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| NCIILANE |
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I have heard of this happening but not to me until Saturday morning. I had the car all loaded up for the Aussie day BBQ with the family and when I started it, there was a massive explosion from the engine. My heart sank instantly and I immediately thought the worst, I'd thrown a piston throught the wall or something. When I opened the hood, there was smoke everywhere and the air box lid was open. I then realised what had happened. The LPG had backfired through the induction system and blown the cover off the air box. It actually bent all 4 of the spring clips to the point that they are now out by about 5mm. I managed to bend a couple of them back and then cable tied the back end down until I can replace or bend the worst of the 2 clips. The surprising thing is that it then started fine and has been running great since.
My question is, could there be more damage that I should be looking for? As I said it is running fine. I am going to get the LPG system checked by the installer anyway as I don't ever want to hear that sound again. 
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| TROYMAN |
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it should be ok.
hows your ign leads ect. it was probably a cross spark through the leads in some cases people with lpg. drill a hole in the airbox and fitt a rubber grommet so if it back fires it will blow the grommet out of the airbox instead blowing the lid off.. ive seen this on taxis more than anything.. |
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| Nevermind |
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Ha Ha the same thing happend to my ed a few years ago, only I thought the gearbox had fallen out. It turned out to be the ignition leads, hey at least you didn't blow the a*** out of your airbox.
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| snap0964 |
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Apart from checking the induction piping, also check the PCV valve before starting the engine - if it's blown to bits, those bits can find their way into the timing chain - I've seen some terrible damage of this.
Another Taxi mod is using hockey straps to hold the airbox cover down instead of the metal clips. One other mod you can do (it's been discussed here before, and some variants of the Tickford LPG do use it)is hole saw a hole in the plastic induction piping, and pop rivet a larger rubber disc over the top. The idea here is that the disc seals through normal induction vacuum, but opens during a backfire, relieving pressure through the rest of the system.
_________________ 96 XH Longreach 'S': LPG, Alarm, 3.23:1 LSD, Cruise, Trip Comp, ABS, Power Windows, Mid Series Dome Lt, Climate Ctrl |
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| surtees |
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Another that people do is again drilling some small holes in the flexi house on the intake and put a stubby holder over it, it seals in normal conditions but will open up under back fire. The worse case of back fire I've seen actually slightly bent the bonnet.
_________________ Have you driven a ford lately?
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| NCIILANE |
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Thanks for the tips fella's. A few good idea's there. The hochey straps will be the first to try. Not sure about the look, but practicality always prevails IMO. Now thinking about it, perhaps cable tie-ing the back of the airbox down was not such a smart move, incase it happens again!
 Forgive my ignorance snap0964, but is the PCV valve part of the injection coupling that was added to the end of the induction piping before the TB?
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| NCIILANE |
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{USERNAME} wrote: Another that people do is again drilling some small holes in the flexi house on the intake and put a stubby holder over it, it seals in normal conditions but will open up under back fire. The worse case of back fire I've seen actually slightly bent the bonnet. Nice idea.  I suppose I could always use a ford stubby holder so that it doesn't look too out of place! 
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| snap0964 |
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{USERNAME} wrote: Forgive my ignorance snap0964, but is the PCV valve part of the injection coupling that was added to the end of the induction piping before the TB? Yeah Mick, the PCV sits at the rear of the intake manifold on V8's IIRC. You can check that piping you mention, as it's part of the ventilation system though the rocker covers - the hoses are all slip on from memory, so no jubilee clips, leave them that way.
_________________ 96 XH Longreach 'S': LPG, Alarm, 3.23:1 LSD, Cruise, Trip Comp, ABS, Power Windows, Mid Series Dome Lt, Climate Ctrl |
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| Nigel |
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ockey strap over the box is the go - or just one clip which will let the box open up.
I made a point of changing spark plugs the moment the car backfired - would take care of the problem. Nigel |
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| splatt |
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I have run lpg cars for the last 20years, I found the easiest way to avoid backfire damage is to not use a hose clip on the flexible rubber hose between the air cleaner and the mixer, hoses are usually a tight fit without the clamp, and if they are not, easy to find one at a wrecker that is, After that once a year"bowel check"bang, just push the hose back on.
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| NCIILANE |
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{USERNAME} wrote: I have run lpg cars for the last 20years, I found the easiest way to avoid backfire damage is to not use a hose clip on the flexible rubber hose between the air cleaner and the mixer, hoses are usually a tight fit without the clamp, and if they are not, easy to find one at a wrecker that is, After that once a year"bowel check"bang, just push the hose back on. I like it. Hit the ground running!  Welcome to fordmods! Thanks for the idea. I will have to have a look at the fitting when this friggin rain pisses off. Another thought also occured to me. I have a K&N air filter and off memory I think they are suppose to be red in colour, but when it happened I was in a bit of a rush, but I vaguely remember it looking a bit scorched. Could it have been burnt/damaged. It was only cleaned about 6 weeks ago and I think the cleaning solution might be flamable?
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| XPFalcon170 |
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maybe try the airbox from a lpg ba, as they have actual springs that hold the lid down, and allow for separation when backfire occurs. I think that some tickford lpg setups on au's had special spring clips on them aswell.
_________________ 84 4runner.......needs boost |
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| NCIILANE |
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{USERNAME} wrote: maybe try the airbox from a lpg ba, as they have actual springs that hold the lid down, and allow for separation when backfire occurs. I think that some tickford lpg setups on au's had special spring clips on them aswell. Thanks for the tip, but that sounds a touch pricey. Wouldn't know what the cost of one of those air boxes would be off the top off your head would ya? Are they the same size/easy swap over etc. etc. Sounds like the correct way to go, would just depend on cost/fitment etc. 
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| XPFalcon170 |
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not too sure on the pricing, but the ba box will fit, but then again it may have a diffenent pipe size to the throttle body. I'm not too sure if on the sizes for the v8 intake piping. Probably try the au spring clips. would be the cheaper option i would think.
_________________ 84 4runner.......needs boost |
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| splatt |
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soft rubber hose (off EL etc) $5 tops at pick and payless.
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