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Triumph TR6 - Cylinder # 6 isn't firing
|I met up with Clive, another poster on here today, and he immediately could tell that 1 of my cylinder's isn't firing. It has spark, at least some. But when you pull the spark plug wire off that plug, the engine sound doesn't change at all.|
It was quite impressive--I hadn't noticed it, and the only thing I noticed today was my oil pressure wasn't as high when I first started the car. As soon as I started it up, Clive picked up on it. Things like that humble me.
Whats the procedure for trouble shooting this?
|You say you have a spark? First thing to do is check the spark plug. If the tip is fouled/bridged over with carbon, that's the problem.|
|JL - I assume that Clive's expertise helped solve the problem, but in case not it's almost certain it's ignition - as Brett says - start at the plug end. |
If it's not firing, it may also be a single plug failure. Check also the ignition lead where the HT lead may have broken from the clip (at both ends). If you have a multimeter check for continuity. Also check the distributor cap and make sure the electrode hasn't gone south.
When you are sorted, enjoy the return to smooooth response.
|I have just posted an eMail to John and have sugested to him that we do a leakdown test to determine the exact cause and not to guess at the problem, I feel that given the age and unknown history and also the fact it uses a considerabe amount of oil, an electrical problem is unlikely, It is very difficult to detect the exact cause when you are just leaving the pub and driving in different directions, I hope to be able to help him in the very near future, All said we hade a great meet up and enjoyed a wonderfull lunchtime in the sun. clive|
|I had the same problem..turned out it was a bad lead. When I ohm'd it and moved it around the reading would change. Turned out to be at the plug end so I took the clip off and stripped the wire back another inch and all ok now. Try another lead or do this test.. pull the coil lead first then hold the lead with the plug in the end against the valve cover (for ground) Use a insulated pliers to hold it. Have someone crank the engine a few times and you should see a nice spark at the plug...pick another plug and compare the spark..should be a regular and strong spark.|
|Charlie B. '75 TR6|
|JL--Another possibility is your cam's intake lobe is wiped down. Ask me how I know!|
|I made it worse now. After thinking about it and looking at the responses, it seemed like replacing the plugs might be a good idea. The old plugs were fouled pretty bad, and they're not that old. So, I popped off the top of the distributor, and everything in there looked okay. Put everything back together, checked the shop manual to make sure all the leads went to the right plugs, and now it won't start. The starter motor turns the engine over just fine, but nothing after that. Its probably something I did or didn't do to the distributor, but until Clive had a look at it, I'm out of commission.|
|Is the rotor still on your bench? ;)|
|Points or electronic ignition ????|
|Charlie B. '75 TR6|
|Everything that was inside the thing is still inside there,Brent. And its points, Charlie. I'm feeling pretty stupid again, by the way.|
|Hey John. Check that he cap is resting properly in the alignment recesses so that it's not "cocked". If it's misaligned the rotor will contact the terminals in the cap and break. Pull the cap again & check the rotor. |
Then check the high tension lead from coil to cap is seated, then that the 12V wires (coil to dist and power to the coil) are not loose. If you have a voltmeter you might want to confirm that 12V is getting to the coil when the key's on,too.
|Everything looks okay. When I try to fire it up, I am getting some nasty smoke and the occasional backfire, but it isn't even trying to start. Its got me worried and I don't know what to do.|
|Did you change anything when you " checked the shop manual to make sure all the leads went to the right plugs"? It kind of sounds like you got the plug wires mixed - maybe off one all the way around.|
Also - "Its probably something I did or didn't do to the distributor" - What did you do?
|Thanks, Brent. I didn't actually do anything except take the top off. First, I replaced all the plugs. The old ones were pretty badly fouled up. I looked at the shop manual to make sure I had 5 and 6 correct, because I had them both off for a while. Then I pulled the top off of the distributor, looked at it and everything looked okay, so I put it back on and that's where I am now. I've checked and re-checked.|
The only thing I can notice visibly is that the manual shows #6 at 0 degrees relative to the head, and mine is a few degrees to the right of that, as you look down at it from the driver's side of the car. But the leads are all in the correct order. Could that be significant? (I don't exactly know how adjusting the timing with the distributor works. Its one of those things I've never been shown and never done).
By the way, our weather today has been awful. We've had high 60's temps, but rain and clouds for about 2 straight days now.
|Triumphs run best when it's 60 degrees and raining. I drove mine around the other day in 20 degree weather, parked it on the street for the night, next morning it's like 0. Just to save the charge and make sure it got back in the driveway in a timely fashion (less shivering) I took a spare battery and cables out to it. Lifted the bonnet, primed the carbs, hooked up the battery, pulled the choke, vrooom. 3 days below 0, I don't want to set foot out the door, but life goes on. I have driven the TR in below 0 weather, to go jumpstart my van.|
Do you know if a spark is getting to plugs? There is supposed to be a spring loaded graphite "button" in the middle hole inside the distributor cap. The piece makes contact with the rotating center of the rotor to allow the spark to get to it. You may want to pull the cap off and check that it's still there - if it broke or fell off the first time you removed the cap there'd be no (or maybe intermittant) spark to the plugs.
|I agree with Brent, the first thing you need to determine is whether or not you are getting spark at the plugs. As Charlie mentioned above, pull each plug wire one at a time, pull back the rubber, and hold the metal lead about a 1/4 inch from the block. Turn the engine over and you should see a nice strong arc between the lead and the block every time the rotor makes one revolution. If this is what happens your problem may be other than electrical. If it does not happen, there are a couple of things that could be wrong:|
1) You may not be getting any current from the coil. Check to make sure the wire from the top of the coil to the top of the distr. cap is well seated at both ends. Also make sure you haven't somehow dislodged the high tension lead wire from the coil to the distr. body.
2) Your points setup has somehow gotten screwed up. With the distr. cap off, turn the car over and make sure the points are gapping open every time the breaker arm hits a lobe on the distr. cam.
Don't know if you have any diagnostic equipment, but that would also help to be able to work backward to find out where the juice stops. Good luck.
|John, what kind of fouling do you have on the plugs? Oily? (That would be bad, you need to check compression, maybe a broken ring, stuck rings, or just worn out cylinder walls). Sooty? Maybe you have a carb problem (too rich). Wet with gas? (Flooded, will make black smoke, but not start). I tend to go toward a sticking float and flooding for your immediate problem. But if you have oil on the plugs, the inevitable engine teardown is in your future. You have a nice car, it's worth getting it back in shape to cruise on those nice days! Let us know how it turns out.|
This thread was discussed between 08/01/2005 and 17/01/2005
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