VlatcheLupo Posted June 7 Report Share Posted June 7 (edited) I have Lupo 1.4 TDI, year 2000. I believe I am the second owner. What part might have a problem when outside temperature is 35 degrees Celsius? So its like being dead. You just hear the engine willing to start when you turn the ignition key, but something is not right and so, you car is useless... And then when the car cools down, during the night, as if that part cooled off, and it starts immediately, the next morning. Hmm I am not a car dude but can understand basics. Could be the Tandem pump? It was leaking fuel, although the mechanic fixed this problem 2 years ago. Or could be the fuel pump? Or could be the fuel heaters? It will not start until I see the yellow coil icon on the dashboard and hear that buzzing noise. The computer relay circuit? The mechanic changed that with new one, so it cannot be electric problem? Edited June 10 by VlatcheLupo Quote Link to comment Share on other sites More sharing options...
VlatcheLupo Posted June 9 Author Report Share Posted June 9 Oki, i guess i should bring the car to the mechanic and leave it there few months until dude finds what is the problem Quote Link to comment Share on other sites More sharing options...
lupo 1.7sdi Posted June 9 Report Share Posted June 9 If the glow plug light does not appear when the ignition is turned on (even for a very short time) then the problem is strictly electrical (the ECU is not being powered). 1 Quote Link to comment Share on other sites More sharing options...
ObjectiveAway Posted June 10 Report Share Posted June 10 (edited) On 6/7/2025 at 11:41 PM, VlatcheLupo said: It will not start until I see the yellow coil icon on the dashboard and hear that buzzing noise. Isnt that buzz from fuel pump in tank? Seems like be your pump is goner, but you can test it very easy, when you cant start the car you need to give the pump a little tapping, for example tapp bottom of the fuel tank with stick or remove the cap under seat and lightly tap the top of fuel pump, that is often enough to make it work once again. The same works for starter motors, thats why bosch made a beautiful sticker: The problem is definitely not glow plugs, you can drive without them, especially no need for them at 35c. Edited June 10 by ObjectiveAway 1 Quote Link to comment Share on other sites More sharing options...
VlatcheLupo Posted June 10 Author Report Share Posted June 10 2 hours ago, ObjectiveAway said: Isnt that buzz from fuel pump in tank? Seems like be your pump is goner, but you can test it very easy, when you cant start the car you need to give the pump a little tapping, for example tapp bottom of the fuel tank with stick or remove the cap under seat and lightly tap the top of fuel pump, that is often enough to make it work once again. The same works for starter motors, thats why bosch made a beautiful sticker: The problem is definitely not glow plugs, you can drive without them, especially no need for them at 35c. Hmm, what an idea! Would have never have thought of. Thanks!! Isn't TDI engine using fuel heaters and not glow plugs? Quote Link to comment Share on other sites More sharing options...
lupo 1.7sdi Posted June 11 Report Share Posted June 11 It has glow plugs (the radiator you see under the car is a cooler, not a heater). They play a role in starting the engine easily at temperatures below 5° Celsius. If the engine is ok, it starts without glow plugs even below this temperature, but more difficult. Be careful with one aspect: the glow plug indicator light has other roles besides signaling the operation of the glow plugs. When you turn on the ignition, it must light up briefly even if the coolant temperature is high enough so that it is not necessary to use the spark plugs. If it does not light up briefly, it means that the ECU is not getting power (if you have a tester, you will notice that it cannot connect to the ECU) and implicitly the fuel pump will not work either. However, from my knowledge, the 1.4TDI does not have a fuel pump in the tank, so you do not hear much. But even if the glow plug indicator light does not light up, the starter should turn over, it has nothing to do with the ECU. 1 Quote Link to comment Share on other sites More sharing options...
ObjectiveAway Posted June 11 Report Share Posted June 11 13 hours ago, lupo 1.7sdi said: the 1.4TDI does not have a fuel pump in the tank I don't really know, because I have never had 1.4 TDI, but google shows me Lupo 1.4 TDI fuel pumps from tank. @mk2 You have this engine, can you tell? 1 Quote Link to comment Share on other sites More sharing options...
lupo 1.7sdi Posted June 11 Report Share Posted June 11 I don't have one either, but neither in Autodata nor in ElsaWin (I consulted both the electrical diagram and the assembly diagram of the fuel tank) I couldn't find the fuel pump. Anyway, it needs to be clarified whether the spark plug light comes on or not when the ignition is turned on when it doesn't start. A diagnosis would be very useful. 1 Quote Link to comment Share on other sites More sharing options...
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