Low mileage/Fuel leakage

I got a Fiat Palio 1.2El, couple of months back(2003 model,70k on odo) . It has an lpg kit in it. I never used lpg. I emptied the tank within the first few days and have been on petrol ever since.
I am just not comfortable with the gas cylinder behind me and getting in a que with autorickshaws at the fuel bunks.

I have done about 2000km on it till date.
Initially I was getting a ~8kmpl in bangalore traffic with AC on 30% of the time(economic driving,no clutch riding,good air pressure all the time and limited reving) I wasn't really bothered, even though I knew that I was getting lower than what I should.
On reving, it gives me just about 7kmpl(all measured from Tank full to tank full)
I have noticed some fuel leakage on getting the tank full. Not just spill, but noticable leakage under the car. At times, I can even smell petrol.
I am not very bothered about the mileage, but I like to keep my car in good condition.
My questions are:
(1)I remember someone mentioning that mileage on petrol goes down once one switches back to petrol. How do I revert that?
(2)What can be other possible reasons apart from fuel leakage?
(3)I'll be taking my car to a garage this weekend. What all should I get checked?

Help would be appreciated 

8kmpl in a petrol palio is low, usually is in the 9-11kmpl range that too with AC.
-get the car on a lift at the service center and have a look at the visible petrol leak.
-the higher octane LPG will cause some expansion of the cylinder head and gasket so the compression in the cylinders will come down. Get this checked(compression at each cylinder).
- replace fuel filter/air filter and also get the injectors cleaned.
- check the brakes for dragging
--and that would be all that would be needed.

First get your fiel lines thoroughly checked for leakage.

 

Your car could be running rich, i.e., a high fuel-air ratio. This could also account for the petrol smell that you  are getting from time to time. One possibility is a clogged air filter. This will definitely bring down the mileage. Injector cleaning and throttle body cleaning would also be a good idea. Get an authorized garage to check the engine tuneup. How is your pickup and is there any knocking/missing? These will give some clues as to what the problem could be.

 

In particular, I  suggest that you ask the garage to reset the ECU (engine control unit) of your car to the original factory settings. During the shift from petrol to LPG, it is quite possible that the ECU was reprgrammed. So when you go back to petrol an ECU reset is probably necessary. Note that it is ECU which controls your fuel-air ratio; get the garage to scan your ECU after resetting it and ensure that it is performing as per the original factory design.

A stage II OBD ECU like on the Palio does not require a ECU remap, as the software is self learning and advances/retards the ignition depending on the fuel/quality of fuel on the run.

There are two issues regarding ECU.

 

1. Did the previous owner remap it when shifiting to LPG? A remap may not be required for this purpose, but could have been done to make the car adapt quickly to LPG rather than going through a learning process. If a remap was done, one again needs to restore the ECU map to the original factory settings.

 

2. Assuming an ECU remap was not done by the previous owner, the ECU can still be reset (by disconnecting the battery terminals for at least 30 mins). What this does is to make the ECU forget all that it learnt about LPG and start fresh with the factory settings (which is for petrol). This is a quicker and more effiicent way to make the car adapt to petrol. Resetting the ECU simply deletes all the data generated when the car was driven around with LPG, which is anyway no longer needed.

I would also like to add some points to you Do check your Engine Gasket for leaks. This will be visible when your lift your hood and you might find that the point where the injector pump will be sorrounded by grease. Then replace the Gasket and you can also change the following things when you give it to service.

1. Replace Oil Filter and Oil if needed. 2. Replace fuel pump and clean the injectors. 3. replace your normal spark plugs to iridium tip( dont worry about the knocking, fiat engines are so advanced to adjust the air fule ratio).

The mail reason to clean injector and replace plugs is because when LPG is used the injectors will not be used and thereby depositing heavy carbon deposits on the walls of the injector which inturns gets spoiles or even the tip gets rusted due to that. Hence do check the same and when you start your car start it with a petrol and change it to LPG after 2-3 min of idiling or driving. And always turn your car to petrol when your are switching off your vehicle. This will increase its performance....The service will not cost you more than 2500. Take it to Bosch service centers they do very good service than the tata's service.

ECU remap is not at all needed as you have used the car for 2000kms with petrol- your engine is set for petrol-period.

Disconnecting both terminals wont reset the ECU without running the car before and after doing so for about 4kms min.

Well, apparently Mitsubishi come out with an LPG version of the Cedia with two ECU's, one for petrol and one for LPG:

 

http://www.hindu.com/mp/2007/09/15/stories/2007091551970300.htm

Quoting from this site:

 

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The LPG version has two ECUs, one for the petrol mode and the other ECU acts as a piggyback for the LPG. The petrol ECU sends information from the oxygen sensor, the manifold-absolute pressure sensor and the engine rpm sensor to the LPG ECU, so an extra set of sensors isn’t required.

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It is not necessary that an ECU designed for petrol will automatically adapt to LPG and then re-adapt to petrol. The performance with LPG may vary from car to car, depending on the design. Here is an interesting thread regarding this issue:

 

http://www.ls1.com.au/forum/showthread.php?t=44273

 

Quoting from one apparently knowledgable poster in this thread:

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The engine starts on petrol and will switch to LPG (if LPG operation is selected) when the coolant temperature reaches 40C (regardless of engine speed). When operating on petrol, we use only 98RON and the engine runs on petrol for at least one day a week.

 

You need to keep the fuel pump and petrol injectors clean, and to do that you need to run petrol (preferrably the good stuff - PULP or 98RON) at least one day per week as recommended by most (if not all) gas fitters. Also, running on petrol will help with lubrication and therefore the longevity of the engine. 98RON definitely makes a difference with the VZ SV6 - smoother idle, more torque down low, and better LPG operation too, remembering that LPG is also a high-octane fuel, and the LPG system calculates injection timing and quantity based on the petrol ECU.

FYI, it may take a couple of tanks of 98RON for the engine to fully adjust itself. It may even take an ECU reset in order for the engine to run optimally, but at the end of the day, you will get better performance on both fuels considering what I have said about the LPG system relying on the state of the petrol ECU.
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Thanks for the info:

A basic question remains!

If one is running both LPG and petrol on a routine basis(as both the articles extort) there will be need of an ECU remap twice a week!!

Friend the current ECU can make changes to ignition maps even with a different density fuel let alone octane/cetane(bio diesel) ratings. IMHO remapping ECU's in our setup is superfluous.

Thanks a lot for all the help so far.
My next door mechanic couldn't find a leak. I'd be taking my car to the service station and getting the leak fixed on monday .
That being said, he did tell me that the silencer cover gasket has broken/needs to be replaced.
Does anybody know what this means? This guy did tell me that this can cause lower mileage.