Happiest customer of the month so far MG V6
Posted: Sun Jul 19, 2015 10:58 pm
Had a customer with an MG V6 come from Skegness here twice recently, long standing issue being his car always ran poorly on LPG whenever he put his foot down but fine otherwise. I don't know who fitted the system but someone he respects as a good mechanic and installer - and it wasn't fitted bad in my opinion either.
System was fitted 5 years ago and this problem had existed since fitted. He had taken the car back to the original installer many times, then visited a few other installers, then visited the importer / supplier of the system (a long way away), but the problem remained. I am being vague on purpose because the importer / supplier is well known. respected, I consider a friend, this car was a bit of a curve-ball.
Problem was a misfire on cyl 6 when under load. The importer / supplier had changed one of the injector rails on the front bank of cylinders (rail of 3) when he visited but with no effect. Maybe no surprises there, because cyl 6 is on the rear bank of cylinders, nearest passenger side, rather than on the front bank of cylinders. The customer explained the front bank rail was changed because the importer / supplier believed cyl 6 was on the front bank of cylinders. I guess they assumed this because injector coil F is on the front bank of cylinders - However, on this engine injector coils A through F do not correspond to cylinder numbers 1 through 6....That's the curve ball but not really too difficult to suss. They may have replaced a good rail (seems likely), or there may have been another problem when he visited them.
I tried software approaches first - adjusting fueling etc, to no avail. Tried swapping injector rails front to back, to no avail. Tried adjusting petrol addition, no avail (thinking along the same lines as the importer / supplier.. they had already set some petrol addition). With any configuration I could overcome the problem by switching cyl 6 to run on petrol...
On this first visit, I told the customer that there were only 3 possible issues behind the problem - Dodgy ignition due to plug or coil pack / Poor compression / A crimped injector pipe. I told him the problem was likely ignition, that since he was confident plugs were fine it could well be the coil pack, would be easier to rule out ignition and compression than crimped pipes on this install. We could easily confirm or disprove by swapping coil packs / plugs / etc, and failing that we could remove the manifold to check for a crimped pipe, but customer was short of time and he was already fairly happy with results - he had seen how it could be set to give good (though compromise) results by setting the system to switch back fully to petrol at high loads. He went away happy to try swapping coil packs with the switch back to petrol disabled, only a bit of petrol addition enabled (to allow him to see any changed from swapping coil pack etc).
Few days later he phoned to say he had changed the coil pack for (what he now knew to be) cylinder 6 and problem remained. He came back and I said 'Let's get the manifold off to sort the crimped pipe'. He asked 'How confident are you that the problem is a crimped pipe' and I said 'Extremely'. He said 'I have confidence in you, you've already shown me you known what you're doing'. We removed the manifold and found the pipe from inj6 to cyl 6 was indeed crimped where pipe went around the petrol rail, I replaced the pipe with a re-routed pipe and we refitted the manifold. Following that the car immediately ran very well on LPG including at high loads but a bit of tweaking to the map was necessary - and the the petrol addition could be completely disabled.
Customer, who was formerly a career army mechanic, couldn't be happier. Insisted on shaking my hand many times and told me he would recommend me to anyone.
Simon
System was fitted 5 years ago and this problem had existed since fitted. He had taken the car back to the original installer many times, then visited a few other installers, then visited the importer / supplier of the system (a long way away), but the problem remained. I am being vague on purpose because the importer / supplier is well known. respected, I consider a friend, this car was a bit of a curve-ball.
Problem was a misfire on cyl 6 when under load. The importer / supplier had changed one of the injector rails on the front bank of cylinders (rail of 3) when he visited but with no effect. Maybe no surprises there, because cyl 6 is on the rear bank of cylinders, nearest passenger side, rather than on the front bank of cylinders. The customer explained the front bank rail was changed because the importer / supplier believed cyl 6 was on the front bank of cylinders. I guess they assumed this because injector coil F is on the front bank of cylinders - However, on this engine injector coils A through F do not correspond to cylinder numbers 1 through 6....That's the curve ball but not really too difficult to suss. They may have replaced a good rail (seems likely), or there may have been another problem when he visited them.
I tried software approaches first - adjusting fueling etc, to no avail. Tried swapping injector rails front to back, to no avail. Tried adjusting petrol addition, no avail (thinking along the same lines as the importer / supplier.. they had already set some petrol addition). With any configuration I could overcome the problem by switching cyl 6 to run on petrol...
On this first visit, I told the customer that there were only 3 possible issues behind the problem - Dodgy ignition due to plug or coil pack / Poor compression / A crimped injector pipe. I told him the problem was likely ignition, that since he was confident plugs were fine it could well be the coil pack, would be easier to rule out ignition and compression than crimped pipes on this install. We could easily confirm or disprove by swapping coil packs / plugs / etc, and failing that we could remove the manifold to check for a crimped pipe, but customer was short of time and he was already fairly happy with results - he had seen how it could be set to give good (though compromise) results by setting the system to switch back fully to petrol at high loads. He went away happy to try swapping coil packs with the switch back to petrol disabled, only a bit of petrol addition enabled (to allow him to see any changed from swapping coil pack etc).
Few days later he phoned to say he had changed the coil pack for (what he now knew to be) cylinder 6 and problem remained. He came back and I said 'Let's get the manifold off to sort the crimped pipe'. He asked 'How confident are you that the problem is a crimped pipe' and I said 'Extremely'. He said 'I have confidence in you, you've already shown me you known what you're doing'. We removed the manifold and found the pipe from inj6 to cyl 6 was indeed crimped where pipe went around the petrol rail, I replaced the pipe with a re-routed pipe and we refitted the manifold. Following that the car immediately ran very well on LPG including at high loads but a bit of tweaking to the map was necessary - and the the petrol addition could be completely disabled.
Customer, who was formerly a career army mechanic, couldn't be happier. Insisted on shaking my hand many times and told me he would recommend me to anyone.
Simon
