Engine: 2.1 Carb B21A: - Backfiring Redblock - Help Please - Page 2

morsing · Sep 15th, 2007, 20:36

Quote:

Originally Posted by MissDMeanor

Ok, it feels just like a flatspot on acceleration does. I tend to keep my foot at the top of the gas pedal in Mildred (bless 'er) and it has loss of power for a few seconds then a very loud bang. It's quite exciting really and has created great amusements (I hope) amongst my new neighbours.

Hi Julie

Next time it starts losing power put your foot to the floor. If it's because it's running rich it might burn off the fuel and not back fire? Not really sure but... And don't worry about abusing the engine. It's a Volvo

BTW, if you come to the midlands meet tomorrow we can all have a look/laugh at it

MissDMeanor · Sep 15th, 2007, 20:59

Lol I wish I could - didn't realise there was a meet tomorrow.

She really is running far too rotten to be driven anywhere. On the way over here fully laden including the dogs she was struggling to get up hills. I'm not going to drive her 'til she's sorted now otherwise I fear I'll be forking out for another back box.

Have fun tomorrow though & maybe you could all say a healing prayer for all the sick Volvos

Rich 264 · Sep 15th, 2007, 21:22

I have in the past fitted all brand new ignition components, and a couple of months later the car packed up completely. Turned out after extensive investigation to be a non-functioning rotor arm. Of course this was last thing on my 'check' list because it was so new!
Good luck
Rich

MissDMeanor · Sep 15th, 2007, 22:31

Checking all the serviced parts is something I can do myself tomorrow so thanks for the suggestions guys....failing that, a trip to the local garage again

Checkpoint Charlie · Sep 16th, 2007, 02:58

Hi Julie,
This is a situation where progressive checking is the order of the day. Whip the distributor cap off and have a look inside for any signs of tracking in the cap or along the rotor arm. Secondly as has been suggested take a look at the points to see what they look like. If you have the socket and ratchet that fits the big bolt in the crankshaft pulley it would be worth cranking the engine over to Top Dead Centre and looking at the position of the rotor arm inside the distributor. If you have a maintenance manual for your year you will be able to follow the process fairly easily. What that will tell you is when the spark is to be expected at cylinder No 1 the rotor arm is pointing at plug lead number one.

Now all the simple things are all the HT leads firmly in place I have known people to have one or more leads not firmly clipped in so after a while they waggle about (a technical term you understand :-) when the engine is running and come loose with resultant misfiring. Second point I take it that all the fuses are clean and the fuse holders are pinched together a bit and holding each fuse with the grip of death :-)

Whilst doing that consider replacing all of the continental bullet type fuses as a matter of course every ten years or so since as they run warm they oxidise and cracks form with resultant bad intermittent connections. Buff the sockets of the fuse holders before seating the new fuses with a little OxGard or similar contact grease to protect the contacts from oxidation and moisture.

On the Mercedes List I inhabit when driving my other car it is a matter of faith for all of them to change all fuses every ten years or so. I have seen tiny sparks in the metal link of what looked like a good fuse and it was only because I was troubleshooting in the dark and happened to point the torch away from the fuse box I could see the tiny sparks going across a crack in the fuse material, no BS I actually saw that on a continental type car fuse.

Last silly thought I remember a friend years ago had his ignition plugs, points and timing done at the garage and they forgot to tighten the distributor bolt so it slowly moved round and running got terrible, just check the distributor is not loose enough to rotate by hand.
Regards,
Checkpoint Charlie.

malb · Sep 16th, 2007, 06:29

If you get a flat spot while accelerating, followed by a backfire, I would suggest that you check the earth braid linking the points mounting plate and the base plate underneath.

The points mount plate moves with changes of engine vacuum to change the timing, while the base plate is fixed to the dizzy body with screws. If the braid connecting them is not in good condition, it can cause dead spots (no ignition) as the vacuum chamber moves the timing. As the engine is still turning, it continues to pump fuel air mixture through the engine to the exhaust. This fuel mixture will then explode on reaching sufficient concentration in the presence of hot exhaust components, or on the arrival of a burning exhaust gas pulse once the ignition returns.

Had this problem with my B21A many years ago and had to provise an alternative earth circuit.

