Spark Plugs & Misfire : cleaning sooty BP6ES + is BP6ET worth a try?

[Jules TR6]

I'm going through the obvious checks relating to the bad misfire issue my TR6 PI is having, and by bad I mean ready bad - it felt like it was only running on 2 or 3 cylinders!

Some details about the car : TR6 petrol injection, ballast ignition system with a compatible new Viper solid-resin ballast coil, currently using electronic ignition (though may go back to new points). Previous owner installed the 3x K&N air-filter intake conversion, i.e. now no plenum (if I keep the vehicle another year I might go back to the cooler-air plenum, but not now).

Injector #3 had 1/5th of the circle missing (this couldn't have been the lone cause of the v.bad misfire), bled, now good. Oddly this was the only injector that the collar stayed in the engine, with the other five the collars came out with the injectors.

These are the plugs (BP6ES) after removal :

#2 and 3 looked best, the others were all similar - covered in fine dry soot (#1 is wet as I'd already given it a petrol rinse, was as the others dry on removal). Would this soot cause a bad misfire? - ok they are sooted-up but not caked in crud or obviously corroded.

Cleaned them with a wire spark-plug 'tooth-brush', a quick wipe with super-fine emery paper and a rinse in petrol before and after this procedure. Then I flicked off excess petrol, re-gapped, and put them back in the engine. I have since read that one should use WD40, will have rinsing the tip in petrol have messed them up?? After a night in the engine I assume they've now evaporated dry.

The gaps were rather various, from #1 to #6 (#6 was the most surprising) : 0.025" 0.024" 0.026" 0.024" 0.025" 0.022"

I've now set them all to 0.026" (which could be seen as 0.025" but not 0.028").

What to you think the plug look like - why are they covered in soot? would you have changed them for new?

I can try to use less choke and push the lever in quickly (I've checked the 2 choke cables, all 'off' when the lever is pushed home), also I can try to avoid short runs, but if not undertaking a longer run surely a 10 minute run every week is better than nothing.

Does timing affect sooting-up of plugs, would a touch more advance help or make matters worse?

I was also alarmed that a couple of the terminals were loose, not falling off loose, just not tight. I've read that this can cause misfire, though some say not. I've tightened them, but they can be easily loosened again, they don't actually grip tight, a rather odd design. I'd like to somehow get them confidentiality tight, or is it not a concern?

/

If I buy a new set, might it be worth trying the multi-electrode BP6ET - what's not to like about them?

Do multi-electrode plugs need gapping? - such as the BP6ET, or just fit from the box, I read it has 0.032" gaps. As there's three electrodes arranged to the side of the central electrode, is 0.032" ok?

Yes lots of questions! - would be grateful for any help here.

Main aim is no misfire, lively acceleration & max performance.

Edited October 2, 2023 by Jules TR6

[RobH]

The plugs are sooty because the mixture is rich, which I understand may be normal for the PI engine because it has no acceleration enrichment device.  You could try 'hotter' plugs - which for NGK would be BP7xx . 

The multi-elecrode plugs can't be gapped. They are pre-set. 

[Jules TR6]

8 minutes ago, RobH said:

The plugs are sooty because the mixture is rich, which I understand may be normal for the PI engine because it has no acceleration enrichment device.  You could try 'hotter' plugs - which for NGK would be BP7xx .

The multi-elecrode plugs can't be gapped. They are pre-set. 

As I understand it, for NGK the lower the number the hotter the plug.

So I could try BP5ES or BP5ET - would anybody else advise this, what might be the down-side of using 6 hotter plugs?

[StuartG]

I have used the multi electrode type for several years and I have found them to be a lot less likely to soot up.

[mleadbeater]

my recommendation is to get yourself a colortune ,  which will instantly show the state of the combustion flame, basically its a window into the combustion chamber, as the engine is running.

Simplest and most reliable mixture tuning device ever made, use mine for 40+ years.

The photo shows a good blue flame, yellow is too rich, white too weak.

