New System seems to be using Petrol as well as LPG!!

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norfolkboy · #1 Post by **norfolkboy** » Sun Mar 26, 2006 10:17 pm

Hi, New to the forum and LPG in general. I got my Merc ML500 coverted and picked her up on Friday (star gas system). Since then I seem to have been using LPG and Petrol at the same time! The fuel gauge is going down almost as fast as it used to without LPG and the LPG is also going down. I did a consumption check of the LPG and it is doing about 16 MPG. I spoke to my installer on Sat and he seems to think that the guage could be dropping and should return when I put a little fuel in it (tried it tonight no joy). There are no obvious signs or smells that petrol is escaping. The system switches after about 2 miles to LPG so it should not use £30 of petrol in 300 miles I hope. Any way anyone heard of this or seen anything like it ?? Could one bank be running on gas and the other on Petrol? Other than this the system is really good on LPG.

richy_boy · #2 Post by **richy_boy** » Sun Mar 26, 2006 10:38 pm

There could be a load of issues that cause this, although using £30 of petrol in 300 miles is shocking! It's possible both banks are injecting, although I'd expect your car to run rough as old boosts due to sever overfuelling. Another issue could be that your petrol injectors are leaking, so are constantly seeping petrol into the cylinder. (Again, that's a looooooooot to petrol going missing!) I'm sure your installer can pin-point the problem quick enough. The first step would be to check which injectors are getting pulsed with the engine running I suppose?! I'd of thought a leak that bad would be obvious too, but worth a good checking over too... Good luck! Rich

norfolkboy · #3 Post by **norfolkboy** » Sun Mar 26, 2006 10:57 pm

Thanks Rich will chat with the installer tomorrow about this. The car runs really well on LPG and no rough running at all. I will let you all know the issue and what it was, when we get to the bottom of it. Steve

alexf2828 · #4 Post by **alexf2828** » Mon Mar 27, 2006 9:14 pm

if u can get to the petrol injectors I would suggest waiting while it switches to gas then disconnect each one in turn putting an LED across to see if it lights,if it does you are still injecting petrol while on gas.Another thing is try pulling the fuel pump fuse when on gas and see what happens-also possible u have leaky petrol injectors allowing fuel to be drawn in when there is no signal to them(turned off)

pete_hill · #5 Post by **pete_hill** » Wed Mar 29, 2006 6:16 pm

It may be using petrol above a cetain rpm or at higher load. Ask your installer. If so it will help focus you on keeping off the gas, well keeping on the gas and off the petrol actually. £30 over 300 miles at 90p/L is about (300x4.54/(30/.9) = 40.86mpg. your 16mpg gas consumption is about same as 20mpg on petrol so your average is (20x41)/(20+41) = 13.4mpg petrol, would that be about "normal" expected petrol consumption? This site says it doesn't get anywhere near claimed consumption on petrol, 17mpg "under relatively gentle motorway use". <a href="http://www.verdictoncars.com/jsp/vocmai ... pageid=428" target=_top>http://www.verdictoncars.com/jsp/vocmai ... eid=428</a>

norfolkboy · #6 Post by **norfolkboy** » Wed Mar 29, 2006 6:35 pm

Hi all, I wish i did have a new ML but alas it is a 2002 model with the cheap interior! Well the issue seems to be my car and its fuel gauge. We put another £10 of petrol in and it shot up to 3/4 of a tank from under a 1/4 !!! So it seems like the fuel guage drops on the assumed MPG from the ECU and only re-reads when you fill it up! I am not to sure if anyone else has come across this before. My Installer (professional as ever) is going to sort it out with an isolation box for the sender in the tank. Thanks for everyone who offered advice, and yes the MPG is awful its doing about 13.5 on LPG (last tank) not to sure if that is any good but the performance is spot on, Oh I also have 2 evaporators as well as the engine knocks out about 300BHP.

luke · #7 Post by **luke** » Wed Mar 29, 2006 7:09 pm

Ring me on 01494 449634 or 07831 494606 from chiltern gas cars come across this before on a ML55 GMC same fult Regards Mike Chiltern gas cars

classicswede · #9 Post by **classicswede** » Thu Mar 30, 2006 10:44 pm

Can I just ask do any of you here now how long ago star gas stopped trading? I seem to think it was a VERY long time ago. Btw what year is your Merc? Is it the old mechanical injection? Has a KJ stop been fitted? Mike

norfolkboy · #11 Post by **norfolkboy** » Fri Mar 31, 2006 12:08 pm

I was unaware that Star Gas was not trading!!! I just had the system fitted. The ML500 is 2002 model. I will also look into lowering the cut over point as well, thanks.

daitheboot · #13 Post by **daitheboot** » Sat Apr 01, 2006 1:42 pm

Anyone on the forum know anything about Star Gas systems circa 2000. I have a Jeep 4.0l which runs fine on petrol and when switched over to gas also runs fine for a time and then for no apparent reason switches back to petrol for a second or two before clicking back over to gas. As you can imagine this makes for an uncomfortable ride.The system is a closed loop with single mixer. Any suggestions where to start looking would be welcomed. I suspect the rpm sensor but do not know where it is connected on this system. Thanks for any info. Dave

classicswede · #14 Post by **classicswede** » Sun Apr 02, 2006 9:29 am

Rpm wires are normaly brown.