No Spark?!

[theduck]

Car was running although it needed final setup I had got it so it was starting with no problems. Now though I have lost spark completely. By leads, spark plus, distributor, coil are all new. Have tried a spare coil and also setup the original distributor with motorcraft amp and none of it has made any difference. I have double checked wiring for the distributor and to coil and accuspark blackbox unit and remade all joins. I have also checked nothing is loose at ignition barrel end. What else can I check or change??

[sj-bradley]

You have to check that there is a signal getting out from the dizzy. If you have a simple multimeter, you can check this although not very well.

 

If it reads either 0 or battery voltage before cranking and then changes to some average value when cranking, you know there is SOME sort of signal getting out. You can check this way all the way to the low tension side of the coil.

 

DON'T try to test this way on the HT side, you will likely blow the meter and / or get a belt from the HT from the leads.

 

If you get something all the way to the coil, then suspect coil onwards.

 

You "can" perform this test 1/2 way through the circuit and if it works, check the last 1/2 or else check the first 1/2 as you'd know in which 1/2 the fault lies.

 

Simon.

[agent_zed]

I lost my spark and ended up replacing coil and module only to find it was the bloody switch i'd installed as a security device had broken.

 

If you have a 12v bulb you can turn the dizzy and it should turn the bulb on and off. Its in the haynes manual. I can copy the section if you want.

[fry61]

You have probably checked the engine earth? Check again between battery positive & block with multimeter -- should be around 12.5 to 12.7 volts with a good battery.

[theduck]

You have to check that there is a signal getting out from the dizzy. If you have a simple multimeter, you can check this although not very well.

 

If it reads either 0 or battery voltage before cranking and then changes to some average value when cranking, you know there is SOME sort of signal getting out. You can check this way all the way to the low tension side of the coil.

 

DON'T try to test this way on the HT side, you will likely blow the meter and / or get a belt from the HT from the leads.

 

If you get something all the way to the coil, then suspect coil onwards.

 

You "can" perform this test 1/2 way through the circuit and if it works, check the last 1/2 or else check the first 1/2 as you'd know in which 1/2 the fault lies.

 

Simon.

 

Sorry Simon, where am I check for these readings?

 

I lost my spark and ended up replacing coil and module only to find it was the bloody switch i'd installed as a security device had broken.

 

If you have a 12v bulb you can turn the dizzy and it should turn the bulb on and off. Its in the haynes manual. I can copy the section if you want.

 

I have a sierra haynes, which section? I will look it up.

 

You have probably checked the engine earth? Check again between battery positive & block with multimeter -- should be around 12.5 to 12.7 volts with a good battery.

 

Unfortunately not that simple, have checked and double checked earths.

[biksz]

Could it be a fuse?

[agent_zed]

I've got the green haynes sierra manual which has an ignition section. Its in the garage but can go have a look in a bit.

 

First things first i guess ... With the ignition on do you get 12v from the positive side to ground on the coil?

[sj-bradley]

As above, you would need to check the wiring diagrams for information.

I don't run a dizzy setup, so I'm afraid this is left as an exercise for the reader ...

 

Simon.

[theduck]

Could it be a fuse?

 

Checked all fuses and all good.

 

 

I've got the green haynes sierra manual which has an ignition section. Its in the garage but can go have a look in a bit.

 

First things first i guess ... With the ignition on do you get 12v from the positive side to ground on the coil?

 

Thank you i will have a look and I will test for 12v from positive of coil to ground.

[theduck]

Ignition on, getting no volts testing between coil positive and ground.

[richyb66]

Run 12v direct from battery to coil positive. If that works, you've got a break somewhere in the harness.

[theduck]

Will give that a go later, cheers.

 

Am I right in thinking there is a relay for switching the power to the coil?

[theduck]

Run 12v direct from battery to coil positive. If that works, you've got a break somewhere in the harness.

 

Well that works. Rather than stripping it all out just run another wire from the ignition barrel to the coil?

[theduck]

Just thinking, if I do just run a new cable from the ignition barrel to the coil, what kind of size/amp rating cable do I need?

[agent_zed]

i'd just use the same size wire that is going to the coil in the loom.

 

I'd probably chase that wire back though and try and find the problem, if you just bypass it you may end up with intermittent faults in the future.