started running rough again, like it was missing. It never died on me, like before, so I ended up making it home. From a stop, I could only get it to accelerate very slowly, with barely any throttle. While moving, it would run alright as long as I kept it around 2k RPM and didn't give it much throttle. As soon as I gave it more revs or throttle it would start missing. In neutral, it seemed to run fine anywhere, so the problem only came up while in gear.

Any suggestions on what I could check/try/replace next?

Thanks a lot for any help you can offer!

 

[mrv8q]

What’s the condition of the gas tank? Fuel lines from the tank to the engine room? Does the new fuel filter flow freely?

Picked up a ‘74 that had sat for many years. Had the tank boiled out and a sealer applied to the tank’s inside.

You will get more suggestions... are you a member of your local Triumph club?

 

[rjc157]

Not a fan of Pertronix go back to points and see what happens . Could be the carbs maybe a time for a rebuild.Check the wire from the dist to the coil make sure it's not cracked and the ground wire in the dist the copper one mine started to fray and the car just shut off.Since it starts to happen when it gets hot sounds like it could be a bad coil even though it's new can be bad.

 

[Gliderman8]

Have you checked the rubber diaphragms in both carbs? Over time and with ethanol fuel they can deteriorate. I agree that you have a fuel issue. Checking the tank and fuel lines as suggested above is a good start.

 

[TR3driver]

I would be looking for restrictions in both the fuel tank vent, and fuel line to the pump.

Had a very similar problem with my TR3 that turned out to be accumulated crud in the line from tank to pump. In my case, I believe it was dust from when the body shop sanded to bare metal for a respray (with the tank inlet left open against my specific instructions), but the issue didn't show up until weeks later. When I blew air backwards through the line, the fuel in the tank turned black as ink.

Also check inside the tank for FOD that can block the outlet. Kids sometimes think it is clever to drop rocks or marbles into the tank, which can migrate to the outlet and partially block it.

You could check for a vent issue by popping open the fuel cap. If you hear a hissing sound, or it cures the problem, you've got a vent issue.

Note that the carbon canister (if you still have one) is part of the tank vent. They are supposed to be replaced periodically, and can plug up with long usage. The early ones can be disassembled and cleaned, but the later ones were welded together.

Another test that might be worthwhile is to connect a fuel pressure gauge and put it where you can see while driving (like under a wiper blade). If the pressure drops off, you'll know its a fuel delivery problem rather than carbs or ignition.

 

[pdplot]

Vapor lock?

 

[trglory]

Maybe just funky gas....shine a light in the tank and see what it looks like. If you see particles in the gas, it needs to be drained and cleaned.

 

[sirrahtap]

Thanks for all the input! Looks like I've got plenty of stuff to start investigating!
I'll keep you all posted as I make progress

 

[edkap2002]

OK....my thoughts are a little more severe than other.....I experienced the exact same symptoms in 1974...........It was the head gasket....heating up and losing compression.....best of luck...Ed (not the best mechanic but a good thinker)

 

[TR3TR6]

I experienced the same thing with my 76 TR6. Mine went for about 8 miles before it started running rough and then quite. It wouldn't start again until I let it set for about 20 minutes. Here was the problem, when I filled the fuel tank, I filled it pretty close to the top. The vent line which goes to the canister got fuel in it, that took care of the fuel flow. When I disconnected the vent line from the canister, the fuel ran out and that took care of the problem. Best of luck.