Posted by Andrew West on November 30, 2006, 11:24 pm
This Golf has come from another garage with a poor starting problem.The other garage had already changed the crank sensor,because of a fault code listing it. I have replaced the in tank pump after looking up posts on the tdi forum about noisey pumps failing & being replaced under warranty, also causing poor start problems & cutting out.I tested the low pressure first before replacing the pump & it was approximately 12 psi.The pump would make a noise when it primed the system, but not every time.When i removed the pump i found that the noise was from the fuel blowing out the pressure relief valve.The new pump that i fitted makes the same noise & the pressure is the same also. I have just made up an adaptor to test the tandem pump pressure & it is about 50psi(3.5 bar) at idle,which autodata states is correct.The pressure doesn't build up until the engine fires up which i assume is probably correct.I have checked for air leaks & replaced the lower "o" ring on the filter "t" piece. I have also tested the heater circuit , which appears to be ok when activated through the scan tool,but doesn't come on when the ignition is turned on, which i think is normal unless the temperature is really low. There was also a fault stored for the coolant sensor,but live data shows it to be about right & the fault didn't reappear after clearing. Scoping the crank sensor (connected across the sensor,not chassis earth),the voltage amplitude is approx 4 volts cranking & 8 volts running.There seems to be a bit of a glitch approx 7 teeth before tdc,but it doesn't always occur & i can't see anything wrong with the teeth & sometimes when testing,the tdc ident mark didn't seem correct,although it doesn't make alot of diference to starting.When testing the sensor wiring i found that all three wires have 2.5 volts with key on ,sensor disconnected.Autodata show pin 3 to the sensor as a shield wire & i would have thought that it should measure less than 200mv,even so, the signal doesn't seem to be noisey.The crankshaft sensor looks like it picks up off a gear on the crankshaft & doesn't look damaged. The dual mass flywheel has just been replaced, because it failed, but the poor starting fault was present before . On the tdi forum there was mention of faults with the t connector to the filter,which i could try replacing or bypassing. sorry about the long post, but the car sales place where it came from is getting worried that the may have to give their customer his money back,if it's not sorted soon. Any help appreciated, Kind Regards, Andrew