NGC - symptoms of a bad condensor in elec ignition

[brider]

I have an older Range Rover that is giving me fits with a mis-fire condition, and I am convinced it's associated with the electronic ignition system. I belong to a couple of Range Rover forums, but honestly the wisdom I've witnessed from the members here FAR surpasses the overall level of responses I've gotten from those sites. Yes, there are some true gurus, but their responsiveness is random, limited, and sometimes with serious attitude.

Without going into the long sad story of my problem, I have gone thru ALL of the ignition system, except I haven't replaced the original condenser which is mounted in grounded contact with the fender well (checked continuity with the engine strap...good), and is plugged in to the neg terminal on the coil.

When I was cleaning all grounds and contacts AGAIN last night, it occurred to me how awful the condenser looks, and why is there a condenser on an electronic ignition anyway?

So, assuming it SHOULD be there, what would the symptoms be if it went "bad"?

[Murray]

You might need to be more specific about the make and model of the electronic ignition there are a few variations to the theme. The condenser exists to suppress arcing across the points. In an electronic ignition obviously this is not required, however it may exist to suppress noise and preventing interference with the radio primarily with the am band.

 It is possible it has shorted and is dragging power down to the ignition the obvious is to try disconnecting it and see what happens however without knowing the ignition system there is a risk. The other thing is for the couple of dollars involved change it anyway and see what happens.

if you'd like to be a bit more scientific if you could get hold of a multimeter that has a min function where it will show the lowest reading it see's not a function typically on a wally world one.

Obviously the plugs and leads have been checked/replaced in living memory, AULRO might be worth signing up too as well. Or get the !@#$'s on with it and assuming the car is still ok replaced the motor with a 4BD1-T Isuzu :D .

[brider]

It's a '93 LWB model with the 4.2 engine.

Engine swap has been on my wish list for a while, but honestly the old 4.2 runs so sweet when it IS running sweet that I lose interest in the motor swap.

Interesting about the function of the condenser in an electronic ignition, if it has no bearing on the ignition output to the engine I may explore removing it as the AM reception in my aft......wait a minute.....maybe THAT'S why my AM reception sings with the engine revs???

[Groover]

I believe it was a trick used back in the day to remove the engine/electrical interfering with the radio (a buzz that would rev with the engine speed through the speakers) I don't know how they were configured though, just rings a bell once I just read that in Murray's post.

[StuCorpe]

I believe it has an effect on the spark coil, tuning the primary or some such nonsense.  I have a similar cap on my MG Midget (another Lucas prince of darkness monster) and when it started failing had a very bad misfiring, when it finally died could not get the engine to start.  Replaced and it runs fine.  I don't know anything about electronic ignition but that was my experience.

[Wayne Orwig]

Sort of repeating what Murray covered:

Generally, a condenser is only needed to slow down the field collapse on the coil, to allow the points to open far enough before the voltages gets high, and arcs at the points. Electronic ignition means there are no points to arc, which usually means you do not need a condenser. That means a little more energy gets to the spark plug faster.
But, as mentioned, condensers and other tricks are sometimes used to reduce spark noise in the radio.

I can't think of a condenser fault that would create a misfire. Have you replaced the usual suspects, plugs and wires?

[Kiwi_Roy]

Stu is correct, with early systems the condenser aka capacitor tunes the coil so the Voltage rushes to and fro producing a larger spark or series of sparks in quick succession.
I seem to recall messing with British cars the coil made no spark at all without it. The Lucas magnetos also had a condenser built into the rotor.

It does have the side effect of reducing sparking at the points but that's not the reason for it.

Early electronic ignitions probably still used a condenser, i'm not sure about the later ones I suspect the coils may be designed differently.

[Murray]

I believe it was a trick used back in the day to remove the engine/electrical interfering with the radio (a buzz that would rev with the engine speed through the speakers) I don't know how they were configured though, just rings a bell once I just read that in Murray's post.

Typically configured between power and earth the capacitance stops the DC shorting and shunts the AC noise to earth.

[oldbike54]

 If it is a true electronic ignition and not some points/black box Frankenstein the OP has it nailed down , it is only an RF filter .

 Dusty