Cold Hard Starting in Volkswagen Jetta TDI

Nothing more aggravating than getting in your car, cranking it over, and having a no start. But the VW Jetta TDI causes this to be even more of a mystery. Your car may have a problem starting from a cold start, say, after sitting overnight, yet, once started, performs fine. The car after being warmed up can then be parked for eight hours and starting it is no problem. So, for some reason, starting it after it sits overnight and temperature seem to be the issue.

It seems to be an anomaly. It is. What makes it more perplexing is if there are no engine lights or flashing glow plug lights. Some possible solutions to be considered and checked are the following:

  • Are the glow plugs within spec and working fine?
  • Are the temperature sensors still good?
  • Is your fuel pump working at full spec? A FP can work in less than full spec before it suddenly stops sending fuel to the engine without warning.
  • Is your Tandem Pump (certain models) still working at full spec? If the pump is working at less than full spec, it will cause hard starts when cold because the pressure is lacking. A bad tandem pump allows air into the fuel system and causing "loss of prime".
  • Check your fuel filters for clogging
  • Possible air in the fuel line somewhere.
  • Check your anti shutter valve for clogging (some models)
  • Make sure you fuel lift pump is also working properly.

The thing to remember is that a diesel engine relies on pressure and fuel to start. There are no spark plugs and usually glow plugs are not the cause if the temp is above freezing and they are working uniformly within range of one another. Of course, if the engine light is lit, get the codes and see what they say. The engine light does not report mechanical problems. I would start with the 3rd and 4th items, first. A new tandem pump costs $320, VW charges $450.

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m abdullah javed profile image

m abdullah javed 23 months ago

Thanks perrya. A very informative hub. Voted up useful.

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