MK9R
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| posted on 19/8/09 at 07:48 AM |
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Problem with LPG on car
The car has ran fine for the past 12 months, but was slowly getting rougher, i.e. lumpy tickover etc, so i changed the plugs (cheap iridium ones, part
number for none LPG focus) and leads and it seemed to be a lot better. A few weeks down the line it started getting rough again, and is now only
running of 3 cyclinders. I changed the plugs again, this time to the the correct ford ones supplied by ford, but the problem still persists. I have
also put the old lead back on the offending cyclinder (cyl 3) but no change. It obviously still runs fine on petrol. The engine management light has
started flashing only when running on gas, but will go out when the car is under load, i.e. accelerating, but as soon as i back off the light comes
back on. I've not had the error code read, but assume its a lambda sensor error dud to the emissions.
Where should i go from here?? Its got be either a weak spark, maybe the coil pack is on the way out, or a gas injector problem.
Not sure if this is related, but i used different gas supplier, a couple of weeks ago, and they subsequently had some problems with @!## in their
tanks, but surely the 2 filters in my car would have filtered out any debris before it hit a single injector??? Could moisture mixed with the gas get
through???
Cheers Austen
RGB car number 9
www.austengreenway.co.uk
www.automatedtechnologygroup.co.uk
www.trackace.co.uk
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britishtrident
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| posted on 19/8/09 at 08:28 AM |
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A lot depends on the type of system fitted to your car and the exact engine type.
Generally LPG needs much narrower plug gaps than petrol and on modern Fords the plug gap setting for petrol is far too wide anyway, for first port
of call is to reset the plug gaps 20% narrower than standard. However if the plug gaps have been too wide the HT voltage looks for another route to
earth it can break down the insulation in the coil pack and the coil pack is history.
On the other hand it could be a problem with the gas injector valve sticking.
But I would also consider the possibility of a valve problem --- with after market LPG conversions some Ford engines suffer from valve seat
resession on LPG the factory fitted LPG Fords had special cylinder heads.
The place to get more info is here http://www.lpgforum.co.uk/
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MK9R
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| posted on 19/8/09 at 08:39 AM |
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quote:
Originally posted by britishtrident
A lot depends on the type of system fitted to your car and the exact engine type.
Generally LPG needs much narrower plug gaps than petrol and on modern Fords the plug gap setting for petrol is far too wide anyway, for first port
of call is to reset the plug gaps 20% narrower than standard. However if the plug gaps have been too wide the HT voltage looks for another route to
earth it can break down the insulation in the coil pack and the coil pack is history.
On the other hand it could be a problem with the gas injector valve sticking.
But I would also consider the possibility of a valve problem --- with after market LPG conversions some Ford engines suffer from valve seat
resession on LPG the factory fitted LPG Fords had special cylinder heads.
The place to get more info is here http://www.lpgforum.co.uk/
Sorry should have said, its a ford factory fit Kotec system, so the head has the specific ford developed harden valve seats and specific intake
manifold for LPG.
The plugs are brand new (fitted yesterday to try and solve problem) and are the specific ones specified by ford for the LPG car, so i know these are
fine.
Have also posted the problem on that forum, but its very quiet.
Ford can read the fault codes if i take it to a LPG specialist garage, and there is one near by, but its 86 quid just to plug it in!!!!! I've
booked it in for next week incase i can't resolve it
Cheers Austen
RGB car number 9
www.austengreenway.co.uk
www.automatedtechnologygroup.co.uk
www.trackace.co.uk
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MK9R
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| posted on 19/8/09 at 08:40 AM |
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I'm leaning towards gas injector valve sticking as it seems ok for the first few minutes when cold, just wondering how i could test this, you
can hear them ticking (this is normal), but they are under the intake manifold so very hard to get to
Cheers Austen
RGB car number 9
www.austengreenway.co.uk
www.automatedtechnologygroup.co.uk
www.trackace.co.uk
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Mr Whippy
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| posted on 19/8/09 at 09:44 AM |
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As above. Sounds like you have some dirt or something like it in a gas injector, especially if only one cylinder is affected
One thing you could do as a test is swap a pair of injectors round, then the misfire should move to the new cylinder.
