The Triumph 2000 / 2500 / 2·5 Register Forum

Hi Folks,

I'd really appreciate your thoughts on a problem with my 2.5PI rally car. When accelerating from a stable speed, the engine first hesitates and feels a little "fluttery" before eventually picking up as normal. This is more than a momentary hesitation - it can last for a few seconds, sometimes more. It seems only to happen on relatively light to moderate throttle - if you boot it, it doesn't happen. It is also intermittent - sometimes doesn't happen at all, and the car feels just as it should.

I have a fuel pressure gauge in the car, and it doesn't dip below 110psi at any point while the problem is happening, so I am not thinking it is a fuel problem. The intermittent nature also suggests electrical/ignition to me. The points and cap were recently changed and I've got a red rotor arm fitted.

My suspects to check at the moment are engine earth, coil, distributor earth and timing (although I did recently check the timing).

Has anyone experienced this problem before on a PI car? Any other suggestions as to what to check would be much appreciated.

Thanks all,

Jonathan

How are your injectors, perhaps they are not giving a great cone spray pattern on a partial throttle. The hesitation or flutter could be down to just one injector (2 or 5 on my pi in the past) being a little 'lazy'.

I also get a problem exiting roundabouts sometimes.......that's due to a build up of oil in the air log flooding into the throttle body and no.6 cylinder and causing a misfire, as the car leans to the left. I should really treat the engine to an overhaul

Colin.

Hello Jonathan,

your initial description sound like the classic 'weak mixture', unusual on a P.I. though. My thought in association with this is does your car have a vacuum advance distributor and is that working properly? If it is it might be worth giving the timing some more advance, as long as it does not pink?

Alec

Thanks Colin. I've had a "lazy" injector before, but this is more of a "whole engine" experience - a light increase in throttle does not cause any acceleration or pick-up, just fluttering, until it seems to wake up and off we go.

Can anyone confirm that on a Mk1, the battery negative cable just goes to the body, and that the engine earth is a short cable on the other side of the engine (right hand side), effectively connecting either side of the engine mount? I don't seem to have an earth cable directly from the battery negative terminal to the engine.

Jonathan

Hello Jonathan,

the engine mount earth strap is what I have.

Is your engine standard by the way?

Alec

Hi Alec,

No, the engine isn't exactly standard! About 180 bhp. There is no vacuum advance on the distributor. I do want to check the timing again, just in case. I usually set it for about 8 degrees at idle, but this is the static setting so maybe some more advance (my idle is set to about 1100rpm) would be right, taking into account that the distributor advance is starting to come in by then. I also need to check whether the white line on the pulley is at TDC or is the actual timing mark!

Do you think the timing being out could cause the problem I'm experiencing?

Jonathan

not got much experiance of the pi system, but does sound like too much air in the mixture at part throttle. is there a "gizmo" on the car that meters the mixture according to throttle opening position?

Hello Jonathan,

it's a very easy thing to try, and nothing to lose.

Presumably you had the metering unit set up for your engine, and if so is this a new problem, i.e. it had run OK before?
As a matter of interest why do you set the idle so high? My engine is tweaked a bit but I can set the idle down to 500 rpm quite easily, admittedly it is quite lumpy at that idle so I normally speed it up another 100 rpm or so?

Alec

I think/hope I've found the problem - the points are not closing properly due to a tiny lump on one of the faces. Only visible when you hold them up to a light! I will probably change the condenser as well, in case this is failing and causing arcing across the points, and therefore the deposition. Sometimes, depending on how the points "land" when they close, the lump is missed and they close properly, so this could be why it's an intermittent problem.

I can't see much else to cause it, anyway! Maybe it's time for an Aldon Ignitor!

To answer your questions Alec, yes, the metering unit was set up for the engine and had always run fine. The problem only started when...the points were changed... The idle is set high to avoid the engine dying during a test on a rally - it's a common problem if you don't set the idle high that during a stop astride or a reverse, the engine(which is obviously being exercised!) can give up on you, swiftly followed by the sound of a frantic starter motor and some harsh language!

Jonathan

Are you allowed to get shot of the points and use an Aldon ignitor or similar ?
I fitted one on my car after a few months of daily driving and it's been reliable since.


Edit.
Sorry will have to learn to read properly missed the bit where you suggested it.

I did have one problem with the plastic rotor bit once. I wrapped a bit of PTFE tape around the cam to make it a really good fit and next time I removed it the plastic came apart and the magnets fell out. I got a replacement and superglued it back together making sure the magnets were the right way round.