My son’s 2000 2.0 liter VW Bettle won’t start (this is his first car). He started having issues with it stalling on him. There was a code for a bad cam position sensor so I replaced it. He took it around the block and it died. This time it said crank positions sensor, so I replaced that. Here’s the part that doesn’t make any sense, it’ll turn over but reads no RPMs. You can put it gear, push it and drop the clutch and then it’ll start fine. We’ve done this several times. Please help me and my son, we’re about ready to get rid of this headache.
Well, that is a puzzle. First step is to test if you are getting a spark at the spark plugs during attempted cranking or not. Ask your shop to do that test for you. If I were to venture a guess. faulty crank position sensor. It might only work when the velocity of the crankshaft as it whizzes past the sensor is fast enough. Maxwell’s equations about electrical induction governing the situation. That would explain why you can start it by pushing.
Hey thanks for the reply!
Okay, my son and tried it again last night. I checked for spark and there wasn’t any. We pushed the car down the driveway and dropped the clutch, then we tried turning it over and it fired right up. Doesn’t make any sense I know but this has worked every time the car has refused to start. I also check a couple days ago and it was giving me a code for crank position sensor which I replaced about three weeks ago.
It could be a bad battery or alternator. How old is the battery? You can get it checked at a chain auto parts store. If the battery is OK, pull the alternator and get it checked.
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My wag, the contacts for the ignition are failing when the switch is turned to the crank position. If you leave a dome light on does it go out when you crank the engine? If so is that normal for the vehicle?
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Replace the ignition coil.
The computer operates the ignition coil in two modes.
These are the start mode and the run mode.
When starting, the computer allows full voltage from the coil to make sure the cold engine with a rich fuel mixture starts. This is the start mode
Once the engine starts, the computer drops the voltage from the coil. If this wasn’t done the high voltage from the coil would fry the coil and plug wires. This is the run mode.
So, what has probably happened is the start mode of the coil has failed, and the engine won’t start. But run mode still functions. And that’s why the engine starts with the ignition switch in the run position, and by popping the clutch.
Tester
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If you see no spark at the spark plugs during ignition key (key in ‘start’) cranking, and that’s consistent, should be easy for a shop with VW experience to diagnose. Good comments above. Common sense says to check for diagnostic codes first. I’m guessing it’s one of these
- s10 (10 A), s229 (15 A) , s237 (10A) fuses
- coil (it appears the coil may also contain the solid state ignition module noted below)
- ignition module (part of coil ass’y?)
- ignition switch
- crank position sensor (or the thing it senses, or the wire from it to the computer)
- battery voltage below 11.5 volts during cranking
- camshaft position sensor
Thanks everybody for all of the suggestions! I should have stated earlier all of the parts and sensors that I have replaced. Cam and crank position sensors, timing belt kit, temp sensor, thermostat, oil pressure switch, spark plugs, and ignition coil pack.
My son bought this car back in February of this year. He had issues a few times where the car would stall out on him but I chalked it up as him driving a manual transmission.
Then one day the thing died on him while he was driving down the road but this time it wouldn’t start again. I pulled him home and started checking things out. I replaced the cam position sensor along with the timing belt kit. He immediately took it for a drive and it made it about three miles before it died again. This time there was a code for the crank sensor.
So I replaced the crank sensor. This whole time my son was telling me the guy that he bought it from is telling him to replace the coil pack because he was having the same type of problems before and he replaced the coil pack and everything was fine.
I eventually broke down and bought the ignition coil pack and installed it. But I’m still having this non-start issue from time to time.
The thing that I don’t understand is how can it start after I push it down the driveway and drop the clutch. It doesn’t even have to start when pushed, its like the engine just has to rotate a little. Then she’ll fire right up by turning the key.
There is currently a P0322 code for the crank position sensor but it’ll start right up.
The spark plugs won’t fire unless the engine computer senses that the engine is turning. It uses the crank position sensor (aka engine rpm sensor) to make that determination. By all accounts when it cranks but doesn’t start, the computer isn’t seeing the engine turning when it actually is. Also if the computer loses the rpm signal, it won’t fire the spark plugs even if you are driving down the road, and hence an immediate stall The p0322 code means the computer isn’t seeing the rpm signal consistently, which it should. That’s a huge clue, and cannot be ignored. That’s what the diagnostic system is supposed to do, give you clues like that.
Suggest to focus on the crank sensor and the wiring harness between it and the ecm (computer). Check the resistance of the crank sensor (i.e. engine rpm sensor). Disconnect the 3 pin harness & measure the resistance between pins 2 & 3 of the sensor. It must be between 480 and 1000 ohms (sensor side). Verify there’s no short circuit between pin 1 and pin 2 or 3, infinite ohms ( the sensor).
If the sensor tests out ok, you could still have opens or shorts in the wires between the sensor and the ecm. Tracing those out probably requires the help of an experienced shop. If you think you can do it yourself, you’ll have to secure a wiring diagram and verify the crank sensor wires make it to where they are supposed to go on the ecm connector.
Also there could be a problem with the gadget the sensor senses, the sensor wheel. When you remove the sensor you can see that. Make sure it is fit securely, is not damaged, and has minimal run-out (same gap between it and sensor independent of rotation angle). There’s different crank sensor part numbers for the other two engines that were available for this car, so make sure you are using the correct part number for the 2L AEG engine.
As a last resort, find a shop with an o’scope and have them watch the signal from the sensor during cranking. They may spot something weird going on. If everything about the sensor checks out ok, then the no-spark must be due to something beyond the crank sensor; i.e. the engine computer actually is seeing the rpm signal, and is firing the coil, but there’s no spark b/c the coil isn’t working. It’s also possible (but unlikely) both the crank sensor and coil are working, but the engine computer is faulty.