Incase you don't know how to find a non firing cylinder, you take off a HT lead (or disconnect a coil pack depending on the engine type) one at
a time and the HT lead or coil pack that doesn't make the engine run worse is the cylinder that’s not working.
[Edited on 19/8/09 by Mr Whippy]
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MK9R
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| posted on 19/8/09 at 09:54 AM |
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quote:
Originally posted by Mr Whippy
As above. Sounds like you have some dirt or something like it in a gas injector, especially if only one cylinder is affected
One thing you could do as a test is swap a pair of injectors round, then the misfire should move to the new cylinder.
Incase you don't know how to find a non firing cylinder, you take off a HT lead (or disconnect a coil pack depending on the engine type) one at
a time and the HT lead or coil pack that doesn't make the engine run worse is the cylinder that’s not working.
[Edited on 19/8/09 by Mr Whippy]
Yeah did this, took off each lead while engine was ticking over, and removing lead from cyl 3 causes no change to lumpyness, so its cyl 3. Had thought
of changing injectors over, just ypical that on this install the injectors are on the underside of the intake manifold and a right b$#$#$ to get to,
the entite intake got to come off to get to them. I can get my hand on cyl 4 injector and can feel it ticking, but just can't get my hand to cyl
3!! 
How easy is it to remove the intake on a zetec??
Just started engine cold and its running fine, so its only happening when engine is warm, mmmmm??
[Edited on 19/8/09 by MK9R]
Cheers Austen
RGB car number 9
www.austengreenway.co.uk
www.automatedtechnologygroup.co.uk
www.trackace.co.uk
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britishtrident
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| posted on 19/8/09 at 11:23 AM |
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The Ford factory fit system is very different from after-market systems check on the LPG forum they will be able to point you in the right direction
with what goes wrong or where to get help.
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Mr Whippy
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| posted on 19/8/09 at 11:50 AM |
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this company seems to sell more of the parts separately rather than whole system kits
linky
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hughpinder
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| posted on 19/8/09 at 01:46 PM |
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If the car is running fine on petrol, but not gas you can discount al the common parts - coil pack, plugs, ignition leads, valves......
I would also suspect a sticky/not working gas valve (I've had this once in 180000 miles and it was a loose wire on the valve itself - recrimped
for nowt). I also had a seal plug perish on the gas mixer that had a similar effect, but was fixed for the price of a pint at my local gas place.
If its a ford fit job, does it still use the ford ECU when its on gas?. Mine is an aftermarket one and basically has its own, so in my case it could
be a cabling fault to or from the LPG ecu to any of the various sensors/parts. By the way , aftermarket systems often bypass the lambda sensor error
signal as it is often faulty - don't forget the stoichiometric mix is different for propane and petrol.
Hope this helps
Hugh
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hughpinder
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| posted on 19/8/09 at 01:50 PM |
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Sorry - just read the bit about removing the cable from injector 3. Does the system use the same injector for the gas and the petrol? If so, check for
wiring faults from the LPG ecu to the injector. Some older aftermarket system just inject the gas into the inlet manifold, and direct injection
systems sont use the injectors in this case. This usually results in the ends of the injectors melting off as they are protected by the fuel flow
through them! This happend to a friend of mine and was very expensive to correct.
hugh
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MK9R
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| posted on 19/8/09 at 01:52 PM |
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quote:
Originally posted by hughpinder
If the car is running fine on petrol, but not gas you can discount al the common parts - coil pack, plugs, ignition leads, valves......
I would also suspect a sticky/not working gas valve (I've had this once in 180000 miles and it was a loose wire on the valve itself - recrimped
for nowt). I also had a seal plug perish on the gas mixer that had a similar effect, but was fixed for the price of a pint at my local gas place.
If its a ford fit job, does it still use the ford ECU when its on gas?. Mine is an aftermarket one and basically has its own, so in my case it could
be a cabling fault to or from the LPG ecu to any of the various sensors/parts. By the way , aftermarket systems often bypass the lambda sensor error
signal as it is often faulty - don't forget the stoichiometric mix is different for propane and petrol.
