Spark plug fouling

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100SRV

Original Poster:

2,126 posts

241 months

Monday 24th June 2013
quotequote all


Plug fouling

Postby 100SRV » Mon Jun 24, 2013 8:14 am
Hi,
I have an annoying problem on my Bowler where it has fouled some of the spark plugs shortly after starting the engine, on both occasions the vehicle was outside overnight with the weather being dry and cool.

The facts:
1. The fuel injection is 14CUX and ignition by lumention.
2. Usually when starting it runs a bit rich but soon clears to a smooth idle.
3. If I recall the fouled plugs are mixed between banks; not all on one bank.
4. The injectors were ultrasonically cleaned and flow rate checked just over two years ago (about 15,000 miles)

First thing I will check is the fuel and coolant temp sensors in case the coolant temp is misinforming the ECU - but it wasn't cool enough to need the choke to start the old petrol Land Rover!

Do spark plugs become more prone to fouling with age?

100SRV

stevieturbo

17,229 posts

246 months

Monday 24th June 2013
quotequote all
What is the ignition system, and what heat range are the plugs.

And how many of these cold starts are you doing ? And when you say it runs a bit rich....just exactly how rich ?

Steve_D

13,737 posts

257 months

Tuesday 25th June 2013
quotequote all
Do you have Rovergauge?
If not then well worth buying the £35 lead and getting the free software download.
This link will show you what it does. http://www.pistonheads.com/gassing/topic.asp?h=0&a...

You can also see if it is running the correct map (14CUX has 5 maps inside), what temps the ECU is seeing, if the stepper idle valve is working etc etc

Steve

100SRV

Original Poster:

2,126 posts

241 months

Tuesday 25th June 2013
quotequote all
stevieturbo said:
What is the ignition system, and what heat range are the plugs.

And how many of these cold starts are you doing ? And when you say it runs a bit rich....just exactly how rich ?
Hi Stevie,
Ignition system is a lumention triggered coil and distributor (I have considered EDIS)
The spark plugs are correct for 3.9 Rover V8 being BRP6ES
One cold start followed by at least an eight kilometer trip
Rich as in it sounds like the choke is being used and will leave sooty deposits on anything within a metre of the exhaust outlet

100SRV

100SRV

Original Poster:

2,126 posts

241 months

Tuesday 25th June 2013
quotequote all
Steve_D said:
Do you have Rovergauge?
If not then well worth buying the £35 lead and getting the free software download.
This link will show you what it does. http://www.pistonheads.com/gassing/topic.asp?h=0&a...

You can also see if it is running the correct map (14CUX has 5 maps inside), what temps the ECU is seeing, if the stepper idle valve is working etc etc

Steve
Hi Steve_D,
no, I'll have a look at that, thank you.

It is using the non-cat map as no cats are fitted.
100SRV

stevieturbo

17,229 posts

246 months

Tuesday 25th June 2013
quotequote all
100SRV said:
Hi Stevie,
Ignition system is a lumention triggered coil and distributor (I have considered EDIS)
The spark plugs are correct for 3.9 Rover V8 being BRP6ES
One cold start followed by at least an eight kilometer trip
Rich as in it sounds like the choke is being used and will leave sooty deposits on anything within a metre of the exhaust outlet

100SRV
I guess it could be anything from airflow meter, coolant temp sensor, or an actual engine issue. Odd thing is you seem to say it is only some cylinders, not all of them ?

How old is the engine, and any idea on condition of the camshaft ?

If it's chucking soot out, then that is seriously rich. Plugs sound fine though

Do you have a multimeter with pw/dwell/or duty cycle ? To test each injector output to see that they are all the same ?

100SRV

Original Poster:

2,126 posts

241 months

Tuesday 25th June 2013
quotequote all
stevieturbo said:
I guess it could be anything from airflow meter, coolant temp sensor, or an actual engine issue. Odd thing is you seem to say it is only some cylinders, not all of them ?

How old is the engine, and any idea on condition of the camshaft ?

