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Hello All, :D
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. :confused:
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;
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.

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 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
http://www.a2resource.com/electrical/CE2.html
http://www.vwbooks.co.uk/vw_info/T4_pdfs/vw_T4_engine_wiring_2002.pdf
http://www.vwbooks.co.uk/vw_info/T4_pdfs/T4_Base_Wiring_from_May_1999_on.pdf
http://www.vagcat.com/epc/cat/vw/TR/
 

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Hi,
Mega thanks Cyclist Rob for this post. My dad had given me his old T4 2.5tdi 1999 van, the AJT one that you based this write up on. It wouldnt start but would turn over fine. Popped out the relay and ran a wire from point 30 to 87 and slapped it back in. Turned the ignition on and hey presto, the glow plug light came on, waited a second for them to warm up and turned the key and suddenly the old girl burst into life! Brill, one very happy chappy! Just gotta order a new 109 relay for my VW garage!
Many thanks again mate,
Paul
 

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Excellent post but, A WORD OF CAUTION, be very careful when probing circuits that are connected to the ecu, you could easily cause expensive damage if you get it wrong.
 

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Sounds like your getting a positive back feed from the relay, remove relay and the small pin on relay is where it should be negative trigger from ecu when ignition is turned on check that first, if not showing an earth go to the wires that go into ecu locate the small black and white wire there and (probe) check if you get a earth feed there when ignition is turned on if theres a earth there theres a break somewhere between there and relay, had the same problem on my van last week, found a break in wire in loam just below brake servo where it runs over top of engine. pm me if you need more help. other easy way to see if its a relay problem is to remove the plastic cover from relay and close it it with fingers manualy with ignition turned on and see if glow plug light comes on and go's out you need to keep it closed and try starting it? hope this helps
 

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Yes, defo sounds like a break in the wire and below the servo is the favourite place.
 

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heiio again the wire black&white from ecu to fuse box __ i have cut it naw ecu side is nagitive and f.box side is positive thats way relay 109 not stay on just keep cutting off -------------------------------------------------------------------------------------------any idia pleaz T: I:
 

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Yes, it will be. The positive from the fuse box needs to find the negative from the ecu to complete the circuit.
 

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Have you done the checks listed at the top of this thread? Have you tried another 109?
 

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yes i did check it and the b&w wire have the nagitive from ecu but wen i conect to new 109 it gos positive and start cutting off have new 109 &103 &coolant sensor is there any more sensor to change plz goude me i am really stuck on thise :*
LOL:
 

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I think you may a problem inside the fuse box. I have seen it before where the contacts spread or burn and then they don't connect properly with the relay. Have a very close look at them.
 

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Think you're missing out on a free holiday here upspex.....
Agree to take your multi-meter with you (all transport costs paid) and just fix it for him!!!
 

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Hey guy's many thanks for the efforts and time put into all this.

I have a 2000 model 2.5 ACV T4 and my glow plug light comes on with ignition for barly a second then go's out. Ive tested the relay and inspected connections and all fuses, everything is ok. All the glow plugs work fine.

Problem is somtimes the relay is not getting energised at all but the glow plug light is still displaying on dash quickly. So I have no power at the glow plugs and the van will not start.

Somtimes I hear it click and click off again after 10 seconds or so and I know the glow plugs have power and my van will start. But this is one in over 100 turns of the key on and off if im lucky.

What can I look at next? where is the computer located for the glow plug timer?

Thanks, Kev.
 
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