Hope this helps
Hugh
LPG shows up a weak spark though, had this problem on a freelander where it ran fine on petrol but terrible on gas, new lead, dizzy and plugs and it
was perfect
Cheers Austen
RGB car number 9
www.austengreenway.co.uk
www.automatedtechnologygroup.co.uk
www.trackace.co.uk
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MK9R
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| posted on 19/8/09 at 01:55 PM |
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quote:
Originally posted by hughpinder
Sorry - just read the bit about removing the cable from injector 3. Does the system use the same injector for the gas and the petrol? If so, check for
wiring faults from the LPG ecu to the injector. Some older aftermarket system just inject the gas into the inlet manifold, and direct injection
systems sont use the injectors in this case. This usually results in the ends of the injectors melting off as they are protected by the fuel flow
through them! This happend to a friend of mine and was very expensive to correct.
hugh
I was referring to the HT lead, not injector, the injector is a pig to get to! There 2 injectors per cylinder, one for petrol and the other for LPG
Cheers Austen
RGB car number 9
www.austengreenway.co.uk
www.automatedtechnologygroup.co.uk
www.trackace.co.uk
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hughpinder
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| posted on 20/8/09 at 08:12 AM |
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Any progress?
It interesting that it doesn't happen when the engine is cold - not sure that helps much though! Does it imply the injector works ok?
Just a thought - can you check you are getting a signal through the injector wiring for no3 by plugging in an injector from the scrappies - saves
taking out the injector from your car then finding its the wiring not the injector. Make sure its the right type of injector though - there are
different sorts with different impediences and drive arrangements.
I like the tip about reducing the plug gap - just about to service mine so will try it.
Is it possible to use a long extension/angle drive etc on a socket set from below with the car on a ramp to get the injector out? I know its a long
shot and theres usually something in the way to stopyou doing this.
Regards
Hugh
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MK9R
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| posted on 20/8/09 at 08:17 AM |
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quote:
Originally posted by hughpinder
Any progress?
It interesting that it doesn't happen when the engine is cold - not sure that helps much though! Does it imply the injector works ok?
Just a thought - can you check you are getting a signal through the injector wiring for no3 by plugging in an injector from the scrappies - saves
taking out the injector from your car then finding its the wiring not the injector. Make sure its the right type of injector though - there are
different sorts with different impediences and drive arrangements.
I like the tip about reducing the plug gap - just about to service mine so will try it.
Is it possible to use a long extension/angle drive etc on a socket set from below with the car on a ramp to get the injector out? I know its a long
shot and theres usually something in the way to stopyou doing this.
Regards
Hugh
Its got really bad now, purely on 3 cyclinders at all revs, engine light comes on and flashes all the time, but goes off when engine restarted or
switched to petrol. It still runs perfect on petrol. I'm towing the race car today so had to stay on petrol except on flat roads and downhill
(had to keep switching as didn't have enough petrol to get to work this morning). Also it seems to run on 3 from cold now.
I'm racing this weekend so going to hard to find time, but going to try the injector cleaning method using wd40 and carb cleaner being squirted
down LPG pipes just infront of injector. If this doesn't work i'm going to buy a new coil (25 quid on ebay for a new one).
Any idea if you can tell if a plug isn't sparking well compared to the others?? Also wondering if a wire could have snagged and melted, i had
something similiar on an old granny, when the car was cold the strater motor was fine, but once hot the starter would earth out and not turn over. I
eventually found that if i tugged the main live wire from the battery where it disappeared into the scuttle it would start (i only discovered this
after continually trying to start it and smoke poured out of the bonnet and when i looked the wiring was smoldering!)
[Edited on 20/8/09 by MK9R]
Cheers Austen
RGB car number 9
www.austengreenway.co.uk
www.automatedtechnologygroup.co.uk
www.trackace.co.uk
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britishtrident
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| posted on 20/8/09 at 08:28 AM |
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Apart from reducing the gap if it is also a good idea to go one grade or even two grades colder on the spark plugs -- on the Rover I use NGK plugs
intended for the Mazda RX5 NGK BKR7E gapped at 0.025" in place of BKR6E
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