Land Rover Repair: A knock on the coil runs it, land rover discovery, john mcinnis

Question
Dear John,

The below describes my situation 95%, except that I had discovered the remaining 5% by that if I knock on the coil by a tiny hammer, the car starts every time!
And when I had to replace my old battery last week with a 110 power instead of the 85 that was on it, the problem has lessened.
I do live in Jeddah, Saudi Arabia, and it never goes below 14 celcius around here...  My question to you after you read the below is;  Do I replce the coil and will it happen again as this is my 2nd coil?

"Expert:John McInnis
Date:12/5/2004
Subject:Intermittent Starting Trouble

Question
Dear John

I hope you are well.

I have a 1998 Land Rover Discovery V8. I purchased the vehicle around 6 months ago. The vehicle had been serviced on a regular basis by the previous owner. In the 6 months I have had this vehicle I have never had an issue with the starting the vehicle.

Around a week ago I had trouble starting. The battery is fine because one can hear it doing its job. Its seems that the final spark required to for ignition is missing. The thing is that this is an intermittent problem and so it's a little difficult to pinpoint. When it happened the first time the distributor cap was removed and the contact points were checked and they all looked fine, after replacing the distributor cap back it started on the first attempt.

I took this as a sign that the vehicle needs a service. So I booked it into a local (reputable) garage and asked for a FULL service. In the full service the spark plugs were changed and also some engine work was done and all the others things associated with a full service. To my shock and horror a day later after driving the vehicle all day I parked it up for a couple of hours (in the evening) and when returning to it, it failed to start. I had told the garage about the starting issue but they said for the whole week they had it they never had an issue with starting the vehicle.

I live in Saudi Arabia. The weather has changed to being a little cooler over the last few weeks. This is one theory. When it gets cool the vehicle fails to start. When the garage had the vehicle it never had the starting issue because they start work at 8:00-9:00am when the sun has been up for a few hours and it's a little warm.

I took it back to the garage but got the distinct impression that those guys do not have a clue as to what the issue may be. Their latest idea is to replace the coil.

Please accept my apologies for going on at length. I wanted to give you as many details as I could. As always your words of wisdom will be appreciated.

Kind regards

Ahmed N Azam
(Dhahran, Saudi Arabia)


Answer
Hello Ahmed,

thank for the kind words and I hope you are well too.

As for your '98 Discovery, I can understand your frustration with this starting problem so soon after having it serviced.

Living in Quebec, Canada, I can state with authority that our Disco's do have trouble with extremely cold temmperatures. For the next 4 months, we here will be seeing average daily temperatures of -10C to -22C. Nights will be obviously colder (-20C to -36C). I always use an electric block heater to prevent my Disco engine from freezing.

You'll have to update me on your climate...I would suspect that your night temperatures could fall to -10C but not to the point where your Disco will not start.

Most cold temperature extremes have an affect on the battery and the cold cranking amps needed to turn over a cold engine. Your Disco would have to be exposed to extreme cold temperatures constantly before it would affect the engines ability to start. Several days at -C temperatures may do this.

I suspect your problem has more to do with the ignition system from the alternator forward or the fuel delivery system.

If you have weak or failing battery, most garage mechanics can test and see this in under 1 minute. Same for the coil, a multi-meter will determine if the coil is actually doing its job.

Many Disco's I've seen with cold starting trouble can be attributed to the spark amplifier module.

Its also possible that the solenoid may be failing on your starter. If this is the cause, both the starter and the solenoid are replaced as they are an integrated unit.

There are other areas that can inhibit starting, such as a vacuum leak, fuel injectors being fouled, fuel filter needs replacement or even low compression in one of the cylinders.

So before you have the coil replaced, go to a Land Rover dealer and have them do some diagnostics. It will save you some money in the long term...you won't be replacing units that are functioning correctly. Most mechanics swap out parts until the problem goes away...this is very expensive and such a waste.

Al Saif Motors is the only dealer that I am aware of in your region:

Al Saif Motors Ltd
Khurais Road
PO Box 5122
Riyadh 11422
Saudi Arabia
00966 1237 0001
00966 1237 002

Best of luck with this. If you have any other concerns, please send me a note and I'll do my best to help you.

Regards,

JohnMc"

Many thanks & best regards,

Badie Darwazeh

Answer
Hello Badie,

without a doubt, if you can tap on your coil and it makes a difference in whether your Disco starts or not....definately replace the coil.

Extreme temperatures has its affect on all things electrical.  The coil is very sensitive to heat and can fail repeatedly under the right conditions.  On my '95 Disco, LR had to move the coil from its original position on the engine to a location just beside the radiator.

It could very well be that your coil is overheated and now is in need of replacement.  Living in Saudi Arabia makes moving the coil a mute point.  That engine compartment will always have high temperatures during daytime driving conditions.

As much as extreme cold affects the battery, extreme heat has its toll on both alternators, coils and coilpacks.

Best of luck,

JohnMc