Remember the bunsen burner you did in your first science lesson at school.

Mike

Edited October 2, 2023 by mleadbeater
additional info

[Mike C]

I had all kinds of sooty plug problems due to an out of calibration PI . The car was horrible to start and drive. Anyway I had the PI system rebuilt and re-calibrated then switched to NGK BUR 6ET plugs 5 years ago- it totally transformed the car.

The car is now reliable, starts easily and has plenty of power.

And the NGK BUR series of  three  electrode plugs do not need the gap to be checked and  reset

 

[RobH]

1 hour ago, Jules TR6 said:

As I understand it, for NGK the lower the number the hotter the plug.

Yes you are right of course.  It's the others that do the numbers the other way round. Apologies. 

 

[Jules TR6]

51 minutes ago, Mike C said:

I had all kinds of sooty plug problems due to an out of calibration PI . The car was horrible to start and drive. Anyway I had the PI system rebuilt and re-calibrated then switched to NGK BUR 6ET plugs 5 years ago- it totally transformed the car.

The car is now reliable, starts easily and has plenty of power.

And the NGK BUR series of  three  electrode plugs do not need the gap to be checked and  reset

 

The BUR6ET has a resistor, I've read this is not always the best route to take (also from the NGK site the plug is always shown without the push-on adaptor terminal).

I presume the BP6ET is basically the same - but without the resistor. Might try a set.

[Jules TR6]

1 hour ago, mleadbeater said:

my recommendation is to get yourself a colortune ,  which will instantly show the state of the combustion flame, basically its a window into the combustion chamber, as the engine is running.

Simplest and most reliable mixture tuning device ever made, use mine for 40+ years.

The photo shows a good blue flame, yellow is too rich, white too weak.

Remember the bunsen burner you did in your first science lesson at school.

Mike

...this would only be of use with carburettor engines - where the mix can be adjusted? I'm with petrol injection.

[astontr6]

1 hour ago, Jules TR6 said:

As I understand it, for NGK the lower the number the hotter the plug.

So I could try BP5ES or BP5ET - would anybody else advise this, what might be the down-side of using 6 hotter plugs?

I have used the grade 5 NGK plugs for years over 40 years. Because of this problem, with sooty plugs. It has worked for me. But if your PI is running super rich ie. black smoke out of the tail pipes, the M/U needs an overhaul? may be. The NGK plugs are lower the number hotter the plug unlike Champion where is the other way round. But a point to note is that BL fitted hotter plugs to the carb engines after lead  in petrol was withdrawn for the US market.

Bruce.

[Jules TR6]

5 minutes ago, astontr6 said:

I have used the grade 5 NGK plugs for years over 40 years. Because of this problem, with sooty plugs. It has worked for me. But if your PI is running super rich ie. black smoke out of the tail pipes, the M/U needs an overhaul? may be. The NGK plugs are lower the number hotter the plug unlike Champion where is the other way round. But a point to note is that BL fitted hotter plugs to the carb engines after lead  in petrol was withdrawn for the US market.

Bruce.

With the very very rough running the engine has had of late, there's now fresh soot in the tail-pipes - not sure I noticed it before though for sure previously when the engine worked sweet the exhaust gas was clean - I did notice that.

I've just ordered a set of BP6ET (the Triple electrode version), if they soot up quick I'll try the hotter BP5ET. If they soot up, a deeper inspection maybe needed, as you suggest the MU.

[BlueTR3A-5EKT]

37 minutes ago, Jules TR6 said:

With the very very rough running the engine has had of late, there's now fresh soot in the tail-pipes - not sure I noticed it before though for sure previously when the engine worked sweet the exhaust gas was clean - I did notice that.

I've just ordered a set of BP6ET (the Triple electrode version), if they soot up quick I'll try the hotter BP5ET. If they soot up, a deeper inspection maybe needed, as you suggest the MU.

Have you done the 'tongue' test on the metering unit vacuum pipe?

