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Triumph TR6 - got gas & spark, it runs for a minute - then dies!

Here's a real brain teaser with my '74 TR6:

The car starts, and runs for about a minute. Then, like someone threw a switch, the car will automatically begin to starve, the revs begin to drop, and it bogs down until it's dead.

Once I wait a couple of minutes, I could repeat the whole thing all over again. . .until the next morning. . .then everything is normal, like nothing went wrong - and it appears I got towed home for no reason.

This time I had two hours to wait for the tow truck, so I got busy.

Now, I pulled the air filters off, and watched the gas flow. Both carbs continiously sprayed gas in the barrel, as it slowly sputtered, and died.

Then I waited, re-started the car, and pulled the number six plug and held it to ground during the minute the car was running.

I got spark up until it sputtered and died.

Two things I did notice was:

1 - I was getting no vacuum to the distributer advance.

2 - The fuel in the clear barrel filter, usually fills halfway when the car is running normally. When it's in this "stalling" mode, the fuel level in the filter is much lower, and there are bubbles in the gas during the minute it does run.

Any help here would be greatly appreciated. . .I'm tired of knowing all these tow truck drivers on a first name basis.

Thanks much,

S.
Switzee

Could be vapor lock - check that the fuel line going to the pump isn't contacting a hot section of block or manifold.

Also, if the emissions hoses aren't quite right at the carbon cannister and the gas tank seal is great, the carbs can pull a vacuum on the tank. Try opening the gas cap next time it happens.

A sticking carb needle valve will also stall the car - but you'll really smell gas!
Brent B

Brent,

Thanks for the quick reply!

I thought of vapor lock too, but the gas lines are not touching the block or manifold. I get a nice squirt of gas through the lines every "second revolution" of the engine, while cranking.

I opened up the carbon cannister today, it looks slightly used, nothing bad at all. (I think this TR6 is a low mileage car, but the speedo was replaced when I bought it, so I'm not sure.)

I also opened the gas cap while trying to keep the car running longer than a minute. It didn't work - she still stalled.

Even though I'm not smelling gas, like you say. I'll still check the carb needles.

As the enging revs up, will gas still spray into the barrel if the carb needles are sticking???

Thank you,

S.
switzee

Air entrained gas. Suction of pump creates a vaccum not being filled by gas.

Rust particles, old bad gas leaves particles and varnish in tank even after replacing stuff floats loose clogging line and filter after suction from pump brings it all to tank exit and filter? Stuff floats. Pumps vac. suction goes away overnight goodies float off to be repeated next day?

Solutions cheap first:

Drain tank. From your description this is most likely. Use a flashlight not a trouble light unless your looking for a facelift and new car! Take a look. Flush out with carb cleaner. Rod out the fuel line connection. Replace the fuel line and filter. Steel fuel lines do rust inside and restrict gas flow. Just a couple of bucks to replace not a long length. Add some Carb cleaner and new gas. Dump or suction off gas in pump. Engine lines from pump to carb are usually OK? But if you have air blow them out. Do them all at the same time. Each one affects the other. That should solve it?

If not?

If you have a vaccum pump next check your vent lines for blockage. Or just blast it with an airline. Use Brents suggestion right away of course to narrow down. Vent lines may cut you out for a short period but almost always come back within a minute or two not next day?

74 does have an anti run on valve. For a trial Remove line from tank and line to carbs. Just in case valve faulty or solenoid weakens hot. In theory the valve should not affect fuel mixture other than at idle? And again should not cause long time frame problem?

May be fuel pump? But not likely.

Bill
Bill Brayford

Is it safe to assume this is only happening when the car is warm? It really sounds like vapor lock if so. Follow the line from the fuel pump to the tank and make sure it's not too close to the exhaust underneath the car. Insulate if it is.

How old is that fuel filter?

On the needle valve, I meant sticking open so it floods out the car. If it stuck closed, though, of course you'd run out of gas, but that's one I haven't experienced yet.
Brent B

Bill,

You had me laughing out loud! I guess I have to buy some batteries for my flashlight, my wife likes the face, and I want to keep the car.

I had the tank out of the car about a year ago, and it looked fairly clean. I ran some water through it, and gave it a couple of weeks to dry before I re-installed it. I had some welding work to do to the differential brackets, so I thought it was a good idea to take the opportunity. . .

I never cleaned out the lines, tho.

So, at this time, I'm putting the car back on jack stands (it's most familiar position) and I'm going to blow those lines out. Both the fuel, and the return lines. If they're crummy, I'll replace them.

I'm also going to rebuild the fuel pump - just to be safe.

Mine '74 does have the anti-run valve, how do you test it???

Thank for the info, Bill.


-------------------------------------------------------
Brent,

Yes, it only happens when the car is warm. Once it cools, it seems to be okay. . .and the next time it acts up is anybody's guess. I really can't duplicate the problem.

The day before it quit - it was running better than it had ever had (that, alone should have raised my suspusions)!

As it was acting up, I did pull off the fuel line - it was spurting, what looked to be, a sufficient amount of gas. Would vapor lock still be a factor?

Oh, the fuel filter was just changed in the spring.

Thanks again, Brent.

