Re: Testing the ignition system, coil and ECU

VW T3 coil;

If an ignition coil fails completely, it will make no spark at all. But if it is performing below par, it can make a weak spark that can cause the van to run badly.

I once tested three used VW coils in search of a good one. All would make the engine run, but none of them were up to spec. The purchase of a new coil made a noticeable difference.

The primary winding of the ignition coil is the first to receive voltage from the battery when the ignition switch is turned on, via terminal 15 (+).

Using a multimeter, place the probes on the small outside wires (terminals 15(+) and 1(-). If the primary resistance between the two is 0.5 to 0.8Ω, the primary winding is ok and you can go on to the next test. If it is out of spec, replace the coil with the spare that you always carry under the seat.

The secondary winding of the ignition coil delivers the spark to the distributor to be sent to the spark plugs. If it's bad, you'll get a weak spark or no spark at all.

To test the secondary winding, attach test probes to terminal 15+ and the centre pole (where the thick wire goes to the distributor). The resistance should be 2.4 to 3.5 kΩ. If it is out of range, toss the coil.

If ignition coil is overheating and breaking down, causing misfiring and lack of power, test the ignition switching function of the control unit

To test the ECU (the black box under the rear seat in a caravelle or camper). (See Bentley manual 28.44).

Connect the multimeter probes to terminals 15 (+) and 1 (-) on the ignition coil.

Disconnect Hall Sender plug on distributor.

Have an assistant switch the ignition ON without starting the engine.

Ground the centre wire of hall sender plug for approximately 3 seconds. The displayed voltage must increase briefly to approximately 4.5 volts.

If not, replace control unit.

(My ECU failed this test – the symptoms were misfiring and backfiring after driving for over 45 minutes. It was more noticeable when travelling uphill at highway speeds. The coil was too hot to hold. I replaced the ECU and it solved the problem.)

Other things to check;

Ignition switches can cause intermittent problems, especially with a heavy bunch of keys swinging around over the bumps. They are cheap and small. Carry a spare.

Replace the Oxygen Sensor at specified intervals. This vital component is often overlooked.

Clean or replace the Air Filter and check that there are no leaks in the intake or vacuum system.

Engine earths; clean the connections on the braided wire between the engine and the bodywork with emery paper and a wire brush. According to an NRMA survey, poor earths are the most common cause of engine breakdowns. Also ensure that the connections on both ends of the battery earth strap under the driver's seat are cleaned regularly. I generally add another earth wire to the cylinder head on the driver’s side of the engine, as it lacks a good track to earth due to the fact it is insulated by gaskets and sealant from the rest of the engine. Some pundits reckon that this causes problems as the spark plugs must earth through the coolant. These earths must be cleaned at least once a year, or more often if beach driving.

Check all electrical connections, check wires for cracked or melted insulation, broken wires or loose connections which can cause an intermittent problem. The fragile connector on the hall sender (on the side of the distributor) is often damaged. Use aerosol "Contact cleaner" on all connections. Go to a wrecking yard and cannibalise a few of the common plastic wiring plugs, which can be spliced into the wiring loom if connectors fail.

Check relays and connections in the engine compartment. Always carry spare relays and replace if in doubt. The "GoWesty"and "Van Café" websites will help to identify the relays that you need.

Ignition leads; test leads for continuity and damage. Replace the wires with best quality units every five years, and carry the old ones as spares.

Suppressor plug lead to distributor cap connectors; 0.6 to 1.4 kΩ

Spark plug connectors; 4 to 6 kΩ. Check that they are dry and undamaged and tightly connected to the ignition leads.

Rotor; 0.6-1.4 kΩ. Check for damage. Always carry a spare and replace if in doubt.

Distributor cap; check for cracks and carbon tracking, and inspect the spring-loaded graphite centre-post as it may wear or break. Always carry a spare and replace if in doubt.

Spark Plugs; Check that the correct spark plugs are fitted, and inspect the condition of the ceramic insulator, the integrity of the electrodes, and clean and set the spark plug gaps. Workshop manuals carry a guide on how to "read" spark plug deposits - these are a great insight into the health of your engine. Now is a good time to carry out a compression test. Lightly dust the spark plug threads with powdered graphite and tighten to the specified torque.

It is best to check all of these items in the comfort of your shed at least once a year (or before an expedition) along with changing oils, fluids and filters, checking all the sensors and adjustments as per the Bentley manual, and lubricating everything that moves.

It is educational to remove the engine lid and run the engine on a dark night. Stray sparks and luminescence can help to identify problems that you cannot see in the daylight.

Roger B.

