The Triumph Dolomite Club - Discussion Forum

when the dolly came to me it had some cracked rubber-carb-mountings, which i now replaced against the alloy ones from the club.

fitted with new gaskets and sealant.

carbs have no play in throttle-shafts, new (waxstat) jets have been fitted. new needles have been fitted. pistons work well. oil-level in carbs is correct and equal
i fitted ABT needles, instead the original ABK...the ABT´s are slightly richer ...really slightly
i adjusted the carbs according to the manual.

engine started (with joke) on the button. i balanced the carbs, checked ingition timing(which is a bit more advanced than necessary)

idle was ok...but not as smooth as i liked it.

anyway, gave it a test drive....and no power...had to pull the choke....and even with joke max. speed was about 55mph

it was running better with the damaged rubber-mounts and un-balanced carbs.

meanwhile the jet-adjusting-nut has been screwed down by around 3 turns, but it doesnt cure my sympthoms.
shoudl i screw them even further down? that would be unusal or not?

i sprayed with carb-cleaner around the manifold, carb-mounts and carbs. idle does not climb-up, so no leakage whcih weakends the mixture.


i´m a bit lost.

That's a huge jet adjustment, with that it should be as rich as the prime minister. My money is on low fuel levels in the float bowls.

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I would... run the engine. Switch off, pull the dome+piston out of 1 of the carbs, yank the choke fully out and see if you can see fuel in the jet.

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As a first time Sprint owner over 30 years ago, I went through a very similar exercise to you with almost exactly the same results!

I'm drawn to your statement as that is what finally guided me to my error; I had crossed two HT leads during reassembly. I wasted hours thinking it was a fuelling issue.

This may not be your problem of course, but don't automatically assume anything...

Are you still on points?

I have an almost similar story to tell on my 1850HL. I rebuilt the carbs with AAA needles and new waxstat jets in and therein turned out to be the problem. When the engine warmed up the waxstats leaned off the mixture so much that the car couldn't perform. It had all the symptoms of fuel starvation, running OK at low speed but incapable of more than about 40 mph foot flat on the floor. I can only assume, as with so many parts these days, that the waxstat cartridges are incorrectly made.

I bought a pair of new standard jets for the SUs, (what Burlen call waxstat conversion) retuned and effected an instant cure. The engine is lively, pulls well and when my son was driving on the M6 I glanced over to see an indicated 85 on the speedo. Obviously it must over-read officer.

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Mike
(1969 MGB GTV8, 1977 Dolomite 1850HL, 1971 MGB roadster now all three on the road)

I'd try the basics first.
Is the accelerator opening the throttles fully at the carb; when fully depressed ?
There is a weak spot on the Sprint which is where the accelerator pedal mounts to the panel. The metal cracks here and you can never get full throttle. Not seen it on an 1850 but that doesn't mean to say it can't happen.
They may also be a problem with the progressive throttle linkage below the carbs;
Tony.

In the case of my car, I had just finished a rebuild of the vehicle after a 26 year storage period and I went through everything including reinforcing the throttle pedal mounting. I originally thought it must be the fuel pump so bought a new one from Robsport, to no avail. My car would start from cold easily with choke and drove well for about a mile until I got onto our local dual carriageway. I could get it up to 70 mph, but not for long as it quickly began to lose power, getting progressively worse until it staggered along at 30 - 40 mph. If I stopped it just died and wouldn't restart until it had cooled down.

Having tried just about everything I could think of as a cure, it occured to me that it happened once the engine was up to temperature. What is affected by engine heat? The only thing that I hadn't considered was the new waxstats. Dispensing with them was an instant cure. I tried substituting the waxstats with penny coins but although it ran better I couldn't get the mixture right. The new plain jets were the final answer to a sweetly running engine that has now done thousands of miles without a problem.

I have heated the waxstats on the bench using a hot air gun and the amount the little piston comes out is remarkable, and is far more than you would ever consider raising the jet by. They obviously were OK in 1977, but I wouldn't touch them now.