If it's chucking soot out, then that is seriously rich. Plugs sound fine though

Do you have a multimeter with pw/dwell/or duty cycle ? To test each injector output to see that they are all the same ?
I think the airflow meter is OK as it is very responsive (I left the AFM unplugged once and throttle response was decidedly laggy) but I will check by substituting for my spare.

The engine was rebuilt by me last March, it is in excellent condition.

For a while I have had the impression that it ran a bit rich bearing in mind that a non-cat fuel map should run as lean as possible rather than rich enough to keep the CATs happy.

I have a multimeter with that facility but the injectors are batch fired RH / LH bank and were ultrasonically cleaned and flow tested by a reputable supplier before installation in the engine in 2011 when I fitted EFI. He observed that they "were the best-matched set of injectors he had ever tested"...

A few things to check this weekend, thank you for suggestions!

100SRV

stevieturbo

17,229 posts

246 months

Tuesday 25th June 2013
quotequote all
100SRV said:
For a while I have had the impression that it ran a bit rich bearing in mind that a non-cat fuel map should run as lean as possible rather than rich enough to keep the CATs happy.
Certainly not the case. If anything running to keep the cat happy will be leaner than best performance.
A non cat map....not that it would really be that much different would certainly run richer most of the time, simply because it will perform better.
It could be tuned leaner on cruise, but that would be the only time you might want it leaner than stioch.

100SRV

Original Poster:

2,126 posts

241 months

Wednesday 26th June 2013
quotequote all
stevieturbo said:
Certainly not the case. If anything running to keep the cat happy will be leaner than best performance.
A non cat map....not that it would really be that much different would certainly run richer most of the time, simply because it will perform better.
It could be tuned leaner on cruise, but that would be the only time you might want it leaner than stioch.
Thank you, leaner running at cruise is what I am after...

stevieturbo

17,229 posts

246 months

Wednesday 26th June 2013
quotequote all
100SRV said:
Thank you, leaner running at cruise is what I am after...
The issue you're referring to isnt cruise though ?

And leaner than what ? If you're fouling plugs, it's just leaner full stop. Either it's a very bad tune, or there is a fault somewhere.
It would be good to know just exactly how rich it is at present.

Either via wideband or gas analyser.

oakdale

1,786 posts

201 months

Wednesday 26th June 2013
quotequote all

100SRV

Original Poster:

2,126 posts

241 months

Saturday 29th June 2013
quotequote all
Hello again,
I had some time in the garage yesterday, the starting point was that I knew the plugs were fouled so I removed them and cleaned off the soot. Then I removed and checked the fuel and the coolant temp senders - similar values at ambient and again at 100 degrees C. I also cross-checked the resistance by measuring at the ECU connector - no problems there. Also they were correctly connected (possible to connect fuel to coolant temp and vice-versa).

Next step was to start up and drive (less than 300 metres) to see whether the problem recurred - it did, badly so. The car sounded like the RV8 had been replaced by a Subaru 22B engine, great in the right car but not my RV8. Usually if it is starting a little rich it will clear within 500 metres or so.

Back to the garage, spark plugs out - all sooty except number 1 which was wet.

Next step - remove the fuel rail, prime and see whether any were dribbling; number 1 injector had a few dribbles but the rest were fine.

I removed all eight and replaced with a known good spare set also changing the spark plugs for another set which were used but with biscuit coloured running marks.

Plenum etc reassembled and start the engine - first impression was that it ran much better and leaner, down on power perhaps at 3000 rpm upwards but I'd rather that than fouled plugs.

I'll send the injectors off for service and also get hold of that diagnostic tool.

Does it sound like I have found the problem?
100SRV


100SRV

Original Poster:

2,126 posts

241 months

Tuesday 31st May 2016
quotequote all
This problem cropped up again on Saturday after about ten miles use on mixed A and B roads. We were trundling through a village, stopped to let some horses pass (I think I turned the engine off) and the next thing I know it is impersonating a Subaru.

Only fault code present at the time was "48" - idle air valve wide open. The valve is a bit temperamental of late but I don't think that would make one bank foul.

Had a chance to tinker tonight so I removed the spark plugs - 3,5,7 sooty while the rest were dirty but had clean noses and electrodes.

