chrispy Posted October 7, 2005 Share Posted October 7, 2005 Hi, I understand that one of the possibilities on the rough running / not starting / dodgy idle check lists is the flame traps. I've searched high and low and found very few references. Could someone enlighten me as to what they are, where they are, what they do and how to check if they are doing it in the way they should? Cheers, Chris Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted October 7, 2005 Share Posted October 7, 2005 On the rocker covers you have a breather pipe, it goes into the intake and recirculates any gases that get past the pistons etc. back into the engine to be burnt up in the combustion process. The flame traps are in the breather hose about 6" from where they attatch to the rocker covers on carb vehicles, on EFi vehicles there is only one and it screws into the rocker cover a bit like the oil filler does, and has a hose leading back into the intake. Their function is exactly what it says on the tin You can check them by removing and looking - they contain what looks like a steel brillo pad, if it's gunged up with oil and crud you can remove them and clean them with petrol/thinners/gunk/fairey liquid/the wife's dishwasher* and replace. Edit for photos Carb type: EFi type: They'd have to be really bad to cause poor running, usually the pressure would vent itself elsewhere (the weakest oil seal on the engine will leak, whichever that happens to be). Don't panic if you find white gunk in them - on the oil cap it's a sign of head gasket failure but in the flame traps it just means there's been some condensation mixed in with the oily fumes. * = May lead to death or severe genital pain Quote Link to comment Share on other sites More sharing options...
chrispy Posted October 7, 2005 Author Share Posted October 7, 2005 Excellent, thank you very much, another little job to add to the weekend list... Cheers, Chris Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted October 7, 2005 Share Posted October 7, 2005 Probably worth checking the flame trap is securely in place, though - else it might be the source of an intake vacuum leak? Incidentally, why is there only one flame trap on the EFI? Surely if one bank needs venting the other one does too? Mine has a small filter hidden at the back of the left hand rocker cover which should just vent to air, but actually has a tiny pin hole behind it which is completely blocked (nothing short of drilling the cack out is going to shift it). Is that all the left hand bank gets? Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted October 8, 2005 Share Posted October 8, 2005 Geoff - I don't think they could cause an intake leak as they are vented before the throtte plate. Otherwise as the engine breathed the revs would rise, it'd be like when diesels run away on their own oil Why only one vent? If you look at the engine's construction you'll see the fumes can travel across under the valley gasket and out through the rocker on the other side, it's not a sealed system in there - because it doesn't need to be. I think the one with the pinhole is supposed to let air in, not sure how well it works though. I'm probably going to tap mine for a vent as I don't fancy having any open holes in my engine, however small, should it end up underwater Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted October 8, 2005 Share Posted October 8, 2005 Geoff - I don't think they could cause an intake leak as they are vented before the throtte plate. Otherwise as the engine breathed the revs would rise, it'd be like when diesels run away on their own oil Not on mine - as well as the main pipe that runs back to the intake side of the throttle, there's a smaller spur that leaves it about half way along and goes to the left hand front corner of the plenum. In face, it was a split in that pipe that was causing my vacuum leak problem a few months back... Why it needs both pipes I've no idea... Quote Link to comment Share on other sites More sharing options...
v8bertha Posted October 10, 2005 Share Posted October 10, 2005 Probably worth checking the flame trap is securely in place, though - else it might be the source of an intake vacuum leak?Incidentally, why is there only one flame trap on the EFI? Surely if one bank needs venting the other one does too? Mine has a small filter hidden at the back of the left hand rocker cover which should just vent to air, but actually has a tiny pin hole behind it which is completely blocked (nothing short of drilling the cack out is going to shift it). Is that all the left hand bank gets? Like a complete plank, I thought mine was blocked with crud and so got me a nice punch and a big hammer and drifted the crud out... hmmm, turns out the crud was actually a brass bung... D'Oh. So next plan is to tap the hole (1/8bsp??) and fit a breather pipe up the snorkel. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted October 10, 2005 Share Posted October 10, 2005 Dan - I've just bought a 1/8" BSP tap for that very purpose, if you ask really nicely I might let you borrow it Quote Link to comment Share on other sites More sharing options...
hangover Posted October 24, 2005 Share Posted October 24, 2005 Also check the the fittings on the carbs where the flametrap hose connects to, these are often blocked solid with carp preventing proper circulation of pressurised gases. And while your at it check the oil level in the carby dash pots, mine was running carp on petrol and lpg untill i topped them with oil and now its running better than ever ! Quote Link to comment Share on other sites More sharing options...
chrispy Posted October 26, 2005 Author Share Posted October 26, 2005 Flame trap found and cleaned out, just full of nice black oily crud. I did notice that the pipe connecting it to the throttle body / plenum was a little brittle where it fits onto the flame trap, so a new one has been ordered. Also ordered every other bit of vacuum pipe I can lay my hands on and a new filter and cap for the breather on the right rocker cover. I'm hoping changing them might make a little difference to my cold stalling (well, almost stalling) issue... Cheers, Chris Quote Link to comment Share on other sites More sharing options...
Niall_CSK Posted October 31, 2005 Share Posted October 31, 2005 * = May lead to death or severe genital pain Save yourself the pain, metailsed plastic pan scourers are less than 50p from Morrisons and do the job nicely. The Efi one on the 1-7 rocker cover has a hole in it, nearest I could measure sticking a small drill down it was 1.5mm. Worth checking the other breating points are clear as well. The small spigots on the plenum chamber for advance etc. can get blocked too. There is also a small brass restrictor inside the plastic T piece that sits in the line from the 2-8 rocker cover, as I found when I broke it it was blocked as well. There should also be a flame dispersant gauze in the inlet to the hot wire air flow meter but that is just trivial pursuit stuff as most 3.9's I have seen they are long gone. It is worth checking the gap between the butterfly and the throttle body and then readjusting the idle mixture, I have found this helped a lot on a couple of engines, I think the throttle mechanism wears and it's not something you check regularly. It is a pig to get at the tiny upside down allen screw at the back of the throttle body to adjust it and it is some odd size like 7/32" a/f. Quote Link to comment Share on other sites More sharing options...
chrispy Posted October 31, 2005 Author Share Posted October 31, 2005 Save yourself the pain, metailsed plastic pan scourers are less than 50p from Morrisons and do the job nicely. The Efi one on the 1-7 rocker cover has a hole in it, nearest I could measure sticking a small drill down it was 1.5mm. Worth checking the other breating points are clear as well. The small spigots on the plenum chamber for advance etc. can get blocked too. There is also a small brass restrictor inside the plastic T piece that sits in the line from the 2-8 rocker cover, as I found when I broke it it was blocked as well. Cleaned it out already, will try the pan scourer next time My T-piece broke while replacing tubes, see my other post here. I don't suppose you have a spare or know the part number? Cheers, Chris Quote Link to comment Share on other sites More sharing options...
Niall_CSK Posted November 1, 2005 Share Posted November 1, 2005 Cleaned it out already, will try the pan scourer next time My T-piece broke while replacing tubes, see my other post here. I don't suppose you have a spare or know the part number? Cheers, Chris Yup I saw that after writing, sorry I don't have it to hand, it was only a few quid, I remember Andrew Varrel at Famous Four being quite surprised how cheap they were. I see you broke yours trying to prise the hardened pipes off same as me Quote Link to comment Share on other sites More sharing options...
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