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Triumph Vitesse Mark 2 - Anyone got an answer for this?
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Jim.Walker



Joined: 27 Dec 2008
Posts: 1233
Location: Chesterfield

PostPosted: Sat Jun 27, 2009 10:33 pm    Post subject: Triumph Vitesse Mark 2 - Anyone got an answer for this? Reply with quote

The car accelerates like the proverbial "bat out of ****", up to 50 mph and then the engine begins to feel rough (unhappy) and will not accelerate any further.

Fuel starvation was the original thought, and though the mechanical fuel pump tested out ok a new one was tried with no improvement.

The ignition timing is spot on and the centrifugal advance is what the book says it should be. Substitute coil etc. have been tried, all with no effect.

The twin SU Carbs are original fitment and correctly balanced and tickover is smooth and even at the recommended 900rpm. Throttle spindles are not worn. The pistons move freely with the needles correctly centred in the jets so that they bottom correctly. The throttle butterflies open fully. Removing the air filters has no effect.

The valve rockers are correctly set and the valve timing is correct.

The exhaust is not restricted (blocked).

I can think of nothing else to check!

Any ideas gratefully considered.

By the way - the car is a twin for my Gentry in my Avatar, but belongs to my son. He is cross because he has trouble keeping up with me even when I am towing my caravan!
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Penman



Joined: 23 Nov 2007
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Location: Lancashire

PostPosted: Sat Jun 27, 2009 10:38 pm    Post subject: Reply with quote

Hi
What gear?
If you have a rev counter, does it happen in lower gears at the self same point in the rev range?
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Jim.Walker



Joined: 27 Dec 2008
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Location: Chesterfield

PostPosted: Sat Jun 27, 2009 10:48 pm    Post subject: Reply with quote

That is the curious thing Penman.

In fourth gear the limit seems to be just over 2000rpm, but the engine will exceed those revs, still accelerating hard in the lower gears.
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victor 101



Joined: 03 Apr 2009
Posts: 449
Location: East Yorkshire

PostPosted: Sun Jun 28, 2009 9:01 am    Post subject: Reply with quote

It might be worth checking the flexible fuel line that connects to the inlet side of the pump, some of the older woven covered rubber pipes can become porous and allow air to be sucked into the pump instead of fuel.
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Rusty



Joined: 10 Feb 2009
Posts: 186
Location: Bunbury, Western Australia

PostPosted: Sun Jun 28, 2009 11:02 am    Post subject: Reply with quote

I like the idea of the air leak from a hose or maybe a small rust hole in the steel pipe.
Something else thats unlikely but easy to check is a blocked fuel tank breather in the fuel cap or wrong unvented cap fitted causing a vacume buildup in the tank ?
Just take the cap off and give it a run, that will soon eliminate that as a problem.
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Scotty



Joined: 23 Nov 2007
Posts: 887

PostPosted: Sun Jun 28, 2009 12:51 pm    Post subject: Reply with quote

Jim.Walker wrote:
In fourth gear the limit seems to be just over 2000rpm, but the engine will exceed those revs, still accelerating hard in the lower gears.


So why, I ask myself, does the engine run ok in higher gears, yet in fourth it has running issues above 2k?

Have you run the car through the gears to establish for certain its only fourth that the roughness appears and acceleration is compromised?

Is the car fitted with an "overdrive" unit - could it be it's engaging the moment you select fourth without you knowing it and the roughness you're experiencing is actually due to the unit causing the engine to "stall" because the unit needs higher revs to run smoothly?

Scotty. Confused
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Jim.Walker



Joined: 27 Dec 2008
Posts: 1233
Location: Chesterfield

PostPosted: Sun Jun 28, 2009 4:43 pm    Post subject: Reply with quote

Thanks Victor 101, Rusty and Scotty.

For starters, the car will sustain over 3000 rpm in any gear but top.

An overdrive is fitted, but it is not engaging when it should not. Using my car as a benchmark, I can easily accelerate from 1500 rpm with overdrive engaged in top gear. The only significant difference between my son's car and mine is that he has 14" wheels while mine are 15", which makes mine slightly higher geared. The engines and transmission etc. are identical. I think the transmission can be eliminated.

The fuel lines are clear and the fuel pump delivers enough to empty the fuel tank in a few minutes. The fuel cap has already been checked and is not the problem.

Perhaps I should have made it clearer about the "unhappy" engine. The engine definitely has a slight roughness at 3000rpm in top, not at all in keeping with the wonderful smoothness normal in the Triumph 6. It does feel as if the engine is trying to fire normally on all cylinders, but is not quite getting enough fuel to succeed. I can hardly be called missing or mis-firing. Oh, and there is no air leak in the induction.

I have met similar symptoms on cars with a siezed centrifugal advance in the distributor and also a pinhole in the diaphragm of a Stromberg carb, but neither fit the bill here.
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peter scott



Joined: 18 Dec 2007
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PostPosted: Sun Jun 28, 2009 5:03 pm    Post subject: Reply with quote

I know that you don't think it's missing but having pretty much covered the fuel and exhaust systems it just might be an ignition fault.