Wow. Thank You Roger. Very comprehensive.
I will go ahead and go through each check.
As mentioned earlier I did replace the distributor so expect that it
will pass the test.
Thanks again. I have a bit of work to do!

Regards

Peter Leolkes
Adelaide

thiOn 2015-12-27 23:37, Roger Bayley gullyraker53@gmail.com
[Syncro_T3_Australia] wrote:
> VW T3 COIL;
>
> If an ignition coil fails completely, it will make no spark at all.
> But if it is performing below par, it can make a weak spark that can
> cause the van to run badly.
>
> I once tested three used VW coils in search of a good one. All would
> make the engine run, but none of them were up to spec. The purchase of
> a new coil made a noticeable difference.
>
> The primary winding of the ignition coil is the first to receive
> voltage from the battery when the ignition switch is turned on, via
> terminal 15 (+).
>
> Using a multimeter, place the probes on the small outside wires
> (terminals 15(+) and 1(-). If the primary resistance between the two
> is 0.5 to 0.8Ω, the primary winding is ok and you can go on to
> the next test. If it is out of spec, replace the coil with the spare
> that you always carry under the seat.
>
> The secondary winding of the ignition coil delivers the spark to the
> distributor to be sent to the spark plugs. If it's bad, you'll get a
> weak spark or no spark at all.
>
> To test the secondary winding, attach test probes to terminal 15+ and
> the centre pole (where the thick wire goes to the distributor). The
> resistance should be 2.4 to 3.5 kΩ. If it is out of range, toss the
> coil.
>
> IF IGNITION COIL IS OVERHEATING AND BREAKING DOWN, CAUSING MISFIRING
> AND LACK OF POWER, TEST THE IGNITION SWITCHING FUNCTION OF THE CONTROL
> UNIT
>
> To test the ECU (the black box under the rear seat in a caravelle or
> camper). (See Bentley manual 28.44).
>
> Connect the multimeter probes to terminals 15 (+) and 1 (-) on the
> ignition coil.
>
> Disconnect Hall Sender plug on distributor.
>
> Have an assistant switch the ignition ON without starting the engine.
>
> Ground the centre wire of hall sender plug for approximately 3
> seconds. The displayed voltage must increase briefly to approximately
> 4.5 volts.
>
> If not, replace control unit.
>
> (My ECU failed this test – the symptoms were misfiring and
> backfiring after driving for over 45 minutes. It was more noticeable
> when travelling uphill at highway speeds. The coil was too hot to
> hold. I replaced the ECU and it solved the problem.)
>
> OTHER THINGS TO CHECK;
>
> IGNITION SWITCHES can cause intermittent problems, especially with a
> heavy bunch of keys swinging around over the bumps. They are cheap and
> small. Carry a spare.
>
> REPLACE THE OXYGEN SENSOR AT SPECIFIED INTERVALS. This vital component
> is often overlooked.
>
> CLEAN OR REPLACE THE AIR FILTER AND CHECK THAT THERE ARE NO LEAKS IN
> THE INTAKE OR VACUUM SYSTEM.
>
> ENGINE EARTHS; clean the connections on the braided wire between the
> engine and the bodywork with emery paper and a wire brush. According
> to an NRMA survey, poor earths are the most common cause of engine
> breakdowns. Also ensure that the connections on both ends of the
> battery earth strap under the driver's seat are cleaned regularly. I
> generally add another earth wire to the cylinder head on the
> driver’s side of the engine, as it lacks a good track to earth due
> to the fact it is insulated by gaskets and sealant from the rest of
> the engine. Some pundits reckon that this causes problems as the spark
> plugs must earth through the coolant. These earths must be cleaned at
> least once a year, or more often if beach driving.
>
