What do these plugs tell you about the mixture....
Discussion
Hi all,
As the title suggests really, what do you think of the look of these plugs? I think the car is running a little rich, due to it only needing choke to fire on a morning, then I can shut it off almost straight away. Also, fuel economy seems low at around 22mpg, however this could be due to lots of short trips/idling as ive only just got it and have had a bit on getting her running.
I put the plugs in 120miles ago, had a 50 mile round trip today, and then pulled 2 plugs straight out. The top pic is from No.3 and the bottom from cylinder No. 1.
Thanks in advance,
Phil
roscobbc said:
Firstly what engine spec/car combo is it. Plugs may well look ok after a period of extended idle. Perhaps you should do the same thing after, say a constant 50 mph run for 5 minutes - knock the car in to neutral, cut the engine and coast to a halt - then check the plugs out.
If that was a result from similar test top above then they look OK colour of centre electrode is a little darker than ideal perhaps - but we are not talking about something with rocket science engine engine management are we? - preferable to be a little bit rich mixture wise than too weak and run a risk of engine damage.You could try the test I mentioned above but at, say full throttle for 30 seconds in third gear and compare.to me those look (in the photo, on my monitor) yellow (and the core tips look sloped(?))
see Insulator Glazing on this chart (bear in mind your short journeys, why not go for a reasonable distance blow out ride and then check the plugs) - http://www.classic-car-magazine.co.uk/articles/spa...
don't fall into the trap of being a carb fiddler, you need to get the whole car fully serviced and as part of that set up in this order - tappets, CB points, plugs, timing then carb mixture - if you adjust any item in this chain then you'll need to adjust/check the items that follow
on any car new to you I suggestion doing a staged 36k-mile service/check up with regularly using the car and by your previous posts I'd strongly recommend it on this car
NGK plugs are considered by many to be the best to use but if you like Champion N9YC then I have about a dozen Champion RN9YC I could let you have cheap
see Insulator Glazing on this chart (bear in mind your short journeys, why not go for a reasonable distance blow out ride and then check the plugs) - http://www.classic-car-magazine.co.uk/articles/spa...
don't fall into the trap of being a carb fiddler, you need to get the whole car fully serviced and as part of that set up in this order - tappets, CB points, plugs, timing then carb mixture - if you adjust any item in this chain then you'll need to adjust/check the items that follow
on any car new to you I suggestion doing a staged 36k-mile service/check up with regularly using the car and by your previous posts I'd strongly recommend it on this car
NGK plugs are considered by many to be the best to use but if you like Champion N9YC then I have about a dozen Champion RN9YC I could let you have cheap
What carbs do you have?
A quick Google for "MBG GT Carbs" shows pictures of SU Type HIF carbs. This model includes the feature that "additional mixture required for cold starting is supplied seperately to that from the main jet" It has a "Cold start enrichment device" that opens an extra orifice when the choke is pulled out, rather than lowering the jet orifice.
Thus, good cold starting may not indicate a mis-set needle, quite the reverse!
Carry on driving!
And I think your plugs show a perfect mixture setting!
JOhn
A quick Google for "MBG GT Carbs" shows pictures of SU Type HIF carbs. This model includes the feature that "additional mixture required for cold starting is supplied seperately to that from the main jet" It has a "Cold start enrichment device" that opens an extra orifice when the choke is pulled out, rather than lowering the jet orifice.
Thus, good cold starting may not indicate a mis-set needle, quite the reverse!
Carry on driving!
And I think your plugs show a perfect mixture setting!
JOhn
The first thing those plugs tell Me is that plugs are so much easier to get at on older cars than they are on modern cars!
On older cars it's:
1) Open bonnet.
2) Pull off plug lead.
3) unscrew plug.
4) Fit new/refit old plug.
5) Refit plug lead.
6) Repeat steps 2~5 as necessary.
7) Close bonnet.
On modern cars it's:
1) Open bonnet.
2) Remove small plastic cover plugs (Try not to drop into the engine bay!).
3) Unscrew plastic cover/covers (Try not to drop screws into engine bay!).
4) Remove plastic cover/covers.