Find the rubber vacuum pipe that feeds between the manifolds and the top of the metering unit.  

Pull it off the manifold adapter.

Suck the end of the pipe and place your tongue over the pipe end.

The vacuum you have created in the pipe should hold your tongue to the pipe.

If not....the pipe is leaking or the capsule in the metering unit is leaking.   This vacuum leak will affect the mixture.

Alternatively use a Mityvac to create and test the vacuum.  https://www.skf.com/mityvac/products/hand-vacuum-pressure-pumps

 

 

Edited October 2, 2023 by BlueTR3A-5EKT

[Jules TR6]

5 minutes ago, BlueTR3A-5EKT said:

Have you done the 'tongue' test on the metering unit vacuum pipe?

Find the rubber vacuum pipe that feed between the manifolds and the top of the meeting unit.  

Pull it off the manifold adapter.

Suck the end of the pipe and place your tongue over the pipe end.

The vacuum you have created in the pipe should hold your tongue to the pipe.

If not....the pipe is leaking or the capsule in the metering unit is leaking.   This vacuum leak will affect the mixture.

no I haven't!  Will do next time I'm in the garage - and report back.

It's connected to the centre of the manifold (the brake assist is connected to the rear, the front blanked off).

[Anschutz]

You need good vacuum to get it to run right, have you good compressions spot on timing valve clearances correct? Do these first

[Jules TR6]

1 hour ago, Anschutz said:

You need good vacuum to get it to run right, have you good compressions spot on timing valve clearances correct? Do these first

I'll check the vacuum from the MU, with the tongue test, and the timing to 11 degrees BTDC (or should it be slightly more advanced - i.e. using a vacuum gauge on the brake assist or T from the MU to see max vacuum?).

Am I right in thinking that more advanced means the spark is delivered when the piston is higher in the cylinder (just after it has started to descend), potentially providing a longer throw of power, and ignition in a smaller more compressed space = richer. Therefore if I wish ignition not to be so rich, I should either stick to 11 degrees BTDC or only advance a fracton more - but not too much? i.e. more advanced = 'richer' in a PI system?

My local garage just replaced the rocker gasket and sealed it, so I'm not getting that off again (any time soon).

I am hearing a regular rasping sound in the engine bay, in time with engine tick over, not immensely loud but noticeable (I can't remember if it was there before or not, or it's something new). The fan belt seemed too tight, slackened it off a bit. Thunderstorms here, too wet to get it up to temp and check all this today.

Edited October 2, 2023 by Jules TR6

[Mike C]

10 hours ago, Jules TR6 said:

The BUR6ET has a resistor, I've read this is not always the best route to take (also from the NGK site the plug is always shown without the push-on adaptor terminal).

I presume the BP6ET is basically the same - but without the resistor. Might try a set.

Worth a try, just a bit dearer than normal plugs. I use resistor plugs to suppress radio interference

[Mike C]

Yep, the vacuum  is a good indicator. I use a vacuum gauge on the brake servo connection and I must have 10 inches of mercury at idle for the  MU to deliver the right mixture.

To set the timing I start at 11 deg BTDC at idle, my distributor is the normal CP model without vacuum advance, then I he creep the advance forward until I get slight pinking at WOT high load, at which time I back the distributor back a tad.

The more you can advance the distributor without pinking  the more power you will get

[astontr6]

18 hours ago, Jules TR6 said:

With the very very rough running the engine has had of late, there's now fresh soot in the tail-pipes - not sure I noticed it before though for sure previously when the engine worked sweet the exhaust gas was clean - I did notice that.

I've just ordered a set of BP6ET (the Triple electrode version), if they soot up quick I'll try the hotter BP5ET. If they soot up, a deeper inspection maybe needed, as you suggest the MU.

You also need to do a compression check and tappet clearance check.

Bruce.

[Jules TR6]

37 minutes ago, astontr6 said:

You also need to do a compression check and tappet clearance check.

Bruce.

