Do BX diesels backfire? Yes they do!!!

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Mothman

Do BX diesels backfire? Yes they do!!!

Post by Mothman »

Last year, May to be precise, on my way back one evening from putting out a moth trap and generator i had a backfire from my motor. This happened again a couple of times, all when i was motoring downhill and has subsequently stopped and it hasnt reoccured.

I didnt think diesels ever did this but the bang was loud enough to convice me that they do.

Since this happened i have replaced the rad and thermostat and the motor is running well cool.

Anyone else had this? Mine is only a 1.9 L reg motor.

Andy
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electrokid
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Post by electrokid »

I didnt think diesels ever did this but the bang was loud enough to convice me that they do.
I didn't think they could either - could be wrong though - it's happened twice this year already :lol:

If the bores or valve guides get really worn they can run on their own engine oil - called 'runaway' the revs just build and build and switching off the diesel supply doesn't stop it - the only way to stop it is to find a wall or tree and park up against it - engage a gear if you can and let the clutch back slowly to kill the engine. It doesn't usually happen these days because emissions tests fail the vehicle before the engine gets to that state.
putting out a moth trap and generator
I'm currently doing battle with the Mint Loving Pyrauthrus Moth - and fortunately winning - I grow some 6 varieties of mint and I'd rather like to consume most of it myself !
1992 BX19 TGD estate 228K Rusty - SORNed
2002 C5 HDi SX estate
Gibbo2286
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Post by Gibbo2286 »

Backfires on overrun are caused by air getting sucked into a poorly sealed exhaust, usually at the manifold flange, the air mixes with unburned fuel in the silencer, becomes explosive and BOOM. :(
Brian
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Post by Brian »

Gibbo Wrote
Backfires on overrun are caused by air getting sucked into a poorly sealed exhaust, usually at the manifold flange, the air mixes with unburned fuel in the silencer, becomes explosive and BOOM.

Just a little confused here.
Diesel engines: If there is an air leak any where in the inlet tract, this will not increase the explosive mixture as there is virtually no induction vacuum.
On the other hand, a petrol engine with a carburetter or butterfly valve on the overrun, will produce an induction vacuum and this will in fact produce the BOOM effect..
Gibbo2286
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Post by Gibbo2286 »

Well if you read my post I didn't say anything about the inlet tract I said the exhaust manifold/flange. Gibbo.

Incidentally the same fault can cause an MOT failure on cars equipped with a catalyser.
Mothman

Post by Mothman »

I did have a very small hole in the exhaust pipe, just before the back box and this may have caused the problem. Sealed it soon after the backfires and all seems ok.
Motor runs very well now, not using any oil and ive even got the fan working as it should.

Andy
Brian
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Post by Brian »

Hi Gibbo,

Must remember to read the thread thoroughly in future...

"Boom Boom"
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