AAArrrrrrrggggggggghhhhhhhh!!!!!!!!

[andynuttz]

Hey guys, i'm so angry i'm actually spitting when i talk :mad: firstly, my 1996 disco seemed a pretty good motor until i installed GAS, i've only had it 2 weeks and it's just been nothing but trouble, firstly, it has a loose connection which causes the gas to completely cut out which means i had to take it back to the place that installed it, not a big issue but i still wasnt pleased that i had to take a day off work to get it fixed, then this morning on my commute to work after 20ks it back fired then as i got to work it back fired again and stalled, the gas won't run now, so i switch it back over to petrol and the revs jump from 500 to 2000 back to 500 rpm every second for about 3 seconds before it stalls, i had it running once but now my car is stuck at my work 30ks away from home and 80ks where the garage installed it absolutely kabut, now i need my car for work as i work in land sales i use it to show people blocks of land in the bush and undeveloped land so basically my car is my office, worse still i was planning taking a trip to glass house mountains on tues for a bit of 4WD couple of days - anyone got any idea how severe the damage is or what the problem is so i can go and speak to the mechanic with a bit of knowledge...

Okay, Rant over, i feel so much better now... (i'm now going to my happy place!)

Andy.

[Debacle]

Where in Brisbane are you ? The best way to find a good lpg mechanic is to talk to a cabbie, they need to run 24/7 so need a good gas man.

[justinc]

Andy,

Have a look around the plenum chamber area and next to the throttle cable bracket for a missing vacuum/ breather hose. These can blow off during a backfire, and you won't get it to idle again with huge vac leaks.

You may have also damaged the airbox, this is a problem as dust can get past the air filter.

Keep looking and get back to us with the results. Can anyone post pics of the hoses I am talking about? specifically the ones to the stepper motor and the breather around the front of the plenum chamber to the flame trap.

Thanks, JC

[p38arover]

I agree with Justin, you probably blown off a hose. It's happened to me a few times.

Ron

[Mark86]

Have a classic injected rangie on gas for a couple years with no probs but usual reasons for backfire are ignition related leads rotor dist cap must be in good order or if motor is getting tired that is only time my backfired then had it rebuilt. Worst case is if the backfire has destroyed your airflow metre and will then run crap on petrol this is why a lot of people do not securely tighten there vacuum hoses to let pressure from backfire out if it happens. Sounds like you have a issue with the installer from the word go. Hope all goes well because these engines run well on gas.

Mark:)

[andynuttz]

cheers guys, i had a look under the bonnet (although not very much mechanical experience) and the air box had been completely blown off, the air filter was resting on the engine, the metal clips had all been broken and the arm to the main engine had come off aswell, managed to do a basic repair job (everything back connected where it should be), do you think if i run it on petrol that should be a short term fix before i get it to the garage on tues as she seems to be running fine... (starts first time and idles where she should do).

Thanks for all your help, it;s so much appreciated... :)

[rangieman]

cheers guys, i had a look under the bonnet (although not very much mechanical experience) and the air box had been completely blown off, the air filter was resting on the engine, the metal clips had all been broken and the arm to the main engine had come off aswell, managed to do a basic repair job (everything back connected where it should be), do you think if i run it on petrol that should be a short term fix before i get it to the garage on tues as she seems to be running fine... (starts first time and idles where she should do).

Thanks for all your help, it;s so much appreciated... :)

if your air box has blown apart use tape to hold it together

it should be fine on petrol consider your self very lucky you didnt damage your air flow metre

[George130]

I managed to bend the diaphram on the ford with a backfire. Ran like crap on Gas. Since a friend had a spare we just swapped out the parts. Good luck.
The ford's air box is held by straps (Similar to those octopus straps but with better clips) THat way a backfire will eith pop the pipe or open the filter box enough to escape before it closes again.

[Mark86]

Sounds like you may have been lucky enough not to have wrecked the airflow metre if it idles and runs normally on petrol can only suggest a short test drive. Safety warning for you when my backfire occured i started it up and idled fine but when i went to take off some how i picked i sticking throttle was quite a surprise when the car kept going but my airflow metre was not damaged.