Good luck

MissDMeanor · Sep 18th, 2007, 21:06

Thank you very much for your help guys.

I have finally got around to checking her over. Everything seems to be present and correct but found this gaping great hole:

Does anybody know what this is called so that I can try and get a replacement hose please?

I bodged it up with insulation tape and took her for a spin. She's still mucking about but not with the loud backfire like before. I'll let you know what transpires to be the problem.

Mike_Brace · Sep 18th, 2007, 23:01

This is one of the things I like about the early 240s - an easily accessible flame trap. The flame trap is in a plastic holder which is effectively the T piece you can see. The pipe can be bests described as the pipe connecting the flame trap to the cam cover. I would suggest replacing this pipe as well as the flame trap and holder - they are not expensive. If you have any problems getting hold of them let me know - they should be easily obtainable - the tape repair is a temporary repair that I have seen last for a long time.

Mike

MissDMeanor · Sep 18th, 2007, 23:06

Quote:

Originally Posted by Mike_Brace

This is one of the things I like about the early 240s - an easily accessible flame trap. The flame trap is in a plastic holder which is effectively the T piece you can see. The pipe can be bests described as the pipe connecting the flame trap to the cam cover. I would suggest replacing this pipe as well as the flame trap and holder - they are not expensive. If you have any problems getting hold of them let me know - they should be easily obtainable - the tape repair is a temporary repair that I have seen last for a long time.

Mike

Thanks Mike - I was just PM-ing you to ask you about the pipe. I'll try 'n order them soon, the pipe had already been repaired with tape previously - best to be safe than sorry.

CTCNetwork · Sep 18th, 2007, 23:29

Hi,

I was thinking "Crank case ventilation system", "Breather system" and "flame trap" and then read Mikes answer.!!!
Getting slow, I am...

Given that the pipe has lasted so long, it may be worth asking a dealer if they can get the part still..
May be worth a try...

Not sure if you can get a silicon replacement for it - as that would likely give longer service...

Des. . .

Sep 15th, 2007, 20:59	#12
MissDMeanor Corruption rules Last Online: Dec 23rd, 2011 08:05 Join Date: Nov 2004 Location: Select from list View Photos By: MissDMeanor	Lol I wish I could - didn't realise there was a meet tomorrow. She really is running far too rotten to be driven anywhere. On the way over here fully laden including the dogs she was struggling to get up hills. I'm not going to drive her 'til she's sorted now otherwise I fear I'll be forking out for another back box. Have fun tomorrow though & maybe you could all say a healing prayer for all the sick Volvos __________________ The Mouthy Blonde is back on the road....& still dangerous Corruption rules.

Sep 15th, 2007, 22:31	#14
MissDMeanor Corruption rules Last Online: Dec 23rd, 2011 08:05 Join Date: Nov 2004 Location: Select from list View Photos By: MissDMeanor	Checking all the serviced parts is something I can do myself tomorrow so thanks for the suggestions guys....failing that, a trip to the local garage again __________________ The Mouthy Blonde is back on the road....& still dangerous Corruption rules.

Sep 16th, 2007, 06:29	#16
malb Member Last Online: Dec 29th, 2013 11:04 Join Date: Apr 2007 Location: Melbourne	If you get a flat spot while accelerating, followed by a backfire, I would suggest that you check the earth braid linking the points mounting plate and the base plate underneath. The points mount plate moves with changes of engine vacuum to change the timing, while the base plate is fixed to the dizzy body with screws. If the braid connecting them is not in good condition, it can cause dead spots (no ignition) as the vacuum chamber moves the timing. As the engine is still turning, it continues to pump fuel air mixture through the engine to the exhaust. This fuel mixture will then explode on reaching sufficient concentration in the presence of hot exhaust components, or on the arrival of a burning exhaust gas pulse once the ignition returns. Had this problem with my B21A many years ago and had to provise an alternative earth circuit. Good luck __________________ Drive it till it drops... Then kick it back to life!!!

Sep 18th, 2007, 21:06	#17
MissDMeanor Corruption rules Last Online: Dec 23rd, 2011 08:05 Join Date: Nov 2004 Location: Select from list View Photos By: MissDMeanor	Update Thank you very much for your help guys. I have finally got around to checking her over. Everything seems to be present and correct but found this gaping great hole: Does anybody know what this is called so that I can try and get a replacement hose please? I bodged it up with insulation tape and took her for a spin. She's still mucking about but not with the loud backfire like before. I'll let you know what transpires to be the problem. __________________ The Mouthy Blonde is back on the road....& still dangerous Corruption rules.

