I am a bit embarrased to be asking this.....

[oldrover56]

86 County V8 with the electronic ignition module.
How do I stop ignition hash in the radio???
I thought I knew a bit about suppressing ignition noise, guess not enough.

I have supression capacitors on the coil +, ignition switch, an inline choke on the radio 12v feed, and nice new inductive plug leads.

Antenna ground is clean and ok.

Distributor cap is near new and clean, carbon brush is ok.

I have even looked under the bonnet in the dark for sparks - nothing.

I can't think of anything else to try.

The noise even wipes out the broadcast FM band and the FM cb.

Anyone had this problem and fixed it??

Help, I am sick of hearing my CD's

Thanks,
Terry

[justinc]

86 County V8 with the electronic ignition module.
How do I stop ignition hash in the radio???
I thought I knew a bit about suppressing ignition noise, guess not enough.

I have supression capacitors on the coil +, ignition switch, an inline choke on the radio 12v feed, and nice new inductive plug leads.

Antenna ground is clean and ok.

Distributor cap is near new and clean, carbon brush is ok.

I have even looked under the bonnet in the dark for sparks - nothing.

I can't think of anything else to try.

The noise even wipes out the broadcast FM band and the FM cb.

Anyone had this problem and fixed it??

Help, I am sick of hearing my CD's

Thanks,
Terry

Terry All I can suggest is that the County and Defender ALL have serious earthing issues at one time or another, I would try and fit a decent earth cable from the battery under the seat to a bolt on the seatbox. Also, remove the radio and earth it directly to the bulkhead. Also, the aerial could do with being earthed to the bulkhead, not using the guard.

Hope you find a solution Although with rubbish on the radio here lately I wouldn't mind 'Ultimate Santana' on repeat for a while...

JC

[bee utey]

Inductive leads: there are good ones and baaaad ones. My top gun leads used to give me quite a lot of interference. The bosch ones don't. Look for at least 1000 ohms per foot, better is 1500 ohms.

Antenna shield needs to be earthed at both ends. Make sure the plug and antenna ends of the lead are both firmly earthed. Make sure the antenna is electrically connected to the plug. You may need a better antenna. Keep the antenna cable run away from the wiring loom.

[oldrover56]

Thanks JC, I will have a good look at earthing everything.
I have already grounded the bonnet with copper braid, I will check a few more places.

The indictive leads are Bosch.

I think the noise is being radiated because I can hear it 20m away on a transistor radio in the house.

[bee utey]

Spark plug gap? Try running 0.8mm gap resistor plugs if you aren't already. Also rotor tip-to-contact clearance may be high. I sometimes check this by laying the rotor sideways in the cap lining up the centre of the carbon. 0.5 to 1mm is good.

Measure each plug lead individually, there have been a few crook leads come through from Bosch last year (around 1% of stock) they have unusually low resistance compared to the others. I traced odd running problems in an old Holden V8 to this problem.

Also if your tranny can pick up the noise try waving it near components under the bonnet to locate the strongest source.

[oldrover56]

Thanks bee utey,
A few good clues there, I will check dist cap & leads again.
The electronic module seems to give a very strong spark, so there must be a leakage somewhere.
If I hold the tranny within a metre of the car all stations are wiped out.
Resistive plugs I hadn't thought of, might try that.
Terry

[justinc]

Thanks bee utey,
A few good clues there, I will check dist cap & leads again.
The electronic module seems to give a very strong spark, so there must be a leakage somewhere.
If I hold the tranny within a metre of the car all stations are wiped out.
Resistive plugs I hadn't thought of, might try that.
Terry

Perhaps you ought to leave well enough alone and send the vehicle as a whole to the ADF for electronic warfare weapons developement research?...

Seriously though, if the symptoms are that bad it should be easy to locate...I hope.

JC

[PhilipA]

OK here are a few things to look at.
1 antenna coax must be earthed at both ends and the body earth must not have potential difference to battery, so earths from Guards etc.

2 obviously the antenna input to the stereo must be well earthed and the stereo body must be earthed with no difference to the battery.

4 as stated resistor plugs which have an R in the number . Ditto bonnet.

5 Are you sure that it is ignition and not alternator? Check that the capacitor on the alternator is good.
Regards Philip A

[oldrover56]

Day off tomorrow so I am going to get into it.

Ans. so far: Antenna coax is good both ends earthed well. guard to firewall don't know, will check that.
Radios well earthed. batt well earthed, inline choke fitted in radio feeds.
Noise is Hash, not alternator whine. could be there but I can't hear it over the hash.
Resistor plugs are a possibility, I will get those if I can't find a problem.
Bonnet is grounded to the firewall with braid, I will do the guards if necessary.
Distributor rotor gap - didn't check that, we'll see.
Weapons research? Might do something with weapons if I can't fix it.....

I will let you know how I go.
Thanks,
Terry

[oldrover56]

Had a look at a few things today,

Plug leads - shortest 1.5 kOhm, longest 2.7 kOhm, rest somewhere in between. all connections to them clean and tight. I think no problem there.

Extra 2.5 kOhm across the carbon brush.

There was a lot of white corrosion on the 8 aluminium contacts, cleaned that off. Rotor tip clearance about 1/2 millimeter.

Plugs gap was ~0.8mm, cleaned and reduced to 0.5mm.

Bond guards to firewall was good (0.5 Ohm) linked with braid anyway. Bonnet already done.

Radios earth ok (3 radios, broadcast, uhf cb, vhf cfa set) all to the same firewall point. No voltage difference from there to battery with everything on.

All 3 radios now powered through the inline choke (It's an inline inductor with a cap. to ground)

FM broadcast is now readable, cb,& cfa radios ok, AM band still useless.

I am starting to believe that its the power of the ignition module. It will throw a 25mm spark to the engine if I hold the plug lead (THICK rubber gloves!!!)

I am thinking of moving the antenna down the back.

Cheers,
Terry