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Anon
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Back firing

Hi Guy's
Need a bit of advice
Ok so last sunday, We took our Mk1 '79' 2.3 petrol CF out for a ride.
Started running low on fuel, so pulled into a BP stn and put £50 worth in.
Got about 2 miles down the road and started hesitating.

Then we got on the A40, soon as we went up a incline, She started misfiring, came to a stand still on the incline, everytime I tried to rev, with the clutch in, she backfired. Had to pump throttle to keep her going, with loads of backfires.

Eventually cleared, started off again, then same thing everytime incline.
Got towed home by RAC
:(
Yesterday on my day off, I.......
Fitted new spark plugs. (the old ones looked ok, wernt fouled up or anything)

Cleaned all the contacts on distributor and rotar arm. (its fitted wth a electric borch type, so no points)

Emptyed the inline fuel filter on the pavement....there was no signs of any water, but had a little bit of rusty looking dust in it.

Fitted a new inline fuel filter.

Sprayed loads of carb cleaner, whilst she was running.

And removed the air filter, case it was blocked.

Took her for a ride today, and still the same

:|

If I drive her around London on normal flat main roads, She dont have a problem.

Could it be contaiminated fuel ? (even though it looks clean & drives fine around town)
weak petrol pump ?

She's been running great up till this.........
I've run out of idea's

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Sun 13 Mar 2011 @ 11:28 Edit this messageQuote this messagePMQuote this message
Anon
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Sounds like there's some water in the carburettor float chamber.

Need to remove the top of the carburettor to be sure: water in the fuel shows up as droplets in the bottom of the fuel in the float chamber. Mop out the float chamber with a lint free cloth & leave the top off a while so that the carburettor completely dries out.

Or put some Wynns Dry Fuel in the tank; if water is the problem then it should see off any water still in the tank as well as any in the carburettor.

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Sun 13 Mar 2011 @ 12:02 Edit this messageQuote this messagePMQuote this message
Anon
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Thanks Phil, I'll give that a go

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Sun 13 Mar 2011 @ 12:44 Edit this messageQuote this messagePMQuote this message
Anon
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You could have a problem in the tank with rust flakes blocking the pick up pipe.

Another place to check is the fuel pump as it could be partly blocked.

Have you checked the filter in the carb it self?

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Sun 13 Mar 2011 @ 14:24 Edit this messageQuote this messagePMQuote this message
Anon
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Ok I've put some wynn's dry fuel in, took her for a drive (bout 10 miles)
Still the same

I have took the carb off, taken off the top.....Dont seem any water in there, just a few particals and a tiny bit of dark sludge looking stuff (technical term)

When it started misfiring, it cut out, so I checked the fuel filter before re starting and it was nearly empty. Also when the vans running,loads of air bubbles coming into the filter from the pump,is that normal.

Just pleased its happened local to home and not on a trip.

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Sun 13 Mar 2011 @ 16:24 Edit this messageQuote this messagePMQuote this message
Anon
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Follow up Gethin's suggestion then. When the tank is nearly empty any crud in the tank will tend to collect in the well where the pick-up pipe end sits (same deal with water that's condensed in the tank).

If enough crud finds its way into the fuel line then it can block it; first place to suspect is the pick-up pipe itself (bend above the top of the tank is favourite) & if any of the hose connections between the tank & pump aren't tight then the pump will pull more air through than petrol.

Disconnect the inlet hose from the fuel pump, stuff a piece of clean tube in the hose then, with the filler cap off, see whether you can blow through back to the tank. Once any petrol in the fuel line is blown through it should be easy to blow bubbles in the tank & anyone listening by the filler neck will hear the bubbling.

Check the screen filter in the top of the pump; on the all metal pump the filter is installed with the 4 small pegs facing upwards. On the Weber carburettor there's also a screen filter inside the big nut under the inlet.

Also check that the hose connections are sound - one on top of the tank and one at the pump - and the metal fuel pipe, the latter for wetness indicating pin hole/s in the pipe. If there's been a blockage then air leaking into the fuel line might be the problem leading to the float chamber not running at the right level & producing a very lean mixture when you need a bit more power.

Another possibility is a fault in the distributor: the trigger wires can break between the trigger and plastic socket on the side of the distributor. A way to check for loss of sparks is with a timing light; breaks in the light pulses when the accelerator is depressed (or when the vacuum advance pipe is sucked) usually mean that there's a dodgy connection inside the distributor.

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Sun 13 Mar 2011 @ 17:19 Edit this messageQuote this messagePMQuote this message
Anon
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Thanks Phil and Gethin for your help, much appreciated

I'll give those a try

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Sun 13 Mar 2011 @ 18:31 Edit this messageQuote this messagePMQuote this message
Anon
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To add to Phil's advice, I'd check the condition of the fuel lines before worrying about rust/water in the tank. Do the blowing thing, then ask yourself how long have the rubber pipes been there.. If unsure, and if they look sad, replace all rubber bits (and the hose clamps) of the fuel line. It's 3 or 4 bits, so not too much work. Make sure you get unleaded petrol rated hose.

Good luck.
Mon 14 Mar 2011 @ 15:07 Edit this messageQuote this messagePMQuote this message
Anon
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Cheers Jim...cant do anything now till next sunday (working) but I'll check em out.
Whilst I got the carb off, I'm going to give it a going over and put the air line thru it, make sure nothings blocked.

Need to get her up and running by following weekend, off to Brighton for a nights camping and to see Elbow in concert

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Mon 14 Mar 2011 @ 20:04 Edit this messageQuote this messagePMQuote this message
Anon
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Back fire.

Hi Terry,

Your motor sounds like mine did when I collected it from the sellers house, ran not too badly until I was over the forth road bridge then started to miss fire, and back fire, a distance of about ten miles.
What cured it, setting the valve gaps to the correct settings and setting the timing using a strobe light, once the engine had heated up to temp there was on valve gaps, add to that the ign timing was too far advanced.
I can now push the old Bedford up to 70mph, not even a spit or a misfire, if your fuel is fired by an early spark at the sametime as the valves are not closed, you have backfire or spit back though the carb.

Doug.

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Mon 14 Mar 2011 @ 20:26 Edit this messageQuote this messagePMQuote this message
Anon
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Cheers Mr D, I'll give the other things a go, then if its not sorted, I'll try yours.............Thank you Guy;s for the replies
;]

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Mon 14 Mar 2011 @ 21:06 Edit this messageQuote this messagePMQuote this message
Anon
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Finally got the prob sorted yesterday
After doing most of the things you Guy's suggested......And it still misfiring.
Scratched me head some more.....And still reconed it was fuel starvation.
On our Ambulance there's a fuel cut off under the drivers door, so I cut out the valve cut off and put a bit of pipe in its place........
Took Her for a long ride, and She's running better than ever
Cant believe it turned out to be that, leaste She's back on the road.
Thanks Guy's for your help
;]

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Mon 25 Apr 2011 @ 09:13 Edit this messageQuote this messagePMQuote this message
Anon
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I was wondering what that block was with what looked to be like a rusty pipe sticking out of the side ?? I thought it may be a non-return or something. I may cut mine out, or leave it in place as an anti-theft device !

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Mon 18 Jun 2012 @ 10:15 Edit this messageQuote this messagePMQuote this message
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