All the best Mark

[justinc]

Sounds like you may have been lucky enough not to have wrecked the airflow metre if it idles and runs normally on petrol can only suggest a short test drive. Safety warning for you when my backfire occured i started it up and idled fine but when i went to take off some how i picked i sticking throttle was quite a surprise when the car kept going but my airflow metre was not damaged.

All the best Mark
Mark,

Avatar pic looks good, where was it and who went with you?
There is something about dusty loaded up RRC's...

Hijack over.

JC

[Mark86]

Hi JC no its not me i found that pic a couple of years ago do not no location i think it may have been in south africa iam having trouble resizing pics for my avatar got photos 19.5kb limit its the 80x80 pixel limit is the probem...

Mark:D

[PeterM]

Keep it on petrol mate. Sounds like a bad install for backfiring like that. Have you had an LPG vehicle before? Just be sure that you have absolutely no throttle on when changing from one fuel to another and wait a couple of seconds before applying throttle again. Helps to reduce the likelihood of backfire.

[Mudnut]

Hello,
I had a 97 Disco on gas, for 7 years. Had it backfire on one occasion, and blew apart the air cleaner box. I pulled over due to the noise. Repaired it with duct tape, and put in a Ford one. I think it was under 30 dollars. The reason was my spark plug leads were old. After replacing them (by recomendation from my mechanic) it worked fine again.
Good luck,

Ken

[justinc]

Hi JC no its not me i found that pic a couple of years ago do not no location i think it may have been in south africa iam having trouble resizing pics for my avatar got photos 19.5kb limit its the 80x80 pixel limit is the probem...

Mark:D

...bet you wish it WAS you every time you look at it!!!

JC

[GrahamH]

I have a 96 SI 3.9 V8 'Disco which I put on LPG shortly after I got it a year ago which is now running 100% reliably on gas (I know - I'm tempting fate by saying that!).

I had a few backfires initially which blew the top off the air-cleaner box and I've had to reform the clips a few times but it's still OK.

The backfires were due to 2 problems:

1. Old and dirty HT leads. Get new 8mm silicone HT leads and keep them clean. Clean the dizzy cap too. Run the engine at night with the bonnet up and the lights out to see where there is arcing - the cross-firing between leads is the killer. Rearrange the leads to ensure there are absolutely no blue sparks. (Do I need to say, best done with the engine stopped?)

2. Broken rubber elbow on the vacuum advance line from the plenum to the dizzy. This lets extra air into the plenum and the engine runs lean increasing the likelihood of a backfire. If the elbows are perished get a new line ($15 from Black Forest LR in Adelaide in Nov 2005) and make sure its not under tension when you install it.

Check the operation of the Mass Airflow Meter as described in the "Oxygen Sensor" thread. I was surprised to find the 'Disco will run with it disconnected entirely (my '88 Rangie wouldn't!) but it will be far from economical on petrol. You may well have got away without damaging it, but check that the voltage out of it varies with revs to be sure. Also, there is a stainless steel gauze on the front of the MAF which may well have blown out - check that. I'm now an expert in cutting a circle out of fine gauze and forming the big folded aluminium washer which holds it intact under the circlip. You'll get the knack.

Apparently some people cut a hole in the air cleaner cover and put a bath plug into it on a chain - it blows out in the event of a backfire and the clips don't get stretched. I haven't felt the need to do this (yet).

In the Rangie I had a back-fire flapper valve just upstream of the plenum but there's not room for one of those in the 'Disco, worse luck.

IMHO it's difficult for an LPG installer to make the engine backfire - it's more likely due to ignition problems as I've described.

BTW, I've recently fitted an Oxygen sensor into my exhaust at the last Y and put a stepper motor type power valve in the low pressure gas line with a closed loop controller. I've lost a smidge of economy as I had the manual power valve wound as lean as I could (about 190Km on 50Lt now instead of 200Km) but it works a treat. There is almost no difference in performance between LPG and petrol now.

[feraldisco]

'IMHO it's difficult for an LPG installer to make the engine backfire - it's more likely due to ignition problems as I've described.'

Yes...but a good LPG installer should ensure that the ignition system is up to scratch...