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TR6 PI starts with a bang, then dies


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Peter, regarding your question about the pulley marks. I got the dgr scale on the pulley, the timing cover has just a static indicator, as you said. The mark on the pulley is made at about 12-13 dgr BTDC (as I understand it). When looking from front of the car towards the front (cyl #1) of the engine, the mark is before coming to TDC on the pulley. Pulley/cranck rotating clockwise. Seems right, doesn't it?

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You should set the valve clearances to the camshaft manufacturers recommendation. However I don't think the difference is anything like enough to cause the problems you describe.

 

My feeling is that the plugs leads are effectively in the wrong order due to either being configured to no.1 cylinder when it on the exhaust stroke (180º out as Neil says) or because the leads or on the cap in the right order but wrong direction of rotation. Both errors that are all too easy to make.

 

Another easy mistake to make is to set the cam timing using no 1 exhaust valve rather than no.1 inlet valve as the exhaust valve is the one at the front making it a tempting target! This seems unlikely in a professionally built engine.

 

Nick

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The valve clearances do vary considerably with 'fast' cams, mine are 24thou.

 

Perhaps post a pic of your distributor cap and leads, we can soon see if they are correct?

 

Steve

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Hi, thanks - I'll post a picture of the distributor w/cables later today.
I suspect that I've done a rookie mistake that I've just gone blind on.

Previously this summer, after the rebuild, I did manage to make the car run fairly ok. Not smooth, but ok. When it got warmed up to working temp, I re-tightened the head nuts to the torque in the brown book. To be able to do this, I had to remove the cam shaft, and put it back on. I followed the proper sequence of nut tightening. I've checked that the camshafts, and they all seem to sit correctly. After tightening the head nuts, I readjusted the valve gaps (to 10 thou).

When doing this low rev test run, the engine stopped after a while. I suspect that it was due to a faulty battery AND that I had not tightened the alternator belt enough, not being able to charge the little capacity left on the battery. Just mentioning it as a digression.

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Peter, regarding your question about the pulley marks. I got the dgr scale on the pulley, the timing cover has just a static indicator, as you said. The mark on the pulley is made at about 12-13 dgr BTDC (as I understand it). When looking from front of the car towards the front (cyl #1) of the engine, the mark is before coming to TDC on the pulley. Pulley/cranck rotating clockwise. Seems right, doesn't it?

Morten, Yes its right. 12 BTDC is one thirtieth of the circumference. All you need now is to check the TDC with the piston stop. Peter

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When doing this low rev test run, the engine stopped after a while. I suspect that it was due to a faulty battery AND that I had not tightened the alternator belt enough, not being able to charge the little capacity left on the battery. Just mentioning it as a digression.

 

It might not be a digression. As the battery volts drop away so will energy of the sparks. If some cycles then misfire that's where the unburned fuel in the exhaust comes from, and the backfiring.

Peter

Edited by Peter Cobbold
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. Bring it to number 1 and post a pic of the dog drive with dizzy removed from the top.

Beat me to it Neil. :)

 

@ Morten, If the disy dog drive or shimming is wrong the rotor arm could be running off the cap contact as you try to rev it due to the centrifugal advance. There's a diagram in the manual of the correct angle and offset of the dog drive, seen when you remove the disy.

Peter

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@ Morten, If the disy dog drive or shimming is wrong the rotor arm could be running off the cap contact as you try to rev it due to the centrifugal advance. There's a diagram in the manual of the correct angle and offset of the dog drive, seen when you remove the disy.

Peter

 

Not 100% sure about the PI and the MU drive, but on 6 whilst its nice if the drive dog is in factory orientation, and thus number one plug lead where expected, it doesn't actually matter what orientation the drive gear is provide that number one plug lead (and the rest) are in the correct place to suit. The critical easy check is to rotate engine until #1 coming up to TDC on the compression stroke (i.e. inlet has just closed ) check the piston is actually just about at TDC a simple probe through the plug hole should suffice, and then check that the leading edge of the distributor rotor (remembering rotation is anti clockwise) is just approaching or on #1 plug lead terminal in the dizzy cap. Without being fancy if you have fuel then it ought to run unless there is another problem.

 

Talking of simple problems that can have a similar effect, I must have 153624 engraved in my brain, but without marked leads the number of times that I have found my self swapping 3 & 5 and as the leads are just about the same length its not visually obvious. In that order #5 fires very late (or not at all pumping air/fuel into the exhaust) and #3 fires very early on the compression stroke. The engine will run but badly!

 

Alan

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Hi all - very good input!
Here is what I've done since last post:

* found the TDC on #1. It was pretty much correct according to the marks on the pulley. Maybe a few degrees off.
* Adjusted the valve gaps for the Sprint 90 cam. It should not be 10 thou as in the brown book, but 15-18 thou.
* Removed the MU / distributor pedestal, Took out the drive between the oil pump and distributor. Turned the drive dog/slot on the oil pump about 30 dgr clockwise.
* Put the pedestal back. Re-timed the MU (port on #6 about 50% opening).

* Put on the distributor.

* When #1 fires, both valves are closed, cyl #6 valves on the rock.

 

How it now looks is pretty much as on the pictures. It sounds different - a bit - but does not really run.

 

Questions:

1) The brown workshop manual and the Haynes manual specifies different positions to be the correct ones for the distributor drive (the slot you look down at for linking the distributor to); the brown book says is should be at 7-8 o'clock (offset towards engine), Haynes says at 6 o'clock. What is better?

