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Anon
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Engine stalling at idle...fuel starvation??
Hi there, I recently bought myself a 1981 Bedford CF 2279cc petrol ambulance conversion with the aim of taking her on a mammoth journey from England to Mongolia!
On purchasing the vehicle she ran pretty well and has only done 75000miles so not a knackered machine. After taking lots of advice I have been trying to refit parts of the engine with new parts, including all the basics (spark plugs, hoses etc) and have also replaced contact breaker points in the distributer as well as a new water pump and brake system.
However, on trying to drive her yesterday she starts fine but has a nasty intermittent cough from the engine and will stall when running on idle unless the choke is partially out. When trying to drive her away she gets to the biting point and then loses power in a large coughing sound, so cannot move her anywhere.
PLEASE PLEASE could anyone shed some light on whats going on and point me in the right direction. I suspect fuel starvation of somesort but it must really be to do with the distributer because its the only major component i've been playing with.
Hope this is an easy fix
Cheers
JJ
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 Sun 03 Jul 2011 @ 20:24
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Anon
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When renewing contact breaker points the faces should be cleaned to remove the coating used to preserve them in storage. Can do this dragging a slip of thin card through the contacts when they're closed.
If the contact faces have blackened & started pitting then they may need polishing with a very fine abrasive (e.g. 600 emery), or renewing again.
Distributor cam should be lightly greased to build up a fillet about 2mm thick on the moving contact heel unless the original lubricator foam pad is intact, in which case this should be oiled, not greased.
Also check that the 2 wires to the contact breaker set are correctly installed between the insulator on the fixed contact and the moving contact spring.
EDIT
If you've had the cab engine cover off at some point check that the wire to the carburettor idle solenoid still is connected.
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Sun 03 Jul 2011 @ 20:38
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Anon
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You could try cleaning the filter in the fuel pump as well.
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Sat 05 Nov 2011 @ 10:13
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Anon
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I would definitely double Phil's edit point about the fuel cut-off solenoid. If all else is fine and it runs if you keep the choke out or keep your foot on the gas pedal, and the only problem is stalling at idle, then my first check would be the solenoid. This is on the side of the carb, with a little wire going to it. Easiest check, with the cab cover out, is to turn the ignition to on (not start) and listen for a click coming from the solenoid. If there's no click, or multiple clicks, or a buzzing/gurgling sound coming from it, it's that. I've replaced three of them this year.
Good luck. The trip to Mongolia sounds awesome.
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Sun 06 Nov 2011 @ 00:09
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Anon
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In regards to the solenoid it's also worth taking it out and checking that the little rubber 'o' ring seal is intact as mine had perished so was letting in air.
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Sun 06 Nov 2011 @ 09:43
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Anon
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Oh, also remember to loosen up the allen tightening screw on the side of the solenoid, before trying to remove the solenoid. The solenoid should unscrew easily, unless it was overtightened in the past, in which case you might need a screwdriver or even locking pliers. When fitting it back or replacing it, only tighten by hand. Then do up the allen screw again, and it will stay put.
If you suspect an electrical fault with the solenoid, check the supply wire first with a volt meter. You should be getting +6 or +12 volts with the ignition on (but not start). If there's a mechanical fault (weird sounds or no sounds) the best way to test it is to remove it, pull the jet (end bit that goes inside carb) off, keep the wire connected, touch the body of the solenoid to a good earth nearby (preferably not on the carb itself due to sparking and fuel, but intake manifold should be fine) and turn ignition to on. The little rod inside should move inwards. If it doesn't, or it vibrates, or it moves in and out, then the solenoid is shot.
The o-ring is also very important, so make sure it is in good condition. Usually though, my solenoids burn out faster than the o-rings can disintegrate....!
A quick cure if you're certain that the solenoid is shot, is to chop the rod completely, then replace the jet, and refit. No need for a wire to be connected then, you're just by-passing the solenoid cut-off action. This may cause flooding of the engine with fuel after turning it off, making it hard to start, and dieseling (the engine won't turn off when you switch the ignition off), but at least you'll be on your way. Useful to keep in mind if you're driving to Mongolia.
Having said that, because of various solenoid and wiring problems, I've been running my high-miler with a chopped solenoid for about 6 months now, been too lazy to re-wire and replace, and I have not experienced any side-effects. Obviously though, if you're running short distances a lot, this is not a good idea because fuel finds its way to the sump and if the engine regularly is not given the time to warm up properly, it dilutes the oil. With mine, it would evaporate quite fast as if I'm firing it up, it is going to run for a good few hours before being turned off again. I am planning on fitting a working solenoid again soon though.
So is the trip to Mongolia part of a race or charity, or is it just an individual thing?
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Sun 06 Nov 2011 @ 11:57
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