2001 Itasca Suncruiser 35U GM Vortec 8.1L LPG Conversion

[Littlebeckets]

Hi Everybody.
I live in the UK and have just converted the 8.1L Vortec engine to LPG. In the UK this effectively halves the running costs due to the difference between the tax on petrol and LPG. After running on LPG the lefthand exhaust pipe is lined with black carbon while the righthand pipe is clean. I am certain that this carbon deposit has only just started with the use of the LPG. (I bought the RV in October and it has not been run much yet)
The engine also doesn,t run quite as smoothly as before the conversion. The guy who did the conversion thought that the spark plugs should be replaced. The engine has only done 14,000 miles and I believe that they should be good for 100,000 miles?? It seems to me that the lefthand cylinders are running too rich. Could this be possible?

I would much appreciate any advice

Thanks

[Littlebeckets]

Hi Everybody.
I live in the UK and have just converted the 8.1L Vortec engine to LPG. In the UK this effectively halves the running costs due to the difference between the tax on petrol and LPG. After running on LPG the lefthand exhaust pipe is lined with black carbon while the righthand pipe is clean. I am certain that this carbon deposit has only just started with the use of the LPG. (I bought the RV in October and it has not been run much yet)
The engine also doesn,t run quite as smoothly as before the conversion. The guy who did the conversion thought that the spark plugs should be replaced. The engine has only done 14,000 miles and I believe that they should be good for 100,000 miles?? It seems to me that the lefthand cylinders are running too rich. Could this be possible?

I would much appreciate any advice

Thanks

[Horsepowerfan]

Hi,

Sounds like a very interesting conversion. Halving your running cost is an outstanding improvement!

While I don't have any experience working on LP fueled engines I'll try to answer your questions as best I know how.

Regarding your plugs, I do believe they are platinum and should last for 100,000 miles. It seems very unlikely to me that they would need replacing at this low mileage (even if they are not platinum tipped).

I would suspect that something done during the conversion has caused your concern. If the engine ran fine on petrol before the conversion then this assumption would seem logical.

To answer your question regarding the left hand cylinders running too rich, YES, this is possible, and here's why. I have run across a situation in which one cylinder bank on a V8 engine runs at a different fuel ratio than the other due to a faulty oxygen sensor. If the left side sensor isn't functioning properly, it could be falsely signaling the ECM to enrich the fuel mixture on the left bank cylinders only. This could cause fouling of the plugs for cylinders 1, 3, 5 and 7, excessive injector on-time, sooty exhaust and a rough running engine.

If possible, monitor the O2 sensors' readings on a scan tool and compare them. If the left sensor reading seems to be more on the low side (100mv to 350mv) this could indicate a problem with the sensor. Also, check to see if any trouble codes have been set in the ECM. You may find left bank O2 sensor codes and/or left bank running too lean/rich codes etc. all of which point to a suspect O2 sensor.

One other thing you could do is possibly switch the sensors from left-to-right and see if the problem moves to the right cylinder bank.

I hope this helps.

[Littlebeckets]

Jim
Many thanks for your thoughts on this. I will investigate and let you know
Much appreciated

[Tom N]

You may have suffered the dreaded burnt plug wire. Check your plug wires.

Tom

["007"]

Good to hear convert is going good for you. The black carbon at tail pipe also appears on the gas only vehicles. Maybe this is something Mike from Brazels could help you with. If you have been following the ECM reprograming posts you will see what I mean. I plan to have ECM reprogramed at irv2 rally in July to improve on the mileage an HP. Mike has been posting on this site send him a PM it would be interesting for all of us maybe we'll convert. "007"

[Littlebeckets]

Tom
Thanks, I'll do that and let you know
John