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Anon
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mpg halved
Just done a 50 mile trip, and suddenly mpg dropped to below 10mpg. I thought it was not driving well, when re-engaging throttle after let-off, the response was poor. I know im running a bit rich (popping and backfire on overrun), but such a sudden drop is alarming.
I suspect carburettor hasnt been the same since the rebuild, and have speculatively bought 2 more on ebay for a snip, but wont get a chance to tinker till the weekend.
I didnt have much confidence in using the old o ring as it looked like its 38 years of use was over- could anyone tell me what to ask for at a motor factors? Im hoping to get a stock in to help other members too; if I can get em cheap by buying in quantity, it might work out.
Ive programmed the throttle spindle dimensions into a CNC package to knock a load up (my current one was bent and might also be the cause of problems if its sticking- but should I use phosphor bronze or brass for making them?
I know its another project on the go, but I will have time this summer to get them done!
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 Wed 23 May 2012 @ 20:54
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Anon
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Check spark plug condition: if deposits are on the very light side of brown then check for brake drag, soft tyre/s; dark brown to soot around the periphery, check the carburettor O-ring (throttle spindle affects idle mostly).
Watch for fuel being drawn from the side of the venturi where the body halves meet when engine running at 2-3,000 rpm; at this sort of speed there should be enough partial depression around the seal to show up any leakage via the venturi.
(Best done with engine under load but driving with the engine cover off & trying to look down the carburettor isn't recommended. Trust me ... ).
Might be an idea to check float level anyway.
O-ring is softer than normal O-rings suitable for petrol; only ever seen them in NOS kits.
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Wed 23 May 2012 @ 21:54
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Anon
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Hi Mike, Thanks for the sealing job, on our van. Try a bottle of Wynns Dry Fuel in the tank, this cured the same problem for us. Brian and Jan.
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Tue 29 May 2012 @ 15:50
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Anon
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Thanks all; Im going through things step by step, following Phils advice, it appears the O ring has indeed seen better days. NOS kit on order from Dingocroft.. hope it arrives with enough time to get up to Rossendale!
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Tue 29 May 2012 @ 16:28
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Anon
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Addressing up the timing, I need to retard the engine further than the dizzy base plate lets me. The only way I can think of doing this is by removing the distributor and moving the arm further than the Haynes guide suggests. If im right in my thinking, should I move the arm more clockwise or anticlockwise?
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Tue 29 May 2012 @ 18:06
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Anon
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Just for a moment there Mikeboy I thought that you were installing Nitrous Oxide,:o but then realised it was new old stock 
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Tue 29 May 2012 @ 18:34
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Anon
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My brakes would probably draw the line at that!
Anyway, fixed my timing light and finally got Moby mobilised- no idea whay it wasnt playing properly then suddenly all was well! Will still get the carb done but then Ill be happy.
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Tue 29 May 2012 @ 19:43
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Anon
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Mikeyboy wrote:
Addressing up the timing, I need to retard the engine further than the dizzy base plate lets me. The only way I can think of doing this is by removing the distributor and moving the arm further than the Haynes guide suggests. If im right in my thinking, should I move the arm more clockwise or anticlockwise?
To retard tooth by tooth, turn distributor mainshaft (& oil pump drive peg!) clockwise from previously installed position.
If distributor does need installing away from installation mark then re-installing a tooth out may not work for Bosch distributor (limited adjustment on distributor flange slot compared to Delco distributor).
Usual reason for ignition timing being much away from centre of adjustment slot in distributor flange (Bosch or Delco) is the auxiliary pulley being out on cambelt timing, or may be a double marked pulley installed with camshaft round mark rather than auxiliary shaft V mark outwards - similar result even if marks line up for belt timing.
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Tue 29 May 2012 @ 20:11
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Anon
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I had a simular problem with mine but mine needed advancing slightly and as Phil said the only way to do it is to rest yor timing belt. On mine someone had put the pulleys on the wrong shafts, since rectifying its pulling much better now.
Dave
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Wed 30 May 2012 @ 06:59
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Anon
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Thanks all- will see the results on the run to Rossendale!
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Wed 30 May 2012 @ 07:09
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Anon
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Read all this with interest as our mpg has sunk to about 11.5 - so low that it is only matched by my ignorance of Bedfords ! Our petrol 2.3 with weber carb will run smoothly only with the choke cable pulled out a short way. Is that a sign that the dreaded O ring in the carb has gone - and if so, pardon my ignorance but where exactly does it fit ?
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Wed 30 May 2012 @ 17:34
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Anon
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According to Zenith, on original sales bumf, they claim that a carb will last 30-40 thousand miles before 'replacement' and used to offer a trade in. As a result, as mines done 70k, Im not surprised. My refurb kit arrived today so will be documenting it well with photos!
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Wed 30 May 2012 @ 17:38
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Anon
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Good luck ! Our's is a Weber though....
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Wed 30 May 2012 @ 18:08
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Anon
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likaleica wrote:
Good luck ! Our's is a Weber though....
Weber is completely different: no O-ring seal to worry about!
Check valve clearances and ignition system before tinkering with the carburettor.
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Wed 30 May 2012 @ 22:54
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Anon
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Thanks Phil. Ignition system thoroughly checked after chronic starting problems (now sorted) but the engine does sound a bit tappety so will check those !
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Mon 04 Jun 2012 @ 13:23
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