Sep 18th, 2007, 23:01	#18
Mike_Brace Former contributor Last Online: Jul 2nd, 2022 07:54 Join Date: Dec 2004 Location: Rhosgoch, Anglesey	This is one of the things I like about the early 240s - an easily accessible flame trap. The flame trap is in a plastic holder which is effectively the T piece you can see. The pipe can be bests described as the pipe connecting the flame trap to the cam cover. I would suggest replacing this pipe as well as the flame trap and holder - they are not expensive. If you have any problems getting hold of them let me know - they should be easily obtainable - the tape repair is a temporary repair that I have seen last for a long time. Mike __________________ A Volvo is for life not just for Christmas!

Sep 15th, 2007, 21:22	#13
Rich 264 Pinball Wizard Last Online: Feb 6th, 2013 00:53 Join Date: Dec 2002 Location: cheshire	I have in the past fitted all brand new ignition components, and a couple of months later the car packed up completely. Turned out after extensive investigation to be a non-functioning rotor arm. Of course this was last thing on my 'check' list because it was so new! Good luck Rich

Sep 16th, 2007, 02:58	#15
Checkpoint Charlie Junior Member Last Online: Aug 15th, 2010 07:17 Join Date: Jan 2007 Location: Auckland	Hi Julie, This is a situation where progressive checking is the order of the day. Whip the distributor cap off and have a look inside for any signs of tracking in the cap or along the rotor arm. Secondly as has been suggested take a look at the points to see what they look like. If you have the socket and ratchet that fits the big bolt in the crankshaft pulley it would be worth cranking the engine over to Top Dead Centre and looking at the position of the rotor arm inside the distributor. If you have a maintenance manual for your year you will be able to follow the process fairly easily. What that will tell you is when the spark is to be expected at cylinder No 1 the rotor arm is pointing at plug lead number one. Now all the simple things are all the HT leads firmly in place I have known people to have one or more leads not firmly clipped in so after a while they waggle about (a technical term you understand :-) when the engine is running and come loose with resultant misfiring. Second point I take it that all the fuses are clean and the fuse holders are pinched together a bit and holding each fuse with the grip of death :-) Whilst doing that consider replacing all of the continental bullet type fuses as a matter of course every ten years or so since as they run warm they oxidise and cracks form with resultant bad intermittent connections. Buff the sockets of the fuse holders before seating the new fuses with a little OxGard or similar contact grease to protect the contacts from oxidation and moisture. On the Mercedes List I inhabit when driving my other car it is a matter of faith for all of them to change all fuses every ten years or so. I have seen tiny sparks in the metal link of what looked like a good fuse and it was only because I was troubleshooting in the dark and happened to point the torch away from the fuse box I could see the tiny sparks going across a crack in the fuse material, no BS I actually saw that on a continental type car fuse. Last silly thought I remember a friend years ago had his ignition plugs, points and timing done at the garage and they forgot to tighten the distributor bolt so it slowly moved round and running got terrible, just check the distributor is not loose enough to rotate by hand. Regards, Checkpoint Charlie.

Sep 18th, 2007, 23:29	#20
CTCNetwork Forum Support Team Join Date: Dec 2004 Location: Liège, Belgium View Photos By: CTCNetwork	Hi, I was thinking "Crank case ventilation system", "Breather system" and "flame trap" and then read Mikes answer.!!! Getting slow, I am... Given that the pipe has lasted so long, it may be worth asking a dealer if they can get the part still.. May be worth a try... Not sure if you can get a silicon replacement for it - as that would likely give longer service... Des. . . __________________ Density:- Not just a measurement ~ It's a whole way of Life.! ! ! I drive a Volvo, Please Don't Get In My Way! OldVolvos4Ever He shows up. People die. He vanishes. People should not be afraid of their governments. "He'll deliver more justice in a weekend than 10 years of your Governments should be afraid of their people... "V" courts & tribunals. Just stay out of his way." "I plan to."

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