5) Disconnect coil-pack earth lead (Try not to drop screw into engine bay!).
6) Disconnect coil-pack solenoid plug.
7) Remove coil-pack (try not to drop screws into engine bay!).
8) Remove plug.
9) fit new/refit old plug.
10) Refit coil-pack (Try not to drop screws into engine bay!).
11) Reconnect coil-pack solenoid plug.
12) Reconnect coil-pack earth lead (Try not to drop screw into engine bay!).
13) Repeat steps 5~12 as necessary (Remember to have a cup of Tea/coffee half way through whilst swearing about what a faff the whole job is! - Especially if you've dropped screws into the engine bay!).
14) Refit plastic cover/covers.
15) Refit plastic cover plugs.
16) Close bonnet.
Note: If you own a Subaru then the procedure is:
1) Open bonnet.
2) try to see where the spark-plugs are.
3) Determine that the car runs so you're sure the plugs must be okay.
4) Close bonnet.
On older cars it's:
1) Open bonnet.
2) Pull off plug lead.
3) unscrew plug.
4) Fit new/refit old plug.
5) Refit plug lead.
6) Repeat steps 2~5 as necessary.
7) Close bonnet.
On modern cars it's:
1) Open bonnet.
2) Remove small plastic cover plugs (Try not to drop into the engine bay!).
3) Unscrew plastic cover/covers (Try not to drop screws into engine bay!).
4) Remove plastic cover/covers.
5) Disconnect coil-pack earth lead (Try not to drop screw into engine bay!).
6) Disconnect coil-pack solenoid plug.
7) Remove coil-pack (try not to drop screws into engine bay!).
8) Remove plug.
9) fit new/refit old plug.
10) Refit coil-pack (Try not to drop screws into engine bay!).
11) Reconnect coil-pack solenoid plug.
12) Reconnect coil-pack earth lead (Try not to drop screw into engine bay!).
13) Repeat steps 5~12 as necessary (Remember to have a cup of Tea/coffee half way through whilst swearing about what a faff the whole job is! - Especially if you've dropped screws into the engine bay!).
14) Refit plastic cover/covers.
15) Refit plastic cover plugs.
16) Close bonnet.
Note: If you own a Subaru then the procedure is:
1) Open bonnet.
2) try to see where the spark-plugs are.
3) Determine that the car runs so you're sure the plugs must be okay.
4) Close bonnet.
I had plugs that colour with a faulty distributor, but the car was noticeably flat and down on power at top end also due to timing fault from the distributor. Never saw a 'rust' colour like that on plugs until I had that fault.
Very different car to yours and carb wise it was on twin dellorto's set up for track use only hence quite rich. After fitting a new distributor the plugs went back to their usual colour. Never quite figured out why the plugs went such an unusual colour in this case but it was all related to the distibutor fault.
Very different car to yours and carb wise it was on twin dellorto's set up for track use only hence quite rich. After fitting a new distributor the plugs went back to their usual colour. Never quite figured out why the plugs went such an unusual colour in this case but it was all related to the distibutor fault.
As a point of interest - the plugs on my stroker 489 Vette are NGK's - plug colour is very similar to photo's shown - however appearances are not always accurate. Mine has a rumpity rumpity 'cam' and to get a reasonable idle quality it needs to run a little rich on the idle screws. Whilst main jets are quite well set up for me it is essential to use an aftermarket high power ignition set-up (MSD) to get it run at its best. Just remember the plugs are the same or a slightly lighter colour than OP's and the 'sooting' around the edges is similar. Irrespectively a set of plugs need changing annually - usually 2 or 3 plugs will eventually go open circuit from carbon build up.
)4rephill said:
The first thing those plugs tell Me is that plugs are so much easier to get at on older cars than they are on modern cars!
On older cars it's:
1) Open bonnet.
2) Pull off plug lead.
3) unscrew plug.
4) Fit new/refit old plug.
5) Refit plug lead.
6) Repeat steps 2~5 as necessary.
7) Close bonnet.
On modern cars it's:
1) Open bonnet.
2) Remove small plastic cover plugs (Try not to drop into the engine bay!).