> CHECK ALL ELECTRICAL CONNECTIONS, check wires for cracked or melted
> insulation, broken wires or loose connections which can cause an
> intermittent problem. The fragile connector on the hall sender (on the
> side of the distributor) is often damaged. Use aerosol "Contact
> cleaner" on all connections. Go to a wrecking yard and cannibalise a
> few of the common plastic wiring plugs, which can be spliced into the
> wiring loom if connectors fail.
>
> CHECK RELAYS and connections in the engine compartment. Always carry
> spare relays and replace if in doubt. The "GoWesty"and "Van Café"
> websites will help to identify the relays that you need.
>
> IGNITION LEADS; test leads for continuity and damage. Replace the
> wires with best quality units every five years, and carry the old
> ones as spares.
>
> SUPPRESSOR PLUG LEAD TO DISTRIBUTOR CAP CONNECTORS; 0.6 to 1.4 kΩ
>
> SPARK PLUG CONNECTORS; 4 to 6 kΩ. Check that they are dry and
> undamaged and tightly connected to the ignition leads.
>
> ROTOR; 0.6-1.4 kΩ. Check for damage. Always carry a spare and
> replace if in doubt.
>
> DISTRIBUTOR CAP; check for cracks and carbon tracking, and inspect the
> spring-loaded graphite centre-post as it may wear or break. Always
> carry a spare and replace if in doubt.
>
> SPARK PLUGS; Check that the correct spark plugs are fitted, and
> inspect the condition of the ceramic insulator, the integrity of the
> electrodes, and clean and set the spark plug gaps. Workshop manuals
> carry a guide on how to "read" spark plug deposits - these are a great
> insight into the health of your engine. Now is a good time to carry
> out a compression test. Lightly dust the spark plug threads with
> powdered graphite and tighten to the specified torque.
>
> It is best to check all of these items in the comfort of your shed at
> least once a year (or before an expedition) along with changing oils,
> fluids and filters, checking all the sensors and adjustments as per
> the Bentley manual, and lubricating everything that moves.
>
> It is educational to remove the engine lid and run the engine on a
> dark night. Stray sparks and luminescence can help to identify
> problems that you cannot see in the daylight.
>
> Roger B.
>
>
> Links:
> ------
> [1]
> https://groups.yahoo.com/neo/groups/Syncro_T3_Australia/conversations/messages/25801;_ylc=X3oDMTJyZzh2dm5lBF9TAzk3MzU5NzE0BGdycElkAzEzMjY3MzE1BGdycHNwSWQDMTcwOTkyNjI0MARtc2dJZAMyNTgwMQRzZWMDZnRyBHNsawNycGx5BHN0aW1lAzE0NTEyMjE2MjY-?act=reply&messageNum=25801
> [2]
> https://groups.yahoo.com/neo/groups/Syncro_T3_Australia/conversations/newtopic;_ylc=X3oDMTJmdmdiMnZoBF9TAzk3MzU5NzE0BGdycElkAzEzMjY3MzE1BGdycHNwSWQDMTcwOTkyNjI0MARzZWMDZnRyBHNsawNudHBjBHN0aW1lAzE0NTEyMjE2MjY-
> [3]
> https://groups.yahoo.com/neo/groups/Syncro_T3_Australia/conversations/topics/25801;_ylc=X3oDMTM3c2ZkOTc5BF9TAzk3MzU5NzE0BGdycElkAzEzMjY3MzE1BGdycHNwSWQDMTcwOTkyNjI0MARtc2dJZAMyNTgwMQRzZWMDZnRyBHNsawN2dHBjBHN0aW1lAzE0NTEyMjE2MjYEdHBjSWQDMjU4MDE-
> [4]
> https://groups.yahoo.com/neo/groups/Syncro_T3_Australia/info;_ylc=X3oDMTJmcW1qOTFtBF9TAzk3MzU5NzE0BGdycElkAzEzMjY3MzE1BGdycHNwSWQDMTcwOTkyNjI0MARzZWMDdnRsBHNsawN2Z2hwBHN0aW1lAzE0NTEyMjE2MjY-
> [5]
> https://groups.yahoo.com/neo/groups/Syncro_T3_Australia/photos/photostream;_ylc=X3oDMTJnMmF0cXJpBF9TAzk3MzU5NzE0BGdycElkAzEzMjY3MzE1BGdycHNwSWQDMTcwOTkyNjI0MARzZWMDdnRsBHNsawN2cGhvdARzdGltZQMxNDUxMjIxNjI2
> [6]
> https://groups.yahoo.com/neo;_ylc=X3oDMTJlNnI5aWQ3BF9TAzk3NDc2NTkwBGdycElkAzEzMjY3MzE1BGdycHNwSWQDMTcwOTkyNjI0MARzZWMDZnRyBHNsawNnZnAEc3RpbWUDMTQ1MTIyMTYyNg--
> [7] https://info.yahoo.com/privacy/us/yahoo/groups/details.html
> [8] https://info.yahoo.com/legal/us/yahoo/utos/terms/

