Register Login
Save up to 15% with Adrian Flux insurance!
Guide Tools
<!-- google_ad_section_start -->SparkPlugs, Leads, Coils - check & replacement [1,4 8V]<!-- google_ad_section_end -->
SparkPlugs, Leads, Coils - check & replacement [1,4 8V]
How to check and change your sparkplugs, cables/leads and coil-pack, DIY.
Published by GrandePunto PL
Difficulty Level: 1

User Rated:Unrated

Show Printable Version  Email this Page 
Smile SparkPlugs, Leads, Coils - check & replacement [1,4 8V]

Quick guide ("3 in 1"), spark plugs, leads, coils. How to check/replace.

0. Remove air filter box/assembly. Watch out (in yellow - two rubber hoses, don't break 'em).
Click image for larger version

Name:	00_Remove_air_filter_assembly.jpg
Views:	34
Size:	95.2 KB
ID:	192829

1. Remove and clean (dust, mud, oil) ignition coil-pack module/unit.
Click image for larger version

Name:	01_Take_the_coils_out.jpg
Views:	20
Size:	91.1 KB
ID:	192830

2. Ignition cables, (high voltage, "high tension") leads are fragile, delicate.
Using pliers like this is a good idea. Rubber likes to seize on spark plugs.
Never pull on cables, damage guaranteed (& for example rough idle after spark plugs change).
Click image for larger version

Name:	02_Better_use_pliers.jpg
Views:	22
Size:	57.9 KB
ID:	192831

3. Some leads are marked, numbered. If you are reusing old ones, check this (and mark yourself).
Click image for larger version

Name:	03_Cables_are_not_equal.jpg
Views:	20
Size:	93.6 KB
ID:	192832

4. Do not attempt spark plugs change job if you are not able to clean the engine around old plugs. Air compressor is ideal. If you don't own one, rinse plug pockets/cavities with brake-cleaner (fresh can has fairly high pressure stream), put some small hose, straw, whatever, on the nozzle/tip as an extension to really get there.
Click image for larger version

Views:	20
Size:	91.3 KB
ID:	192833

5. To undo the plugs you'll need 16 mm hex socket, but extended, long one. Doesn't have to be "special" posh one for spark plugs (with rubber grommet/insert, to hold/retain the plug). Plugs can be seized, don't be afraid to use some force (torque) or "jerk" it (but, be moderate).
Click image for larger version

Name:	05_Long_socket_16_mm.jpg
Views:	19
Size:	87.3 KB
ID:	192834

6. Old plugs. Almost a textbook example of good (used) sparkplugs. Proper combustion process (no obvious problems like black soot, oil, etc.). But gap was too big (1,3-1,4 mm range). That means: little too much mileage.
Click image for larger version

Name:	06_OK_but_gap_too_big.jpg
Views:	25
Size:	67.5 KB
ID:	192835

7. Brand new plugs come pre-gapped, in 0,8-1,0 mm range (depends on maker, Denso, NGK, Bosh, etc.). There is a resistor built-in, for NGK value is 5 kilo ohms. You should check both (gap and resistance), "just in case".
Click image for larger version

Name:	07_Confirm_gap_thread_resistance.jpg
Views:	20
Size:	94.6 KB
ID:	192836

8. Be careful where you check your numbers (like torque specs). Some service manuals, etc., are misleading. This is an example (so called "eLearn"). My Grande (8-valves) has M12 thread plugs (not M14, like many older FIAT engines from "FIRE" family). Check that if you can, before you order the sparkplugs. Normally, you don't use any lubrication around ignition system (I know, there are anti-seize compounds for thread, and insulating silicone grease for leads rubber boots). Use one, if you really need it, and know what you're doing.
Click image for larger version

Name:	08_Dont_trust_any_manual_blindly.jpg
Views:	20
Size:	51.9 KB
ID:	192837

9. How to judge engine condition by sparkplugs look/appearance. Example. Back in the days, B.I. (Before Internet) there were books. Now you have similar charts on-line. If you want to know more, find one (Google)...
Click image for larger version

Name:	09_Judge_plug_by_appearance.jpg
Views:	27
Size:	78.7 KB
ID:	192838

10. Spark plugs are resistive. Leads too. Forgot to measure new leads, but old ones were in 200-300 ohms range. More important thing is, that all leads are close, similar readings. When one is clearly "off", and/or readings jump all over the place when you measure (move leads, bend them), it's "shot". Replace complete set.
Click image for larger version

Name:	10_Leads_are_resistive.jpg
Views:	9
Size:	66.1 KB
ID:	192839

11. Coil-pack module has 4 independent coils ("transformers").
► Low voltage side (primary) has common positive lead (pin 1).
► High voltage (secondary) has common ground (pin 6).
No service manual ever mentions internal diodes...maybe first batch had none, they added this in later coil unit models(?). Who knows...
Click image for larger version

Name:	11_Coil-pack_unit_schematic.jpg
Views:	19
Size:	114.4 KB
ID:	192840

12. So, if you have such coils, you can NOT check the secondary side resistance. Ohm-meter will tell you "break", "open" circuit (no continuity). High voltage diodes are there to suppress unwanted small spark that is generated when coil is switched ON. Coils produce sparks when there is any CHANGE of the EM field (that's the true principle of the operation).
► www hella com/techworld/uk/Technical/Car-electronics-and-electrics/Ignition-coil-2886/
Click image for larger version

Name:	12_Suppressing_diodes.jpg
Views:	14
Size:	74.3 KB
ID:	192841

13. To detect presence of such diode(s) you can perform simple tests at home. First is voltage check. You'll need some source, DC, voltage level doesn't matter much, let's say 5-25 V range. Mains power supply (DC) or battery. Most important thing is to limit the current! Voltmeter must be digital exactly for that reason. It has so called "high input impedance", typically 1 Mega ohm and more (like 10 M). Remember, coil is high voltage, but low current on secondary side. You can kill it with...continuous low voltage source (at first glance, that "doesn't make sense", but it's just the way it is).

