My 2001 Volkswagen Jetta VR6 will crank and crank but it will not start. I have replaced the fuel pump and the fuel pressure regulator.

The fuel pump relay does work, and the number one spark plug fires.

I was told by local mechanic that works on foreign cars and said I need to reset the computer. Is that true, or do I need to do something else?

3 Answers 3


It is rare that the ECU (computer, engine control unit) fails. They are designed to require no resetting, and also, consider this: if you turn the ignition off, the car computer will anyway reset mostly (well, it will keep some parameters in memory, but it is unlikely that those parameters would cause a failure to start). If you really want to reset the computer, you can do that simply by detaching the battery. I don't believe, however, that this would help.

What is the cause, then? Could be anything. No spark could be one possibility. Do cylinders 2, 3, 4, 5 and 6 have spark? You only said that cylinder 1 has spark. No fuel could be another possibility. You said that fuel pump is brand new, but it is in theory possible (although unlikely) that it doesn't work. You need to somehow find out if fuel is injected into the cylinders. Lack of compression or a huge vacuum leak could also cause an inability to start, but there's plenty of redundancy in 6 cylinders so I don't believe lack of compression is the cause. Consider also the possibility that some critical sensor such as the crankshaft position sensor has failed.

In my case, on my 1989 Opel Vectra, I had exactly the same problem. The cause? Bad ECU relay. Occasionally it started, occasionally it didn't, and I diagnosed the ECU relay to be the cause. Replacement solved all problems.

  • I will check all spark on all wires and will try and find ecu relay and replace . I will get back to you Feb 11, 2017 at 19:56
  • Where is the ecu located please ? I've googled like crazy Feb 11, 2017 at 21:30
  • I don't believe your ECU is the cause. ECU relay? Could be, but that was just an example. Not all cars have an ECU relay. Your car is definitely newer, so it may be it has no ECU relay. Usually, the relays are in a relay and/or fuse box inside the engine compartment.
    – juhist
    Feb 12, 2017 at 7:35
  • Going to start with the crank sensor Feb 13, 2017 at 2:55

If any of your sensor etc. are broken, it would be logged in the computer. You need a VAG tool to read the computer log. If it is not logged, you can still read runtime values and determine what malfunctions exactly.

Resetting ECU is NOT a solution, it may work in some cases because computer records runtime values and adapts so resetting may force it to behave slightly differently. But resetting ECU would just be a bad workaround which will last for a short while. So your mechanic thinks the 2001 model car was working fine until today but now it needs a reset? :) it seems unlikely to be true, doesnt it?

If your mechanic does not have VAG tools, you must switch to another place which utilizes "modern" (used since 90s) tools. If you don't use the tools, you will keep replacing components until you find what is the real problem. Just a big waste of time and money.

For your car, I believe cheap chinese KKL usb interface should work (I use one on my vw 2002 golf mk4) and costs ~$5. You should be able to use it with VCDS-Lite for basic diagnosis. http://www.ross-tech.com/vag-com/cars/applications/golfjetta.html

Surely, it is a good investment to buy the cable for yourself. But most importantly, your mechanic should read your computer for errors anyway. Just as a notice, OBD and VAG interfaces do not work the same way. OBD may give basic info about a problem but it is very limited. You need to use a VAG specific tool.


I suspect the car isn't starting because it isn't seeing the transponder in the key. These cars are immobilised by a system whereby the ignition key, instrument cluster and ECU all talk to each other. The car will only start when all components are happy. The key contains a chip which communicates via a ring embedded within the housing of the ignition cowl.

Your best bet is to find someone with VCDS / VAG-COM software to interrogate the car for fault codes.

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