Ignition Amp?

Ignition Amp?

Author
Discussion

Jhcolling

Original Poster:

72 posts

133 months

Sunday 7th January 2018
quotequote all
Around every 10 days through winter I take the car out of the garage and let it idle on the driveway until she is up to temperature, I then take it for a 5 min drive around the estate before returning back to the garage.
Same scenario today but around 2 mins after I started the car she just died as though the ignition had just been turned off. The car was running fine up the the engine stopping. The car now cranks but won't fire.
A bit of searching has led me to believe the issue lies with the ignition, specifically the ignition amp or maybe the ignition coil. Before I go out shopping for parts is there anything I may have missed?

I have checked the HT leads are all connected, unplugged and plugged the relays back in.

The relays all click when starting and i can hear the fuel pump too.

Minor confession: I forgot to unplug the trickle charger before I started the car, the car did start fine and i immediately noticed my error and un plugged, the car ran for a few minuted after this error before stopping but not long enough to get up to temperature.

Thanks in advance.

BIG DUNC

1,918 posts

223 months

Sunday 7th January 2018
quotequote all
The two occasions in the past that I have had ignition amps fail (on different rover V8s) the symptom has been that the car was really difficult (read almost impossible, if not very actually impossible) to start, but once started it ran fine.

Could the charger have caused an issue with the 100 amp fuse?

Simple things are coil, rotor arm, cap, leads, ignition amp, plugs and airflow meter. Obviously its expensive to change all that "just in case". Anyone near you who you can swap a few parts with to see if it makes a difference?

Jhcolling

Original Poster:

72 posts

133 months

Sunday 7th January 2018
quotequote all
I suppose it could be the fuse but would that cause it to stop suddenly, I have no experience with the 100amp fuse going yet so can't really comment on how they go. The car is a 98 reg 450, where would i locate the fuse?

wseed

1,509 posts

130 months

Sunday 7th January 2018
quotequote all
Are you getting a spark? A cheap in-line plug tester would help.

Where up north are you up? I replaced most of my ignition components shortly after buying the car and kept the old parts as spares if you're near by (Manchester work near Chorley) you'd be welcome to test any as swap outs I think I have a plug tester too.

N7GTX

7,855 posts

143 months

Sunday 7th January 2018
quotequote all
Disconnect the king lead from the dizzy cap (it runs to the coil) and place the end so it is about 1/4" from the engine lifting eye. Crank the engine. You should see a continuous series of healthy sparks jump the gap. If you do, then the fault is not likely the coil or amp. The fault would then be the distributor cap, the rotor arm inside or the dizzy itself.
If you do not get the sparks, then likely to be the coil, amp, wiring. First check is to make sure the coil is being triggered and has voltage to it.

QBee

20,953 posts

144 months

Monday 8th January 2018
quotequote all
There are two big fuses on a later car, both in plastic in-line holders:

The 80 amp fuse is in the footwell rats nest. Failure is indicated by not a lot working.
The 100 amp fuse is under the car, due south of the alternator. Failure is indicated by all being fine until you have driven 50+ miles, when the car goes slower and slower and eventually conks out - you have been running on battery, not alternator, for those 50 miles.

Jhcolling

Original Poster:

72 posts

133 months

Monday 8th January 2018
quotequote all
Thanks everybody, much appreciated.

I think I can rule out the fuses as everything seems to still work and the car battery still has plenty of life so it would appear the car wansn't running on the battery.

I will try the spark method and see if it sparks and take it from there. Just to check, is the yellow circled lead the king lead you refer to?



Edited by Jhcolling on Monday 8th January 12:40

GR_TVR

714 posts

84 months

Monday 8th January 2018
quotequote all
Yes - it's the other end at the distributor cap that you want to remove.

Jhcolling

Original Poster:

72 posts

133 months

Monday 8th January 2018
quotequote all
OK, I'll try to have a crack at it tonight.

TwinKam

2,962 posts

95 months

Monday 8th January 2018
quotequote all
...and it's not a good idea to hold that lead (whilst the engine is being cranked).
Rather, get your wife to hold it .....evil

Edited by TwinKam on Monday 8th January 16:10

QBee

20,953 posts

144 months

Monday 8th January 2018
quotequote all
Jhcolling said:
Thanks everybody, much appreciated.

I think I can rule out the fuses as everything seems to still work and the car battery still has plenty of life so it would appear the car wansn't running on the battery.

I will try the spark method and see if it sparks and take it from there. Just to check, is the yellow circled lead the king lead you refer to?



Edited by Jhcolling on Monday 8th January 12:40
Standing the car on its nose for extended periods of time can lead to flooding, I hear......

Jhcolling

Original Poster:

72 posts

133 months

Monday 8th January 2018
quotequote all
Excuse the ignorance here, but how do I hold it without actually holding it? I assume I or the wife is at risk of electricution?

Classic Chim

12,424 posts

149 months

Monday 8th January 2018
quotequote all
Just a bit, a rubber handled something or wedge it so you don’t have to handle it.

But if you want to laugh your head off let the missus do it biglaugh

TwinKam

2,962 posts

95 months

Monday 8th January 2018
quotequote all
Sorry (but pleased if I've saved a life by raising awareness wink )
HT voltage is massive, IRO 35,000v but the current is low so it shouldn't kill you (unless you have a pacemaker...) but it is unpleasant and avoidable.
NG7TX used the word "place"...by that he meant lay the lead so that the end terminal is near (but not touching) a bare metal part of the engine. You might have to weight it down with a tool or prop it up with a rag to achieve this. Ensure that there is nothing easily flammable nearby too (eg petrol soaked rag)
HTH

Beaten to the post by CC!

Jhcolling

Original Poster:

72 posts

133 months

Monday 8th January 2018
quotequote all
I’m alive and can confirm I have no spark. I don’t really know how to use a multimeter but I can copy parrot fashion. What’s my next step?

Penelope Stoppedit

11,209 posts

109 months

Monday 8th January 2018
quotequote all
You could check to see if there is a 12 Volt supply to the ignition coil

blitzracing

6,387 posts

220 months

Tuesday 9th January 2018
quotequote all
As the man says- with the ignition on and the engine stopped you should see 12 volts on both the positive and negative side of the coil. Then unplug the ignition amp, and attach a wire to the negative side of the coil, and then dab it onto the ground- you should get a sharp crack and spark from the coil as you disconnect the ground wire. If this works, the issue is the ignition amp or the trigger head tin the dizzy.

Jhcolling

Original Poster:

72 posts

133 months

Tuesday 9th January 2018
quotequote all
I can confirm there is 12v to the ignition coil. So it is either the coil or ignition amp?

Penelope Stoppedit

11,209 posts

109 months

Tuesday 9th January 2018
quotequote all
Ok This is good, you have 12 volt to the coil
Now make sure the distributor is turning, remove the distributor cap and have someone crank the engine over while you look to see if the rotor arm turns