Hello All, 
Seeing myself and a few others have been having trouble with the van not starting but having no GLOW plug light when turning the ignition on, but engine is turning but not starting.
I had a lot of help from other forum members A: so I thought I put something back.
I AM NOT A VAN MECHANIC. I am going to be quoting plug/pin/wire numbers/colours BUT THEY MIGHT NOT BE THE CORRECT ONES IN YOUR VAN. So I may NOT be correct in some of the things written below. Hopefully thou this will give you a idea/pointers/starting point.
But before I start here are a basic observation:
1) Part of the key ignition switch goes to relay 109 “engine control module power supply relay”, 109 “coil” side goes to ground Via the ECU. 109 “switch” side goes ECU fuse and then into the ECU. SO if 109 has no earth it can’t “switch on” power to the ECU so it’s not doing it’s “thing” when engine is cranked over = no start.
2) A multi meter and spare wire/cable will be very handy!
This is what I did ON A T4 65KW 2.4 TDI AJT engine. Check fuse’s inside the van, below right of the steering wheel and fuses inside the engine bay normally in front of battery. (In a black cover/box) if they all ok.
Find relay 109 (2nd row up 3rd one in from left) remove it and test Voltage at slot 4, slots should be numbered. (Terminal 30 slots into 4) page 80/3 http://www.vwbooks.co.uk/vw_info/T4_pdfs/vw_T4_engine_wiring_2002.pdf It should read 12V. If not it’s power supply to the relay. (can’t help you on this one!)
If 12V there, take the removed relay 109, there should be a little circuit diagram on the side, get a small length of wire and join it to terminal 30 then terminal 87, so you got a small loop, basically you bypass the switch in the relay. Put the relay back in the fuse block/box. Put in key and see if the glow plug light comes on and try starting.
IF it works it be relay 109 OR relay (fuse) box OR wiring. If not it’s fuse box/ wiring to the ECU fuse. (Goto REF A for further T/S)
Simple test remove wire loop from relay, connect one end of wire to terminal 85 of 109 relay. the other end of wire put to ground (so long bit of wire be good) you should hear a click, turn key and see if glow plug light is on and start van. It still no go, looks like the relay is U/S (you could take cover off relay and hook it up to 12V to double check).
If the van started, it’s the earth side of the relay = fuse box/wires
Quick check the wires/plug on the back of the fuse box. You looking for plug G1 it's white (middle one of 3 white plugs, bottom row) http://www.a2resource.com/electrical/CE2.html THIS MIGHT NOT BE YOUR YEAR/MODEL but give you a idea. It could be a loose wire, look for a black and white wire.
If looks all ok, remove the white plug, best to un hook the side clips on the fuse box and let it hang, there is a little lever on the right side in-between the two row of plugs slide/pull it to the side. (Release’s the lock on the plugs)
Now we check the continuity of the circuit inside the fuse box. Remove relay 109, put one wire of the multi-meter in relay hole #5 (relay pin85) to pin 7 in terminal G7. (Make sure you're on right pin). If all ok it’s not fuse box.
Next step is to check the continuity of the wire (black & white) going from Plug G1, pin 7 to pin18 T121 which is the ECU. Bigger of the two connectors into the ECU (in front of Battery, low down).
I got access to back of the plug to see the wires and found which pin the black and white wire goes into. So if there is continuity looking like you ECU and you need to get a 2nd opinion!
REF A, continuity test, relay hole #8 (relay pin87) to pin 10 in terminal G7, to check fuse box. If ok check wire from plug G1 pin 10 to ECU T121 pin 1 and 2 (via ECU fuse) Black and Yellow.
If the Black and White wire failed the test, it is the wire, it is a long wire loam that comes in the engine bay drivers side then over the front/top of engine etc. to the ECU. Just below the brake master cylinder is a common place for a break. Remove wires from the cable wrap/protector and fine the black and white wire and trace/insp it.
If you can’t see anything on the top, easy access to the wire, you can break down the continuity test by removing a LITTLE insulation of the black and white cable and then test plug G1 pin 7 to you new test point. Best also test from new test point to pin 18 in the ECU plug. Hopefully you now know which half/section of wire it is. (Don’t for get to re-protect the wire with tape after. I
Hope this helped. Below are some links that I found help full. (Most found in T4fourm)
And a big THANKS to Stero Steve, kfphil, nogdo, Tim at Phirm and my mate Chris M for helping me.A:
http://www.vwbooks.co.uk/t4.htm
Central Electric 2
VW Books
VW Books
http://www.vagcat.com/epc/cat/vw/TR/
Seeing myself and a few others have been having trouble with the van not starting but having no GLOW plug light when turning the ignition on, but engine is turning but not starting.
