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Cardoctor74
Cardoctor74, ASE Certified Technician
Category: VW
Satisfied Customers: 25955
Experience:  Certified to fix all makes and models
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Vw: tdi..Wont start if glow plug light comes on van will start..ecu

Customer Question

vw caddy 1900 tdi 2003 diesel. Wont start if glow plug light comes on van will start immediately. 99 times out of a hundred it doesnt come on I have the ecu unit checked and they say it is ok. What next
Submitted: 7 years ago.
Category: VW
Expert:  Cardoctor74 replied 7 years ago.
Are there any codes stored in the computer?
Customer: replied 7 years ago.
no
Expert:  Cardoctor74 replied 7 years ago.
Do you have battery voltage to the glow plugs when the glow light does not come on?
Customer: replied 7 years ago.
still waiting for a reply to my last answer
Expert:  Cardoctor74 replied 7 years ago.
Yes do you have power to the glow plugs when the glow light is not on?
Customer: replied 7 years ago.
no
Expert:  Cardoctor74 replied 7 years ago.
Ok there are numerous issue with the main power relay failing under drivers dash.The other common issues is the water temperature sensor and wiring to the ecm .Least common is a faulty ecm.I would start with the main power relay.
Customer: replied 7 years ago.

thank you for this information it would appear that all the relays would have numbers on them, could you please tell me the number on the main power relay

Expert:  Cardoctor74 replied 7 years ago.
Should be labeled 109.
Customer: replied 7 years ago.
thank you have already replaced relay 109 where is the water temperature censure located and if i disconnect will that rule out that problem?
Expert:  Cardoctor74 replied 7 years ago.
The sensor is located on the right side of the engine near the top, at the back. It is in the coolant fitting directly behind the hose from the rad, just left of the thermostat. Be careful to disconnect the wires, and not remove the sensor, or you will loose a lot of coolant. The sensor is held in by a separate plastic clip, and the harness just has a little built in clip on the side.
Customer: replied 7 years ago.
disconnected the plug off the overhead sensor and this plug has 4 wires but it has made no difference
Expert:  Cardoctor74 replied 7 years ago.
Ok the glow light did not come on when it was disconnected.If not then you need to check the wiring at the ecm alot of times the wires get corroded and break.If not then is could be the ecm itself.This is the next step.
Customer: replied 7 years ago.
is the ecm located under the bonnet right in front of the driver with 2 multisockets 1 larger than the other
Expert:  Cardoctor74 replied 7 years ago.
Yes.
Customer: replied 7 years ago.
what colour of wire is most likely to cause the problem. would it be more likely to be in the big socket or the small one.
Expert:  Cardoctor74 replied 7 years ago.
Check to see if the harness rubbed against the ecm and rubbed through.Also it would most likely be in the big connector.If it all checks out ok then it can be the ecm itself.
Customer: replied 7 years ago.
have checked all wires inside the 2 sockets, all clean and intact. Can you sugest anything else? Is it possible for you to tell me which wires feeding the ecm should have power in them, to ascertain if voltage is going to the ecm unit.
Expert:  Cardoctor74 replied 7 years ago.
You checked the glow plug relay correct?
Customer: replied 7 years ago.
I bought a new one.
Expert:  Cardoctor74 replied 7 years ago.
Ok still same issue correct?
Customer: replied 7 years ago.

yes. Is there anything else we can try?

 

Expert:  Cardoctor74 replied 7 years ago.
OK if all checks out then its very possible the issue is in the ecm itself .Could be shorted internally causing this issue.
Customer: replied 7 years ago.
would it be possible to speak to someone over the phone. Our number is XXXXX Cheers
Expert:  Cardoctor74 replied 7 years ago.
Unfortunately we are not able to contact customers directly Just Answer policy.