Ignition Coil 3.9 V8

[BigJon]

We have a Range Rover in the workshop that has been retrofitted with a 3.9 EFI V8 out of a '96 Discovery.

The conversion was carried out elsewhere, we have been called in to try to sort out the mess.

I have thus far replaced the failed air flow meter and the spark plugs (badly fouled).

The ignition was wired through a ballast resistor (now bypassed) and I don't know the history of the ignition coil. I am assuming it is the old ballast type for use with points.

Does anyone know of a part number for a Bosch replacement coil? My local suppliers have no listing for Land Rover.

The problem I am facing is that the engine doesn't want to idle. To get it started the ignition has to be advanced (12 degrees or more) and if I retard it the engine stalls. The engine seems to rev cleanly, just won't idle. I haven't yet had a close look to check if the harmonic balancer has spun, giving incorrect timing marks.

Cheers,

Jon

[Scouse]

Does anyone know of a part number for a Bosch replacement coil? My local suppliers have no listing for Land Rover.

Any 12v coil will do the job. Some have different HT connections but that's about it.

Check the base of the original coil - does it say 9v or 12v ?
9v = ballast resistor type coil
12v = non resistor type

[BigJon]

I thought any 12v coil would do, but I seem to remember from my past (trade school perhaps) that the incorrect coil can lead to early ignition module failure (wrong resistances, etc).

[PhilipA]

Yes it is a very specific Bosch coil which has an unusual resistance etc.
Bosch sold all their stock to an auto electrician in Melbourne I think.
Call Bob Tait on (03) 9541-5559 at Bosch technical assistance and he will give you the info.

Regards Philip A

[BigJon]

Thanks Philip, I tried that number, but too late. Everyone has gone home for the weekend. I will try them again on Monday. In the meantime I fitted a new 12v coil for electronic ignition (Bosch) with no change to how it runs.

[Scouse]

Sorry for the bum steer Jon :( .
That's the first I've heard of the LR coil having a specific resistance value.

Maybe I shouldn't have run one in my Morris Minor for the last 10 years ;) .

[Rovernaut]

I have run a Bosch electronic coil (the square ones) on my 96 EFI Disco for the last 4 years without any drama.

[timberwolf_302]

I recently changed my Bosch GT40R (meant for Ballast resistor) to a GT40 (for use without resistor), also removing ballast resistance wire and replacing it with 4mm wire (ran from the electric fuel pump wire).

Bosch GT40s are around $35-40. Make sure you ask for a GT40, not a GT40R.

It runs very nicely now, starts easier and has a bit more low down torque.

This is on a Rangie with a Pirahna electronic ignition.

[PhilipA]

Now I am not a tech but I know from bitter experience.
A Pirahna or other replacement transistorised ignitions must have a points type coil , as this type of coil is current limiting. They are only switches which take the place of the points
If you use an electronic coil you will blow up the transistors in about 10 seconds. Ask me how I know.
A factory high energy ignition limits the current going to the coil, and the coils are quite different, and each coil is designed to go with a particular ignition. I understand that the current draw cannot be too high for the amplifier.
I was told that you could NOT use a Bosch 727 with the Dizzy amplifier, and most shops eg Graeme Cooper will not do it. But the above is guy who has done it without problems. I run a Bosch 727, but I have a Bosch remote amplifier running through the Unichip. The Unichip will not run with a factory amplifier. ( or that is what I am told!!)

Regards Philip A

[lokka]

We have a Range Rover in the workshop that has been retrofitted with a 3.9 EFI V8 out of a '96 Discovery.

The problem I am facing is that the engine doesn't want to idle. To get it started the ignition has to be advanced (12 degrees or more) and if I retard it the engine stalls. The engine seems to rev cleanly, just won't idle. I haven't yet had a close look to check if the harmonic balancer has spun, giving incorrect timing marks.

Cheers,

Jon

Gday jon

Sounds like your havin fun mate will it idle at the 12 deg or more or dose it die ..
Have you driven it at 12 deg or more to see if it pings or runs fine
Has the engin harness and all the bits been hooked up proper and all vacume lines hooked up ..