I had a lot of help from other forum members A: so I thought I put something back.
I AM NOT A VAN MECHANIC. I am going to be quoting plug/pin/wire numbers/colours BUT THEY MIGHT NOT BE THE CORRECT ONES IN YOUR VAN. So I may NOT be correct in some of the things written below. Hopefully thou this will give you a idea/pointers/starting point.
But before I start here are a basic observation:
1) Part of the key ignition switch goes to relay 109 “engine control module power supply relay”, 109 “coil” side goes to ground Via the ECU. 109 “switch” side goes ECU fuse and then into the ECU. SO if 109 has no earth it can’t “switch on” power to the ECU so it’s not doing it’s “thing” when engine is cranked over = no start.
2) A multi meter and spare wire/cable will be very handy!
This is what I did ON A T4 65KW 2.4 TDI AJT engine. Check fuse’s inside the van, below right of the steering wheel and fuses inside the engine bay normally in front of battery. (In a black cover/box) if they all ok.
Find relay 109 (2nd row up 3rd one in from left) remove it and test Voltage at slot 4, slots should be numbered. (Terminal 30 slots into 4) page 80/3 http://www.vwbooks.co.uk/vw_info/T4_pdfs/vw_T4_engine_wiring_2002.pdf It should read 12V. If not it’s power supply to the relay. (can’t help you on this one!)
If 12V there, take the removed relay 109, there should be a little circuit diagram on the side, get a small length of wire and join it to terminal 30 then terminal 87, so you got a small loop, basically you bypass the switch in the relay. Put the relay back in the fuse block/box. Put in key and see if the glow plug light comes on and try starting.
IF it works it be relay 109 OR relay (fuse) box OR wiring. If not it’s fuse box/ wiring to the ECU fuse. (Goto REF A for further T/S)
Simple test remove wire loop from relay, connect one end of wire to terminal 85 of 109 relay. the other end of wire put to ground (so long bit of wire be good) you should hear a click, turn key and see if glow plug light is on and start van. It still no go, looks like the relay is U/S (you could take cover off relay and hook it up to 12V to double check).
If the van started, it’s the earth side of the relay = fuse box/wires
Quick check the wires/plug on the back of the fuse box. You looking for plug G1 it's white (middle one of 3 white plugs, bottom row) http://www.a2resource.com/electrical/CE2.html THIS MIGHT NOT BE YOUR YEAR/MODEL but give you a idea. It could be a loose wire, look for a black and white wire.
If looks all ok, remove the white plug, best to un hook the side clips on the fuse box and let it hang, there is a little lever on the right side in-between the two row of plugs slide/pull it to the side. (Release’s the lock on the plugs)
Now we check the continuity of the circuit inside the fuse box. Remove relay 109, put one wire of the multi-meter in relay hole #5 (relay pin85) to pin 7 in terminal G7. (Make sure you're on right pin). If all ok it’s not fuse box.
Next step is to check the continuity of the wire (black & white) going from Plug G1, pin 7 to pin18 T121 which is the ECU. Bigger of the two connectors into the ECU (in front of Battery, low down).
I got access to back of the plug to see the wires and found which pin the black and white wire goes into. So if there is continuity looking like you ECU and you need to get a 2nd opinion!
REF A, continuity test, relay hole #8 (relay pin87) to pin 10 in terminal G7, to check fuse box. If ok check wire from plug G1 pin 10 to ECU T121 pin 1 and 2 (via ECU fuse) Black and Yellow.
If the Black and White wire failed the test, it is the wire, it is a long wire loam that comes in the engine bay drivers side then over the front/top of engine etc. to the ECU. Just below the brake master cylinder is a common place for a break. Remove wires from the cable wrap/protector and fine the black and white wire and trace/insp it.
If you can’t see anything on the top, easy access to the wire, you can break down the continuity test by removing a LITTLE insulation of the black and white cable and then test plug G1 pin 7 to you new test point. Best also test from new test point to pin 18 in the ECU plug. Hopefully you now know which half/section of wire it is. (Don’t for get to re-protect the wire with tape after. I
Hope this helped. Below are some links that I found help full. (Most found in T4fourm)
And a big THANKS to Stero Steve, kfphil, nogdo, Tim at Phirm and my mate Chris M for helping me.A:
http://www.vwbooks.co.uk/t4.htm
Central Electric 2
VW Books
VW Books
http://www.vagcat.com/epc/cat/vw/TR/
