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backfiring through the carb
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bopper59



Joined: 07 Mar 2009
Posts: 17

PostPosted: Sat Mar 07, 2009 1:11 pm    Post subject: backfiring through the carb Reply with quote

hi all,
hope you can help,
i have a '61 ford consul mk2 as my project, she hasn't run for a while, tried starting her for the first time this week, there is only the down pipe part of the exhaust at the mo so i new she was going to be noisy, put a drop of fuel directly into the carb and turned her over, after a little struggle she fired and ran til the fuel in the carb burnt, i had some backfiring through the carb, is this because she was burning a very stong mixture? also, how can i check if the fuel pump is operating as no fuel was drawn up from the fuel tank, well the glass chamber didn't fill up when the car turned over,
any advise would be greatly received,
many thanks,
mark
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47Jag



Joined: 26 Jun 2008
Posts: 1470
Location: Bothwell, Scotland

PostPosted: Sat Mar 07, 2009 1:49 pm    Post subject: Reply with quote

Mark,

If the engine hasn't been started for a while the backfiring could be down to a stuck valve. How old is the fuel in the tank? If it's old the chances are that it will be crap. You should really clean the tank out and blow the fuel lines clear. If there was any rust in the tank it might now have gotten into the fuel pump valves. I know you will be desparate to get the engine running ASAP but there are precautions that you should have taken first E.G. Oil down the bores, Checked that all the valves open/close, fresh oil in the sump. Other things that cause backfiring are retarded timing & weak mixture (air leak).

Art
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Rick
Site Admin


Joined: 27 Apr 2005
Posts: 21021
Location: North-west UK

PostPosted: Sat Mar 07, 2009 6:29 pm    Post subject: Reply with quote

47 has covered pretty much what I was going to say - it'd be worth rigging up a temporary feed into the fuel pump, say from a tin or similar, at least to establish that the pump is a pumping, and fuel is getting to the carb ok. Once you've established that, blow the lines through, drain the tank, put a gallon in, and see if it'll pull fuel from the tank.

Stuck valves could cause backfiring, and the timing might also be out.

R
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Rick (OCC Admin)
Various 1920s-1960s - Austin, Morris, Commer, Dodge etc.
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47Jag



Joined: 26 Jun 2008
Posts: 1470
Location: Bothwell, Scotland

PostPosted: Sat Mar 07, 2009 7:11 pm    Post subject: Reply with quote

Mark,

It occured to me after I sent my reply that the fuel line to the tank is probably rusted through and therefore the pump would only suck air. Rick's idea of a separate container to the pump inlet is the way to go initially.

Art
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buzzy bee



Joined: 23 Nov 2007
Posts: 3397
Location: South Cheshire

PostPosted: Sat Mar 07, 2009 7:14 pm    Post subject: Reply with quote

Hi

Go one better and miss the pump out, have a gravity tank, then you can isolate issues to the carb instead of either the pump or the carb/engine.

Good luck, and let us know how you get on!

Cheers

Dave
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bopper59



Joined: 07 Mar 2009
Posts: 17

PostPosted: Sat Mar 07, 2009 11:45 pm    Post subject: backfiring through the carb Reply with quote

hi,
thanks to all for the advise, will try and free up the fuel delivery problem,
when i purchased the car in oct 2008 i was told the car could start on the key but had all the electrics disconected under the bonnet thats why i havn't tried starting her til now, with a new fuse box and allthe wires clean, i thought i would give it a wurl,
thanks again,
mark
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bopper59



Joined: 07 Mar 2009
Posts: 17

PostPosted: Sat Mar 07, 2009 11:57 pm    Post subject: backfiring through the carb Reply with quote

hi again,
as rick & 47 pointed out, the backfiring could be a sticking valve,
whats the best way of checking the valves?
thanks again,
mark
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47Jag



Joined: 26 Jun 2008
Posts: 1470
Location: Bothwell, Scotland

PostPosted: Sun Mar 08, 2009 1:08 am    Post subject: Reply with quote

Mark,

Take off the rocker cover, turn the engine over and see if any of the rockers have excessive play. Normally the valves should snap back closed but when they stick they can be slow to close. If you have a compression guage then do a compression test and it may point you to a specific cylinder.

Art
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bopper59



Joined: 07 Mar 2009
Posts: 17

PostPosted: Sun Mar 08, 2009 3:29 pm    Post subject: backfiring through the carb Reply with quote

hi all,
thanks a 1,000,000 to all those who posted advise, it has given me some positive avenues to go down,
regards mark
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Ray the rocker



Joined: 01 Aug 2008
Posts: 187
Location: south wales

PostPosted: Mon Mar 09, 2009 12:33 pm    Post subject: engine backfire. Reply with quote

Mark,there are many associated problems with engine backfire as 47 and rick have listed--but if you put petrol down the venturi ,for the initial start---chances are you took the air cleaner off to pour fuel down.
the focus of this is it will backfire through the venturi as the constant air /petrol mixture is totally different as the throttle is opened.couple this to no resistance or backpressure with just a downpipe fitted will give you the same symtoms.I would`nt worry about backfire until you correct the fuel starvation and muffle the exhaust.


Cheers----Ray the Rocker...
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bopper59



Joined: 07 Mar 2009
Posts: 17

PostPosted: Mon Mar 09, 2009 2:22 pm    Post subject: backfiring through the carb Reply with quote

thanks ray and again all for your help,
now i have rigged up a temperary fuel tank going straight to the fuel pump and the car started almost straight away. running very sweet with no knocking or nasty noises, so now i know my problems from the tank to the pump,
regards mark
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baconsdozen



Joined: 03 Dec 2007
Posts: 1116
Location: Under the car.

PostPosted: Mon Mar 09, 2009 3:50 pm    Post subject: Reply with quote

A weak mixture without any other faults can cause spitting back through the carb.Seems like the problem will resolve itself when you sort out the fuel line.
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