So, if you connect in right polarity (according to schematic below and coils layout - image number 11), you should see your voltage source (roughly). If not, there really is a open circuit (but try to flip polarity anyway).
Click image for larger version

Name:	13_Diode_Forward.jpg
Views:	11
Size:	119.7 KB
ID:	192842

14. Flip polarity (swap leads) on your source. Now it should be "no reading" ideally - in reality there can be small negative voltage (diodes are not perfect, they "leak" in reverse) or your multimeter will keep auto-ranging. That's OK (good sign).
Click image for larger version

Name:	14_Diode_Reverse_leak_OK.jpg
Views:	10
Size:	130.8 KB
ID:	192843

15. Similar test, same idea, and schematic. If you don't own voltmeter. You can substitute it with LED and resistor (remember, you must limit current somehow), a few kilo (ohms) for example. LED's are sensitive and start to glow in micro-amps range. This time you flip polarity only on the coils (LED will light on, only in one direction, so you don't change polarity on LED and battery, those elements stay coupled correct way - you want to prove that coli has diode, not that LED is one directional).
Click image for larger version

Name:	15_Test_LED_R_and_battery.jpg
Views:	11
Size:	113.3 KB
ID:	192844

16. No voltmeter, no batteries, no resistors. Mains AC supply test. To limit the current (again), you can use screwdriver type voltage probe (neon bulb with resistor). Put live ("hot", phase) wire into common ground pin, and probe on high voltage side. Instead of completing circuit by touching the probe end directly, again, use LED. If module is good, LED will glow only in one direction (when you hold it by one of the legs, not the other one). If there are diodes inside coils (of course check all 4), they must perform rectifying action. Of course be careful, shock hazard.
Click image for larger version

Name:	16_Test_230V-AC_Probe_and_LED.jpg
Views:	14
Size:	102.1 KB
ID:	192845

17. For electronics hobbyists. You can feed small AC signal into any side of the coil, and watch the other. If there is a diode, it must rectify (make "DC").
Click image for larger version

Name:	17_Test_Generator_and_scope.jpg
Views:	10
Size:	101.6 KB
ID:	192846

18. If you are not familiar with electricity do not try to make real sparks using coils-pack from the car. You can overload it, kill it, etc. Plus safety...
Click image for larger version

Name:	18_Playing_with_High_Voltages.jpg
Views:	16
Size:	38.0 KB
ID:	192847
If you want to know more, check this YouTube channel: Photonicinduction

19. Finally, you can not fully check plugs, leads and coils at home, and be 100% sure that everything is fine perfectly. Important factors are: real load (electrical) and (high) operating temperature. No easy way to mimic this at home. Old-school methods like spraying water can actually cause, initiate the failure (not help to find, diagnose one).
Click image for larger version

Name:	19_Spark_animation_GIF.gif
Views:	18
Size:	483.8 KB
ID:	192848
========= The End =========
Likes Eklipze3k liked this post
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

Old 10-08-2018   #1
Join Date: Apr 2018
Posts: 33
Thanks: 8
Trader Rating: 0
Re: SparkPlugs, Leads, Coils - check & replacement [1,4 8V]

My new leads, "Magneti-Marelli" are different type from old ones ("Champion"), more resistance and values scatter pretty much. Old cables were 200-300 ohm range. Brand new range is 2,7-4,3 kilo. So, some differences may occur, but still, should not be too crazy, like 3 times (or bigger) variation.
Click image for larger version

Name:	New_Leads_Differ_Much.jpg
Views:	14
Size:	124.2 KB
ID:	193103
And strange thing...the longest lead is not the highest resistance one (counter-intuitive).
Car runs fine, so "who cares" (right?).
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

GrandePunto PL is offline Reply With Quote Quote 
Currently Active Users Viewing This Guide: 1 (0 members and 1 guests)
Guide Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump
Similar Threads
Guide Guide Starter Category Comments Last Post
(T) Punto 1.2 8v 2 cylinders after ECU, Coils, HT and sparkplugs changed MK2lover Punto (Mk2/2b) 17 21-09-2017 07:25
(T) plugs, leads and coils?? neilhaj Punto (Mk2/2b) 10 25-03-2015 22:50
bravo hgt ignition leads/coils simon FIAT Boo Archives 11 27-10-2010 21:37
(T) sparkplugs/ht leads brava 1.280sx 2001(y) ramiuk1 Bravo / Brava 14 24-10-2008 16:22
(G) How to check coils and spark plugs swansea2007 Stilo 2 21-06-2008 16:49