Bedford CF Ignition system

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Bedford CF Ignition system

Postby Avdr » Fri Oct 19, 2012 6:17 pm

Right, basically to help make ends meet I work two days a week on a small holding. Typical farm setup, maintenance schedule is better than most farms, but renewal is still abit of a dirty word. I do practically all maintenance there, but resist getting too involved with certain things - because I rarely get a free hand to do a propa' job on things.
The directive is always 'we should renew this and this and this and that' - but the top and bottom of it is 'close enough is good enough'...
Guy runs a circa 82 beford CF, 2.0 petrol with electronic ignition.


Lately its been cutting out intermittently, lack of spluttering tended me toward ruling out fueling issues - carburrated. Would usually restart within hours of failure - and run for atleast 2 days, sometimes two weeks or more.
Always seems to cut out at times when I'm not there, or in the evenings etc. It cut out while I was supposed to be away for a few days and the guy took some advice to change the coil.

Upon my return a new coil was fitted. Had no more trouble after that for a while - until yesterday night, boss confirmed it wasn't sparking.

Went this morning with Pico and started to have a look, wouldn't run upon my arrival but soon started with no physical replacement of parts.
Its an electronic ignition system (as standard), on the distributor is what I believe to be a hall effect sensor (3 wire plug), with a reluctor wheel passing through the sensor (sensor itself is a sort of U shape), 4x cut outs in the reluctor wheel at 90 degrees apart.

Small transistor unit doing the actual coil switching, and then rotor arm doing the distributing - all fairly standard.
Got a capture of the ignition secondary and all three wires from hall effect, quickly worked out which was ground and swapped that probe to coil primary.
Capture below taken during cranking with plugs removed:
TRUCK2.psdata
(3.89 MiB) Downloaded 251 times


The hall signal looks strange, I can't understand why there are the slightly raised portions at the ends of the high voltage regions, nothing in the reluctor shape would give rise to this, nor why the switchings do not all appear to be vertical lines (could be due to rotation of plate for advance/retard but that doesn't ring true really). Also can't understand the powerline voltage varying in unison with the signal line. Primary doesn't get pulled to ground either...
Earth to scope had to be provided by a long jump lead due to battery position. Also had the scope setup for positive ignition signal, so had to invert with a maths channel.
This is the only capture I got before putting the plugs back in and it starting up - bloodly laptop battery let me down (usually get 2 hours out of it but only seemed to get 20 mins) typical.

After this capture it ran again for a while before refusing to start having been parked for some 40 minutes. Changed the ignition module for an unknown condition second hand unit, and its running again, but for how long?...



On a separate note, does anybody else have trouble with the forum when typing a post longer than the initial window size? Seems to bounce around with every keypress, really annoying.
Avdr
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Re: Bedford CF Ignition system

Postby Fat Freddy » Sat Oct 27, 2012 10:05 am

I'm not sure of your set up: A - signal (20:1 attenuator selected) B - Primary ( +/- 20v selected) C - Your power supply is being pulled closer to gnd than the primary :?: D - Not sure what was going on there but you could of just used 'Secondary ignition probe (Pos)' No need for Math channel.
Also see alot of noise has been filtered out.

I think you may need to recheck your set up. I like to see current through the primary along with voltage, sample rate at 1MSs.

Regards
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Re: Bedford CF Ignition system

Postby Avdr » Sat Oct 27, 2012 3:51 pm

thanks for the reply. I have written a proper reply twice now and the forum refuses to post it. My patience wont stand a 3rd attempt at the moment. Will try again in a few days.

Andy
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Re: Bedford CF Ignition system

Postby Avdr » Sun Oct 28, 2012 3:27 pm

Right, try again.
Basically the attenuator was a blonde moment, I got the probes mixed up. Had intended to use that channel for coil primary but it ended up being sensor signal. The laptop battery died immediately after that trace, so couldn't get another. Also same script with the secondary. Had to add the maths channel afterward to put the signal right way up.

I noticed the coil primary not being pulled low myself, but the thing was sparking at the time, so just whats going on there I don't know. Its running well still upto now with the replacement ignition module. Which I have since found to be of bosch 0227100124 type.

As usual, once running its issue over and no more has been said about it.

Thanks
Andy
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