Roger,

Great information!  I have added this to Files.

Les

 


From: Syncro_T3_Australia@yahoogroups.com [mailto: Syncro_T3_Australia@yahoogroups.com ]
Sent: 28 December 2015 00:07
To: Syncro_T3_Australia@yahoogroups.com
Subject: [Syncro_T3_Australia] Re: Testing the ignition system, coil and ECU

 

VW T3 coil;

If an ignition coil fails completely, it will make no spark at all. But if it is performing below par, it can make a weak spark that can cause the van to run badly.

Thanks Roger,
A great contribution to our knowledge.
Peter S


--Original Message Text---
From: Roger Bayley gullyraker53@gmail.com [Syncro_T3_Australia]
Date: Mon, 28 Dec 2015 00:07:03 +1100





VW T3 coil;

If an ignition coil fails completely, it will make no spark at all. But if it is performing below par, it can make a weak spark that can cause the van to run badly.

I once tested three used VW coils in search of a good one. All would make the engine run, but none of them were up to spec. The purchase of a new coil made a noticeable difference.

The primary winding of the ignition coil is the first to receive voltage from the battery when the ignition switch is turned on, via terminal 15 (+).

Using a multimeter, place the probes on the small outside wires (terminals 15(+) and 1(-). If the primary resistance between the two is 0.5 to 0.8âó¦, the primary winding is ok and you can go on to the next test. If it is out of spec, replace the coil with the spare that you always carry under the seat.

The secondary winding of the ignition coil delivers the spark to the distributor to be sent to the spark plugs. If it's bad, you'll get a weak spark or no spark at all.

To test the secondary winding, attach test probes to terminal 15+ and the centre pole (where the thick wire goes to the distributor). The resistance should be 2.4 to 3.5 kâó¦. If it is out of range, toss the coil.

 If ignition coil is overheating and breaking down, causing misfiring and lack of power, test the ignition switching function of the control unit

To test the ECU (the black box under the rear seat in a caravelle or camper). (See Bentley manual 28.44).

Connect the multimeter probes to terminals 15 (+) and 1 (-) on the ignition coil.

Disconnect Hall Sender plug on distributor.

Have an assistant switch the ignition ON without starting the engine.

Ground the centre wire of hall sender plug for approximately 3 seconds. The displayed voltage must increase briefly to approximately 4.5 volts.

If not, replace control unit.

(My ECU failed this test †the symptoms were misfiring and backfiring after driving for over 45 minutes. It was more noticeable when travelling uphill at highway speeds. The coil was too hot to hold. I replaced the ECU and it solved the problem.)

Other things to check;

Ignition switches can cause intermittent problems, especially with a heavy bunch of keys swinging around over the bumps. They are cheap and small. Carry a spare.

Replace the Oxygen Sensor at specified intervals. This vital component is often overlooked.

Clean or replace the Air Filter and check that there are no leaks in the intake or vacuum system.

Engine earths; clean the connections on the braided wire between the engine and the bodywork with emery paper and a wire brush. According to an NRMA survey, poor earths are the most common cause of engine breakdowns. Also ensure that the connections on both ends of the battery earth strap under the driver's seat are cleaned regularly. I generally add another earth wire to the cylinder head on the driver’s side of the engine, as it lacks a good track to earth due to the fact it is insulated by gaskets and sealant from the rest of the engine. Some pundits reckon that this causes problems as the spark plugs must earth through the coolant. These earths must be cleaned at least once a year, or more often if beach driving.

Check all electrical connections, check wires for cracked or melted insulation, broken wires or loose connections which can cause an intermittent problem. The fragile connector on the hall sender (on the side of the distributor) is often damaged. Use aerosol "Contact cleaner" on all connections. Go to a wrecking yard and cannibalise a few of the common plastic wiring plugs, which can be spliced into the wiring loom if connectors fail.

Check relays and connections in the engine compartment. Always carry spare relays and replace if in doubt. The "GoWesty"and "Van Café" websites will help to identify the relays that you need.

Ignition leads; test leads for continuity and damage. Replace the wires with best quality units every five years, and carry the old ones as spares.

Suppressor plug lead to distributor cap connectors; 0.6 to 1.4 kâó¦

Spark plug connectors; 4 to 6 kâó¦. Check that they are dry and undamaged and tightly connected to the ignition leads.

Rotor; 0.6-1.4 kâó¦. Check for damage. Always carry a spare and replace if in doubt.

Distributor cap; check for cracks and carbon tracking, and inspect the spring-loaded graphite centre-post as it may wear or break. Always carry a spare and replace if in doubt.

Spark Plugs; Check that the correct spark plugs are fitted, and inspect the condition of the ceramic insulator, the integrity of the electrodes, and clean and set the spark plug gaps. Workshop manuals carry a guide on how to "read" spark plug deposits - these are a great insight into the health of your engine. Now is a good time to carry out a compression test. Lightly dust the spark plug threads with powdered graphite and tighten to the specified torque.

It is best to check all of these items in the comfort of your shed at least once a year (or before an expedition) along with changing oils, fluids and filters, checking all the sensors and adjustments as per the Bentley manual, and lubricating everything that moves.

It is educational to remove the engine lid and run the engine on a dark night. Stray sparks and luminescence can help to identify problems that you cannot see in the daylight.

Roger B.