I put a clean set in and the problem instantly recurred. Sadly it was half nine so I've given up for the evening.

First thing I wondered was perhaps a fault with the transistor which drives the LH bank?
Next suspect is the recently "refurbished" air flow meter.
Plenty to get on with tomorrow evening.

SU HIF6's on RV8 manifolds are quite cheap on ebay...

Boosted LS1

21,167 posts

259 months

Wednesday 1st June 2016
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OP, out of interest are the fouled plugs sooty or oily, dry or wet? What were they like after the last swop?

100SRV

Original Poster:

2,126 posts

241 months

Wednesday 1st June 2016
quotequote all
Boosted LS1 said:
OP, out of interest are the fouled plugs sooty or oily, dry or wet? What were they like after the last swop?
Hello Boosted,
most definitely sooty - really fluffy soot.
Cylinders 3,5,7 very sooty and the rest looked OK if a bit sooty.

I'd swapped the fouled plugs for a just-cleaned set and took it for another run - same symptoms so I am fairly confident that the fault is still present which should make it easier to find the cause.

I suspect an ECU fault but I need to check the harness for any chafing too.

Sylvaforever

2,212 posts

97 months

Wednesday 1st June 2016
quotequote all
Hmm.
Had similar on 1.8t q recently amazingly dirty exhaust [water and soot uugh] found two porous vacuum pipes and a gubbed maff-running as it should now.
BUT curious about fuelling in individual cylinders scratchchin

Edit sorry I was wondering about spark plug fouling but instead of pulling them a bottle of Forte petrol additive added to a tank of nitro plus and a good run seems to have helped in that department..

EFA..Fowl is a duck foul is dirty banghead

Edited by Sylvaforever on Wednesday 1st June 15:33

100SRV

Original Poster:

2,126 posts

241 months

Wednesday 1st June 2016
quotequote all
Remember that 14cux uses bank injection, odd/even triggered as a set of four rather than being sequential.

100SRV

Original Poster:

2,126 posts

241 months

Thursday 2nd June 2016
quotequote all
Problem found!

I measured the resistance of the injector banks from the ECU connector, results are:
RH bank 4.2 Ohms
LH bank 6.9 Ohms

Next step was to remove the plenum chamber so I could get at the injectors more easily (especially the LHS).

Connectors removed from LH injectors and resistances measured, results being:
1 = 4.2 Ohms
3 = 4.2 Ohms
5 = 4.2 Ohms
7 = open circuit

Spare set of injectors retrieved from the spares box and awaiting installation.

Steve_D

13,737 posts

257 months

Thursday 2nd June 2016
quotequote all
That still does not answer why the whole bank is fouled in fact the opposite as 7 would just not be opening.

My money is still on a short to earth on the return wires to the ECU from the injectors.

On TVR RV8 installation the coil is mounted on a bracket hanging off the front plenum fixing and hangs down the side of the plenum. I have twice seen injector wiring shorted to the bottom edge of the bracket causing all that bank of injectors to be open all the time.

Steve

100SRV

Original Poster:

2,126 posts

241 months

Thursday 2nd June 2016
quotequote all
Hi Steve,
I am puzzled but the evidence present is:
All spark plugs very sooty
Number 7 open circuit

There *could* be more than one fault - perhaps defective AFM causing rich running. Unfortunately the car is in a garage under a flat and I've not been able to work on it until late in the evening.

The injector harness runs within split conduit, there may be worn insulation I will check this tonight.
This installation is in a Bowler and uses Range Rover style harness, the ignition coil is not mounted on the plenum chamber.

To recap jobs to do:
check injector wires for damage
change injectors
reassemble


Steve_D said:
That still does not answer why the whole bank is fouled in fact the opposite as 7 would just not be opening.

My money is still on a short to earth on the return wires to the ECU from the injectors.

On TVR RV8 installation the coil is mounted on a bracket hanging off the front plenum fixing and hangs down the side of the plenum. I have twice seen injector wiring shorted to the bottom edge of the bracket causing all that bank of injectors to be open all the time.

Steve