P.I running issues.

[sahtuning2000]

So after solving the P.Is tapping noise its now developed a misfire!
I find this a bit annoying as it was running nice before i replaced the manifold gasket today,it did have a slight miss but not to obvious.
Now it does have an obvious miss and is like it has a lead bnreaking down.
Today i replaced all the manifolds etc and i didn,t mess with the inlets,all were kept together and just placed in the boot overnight,done the manifold gasket and replaced all the inlets in one go,i checked the tightness of the balance tubes,all fine.
I checked plugs(these are black)
Replaced with new points
Swopped for another dizzy cap/Lucus rotor and another set of leads,no change.
I checked all injectors for spraying and all 6 are fine,i did have these removed and gently placed on the coil side of the engine to keep out of the way.
The car IS running rich and any tips on this will help,i wonder if now the manifold gasket is done is now choking itself as its running so rich?
It doesn,t cutout or stall,and i drove it up the road and back and goes well but you can hear its not 100% happy,and a miss on the exhaust note can be heard.
I just need to smooth it out and i think it will be nice,i can,t understand why this has appeared today after removing/replacing the manifolds.
I,ve checked the timing and its fine,haven,t moved the dizzy(is TDC correct for a late P.I)thats what the manual says.
One think i do notice is the pump does have abit of a whine to it,i touched it when the car had run for about 30 mins and it was cool,no heat,a gentle tap on the pump does change its note,i was told by the previous owner that this was replaced the year it was removed from the road.
Getting it to run weaker is a must i think,but it did run well if rich until today,

[leesellars]

Sounds like it's pulling air inbetween the head and throttle body. Also check the vacume hoses. Including the one in between the throttle body's and one onto the MU. The hoses should be supple

Lee

[leesellars]

Where are you.

Lee

[Alec]

Hello SAH,

assuming the air cleaner element is clean, then it should just be a matter of getting the engine tune correct. TDC doesn't sound right for the timing but I don't have a manual to hand. However the best way to ensure the timing is right is by road testing, and aim to have the timing just short of pinking. Drive the car and slowly advance the timing until you get the engine to pink, then retard a shade, so it doesn't. That should be the optimum; a vacuum gauge is a handy tool for a P.I. so you can see what effect your adjustments are having.

Alec

[sahtuning2000]

When i drove it to the MOT a few weeks ago it went well,no pinking,run on and it starts well hot/cold but just runs rich,it seems to have all gone back together exactly as i removed it and i did take my time to make sure everything was correct.
I,ve checked the manifold hoses,and the servo ones aswell all seems fine.

[Jonathan Lewis]

Are all of the injectors pulsing when the engine is running, i.e. one short burst per cycle with no continuous spraying or significant dribbling?

As Lee (?) has already noted in another thread, the original-spec MU seals and O-rings do not always take kindly to modern unleaded fuels, and can begin to break up. Failure of the O-rings in the injectors can cause dribbling, whilst failure of the bung seals between the rotor and outlet ports of the MU can result in a continuous feed of pressurised fuel to one or more injectors, overfuelling and even hydraulic lock of the afflicted cylinders...

Excess fuel pressure will also cause overfuelling, though I don't quite understand why the pressure would have increased over the last few weeks (unless, of course, some debris has got lodged in the return line from MU to tank and is causing pressure at the MU to be increased as a result).

Other possibilities that come to mind are a split diaphragm in the vacuum part of the MU or an out-of-adjustment camtrack or full load setting screw, though again, I would have expected the latter condition to be evident from when you first had the car running.

[Alec]

Hello SAH,

one thing that slipped my mind is the adjustment of the fuel enrichment lever (Choke), there must be a small clearance between the two levers at the rear of the metering unit . It's a little difficult to see when on the car but should be obvious if you look closely and manually operate the lever that is connected to the cable.

The fact that the car does not pink does not mean the timing is correct, the idea is to advance so it does then just back off so it doesn't.

Alec

[sahtuning2000]

Many thanks for the tips,ive read them a few times and must admit i,am a bit worryed about touching anything involving the injection.
I,ve had all 6 injectors out several times to sort the rockers and check the spray pattern,but i haven,t touched the pump or metering unit.
Its running shell V power,i did notice the fuel light came on yesterday and i turned it of and went and got £20 V power for it.
I feel my lack of P.I knowledge could be and issue heard and reading all the tips/hints is very helpful but i don,t want to spend anymore time on it chasing issues like this.
I could buy a set of injectors(CW only has 2)but could find it has a MU issue,more money wasted and time,the car has had a serious impact on me both with wife who has complained how much time i,ve spent on it,my work as i,ve overlapped a few lunchtimes and my neighbours as its been running a fair bit,but smells rich and has a semi sport exhaust on it,i,am sailing VERY close with the car.
What i could do with is someone not far away from me who could visit me and have a listen,i,am in Surrey near Jun 11 M25.At the moment the webasto has been removed as its being recovered and i,am not taxing it until April the first.
If someone was prepared to visit me to cast there eye over it for me i will pay for there travelling and give them a drink for having a loook for me??
Its the last resort i really can,t spend more time/money chasing problem after problem,i just need it to run smooth and weaker to improve matters,i even got my Heritage certificate for it yesterday.PLEASE HELP!!!!!!!!!

[Alec]

Hello SAH,

hopefully there is someone nearby who can have a look for you.

What you need to keep in front of everything is that the last thing you ever touch with a poor running P.I. is the metering unit. Ensure that all other timing and engine tuning aspects are spot on. You have set the tappets which is often overlooked so spark timing, state of the plugs, air cleaner, choke setting etc should be verified. As I said earlier a vacuum gauge gives a good guide.
I just had a look at a manual I have in the house and it gives a post 1973 P.I. ignition timing as 2 degrees BTDC (stroboscopic) at 800 rpm. Now if you set the timing statically then you may well be setting the timing too retarded as at 800 rpm the distributor will have advanced a degree or two.

Incidentally when I first bought my P.I. there was a thin shim of steel between the roller linkage and the datum track, obviously that was tried as a cure for over rich mixture!

Alec

[leesellars]

Why are you running it on super unleaded. Normal unleaded will do. No additives. I take it that the head has been done. I am willing to pop
Down but I'm in nottingham an would have to be during the week. Weekend are out for me as i will be on my next event soon.

Lee