3) Unscrew plastic cover/covers (Try not to drop screws into engine bay!).
4) Remove plastic cover/covers.
5) Disconnect coil-pack earth lead (Try not to drop screw into engine bay!).
6) Disconnect coil-pack solenoid plug.
7) Remove coil-pack (try not to drop screws into engine bay!).
8) Remove plug.
9) fit new/refit old plug.
10) Refit coil-pack (Try not to drop screws into engine bay!).
11) Reconnect coil-pack solenoid plug.
12) Reconnect coil-pack earth lead (Try not to drop screw into engine bay!).
13) Repeat steps 5~12 as necessary (Remember to have a cup of Tea/coffee half way through whilst swearing about what a faff the whole job is! - Especially if you've dropped screws into the engine bay!).
14) Refit plastic cover/covers.
15) Refit plastic cover plugs.
16) Close bonnet.
Note: If you own a Subaru then the procedure is:
1) Open bonnet.
2) try to see where the spark-plugs are.
3) Determine that the car runs so you're sure the plugs must be okay.
4) Close bonnet.
4rephill, that's all so true, especially as i own all of these. changing plugs on the subaru needs a practiced approach but is very easy once one knows 'how' On older cars it's:
1) Open bonnet.
2) Pull off plug lead.
3) unscrew plug.
4) Fit new/refit old plug.
5) Refit plug lead.
6) Repeat steps 2~5 as necessary.
7) Close bonnet.
On modern cars it's:
1) Open bonnet.
2) Remove small plastic cover plugs (Try not to drop into the engine bay!).
3) Unscrew plastic cover/covers (Try not to drop screws into engine bay!).
4) Remove plastic cover/covers.
5) Disconnect coil-pack earth lead (Try not to drop screw into engine bay!).
6) Disconnect coil-pack solenoid plug.
7) Remove coil-pack (try not to drop screws into engine bay!).
8) Remove plug.
9) fit new/refit old plug.
10) Refit coil-pack (Try not to drop screws into engine bay!).
11) Reconnect coil-pack solenoid plug.
12) Reconnect coil-pack earth lead (Try not to drop screw into engine bay!).
13) Repeat steps 5~12 as necessary (Remember to have a cup of Tea/coffee half way through whilst swearing about what a faff the whole job is! - Especially if you've dropped screws into the engine bay!).
14) Refit plastic cover/covers.
15) Refit plastic cover plugs.
16) Close bonnet.
Note: If you own a Subaru then the procedure is:
1) Open bonnet.
2) try to see where the spark-plugs are.
3) Determine that the car runs so you're sure the plugs must be okay.
4) Close bonnet.
Thank you all - I didnt expect this thread to still be running 
The colour is 'rust' and there's lots on the internet suggesting all different things, however it seems to be running well and I'm not going to start fiddling. I'm happy to think the mixture must be about right and I'll check again if it starts running rough
As per Nigel's advice I'm going to check the timing before fiddling with carbs, although this cant be far out as it starts with no trouble. (And thank you for the offer of cheap plugs - however I think I'm good currently thank you).
I've spent all today out fixing other issues (heater/washer/faulty switches) which have about torn my arms to shreds - so maybe that's my bit for this weekend. What I did find, quite worryingly, was an unlabeled switch behind the dash - it has power to it, but I cant work out what it does and switching it off makes no difference! That's maybe one to leave alone for now and forget I ever found
Phil
The colour is 'rust' and there's lots on the internet suggesting all different things, however it seems to be running well and I'm not going to start fiddling. I'm happy to think the mixture must be about right and I'll check again if it starts running rough
As per Nigel's advice I'm going to check the timing before fiddling with carbs, although this cant be far out as it starts with no trouble. (And thank you for the offer of cheap plugs - however I think I'm good currently thank you).
I've spent all today out fixing other issues (heater/washer/faulty switches) which have about torn my arms to shreds - so maybe that's my bit for this weekend. What I did find, quite worryingly, was an unlabeled switch behind the dash - it has power to it, but I cant work out what it does and switching it off makes no difference! That's maybe one to leave alone for now and forget I ever found
Phil
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