S.


switzee

Might be a distributor problem instead? As it cools, contacts contract and produce better spark? Just a thought but that sort of problem happened on my Honda some time ago.
Bryn

Hi

ChrisW had a close problem. Look for HOW TO GET RICH on this page and have a read. Chris tried a lot of things may give you some ideas.

The anti run on can be tested as I stated just take out of the loop. I really don't know enough about them to give suggestions.

I had a bad ignition switch on my 72 that caused a cut out after the internal contacts got hot due to wear and high resistance? But I lost spark and power to coil when it quit.. Carried the garage around in the trunk for 2 weeks to find that one? :)

Both Brent and Bryns ideas are good. Might be a combination. I was following the half full bowel and bubbles. Failing fuel pump will give air as well. If the gas has a lot of air bubbles I think it would be more likely to have vapor lock problems as well?

Bill
Bill Brayford

Hi,

I had a similar problem on my 76. Ran great when cold, but sputtered and missed when hot (never quit though). I tried everything, jumping from onr side of the engine to the other in an effort to find the problem.

Turned out to be a points problem. The book calls for a gap of .014-.016". Since the dwell was always constent and never wavered as the car heated up or as the rpm changed, I figured the problem was elsewhere, but I was wrong. As a last ditch thing, I closed the gap to .010 and presto, no missing when hot. The points seemed to be floating somewhat when hot (detected with a strobe on each spark plug wire in turn).

Why they did this I don't know. Could be cheap points with weak spring, but I tried 2 sets, both floated. I think the Distributor shaft got more play in it as it heated up. I always thought that that would affect the dwell though, which it did not.

Anyway, just something you might try.

Chris
C Wiebe

Bryn & C Weibe - While the car was in it's "run for a minute, then die" mode. I replaced the points with a spare set I had in the trunk. Replaced the cap & condenser, too. No change, it still did the same thing - ran a minute, then starved, and died.

Bill - I checked "how to get rich," and there were some things I can look into. Even tho, he was having a "run badly" issue after thirty minutes.

In my un-professional opinion, I don't think the carbs are causing my problems. If the car was running badly, I would consider them. But it's just dying, I think the problem lies before the carbs.

I'm liking the idea of the fuel pump sucking air. I'm looking into a re-building kit for the pump.

I'm also going to mess around with the anit-ran valve, do some tests. . .make a mess. . .you know. . . break it!


Thanks guys,

S.
switzee

. . . and I still cannot figure out why I get no vacuum to the distributor, or to the carbs!!

Could it be that temperature vacuum valve attached to the upper radiator hose???

Would THAT make the engine starve and die after a minute?

Thanks,
S.
switzee

Switzee-Just a thought, but several people have had problems with the clear barrel type fuel filters clogging to the point of killing the engine. You might try removing the element inside the filter and see if this makes a difference. Also, if you still have the original type fuel pump, there is fine mesh strainer in the top that could be clogged.
Berry

Berry,

This problem as been, somewhat, ongoing. The first time it went into this "run for a minute, then die" mode I cleaned out the distributor. It ran great for about two weeks, then it happened again. After I got towed home the second time, I pulled the fuel pump and found about a pound of crap in the bowl under the screen.

With that, I cleaned out the pump , and replaced the fuel filter.

I've got to blow out the lines next. . . .and figure out why I'm not getting any vacuum to my distributor.

Thanks,

S.
switzee

That temperature vacuum valve is only supposed to open if the car gets too hot. It opens and kills the vacuum retard so the timing advances and idle speed goes up.

Be sure the hose is still attached to the vacuum port (on the rear carb, your model?) Pull the hoses and check for cracks/leaks. Then try blowing into the hose to the carb while the engine's running - if you can't then the small hole in the carb is plugged. I don't think that has anything to do with your other problem, BTW.
Brent B

I recently experienced the same problem you described at the start of this thread with my '74 TR6.

It would run for a few minutes and then just starve on me. After a couple of minutes I could restart the engine and it would die on me again. After a while the problem would disapear to hit me again the next day.

I looked for a lot of the suggestions described in the thread above. The very last action I did was to clean he fuelpump and top of the dampers on the carburators. The car has now been running for a week without any problems.

I am quit sure that the low oil level in the carburator dampers was causing the problem although I do not quit catch the logic.

Perhaps someone can explain the function of the damper mechanisme in the suction chamber of the carburators in relation to the main jet.
E. Creyghton

Simple and clever! When you hit the gas (ie, open the throttle butterfly) vacuum is dumped reducing airflow.Undamped, the throttle piston would lift instantly, leaning the mixture.The damper slows the lift of the piston (creates a controlled lag) so that air is caused to accelerate through a restricted passageway beneath the piston (over the saddle containing the jet) thus sucking more fuel momentarily to enrich the (leaned) mixture.Or something like that. Seems to be totally self compensating, responding to pressre (air density) changes. My car runs as well at 10,000ft as at sea level. Coming to love my Stroms. Peter
Peter Gooch

Thanks Peter, it is quit clear now.
By the way, my car is fitted with SU-HS6 the principal remains the same.
Erik
E. Creyghton

E.

Good idea to check those carbs. That is actually the first place I turn whenever my TR6 dies.

I'm always checking the level constantly. . . doesn't everybody???

I'm going to blast out the fuel lines this week. I hope to see some crud - then maybe my problem will be solved.

Thanks,

S.
switzee

This thread was discussed between 19/06/2003 and 23/06/2003

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