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Mike
(1969 MGB GTV8, 1977 Dolomite 1850HL, 1971 MGB roadster now all three on the road)

ok...basics:

throttle opens fully.
ignition is still on points (electronic module is on my desk, when car is running well, i will convert it...dont want to touch to many items at once)
tests were performed in cold weather with cold engine and cold-engine-bay

car was running reasonably well b4 i changed the leaking rubber-carb-mounts to alloy ones and changed the old (and original) waxstat jets to new ones (one was leaking on the hose-connection to the float-chamber, so i was obliged to change them).

i dont want to argue about waxstat or not....the system from its orginal way of thinking is not bad...and generally saying "waxstat is bad", i do not agree, otherwise not one car, when they were new, would have run...so please no discussion about waxstat or not.

engine has low power straight away from start...means the engine is not warm, and in this condition i dont think that the waxsat´s will really come into force, especially not now in winter time.

summary:

fully open throttle
balanced carbs
no air leakage
igniton timing is enough advanced
firing order is ok (incl. HT leads)
problem remains with old and with new igntion coil
float-chamber level is ok
fuel pump works correct well
ventilation of fuel-tank checked and ok

Sounds like you should start from first principles again, put the carbs back to their base setting etc etc.
Was the engine properly HOT, when you tuned it?
Can I assume you balanced the carbs with the linkages disconnected? And are they correctly set again?
The flexible pipes from the float chambers to the jets require a gentle touch to seat and tighten correctly, it's possible to limit fuel flow if you overdo it.
Also, as somebody mentioned above, removing the pistons and looking at the fuel height in the jets will tell you a lot.
Are the needles centred, and the pistons dropping freely?
What does the exhaust sound like?
What do your plugs look like?

Can I assume you balanced the carbs with the linkages disconnected? YES

And are they correctly set again? YES

The flexible pipes from the float chambers to the jets require a gentle touch to seat and tighten correctly, it's possible to limit fuel flow if you overdo it. GENTLY TIGHTEND

Also, as somebody mentioned above, removing the pistons and looking at the fuel height in the jets will tell you a lot. NOT DONE

Are the needles centred, and the pistons dropping freely? PISTONS DROP FREELY; NEEDLES ARE SPRING LOADED, so self centering i guess? springs are straight, so needles stick-out reasonbaly straight

What does the exhaust sound like? exhaust note is exrtemely quite and smooth

What do your plugs look like? not checked

And is your timing checked with the vacuum disconnected?
How much more advanced than need be is it?

And is your timing checked with the vacuum disconnected? obviously
How much more advanced than need be is it? timing is set about 3 degrees earlier than "usually" necessary

poor in power is never related to slightl early ignition timing, only to retarded.
early timing gives low end power with evtl. pnking at top end.

i´m 30y into automotive...mainly into old ford´s / alfa romeos and into weber/dellorto double sidedraughts....so if i have a problem, its usually really a strange problem or something which is outside the usual things to check.

And yet new needles in a pair of SU's has you flummoxed...
'Assumption is the mother of all Feckups' as the saying goes.

I was gonna leave this one alone, it's obviously something that's NOT obvious and may well need a second opinion in person. We're all trying to give you ideas of possibilities, diagnosing though the internet is often less than satisfactory! But I have a feeling this is going to end in a "D'OH" moment.

I only have a couple of suggestions to offer, is the pumped fuel pressure high enough? No blockage or partial blockage of the fuel line/filter (if fitted) Are the breather pipes in good condition and not cracked, split or leaking at loose ends?

Finally, a warning! I too deeply mistrust waxstat jets. They were only marginally useful and caused many problems when in production cars ( I remember those days, having over 50 years in the motor trade) The years have generally NOT been kind to waxstats. Couple this with the generally poor quality of nearly everything you can buy these days and, IMO, you may well have a duff pair. "New" these days doesn't necessarily equate to "Good"! Faced with the choice you were, where you HAD to replace at least one anyway, i'd have opted for the fixed jet conversion as a no brainer.

A fixed jet is pretty foolproof as it has no moving or quasi moving parts, there's nothing to go wrong! My strict adherance to the KISS principal, the first law of good engineering (Keep It Simple, Stupid!) goes on auto in cases like this!

HTH, Steve

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'78 Sprint Auto with Vauxhall Omega 2.2 16v engine (The Dolomega)
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lets consider i would have bought a pair of waxstat´s made of poor quality .

would those "confuse" my mixture even when the engine is still cold and with winter-climate the engienaby remains cold as well for the first few miles of driving?

as listed already above, fuel supply is more than enough, also tested with a low-pressure electic-pump...without any change.

so if temperatues allow i might work on my car 2moro...garage is quite cold at the moment....