Problem SPRINT (misfire)

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TREV THE REV · #1 Post by **TREV THE REV** » Mon Mar 01, 2004 10:25 pm

Can any help me with a problem with my Sprint? 
I have a 1978 Sprint which is giving me BIG problems. 
When under acceleration the car starts to miss fire but not like an electrical problem but fuel. When carbs are balanced and CO set at 4.50 the car will miss when revs are applied even in the garage. Out on the road it miss and will not pull. When CO is set at 20.00 she will go a bit better but does not like going much over 4000 RPM. 
Work carried out so far 
New needles and jets Rimmer overhaul kit 
New float needles 
Fuel pump cleaned and checked 
Changed rubber mounts 
Changed coil 
Electronic ignition 
Cleaned plugs and checked leads 
Oil in pots 
Can anyone help me out as i am lost and might change to MG

Edited by: <A HREF=http://p206.ezboard.com/bthetriumphdolo ... omiteuk</A> at: 19/10/06 1:24 pm

C Mallock · #2 Post by **C Mallock** » Mon Mar 01, 2004 11:43 pm

I have the same problem with my 1500, it seems to be running on 3 when no load is on the engine but clearing soon as i start moving, my only thought is that i had my carbs set up last month as i failed the mot on co, and as i did not know what time the guy that was doing the set up was coming i had my car in the corner of the workshop all day at a nice 21'c, the co came out at 3.5% maybe its a bit lean for the cold weather maybe yours is the same?

TREV THE REV · #3 Post by **TREV THE REV** » Mon Mar 01, 2004 11:59 pm

My does not go of cylinders but has no power and vapour coming out of the cards when reved hard

Jon Tilson · #4 Post by **Jon Tilson** » Tue Mar 02, 2004 12:08 am

The first place to start with a misfire is always the ignition. Carb problems usually casue a flat spot, not a misfire. 
As youve chenged the coil and leads and have electronic ignition I suugest you look at the distributor cap and rotor arm. Its a good idea to look yber the bonnet in the dark for tell tale blue flashes. Sometimes the human hand is a good electric leak detector...ouch! 
Check the dizzie advance and timing with a strobe too. 
Having eleimated all ignition problems then its on to carbs. AGian you have lots of new bits. Why? What was wrong with the ols ones. Breather hoses often cause grief, especially the two small balance pipes which are prone to splitting. 
Tell us more...how did it first start misbehaving. 
Where are you? Happy to look if not to far from West London... 
 
Jonners

Riff Raff · #5 Post by **Riff Raff** » Tue Mar 02, 2004 11:35 am

2 problems I had (one on a 1500 lump and the other on an 1850 lump) 
 
Car ran fine for several years. Had the engine tuned and carbs set. Ran fine until it was warmed up then would misfire, and die. No heat shield between the carb and exhaust manifold. Fuel was vapourising before it entered the engine. £5 for a second hand one and problem cured. 
 
1850 ran fine at low revs, but as you tried to accelerate, or reached the higher speeds, the endine would start to mis-fire and lose all power - she would not go above 55mph. 
Worn dizzy - the bearings were worn, so as the revs increased, the centrithingy force would move the arm out (or at least that's what I think was happening). new dizy and problem sorted! 
 
Any help? 
 
Tim

alun n · #6 Post by **alun n** » Tue Mar 02, 2004 12:35 pm

.... I'd suggest you have either: 
 
a) your ignition leads mixed up; check firing order with rotation in the cap (NB the cap can be confusing as which lead goes where is not immediately apparent) or you may find one of the leads hasn't been properly nipped up by the screw. 
 
b) old fuel 
 
or 
 
c) a pourous fuel pipe from the tank so your pump is sucking in air. 
 
My money is on a.

Carl · #7 Post by **Carl** » Tue Mar 02, 2004 6:22 pm

Change the ignition leads !

Dave · #8 Post by **Dave** » Tue Mar 02, 2004 8:31 pm

Might be worthwhile just to eliminate gasket/valve problems.

ajsamuels · #9 Post by **ajsamuels** » Tue Mar 02, 2004 9:37 pm

I had a similar sort of problem on my 1850 a few years ago - it had me totally stumped for weeks. Checked all the usual obvious things and nothing made any difference. 
Eventually it turned out it was the needle valve seat in the one of the carbs (the hexagonal brass bit that screws into the underside of the float chamber lid) that had come slightly loose. This meant that the valve was not opening properly when the float dropped, hence not enough flow to keep the float chamber filled when the engine was under load. 
Maybe nothing to do with your problem but worth checking just in case.

TREV THE REV · #10 Post by **TREV THE REV** » Tue Mar 02, 2004 10:31 pm

Leads,cap and rotor all ok 
When I say a miss fire it is more of a hesitation/hold back with a loss of power. If you drive on light throttle the car will drive fine but put the shoe down and the problems start.???????????????

Silvery · #11 Post by **Silvery** » Tue Mar 02, 2004 11:35 pm

Stating the obvious, and you've prolly already checked, but is there oil in the carb dashpot dampers? 
 
A car with SUs will fire up fine, run at part throttle or very gentle opening of the throttle OK, but miss like crazy if the dashpot's run dry. 
 
I got a Mini at the weekend to run around so I can get the Triumphs off the road and sorted out a bit - That fired up first time, engine is very sweet (A series in good nick always are smooth though, IMO), but driving to Weymouth on Sunday it was stuttering like a drunken pig with a speech problem. Checked the SU damper, dry. 
 
Topped it up later, seems alot better now, although the rest of the engine needs a good service too. 
 
Had the same with the TCs. 
 
And on a couple of cars I've also found the carb springs inside the carbs seem to get weak over time, which upsets things a bit too. I'd start by checking the oil though, 2 minute job <img src=http://www.ezboard.com/intl/aenglish/im ... /smile.gif ALT=":)">

dollysteve · #12 Post by **dollysteve** » Wed Mar 03, 2004 9:31 am

I had a similar problem on an austin princess that I did some work on, going back to the chap who said about the needle valve seat, the other thing worth looking at is the float itself, on the princees it was plastic and had somehow perforated and was full of petrol, "consequence" put foot down go nowhere.

Carl · #13 Post by **Carl** » Wed Mar 03, 2004 9:45 pm

Your description of the problem ie runs OK on a light throttle but misfires when you put your foot down, is exactly what I experienced just recently. It was the ignition leads. I had a similar problem years ago on another car. The leads partially break down, severely weakening the spark at the plug. Hence when you put your foot down the spark is drowned out. When you say the leads are OK, does this mean you've tried another set ? As for your threat to trade for an MG, how could you even think such a thing ? <img src=http://www.ezboard.com/intl/aenglish/im ... s/wink.gif ALT=";)">

C Mallock · #14 Post by **C Mallock** » Fri Mar 05, 2004 12:01 am

I had a problem like this a few years ago with a marine volvo engine that suddenly lost power started and ran fine but soon as heavy load went on vapor came out the carbs turned out to be cam timing, Anyone known a chain to jump/stretch?

hez37 · #15 Post by **hez37** » Sat Mar 06, 2004 11:09 pm

I used to get the same problem when my points closed up (they closed as a matter of course every 3K or so). I've changed to electronic ignition so don't have the problem anymore. It makes me think though that it's worth getting your electronic ignition checked - I'm sure the local garage can plug in and check while you wait.

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