Ignition Coil

[B16 RFF]

Just noticed my coil is weeping oil from the HT tower, so I need to replace it before it overheats and fails.
It's manufactured by Ducellier (French ), so I doubt if it's original. Would anybody care to stroll out to their car and tell me the make and model of the coil. It's a '96 500 with a serpentine engine by the way.

Many thanks,

Paul.

>>> Edited by B16 RFF on Sunday 18th April 14:59

[Joolzb]

Hope this is of help

www.tvrcc-south-wales.co.uk/chimaeraparts.asp

it's a chimp list but the part is the same, the Bosch seems to be the chosen one.

edited
Just checked the bible, page 68 has the PRC6574 reference.

>> Edited by Joolzb on Sunday 18th April 16:56

[B16 RFF]

Joolzb said:

Hope this is of help <a href="http://www.tvrcc-south-wales.co.uk/chimaeraparts.asp">www.tvrcc-south-wales.co.uk/chimaeraparts.asp</a> it's a chimp list but the part is the same, the Bosch seems to be the chosen one. edited Just checked the bible, page 68 has the PRC6574 reference. >> Edited by Joolzb on Sunday 18th April 16:56

Thanks.
I have the 1st edition which doesn't mention it.
I see PRC6574 is also listed as the ignition module !!!
I will try out these numbers on my local Bosch agent, although they don't appear to be Bosch-type numbers.
Maybe Lucas??

Paul.

[Joolzb]

That part# should be the Bosch one, the Lucas one is RTC5628, maybe those code numbers are internal to Land Rover? Just guessing.

[Ballistic Banana]

My lucas one has DLB198 on the box?? Landrover on it too.

I believe Bosch are the Better ones for some reason said on a previous post.

BB

[red griff 500]

I just replaced my coil this weekend for the same reason (oil leaking)- I wanted to fit the Bosch part but could not find a stockist (anyone know the whereabouts of said stockist in the Gloucestershire area?), fitted Lucas part instead. It hasn't solved the serious misfiring I'm experiencing at the moment.
Has anyone got any ideas on relatively simple checks to make before I give up and book it in?

Steve

[Apache]

red griff 500 said:

I just replaced my coil this weekend for the same reason (oil leaking)- I wanted to fit the Bosch part but could not find a stockist (anyone know the whereabouts of said stockist in the Gloucestershire area?), fitted Lucas part instead. It hasn't solved the serious misfiring I'm experiencing at the moment. Has anyone got any ideas on relatively simple checks to make before I give up and book it in? Steve

Try running it in the dark to see if there's any arcing from dodgy leads or supressor caps, have a look at the distributor and rotor arm. Any auto electrician will find a problem like this

[red griff 500]

Thanks for the super-quick response Apache. I will do the night time antics as you say, but the leads were renewed about 5 months ago and I did check inside the Dist cap yesterday which was as clean as a whistle. This is all I've checked so far.

Any other suggestions?

Steve

[greenv8s]

Back in the good old days you only needed to know whether it was ballasted or not, but these days there seem to be umpteen different coil specs used by different manufacturers. When I was stranded and fitted the wrong spec to get me home the engine ran but developed a flat spot under acceleration. All the components were fine but it was the wrong coil. Replaced it with the right one when I got home and it has been fine since. (Still keep the wrong coil in the car for emergency use because I'm too mean to throw it away!) If it isn't the coil, the problem could be with the ignition amplifier although I think these tend to cut the engine completely when they fail.

[Ballistic Banana]

red griff 500 said:

Thanks for the super-quick response Apache. I will do the night time antics as you say, but the leads were renewed about 5 months ago and I did check inside the Dist cap yesterday which was as clean as a whistle. This is all I've checked so far. Any other suggestions? Steve

Steve One of my HT leads was trapped under the Alternator and had been like that since i had brought it, even though it wasnt breaking down the sheath had came off in places so worth a check just incase a similiar thing may of happened when they were replaced.

BB

[red griff 500]

Thanks for the reply BB. I'm 99% sure I've now found the problem. Started her up last night, tickover was slightly high (@ 1200rpm) but smooth, although serious misfiring when initially opening throttle, fitted a timing strobe and observed that the vacuum avance/retard mechanism had no effect whatsoever on the timing (the mechanical speed advance/retard worked OK).

However, after about 20-30 minutes of tickover and blipping the throttle with the same result (ie the misfiring) I started to carefully wiggle the low tension wiring, and hey presto the revs dropped to the normal 800/900 rpm and the engine responded to blipping with no misfiring at all - as sweet as a nut. The only reason that i'm not 100% sure I've found the problem is that I could not get the thing to run rough again by further vigorous wiggling and tugging (the wire that is!). I'll re-make the connections and see if she continues to behave herself.

There's still the unexplained behavoiur with the vacuum though (I'll start another thread about this).

One other point, I noticed that if the low tension wire (-ve side of the coil) is resting against one of the HT leads (easily done as it's quite crowded in that area) the tickover is very slightly rougher, although the engine doesn't misfire.

