Weird starting problem with solution
12-12-2008, 09:07 AM
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Weird starting problem with solution
Perhaps this will help others who might encounter the same problem.
99 A4 1.8T Quattro Tiptronic: go to start the car and starter fires but hear relay(s) clicking under dash and car will not start. Same clicking sound happens when the ignition is turned on but starter is not engaged. Clicking is the fuel pump relay enaging and dis-engaging. Replaced battery, no change. Verified that the fuel pump relay is working (it was). Discovered that if I unplugged the throttle-body connector the clicking stops, but car will not start. Removed the throttle-body and verified all the sensors are OK. Pulled fuses one at a time to try and isolate the problem based on the assumption something is loading down the battery. No luck. Finally gave up and took the car in to local Bosch certified mechanic (whom I trust).
He pulled the ECU and noticed there was coolant on one of the connectors. Cleaned up the connector and now the car starts perfectly. Traced the coolant back to the coolant sensor which was leaking into the wires and under pressure forcing the coolant back into the ECU connector. He replaced the sensor and completely cleaned and dried the ECU connector. Car has started and run perfectly for 3 days now.
Not sure if I would have figured this one out myself.
99 A4 1.8T Quattro Tiptronic: go to start the car and starter fires but hear relay(s) clicking under dash and car will not start. Same clicking sound happens when the ignition is turned on but starter is not engaged. Clicking is the fuel pump relay enaging and dis-engaging. Replaced battery, no change. Verified that the fuel pump relay is working (it was). Discovered that if I unplugged the throttle-body connector the clicking stops, but car will not start. Removed the throttle-body and verified all the sensors are OK. Pulled fuses one at a time to try and isolate the problem based on the assumption something is loading down the battery. No luck. Finally gave up and took the car in to local Bosch certified mechanic (whom I trust).
He pulled the ECU and noticed there was coolant on one of the connectors. Cleaned up the connector and now the car starts perfectly. Traced the coolant back to the coolant sensor which was leaking into the wires and under pressure forcing the coolant back into the ECU connector. He replaced the sensor and completely cleaned and dried the ECU connector. Car has started and run perfectly for 3 days now.
Not sure if I would have figured this one out myself.
12-17-2008, 03:56 AM
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Re: Weird starting problem with solution
Any idea which coolant sensor?
I had my ECU out over the weekend while installing a Boost Gauge and noticed fluid at the connector? I cleaned it up and after I reinstalled the ECU IU had trouble getting it to do the TB adaptation, but finally did get it and all way fine. The last couple of times I've tried to start the car I noticed what I thought was and electrical short or something just as I turned on the car but it immediately stopped once the car started. Now this morning the same thing happened but the car started fine then wile driving in to work, it made the noise again after hitting some bumps, the CEL came on and I had no power for a about 45 sec.
I pulled the codes and Fuel pump relay among others was listed. Now I'm thinking that maybe the fluid at the connector to the ECU could be the problem.
I had my ECU out over the weekend while installing a Boost Gauge and noticed fluid at the connector? I cleaned it up and after I reinstalled the ECU IU had trouble getting it to do the TB adaptation, but finally did get it and all way fine. The last couple of times I've tried to start the car I noticed what I thought was and electrical short or something just as I turned on the car but it immediately stopped once the car started. Now this morning the same thing happened but the car started fine then wile driving in to work, it made the noise again after hitting some bumps, the CEL came on and I had no power for a about 45 sec.
I pulled the codes and Fuel pump relay among others was listed. Now I'm thinking that maybe the fluid at the connector to the ECU could be the problem.
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