2) I'm not sure if the rotor is fully at #1 when the contact breaks - could it be that the distributor is not lowered far enough? I know that the drive to the oil pump engaged properly.

Also 1-5-3-6-2-4 is pretty much in my head. And the MU injectors are correct order.

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Edited by MortenHoyseth
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The angle of the drive dog and the tacho cable look good to me.

Edit: BUT....the 12 volt connector recessed in the disy casing should be around 9 to 10 o'clock not 12.

Compared with mine I think the disy casing is 45 deg too far clockwise. That could happen ( I think) if you are setting the static as the points are closing, not opening. Are you timing the points opening ? - the cam that opens the points rotates anticlockwise viewed from above. The bulb should be out between lobes ( ponts closed) and come on as the plastic cam follower is pushed outward by the rising cam lobe, to open the points.

Mistiming when the points are closing will have the effect of way over-advancing the sparks !!! By about 50 crank degrees !!

I think that's the problem. Hope so as there are not many simple solutions left.

 

Ignore the stuff bwlow and focus on timing those points.

 

Peter

 

===========================================

 

And the rotor arm ( if its at TDC #1) But check when static is set to 12BTDC the leading tip of the rotor is opposite the contact in the cap.

 

Thats not a PI disy. Its a USA-spec distributor with a vacuum-retard capsule.

http://www.tr-register.co.uk/forums/index.php?/topic/47883-hs6-su-carb-vacuum-setup/

 

There are spark timing data for the various TR6s here:

http://www.tr-register.co.uk/forums/index.php?/topic/24915-tr6-ignition-timing/page-2

 

With the vac-retard capsule disconnected, set the static to 12BTDC.

I dont know which of the disy listed as F to L you have. But I would expect them all to

work well. They give more advance at 3000rpm than the PI but should still work.

 

Leave the vac-ret disconnected its not needed.

 

What does the engine sound like now? is it still backfiring, does it rev up OK?

Peter

Edited by Peter Cobbold
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* Removed the MU / distributor pedestal, Took out the drive between the oil pump and distributor. Turned the drive dog/slot on the oil pump about 30 dgr clockwise.

* Put the pedestal back. Re-timed the MU (port on #6 about 50% opening).

 

Questions:

 

1) The brown workshop manual and the Haynes manual specifies different positions to be the correct ones for the distributor drive (the slot you look down at for linking the distributor to); the brown book says is should be at 7-8 o'clock (offset towards engine), Haynes says at 6 o'clock. What is better?

 

 

I'm assuming that when you say you moved the drive dog around 30deg, that meant when you replaced the distributor it too then had to be rotated 30 deg from where it was before? If not I'm confused how it ran at all before or is running now.

 

Re distributor drive slot, you need to be careful which slot is being described, the one in the drive gear that engages with the oil pump and the distributor on non PI systems, or the slot in the upper drive on PI systems. According to my Factory PI book the lower gear slot should be at angle between about 7 o'clock and 1 o'clock but the the distributor drive slot shoulb be between 6 o'clock and 12 o'clock.

 

 

 

 

The angle of the drive dog and the tacho cable look good to me.

Edit: BUT....the 12 volt connector recessed in the disy casing should be around 9 to 10 o'clock not 12.

Compared with mine I think the disy casing is 45 deg too far clockwise.

 

Thats not a PI disy. Its a USA-spec distributor with a vacuum-retard capsule.

 

Leave the vac-ret disconnected its not needed.

 

 

 

Yes it is a retard distributor, I have one on the Vitesse and the orientation shown in the pictures would be correct for that dizzy.

 

He does not appear to have a vacuum hose attached, and as you say does not need it. I use a retard one as the are available as NOS, and as I run neither vacuum advance or retard its much safer to have a dizzy that cant go over advanced.

 

Looking closely at the picture it appears to be a Dizzy Doctor reconditioned unit, so I hope that he would have supplied it correctly set up for the PI? and as PI requires neither vac advance or retard it should be fine,

 

It should run,is this a us coverted car?and do you have the right head fitted?

 

Ah a slightly more fundamental question, that might negate all the tinkering around the edges trying to get it to run.

 

Alan

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Let me just elaborate, since it came up:

The engine is a '71 2.5 PI engine, fitted in a US car. It was converted late 80s/early 90s. The dizzy (22D6) is probably from the US car. I've had the car for 8 years or so, and it has been running quite smoothly, until this major restauration job.The MU and distributor were both overhauled in UK (Prestige Injection / Distributor Doctor - yes, for PI / no adv.), and I've been using them both after I got them back, but that was before the car was taken appart. So I am pretty confident that both the MU and distributor are all good.

I'm pretty sure the engine/head is good as well - everything was done by Moss in the UK, and the entire engine was there; I haven't fiddled with the engine's internals myself.

And also appoligies for my english being far from perfect :)

Peter/Alan - I'll read through and check/test t

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Peter, I moved the distributor body anti-clockwise; connector to coil now at about 10 o'clock. With the engine set at about 12dgr BTDC #1 firing , I set the static timing by having a lamp between the battery + and the cable (disconnected from coil) going to the - on the coil. I rotated dist. body anti-clockwise until the lamp shuts of. Then I rotated it clockwise until the lamp just goes on? I've tested so many things now that my head is getting messed up. It's supposed to be the other way around?
I tried to start it up in this position - and pretty much same result. Sounds like some petrol is firing with a mild boof, and some smoke comes out of the air manifold.

On the cam on the distributor. When the lamp goes on (turning clockwise), the plastic thingy touching the rotor, has just passed the heel of the rotor. Rotor turning ccw.

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