Harmonic balancer could have spun on its rubber ring or you may have a vac leak or one of the EFI components is having a rest ..

Cheers

Chris

[Reads90]

Any 12v coil will do the job. Some have different HT connections but that's about it.

Check the base of the original coil - does it say 9v or 12v ?
9v = ballast resistor type coil
12v = non resistor type

Have they got the winter plug thingy disconected. The green plug on the side of the top of the engine. Can't remeber what it is called but tells the ecu what the temp of the engine is and then does the choke accordingly, but if this is not pluged in then it will over fuel and not run on tick over , but will run with a bit of throttle

[BigJon]

Thanks to everyone for their input.

I haven't yet checked to see if the balancer has spun, this Rangie is very much a fill in, in between type of job.

It does idle OK at the 12+ degrees of ignition advance, but only for a short while. Then it surges a little and dies. During the surging it won't react to the throttle (ie, it won't rev up and it will die, nothing can be done to prevent it).

[HangOver]

Bosch GT40s are around $35-40. Make sure you ask for a GT40, not a GT40R

This is on a Rangie with a Pirahna electronic ignition.

Hmmm I have a Rangie I'm running a GT40r with a CraneCams Fireball electronic ignition, I've been running it like that for about a year-ish and it runs very well.

I'm not sure why using a GT40r would be a bad thing, can you explain in simple terms for me?

[Scouse]

Hmmm I have a Rangie I'm running a GT40r with a CraneCams Fireball electronic ignition, I've been running it like that for about a year-ish and it runs very well.

I'm not sure why using a GT40r would be a bad thing, can you explain in simple terms for me?The GT40R is designed to be used with a ballast resistor.
Basically, it's a 9 volt coil & the ballast resistor drops the 12 volts from the battery down to 9 volts for the coil.

The idea of this being is that when the motor is being cranked over with a full 12 volt system, the battery voltage drops & weakens the spark from the ignition coil, making it harder to start at times.
With the 9 volt coil & ballast resistor system, the resistor is bypassed when cranking giving the coil extra voltage so producing a bigger spark which makes starting easier.

If you fit a GT40R to a non-ballast resistor system, the coil will be receiving this extra voltage all the time & while it will work great, it won't last.
Most electronic ignition systems don't use the ballast resistor so you might find you have the wrong coil fitted to your car.

[HangOver]

Tit will work great, it won't last.

So that means my choice is to change to a coil that is designed NOT to work with a ballast resistor OR fit a ballast resistor?

If that's the case it seems the cheaper option would be to fit the resistor.
Is it better to fit a different coil or fit a resistor or does it matter either way??

[PhilipA]

Most older Rangies have a resisitor wire running from the ignition switch to the coil.
If you have two wires to the coil, one comes from the starter solonoid and is 12 volts for starting, and the other should be a white covered stainless steel looking wire with bands every now and then ( it may have resistor wire written on it). This one drops the volts to 7-8 for normal running. AFAIK no rangies have a ballast resistor but they do have the resisitor wire.
Do not cut and shorten this wire (significantly) as the resistance is dependent on its length.
Regards Philip A

[HangOver]

Most older Rangies have a resisitor wire running from the ignition switch to the coil.
If you have two wires to the coil, one comes from the starter solonoid and is 12 volts for starting, and the other should be a white covered stainless steel looking wire with bands every now and then ( it may have resistor wire written on it). This one drops the volts to 7-8 for normal running. AFAIK no rangies have a ballast resistor but they do have the resisitor wire.
Do not cut and shorten this wire (significantly) as the resistance is dependent on its length.
Regards Philip A

Nope no wire on mine, someone probably removed it at sometime.

[HangOver]

OOOps sorry I just realised I think this is what known as a post hijack :blush:

[lokka]

Thanks to everyone for their input.

I haven't yet checked to see if the balancer has spun, this Rangie is very much a fill in, in between type of job.

