One for Jug! How to test pencil ignition coils?

[JoskeJTD]

Hi Jug, wonder if you can help me. I have another car a 05 Renault Megane 1.4 16V which has a slight but noticable shake at idle which is felt when sat inside. Passengers feel it too. The car idles fine, no change in revs, but it sort of jolts slightly here and there when idling. If i dip the accelerator and let go, i'll feel one bigger small noticable jolt/shake. If that makes sense.

Im assuming its the ignition coils, now the Reno has pencil type ignition coils which are all individual, to save myself money i just want to check each coil individually for any faults. So i was wondering how i can test my coils?

This is how it looks...

I guess im checking for the OHMs reading but what figures am i looking at? Also do they need to be connected? Removed? Ignition On? etc.

Sorry for being non Fiat Related but i know Jug hits the Bravo section quite a bit. Plus i guess the principle is the same on the Fiats.

 

[EI4GGB]

It would be quite difficult to test them other than by looking at the primary waveforms on a scope, or diagnostics.. those newer COPs have a fairly low primary impedance, so its very difficult to test them statically (ohms). rob or borrow one off another car if you can..

 

[The Sultan]

if you can identify witch cylinder is causing the fault maybe from the plugs i know it's hard to do unless diagnostics equipment can tell or even scope the crank sensor and then swap the coils and see if it moves

i know renault have been know for non conforming injectors have had a few maybe something to check

i asume you have changed / checked plugs aswell

 

[JoskeJTD]

if you can identify witch cylinder is causing the fault maybe from the plugs i know it's hard to do unless diagnostics equipment can tell or even scope the crank sensor and then swap the coils and see if it moves

i know renault have been know for non conforming injectors have had a few maybe something to check

i asume you have changed / checked plugs aswell

All the plugs have been renewed with new ones and there was no discolouration to any that showed signs of a fault.

The car drives fine just the idle has a noticable shaking your ass feel. Excuse the pun.

I've found this site, not sure if its exactly shows how to test the coils I have...

Coil Test Link

Coil Bench Test Link

 

[The Sultan]

well it stands to reason that you can bench test any coil primary and secondary windings there all the same really in the way they work your problem is finding the data for them and what they should be showing

also it's hard to identify a problem that happens when engine is warm so many people dont test pencil coils this way it doesent really tell you much about how the resistance can change

you also need to check the common power feet to them holds voltage under operation as the ultrasonic welds in harnesses spliting 1 to four have bveen known to break apart not specifically on renaoult well i wouldnt know really

 

[JoskeJTD]

In English please.

 

[T14086]

buy a coil (£32) because they are crap (make stilo coils look good!)

 

[The Sultan]

buy a coil (£32) because they are crap (make stilo coils look good!)

case closed

and not a single jug anywere

the best layed plans

 

[The Sultan]

In English please.

sory my english is very poor even thou i am english

in short: if the coil says bosch or denso or trw on the top chuck it in the bin

get a magneti marelli one

 

[jug]

it takes 30secs to test both the primary and secondy windings. first use a multimeter to measure the primary resistance across the 2 LT wiring connector pins (usually left and right pins, not centre pin). it should be a low resistance, usually less than 1ohm. compare the result on all coils to see if one is significantly different.
next measure the resistance from the contact that sits on top of the plug to the earth lead pin where the wiring connector attaches (usually centre pin). this should be a much higher resistance so you'll need to sue a different multiemter setting. approx 1000ohms is normal for most coils, but again compare al yours to decide if one is different.

buying a new coil before you do this diagnosis is very foolish.


EDIT: just looked at the pic above, that type of coil will only have 2 pins and the 3rd pin (earth) is that metal bolt hole.

 

[T14086]

Personally wouldnt trust a resistance reading with the component not working (under load) a scope pattern would be my 'weapon of choice.

 

[jug]

Personally wouldnt trust a resistance reading with the component not working (under load) a scope pattern would be my 'weapon of choice.

i agree, but how many people have an oscilloscope at home?

 

[T14086]

you mean you haven't

 

[JoskeJTD]

Cheers Guys, will give it a try. Thanks for all your replys.

 

[jug]

you mean you haven't

my oscilloscope was made in england in the 70's and it still works mint, the leather pounch even smells brand new.

 

[The Sultan]

my oscilloscope was made in england in the 70's and it still works mint, the leather pounch even smells brand new.

i wish i was made in the seventies

 

[PNL]

(make stilo coils look good!)

And they are crap .. you can also tell by smell if the coil has gone ..have a sniff and find out distinct smell of burning..:yuck:

 

[custard]

i wish i was made in the seventies

i was



(i dont smell new)

 

[The Sultan]

atleast fiat changed the maker of the stilo coils
get a full set and problem sorted