Perhaps bad earthing of the contact breaker plate. Loose screws into the distributor body perhaps.

Might be worth trying another coil or condenser too.

Peter
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Last edited by peter scott on Sun Jun 28, 2009 9:04 pm; edited 1 time in total
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Jim.Walker



Joined: 27 Dec 2008
Posts: 1233
Location: Chesterfield

PostPosted: Sun Jun 28, 2009 5:10 pm    Post subject: Reply with quote

I like that one Peter. Though that often shows up on startup (and hasn't), it is something I have not checked.
I will do voltage drop tests across points, points to baseplate, baseplate to distributor body and distributor body to engine block.
You have also brought to mind the condition of the pigtail lead. And the coil to distributor lead.
I'll keep you posted.
Coil and condenser have both been checked by substitution.
Thanks.
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victor 101



Joined: 03 Apr 2009
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Location: East Yorkshire

PostPosted: Sun Jun 28, 2009 10:29 pm    Post subject: Reply with quote

Its certainly looking more like an ignition related problem, if it revs at 3000 rpm whilst stationary for more than ten or fifteen seconds or can stay in a lower gear on the road for the same sort of time, maybe your spark plugs are breaking down under load which might explain the roughness you describe.
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Phil - Nottingham



Joined: 01 Jan 2008
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Location: Nottingham

PostPosted: Sun Jun 28, 2009 10:41 pm    Post subject: Reply with quote

Whilst I think it is likely may be ignition related (especially the distributor earthing problem if it relies on teh baseplate screwes rather than a lead which canb eeasily checked) I had a very similar problem on my Rover P5B (VCool.

Tried everything including fueling problems and was suspecting camsahft or head gasket problems - it turned out to be a failing UJ which when replaced I discovered that it cured completely this "engine" roughness at higher revs.

Until I got the more familar loud metallic tinkle after another copuple of thousand miles and interior mirror vibration there were no other symptons. No play was apparent until prop shaft was disconnected either.
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Jim.Walker



Joined: 27 Dec 2008
Posts: 1233
Location: Chesterfield

PostPosted: Tue Jun 30, 2009 5:52 pm    Post subject: Reply with quote

Thanks for all the interest everyone. Sorry I have not responded sooner, but I have had my hands full with other things for the last day or two.

Sadly all the suggestions came to nought.

Voltage drop test across the entire distributor from the coil connection to earth on the engine gave 0.1volt. As I remember the acceptable limit is 0.2volt. Scratch that one. We did find though that the pig-tail lead only had two or three intact strands which could possibly limit larger current flow (high hopes here), but changing that had no effect. (Carbon) plug lead resistance was well within the 25k Ohms per metre everywhere, but the cap, copper leads and rotor arm were substituted from my car with no improvement.

Compression test showed rather low pressures hovering around 100lbf/sq. in., the highest being 107. I don't feel that would cause this problem.

Jumping straight from the battery to the coil to eliminate the ignition switch and its associated wiring did nothing either. Nor did tearing hair out!

I'll keep trying. Thanks for the suggestions.
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PAUL BEAUMONT



Joined: 27 Nov 2007
Posts: 1280
Location: Barnsley S. Yorks

PostPosted: Wed Jul 01, 2009 1:07 pm    Post subject: Reply with quote

I am surprised at the lowish compressions. I would begin to suspect valve issues. Do you know the history of the car? Has the situation suddenly happened, declined over a period, or always been like it in your son's ownership?
Could it have the wrong valve springs fitted which are allowing valve bounce at higher engine revs?
Paul
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Kelsham



Joined: 18 Jan 2009
Posts: 349
Location: Llandrindod Wells Powys

PostPosted: Wed Jul 01, 2009 5:31 pm    Post subject: triumph vitesse Reply with quote

Hi, recently suffered a loss of performance on my 1932 BSA Trike. it turned out a new rotor arm restored performsnce. I couldnt see any tracking.
I agree the compressions seem low. Was the throttle fully open when you took them. regards Kels
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Jim.Walker



Joined: 27 Dec 2008
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Location: Chesterfield

PostPosted: Wed Jul 01, 2009 6:04 pm    Post subject: Reply with quote

Perhaps I did not tell the whole story of the compression test.

The engine was hot, the throttle fully open and was the result of the same number of compression strokes each time - as it should be.
A squirt of oil in each cylinder to reduce ring leakage raised all pressures to acceptable levels, showing that low compressions are due to ring leakage and not valve problems.
By removing the dampers and placing pieces of light dowel in the tops of the pistons we found that after about mid-throttle the back carb. piston started to lag behind the front one and never lifted more than about half its travel. The reason was traced to a dodgy clamp on the transverse rod connecting the throttles which was slipping round as the return spring tension went up. When the throttle was closed the clamp returned to its normal position. A new clamp cured that AND THE PROBLEM! Not the piston rings of course, but they are now standing dosed in Redex in case carbon is to blame. Oil consumption is very low and performance is good, so I think we can live with the compression problem for a while at least even if the Redex does nothing.

Oh my! What do I say now? Except thanks everyone!
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