Testing HT Leads?
Discussion
Hey all,
Is there a way to test HT leads, with a multimeter or something else.
Symptom - the car (Volvo 850), had starting a week or two ago started to miss at low revs on a short drive back from the shops (currently the car isn't do many miles), with the only difference is that is really started raining hard in the 30 minutes I was shopping. Since then, over about 30 miles, it occasionally kept doing it at <1800 revs, usually worse after a short run, stop, then start again.
Today went for a 10 mile/20min drive missing under 1800 rpm (wet again), stop for 2 hours, and on the way back, it was much worse, missing under 2500rpm.
I suspect it is the leads, and a moisture is making it worse. Haven't checked anything yet, waiting for the rain to stop!
Anyone have advice on this? Cheers.
Is there a way to test HT leads, with a multimeter or something else.
Symptom - the car (Volvo 850), had starting a week or two ago started to miss at low revs on a short drive back from the shops (currently the car isn't do many miles), with the only difference is that is really started raining hard in the 30 minutes I was shopping. Since then, over about 30 miles, it occasionally kept doing it at <1800 revs, usually worse after a short run, stop, then start again.
Today went for a 10 mile/20min drive missing under 1800 rpm (wet again), stop for 2 hours, and on the way back, it was much worse, missing under 2500rpm.
I suspect it is the leads, and a moisture is making it worse. Haven't checked anything yet, waiting for the rain to stop!
Anyone have advice on this? Cheers.
remove one plug at a time from the engine and push the plug into the corresponding HT lead, hold by a rubber piece of the HT lead and put the spark plug against/very close to the engine block and have someone turn the engine over - no spark, knackered lead/plug/coil pack etc - if there is strong spark move on to next plug and repeat!!... this is an old method, I am sure someone will come along with a modern alternative!!
Wear rubber gloves if you can and do not do it if damp on the leads as the current can give a hell of a kick if ther HT lead insulation is fooked!!!!
HTH
Wear rubber gloves if you can and do not do it if damp on the leads as the current can give a hell of a kick if ther HT lead insulation is fooked!!!!
HTH
Edited by Reedy156 on Wednesday 31st March 16:48
Pulled the HT leads of yesterday, and found one lead has a break in it, fluctuating/lossing resistance with I move it. So I guess it was arcing in the lead over the last 50 miles, and burning the copper, slowly making it worse.
Though I doubt I will be able to get replacement leads until Wednesday thanks to Easter....
Though I doubt I will be able to get replacement leads until Wednesday thanks to Easter....
Leave the engine running on a very dark night, look under the bonnet for sparking/ arcing. If there is thats your problem.
You can also get a spray bottle and spray water on the leads, if the car starts to splutter your leads are fooked. Remember to thoroughly dry and spray wd40 on afterwards.
2 tried and tested methods.
edited to add:
It could be the dizzy cap cracked. I had the same problem on my Golf. Changed dizzy cap, leads and rotor arm, whole lot was £50 and cured it!
You can also get a spray bottle and spray water on the leads, if the car starts to splutter your leads are fooked. Remember to thoroughly dry and spray wd40 on afterwards.
2 tried and tested methods.
edited to add:
It could be the dizzy cap cracked. I had the same problem on my Golf. Changed dizzy cap, leads and rotor arm, whole lot was £50 and cured it!
Edited by nottyash on Sunday 4th April 21:17
average resistance is 15Kohms per metre of pluglead
DIS sytems usually use leads with 30Kohms per metre
so for a Monjo with DIS a lead .5 mtr long ought to measure about 15K (give or take a bit 'cos I am useless at sums)
if you can get the burnt/broken end out of the connection you can often make a temporary repair good enough to last over Easter. Continuity is often made by a piece of wire in the core that contacts a metal part of the cap interior
DIS sytems usually use leads with 30Kohms per metre
so for a Monjo with DIS a lead .5 mtr long ought to measure about 15K (give or take a bit 'cos I am useless at sums)
if you can get the burnt/broken end out of the connection you can often make a temporary repair good enough to last over Easter. Continuity is often made by a piece of wire in the core that contacts a metal part of the cap interior
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