Hopefully the end of my Griff Grief - at least for the moment.....

[greenv8s]

If you still have the 1-way valve in the vac line between the throttle and the dizzy, get rid of it.

[B16 RFF]

These vacuum units often fail; not surprised if it no longer works on a car that old.
I'm a bit dubious about making it work just with lungpower though. As far as I can recall from my Hometune days, you had to suck bloody hard to make this work. Much better to use a hand held vacuum pump. You can get one called a Mityvac from specialist tool outlets. Probably best to just replace the unit if you can. They didn't use to be expensive (£5-£10 in 1990), but now so few production cars use them, they might be relatively expensive. Perhaps try a Land Rover dealer or a Lucas agent if you get the numbers from it?

[red griff 500]

Thanks guys! - Why do you say get rid of the 1 way valve Green V8S?

Also, changing the vac unit means removing the plastic plate under the rotor arm which has "do not remove" moulded into it. Are there any problems to watch out for when disconnecting and re-connecting the vac pull rod which lives under this plate or is there an easier way to do it without removing the plate?

[griffter]

Because they fail!

I think he meant to remove the one way valve which is located partway along the vacuum line, between the vacuum unit (NOT the one way valve) and the plenum. If you've got a single continuous length of vacuum pipe running between the plenum and vacuum unit already, then the one-way valve has already been removed.

>> Edited by griffter on Thursday 22 April 12:53

[tvr4ever]

GreenV8S

Peter you say remove the one way valve all together. But they must have had a reason to fit them, BIG QUESTION MARK. Why are they fitted to begin with, and what are the effects (benefits ?) of removing the valve. I know it's still on mine (4.3 with cat).

Fred

[B16 RFF]

red griff 500 said:

Thanks guys! - Why do you say get rid of the 1 way valve Green V8S? Also, changing the vac unit means removing the plastic plate under the rotor arm which has "do not remove" moulded into it. Are there any problems to watch out for when disconnecting and re-connecting the vac pull rod which lives under this plate or is there an easier way to do it without removing the plate?

You might be lucky and be able to remove it without taking out the baseplate. It's many years since I have changed one. If you remove the fixing screws and wiggle it about (technical term), you may be able to disengage the arm from the connection. Best of luck!!

I think the non-return valve is to keep the emissions down on the overrun. So removing it is no big deal.

Paul.

[GreenV8S]

The 'one way valve' is actually a one-way restrictor. Its purpose is to prevent the vac advance from operating transiently when the throttle is opened from idle. In theory this improves the throttle response as you come off idle. In practice it's all well and good if its in perfect working order but when it blocks up you end up with tha vac advance not coming in at all, or staying on when it shouldn't. As well as getting blocked, they have been known to be taken off for checking and then replaced the wrong way round. In eitehr case the ignition timing is basically screwed. This is a far worse problem than the one the valve is supposed to solve. By removing the valve you introduce a slight flat spot at idle which is barely noticeable, but you also eliminate this potentially very troublesome problem.

In case you're curious why the valve is needed at all, the reason is that the vac advance unit is connected to a throttle edge tapping so at idle it sees normal presure and leaves the ignition retarded, under cruise conditions it sees vacuum and advances the ignition (better economy) and under full power it sees normal pressure again (timing retarded again to avoid detonation). But at idle as you open the throttle the throttle edge tapping produces full depression briefly as the tapping is unmasked, then quickly returns to normal pressure as the throttle opens. Without the valve the vac advance briefly advances the timing when this happens which can upset the throttle response. The one-valve prevents the vac advance from being pulled in until the vacuum has been applied for several seconds so it comes in during cruising but not during throttle transients.

Hope that makes sense to somebody!

[red griff 500]

thanks Paul and Green V8S.

I'm glad you explained this because I was beginning to worry that I couldn't feel any vacuum being pulled at the plenum spigot at tickover, but the vac increased when the throttle is opened - this is opposite to what I was expecting, however you've explained that this is normal.

I noticed last night that the vac take-off spigot is located in line with the throttle which puzzled me because I thought that it should be between the throttle and the inlet valves - oh dear, so much to learn!!!

Now to this damn one way valve, on one end of the moulded body it says "DIST" and the other end it says "CARB" - all very straightforward so far. The Dist side was piped to the dizzy, and the Carb side piped to the plenum-this seems correct.

However, I can blow air through from the carb to the dist side i.e. the valve allows higher pressure on the carb side to flow to the dist side, but it will not allow air to flow from the dist side to the carb side. Thus the vac advance diaphragm cannot see...........

Oh blimey, I think the penny's just dropped whilst writing this.Perhaps the restriction in the valve is set high enough that the rate of flow from the dist to the carb side is very small (you did say that it takes a few minutes for the vac to take effect) that I didn't notice it when I was blowing, thus you get a very slow change in timing when under part load, but the fact that air can easily flow from the plenum to the dist means that the vac immediately disappears when the throttle is closed.

Have I got it yet?

Steve

[tvr4ever]

Thanks Peter for your answer. I'll just remove the valve and see how she runs without it.

Fred