It does idle OK at the 12+ degrees of ignition advance, but only for a short while. Then it surges a little and dies. During the surging it won't react to the throttle (ie, it won't rev up and it will die, nothing can be done to prevent it).

Gday jon
Sounds like you have sum lucas gremlins in the EFI system if its a hack that someone else has done id leave it well alone as im not a fan of the rangie EFI and if i had to sort it id go back to the start and check every wire and every EFI component as the problem sounds more like a fuel problem than an electrical problem .....


Hmmm I have a Rangie I'm running a GT40r with a CraneCams Fireball electronic ignition, I've been running it like that for about a year-ish and it runs very well.

I'm not sure why using a GT40r would be a bad thing, can you explain in simple terms for me?

Gday steve
Wich crane unit are you runing is it the 700 series or the 3000 series unit as if its the 700 you are supose to run a resistor with the coil or you can damage the ignition module ..
Simple terms are that the gt40r coil or the gt40 are both preaty well a crap coil they are just your avarage coil with a flash sticker ...

So that means my choice is to change to a coil that is designed NOT to work with a ballast resistor OR fit a ballast resistor?

If that's the case it seems the cheaper option would be to fit the resistor.
Is it better to fit a different coil or fit a resistor or does it matter either way??

My rangie is runin a crane 3000 series unit which dosent require a resistor coil and im using a MSD blaster coil which is designed to run at 12v and it gives off a spark that could kill a man as it got me once and it was worse than a 240v shock it made me sick in the gut and i had to sit down for a while to get over it ..
IMHO id eiher stick with wat u have if its a 700 series crane unit and fit a balast resistor or if its a 3000 series id get another coil either a MSD blaster like mine or the big crane jobbie and you will get a even better spark and easier starting and better power/economy

Cheers guys

Chris

[HangOver]

Gday steve
Wich crane unit are you runing is it the 700 series or the 3000 series unit as if its the 700 you are supose to run a resistor with the coil or you can damage the ignition module ..

IMHO id eiher stick with wat u have if its a 700 series crane unit and fit a balast resistor or if its a 3000 series id get another coil either a MSD blaster like mine or the big crane jobbie and you will get a even better spark and easier starting and better power/economy

Cheers guys

Chris


Thanks for that excellent info.
Most people I talk to have never even heard of crane never mind the different models, you work in the motor industry?

Anyhow, I have the Fireball XR700 so it looks like I'll be getting a ballast resistor before I drive it again.

I'm guessing that I fit the resistor on the + side of the coil between the ingnition unit and the coil?

[rovercare]

Thanks to everyone for their input.

I haven't yet checked to see if the balancer has spun, this Rangie is very much a fill in, in between type of job.

It does idle OK at the 12+ degrees of ignition advance, but only for a short while. Then it surges a little and dies. During the surging it won't react to the throttle (ie, it won't rev up and it will die, nothing can be done to prevent it).

Fuel pressure, or lack therof can cause similar symptons, it out there, but always pays to eliminate, have you actually looked at the spark, with block out touching the block, is it strong?? If these come up trumps, its time to look at fault codes etc.

[p38arover]

so it looks like I'll be getting a ballast resistor before I drive it again.

I'm guessing that I fit the resistor on the + side of the coil between the ingnition unit and the coil?

It's not as simple as that.

During cranking, the ballast resistor (or resistive wire) is bypassed so that the coil receives full battery voltage (which could be as low as 9 volts).

After the key is released, the ballast is switched back into circuit to reduce the voltage to 9 volts.

Note that the ballast resistor, in theory, has to be a specific value to suit the coil if it is to drop the battery voltage to the right value for the coil. In practice, it may not be too critical as there are a number of other vasriables, e.g. state of charge of the battery, battery voltage owing to age, alternator charge voltage/current, etc.

Ron (not a mechanic or auto elec)

[HangOver]

It's not as simple as that.


now your just trying to confuse things ! :D

[p38arover]

now your just trying to confuse things ! :D

I do my best.

Ron