...ok well that's a job for next year. I will try with the new plugs, checked injectors, and timing, first.

[BlueTR3A-5EKT]

19 hours ago, Jules TR6 said:

I'll check the vacuum from the MU, with the tongue test, and the timing to 11 degrees BTDC (or should it be slightly more advanced - i.e. using a vacuum gauge on the brake assist or T from the MU to see max vacuum?).

Am I right in thinking that more advanced means the spark is delivered when the piston is higher in the cylinder (just after it has started to descend), potentially providing a longer throw of power, and ignition in a smaller more compressed space = richer. Therefore if I wish ignition not to be so rich, I should either stick to 11 degrees BTDC or only advance a fracton more - but not too much? i.e. more advanced = 'richer' in a PI system?

My local garage just replaced the rocker gasket and sealed it, so I'm not getting that off again (any time soon).

I am hearing a regular rasping sound in the engine bay, in time with engine tick over, not immensely loud but noticeable (I can't remember if it was there before or not, or it's something new). The fan belt seemed too tight, slackened it off a bit. Thunderstorms here, too wet to get it up to temp and check all this today.

Advanced means the spark happens earlier than the piston getting to top dead centre, not later.  So advancing will set the spark to be when the piston is lower or sooner in its compression stroke as it is rising.  

[Jules TR6]

2 hours ago, BlueTR3A-5EKT said:

Advanced means the spark happens earlier than the piston getting to top dead centre, not later.  So advancing will set the spark to be when the piston is lower or sooner in its compression stroke as it is rising.  

...ok I understand now, crystal clear many thanks. I'm still learning, but fast.

Edited October 3, 2023 by Jules TR6

[Mike C]

The idea is to get the combustion process underway early so it's energy is fully expended on the piston down stroke, but not  so  early that it pushes against the rising piston. It's a fine balancing act and it's different for every old engine set up.

[Jules TR6]

12 hours ago, Mike C said:

The idea is to get the combustion process underway early so it's energy is fully expended on the piston down stroke, but not  so  early that it pushes against the rising piston. It's a fine balancing act and it's different for every old engine set up.

...much appreciated explanation. I'm sure this is super basic info for everyone, but I'm glad the pennies are dropping for me!

So if ignition occurs too early / too advanced, is that the cause if pinking/pinging (+ when there's too much throttle or too much load) - ignition pushing against the rising piston? - that's the ping sound?

Does this also result in a poorly burnt fuel mixture, and so contribute to sooty plugs, i.e. can excessive pinking be one cause of sooty plugs?

[RobH]

Not only due to over-advanced ignition.  Pinking is due to the fuel mixture burning very rapidly in an uncontrolled way - basically a small explosion. It is supposed to burn progressively so that a 'flame front' progresses across the ignition chamber from the plug.  Pinking can happen even with correct spark timing due to excess compression or fuel with too low an octane rating.  The ping is caused by the shock-wave from the 'explosion'. 

Rather than causing sooting, pinking can be caused by it because the carbon can get hot and glow, causing the mixture to ignite prematurely instead of by the spark.  That's one reason why in the old days of low octane fuel, engines had to be decarbonised regularly. 

Edited October 4, 2023 by RobH

[Mike C]

8 hours ago, RobH said:

Not only due to over-advanced ignition.  Pinking is due to the fuel mixture burning very rapidly in an uncontrolled way - basically a small explosion. It is supposed to burn progressively so that a 'flame front' progresses across the ignition chamber from the plug.  Pinking can happen even with correct spark timing due to excess compression or fuel with too low an octane rating.  The ping is caused by the shock-wave from the 'explosion'. 

Rather than causing sooting, pinking can be caused by it because the carbon can get hot and glow, causing the mixture to ignite prematurely instead of by the spark.  That's one reason why in the old days of low octane fuel, engines had to be decarbonised regularly. 

I agree with you, every engine/fuel/load combination is different, the idea is to get as much power out of controlled combustion without uncontrolled detonation of the air /fuel mix.