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Mk3 jetta cranking no start!!

17K views 28 replies 7 participants last post by  brian500 
#1 ·
I have a 1995 Jetta GLX Vr6 that I picked up about a year ago.
-Manual
-153k
-european obdII (Got a mil on the dash right before it wouldnt start at all, but was unable to read it because no shops in my area had the right connector to fit) The starts were getting harder at this point.

Since the middle of summer I have been having a hard starting problem, not all the time but often enough to be annoying. In reading some of the fourms here it looked like it was the coolant sensor. So I replace that and nothing changed. The car was still drivable even though it didn't start the first time every time. pinning the gas pedal to the floor or feathering it seemed to help in the beginning. After a while this didn't even help. I would cycle and crank the ignition 15 or 20 times and eventually start.:banghead: I noticed that when cranking the engine would only fire if the lights on the dash flickered right after i turned the key over.(not sure what that means). I pulled it into my driveway a couple weeks ago and haven't been able to start it since.

Since it died I have:
- tested the crank sensor I had and it was reading 900ohms
- checked for spark at the plugs, NONE. Spark at the coil, NONE.
- checked for power to the coil, GOOD. checked the resistance in the coil module, GOOD.
- checked for a singal from the crank sensor to the injectors, NONE.
- checked for fuel pressure, GOOD.
- tested all the relays under the dash and the one in the engine compartment, GOOD.
- checked all the fuses, GOOD.

Everything seemed to point to the crank sensor and in talking to a couple of mechanics, was told that checking for resistance in the sensors wasnt that good of a test so I replaced it, STILL WONT START.

- Cleaned all of the electronic connections under the hood.
- Pulled the ECU and checked it for any kind of damage or bare wires, NONE.

There are a couple of interesting things that are also happening at the same time, the back windows are tempermental, only going up or down when they feel like it (since I bought the car). The trunk would only pop if I pressed the buttion a million times.

Also when the car did start it was easier to start in the morning when it was cooler.


Where is the ecu Relay? is that the one under the hood? I have read in these fourms that a bad one can cause similar no start problems, but nobody stated the location of this relay.

Also when I was looking over the engine bay when It died I noticed a small fuse block inline of the ground cable right off the battery. The thin piece of metal that connected the two ends of the ground cable was blown apart, but the 20amp and 5amp fuses that also reside in this block were intacked. I dont know what this thin peice of metal is, nor do any of the mechanics I know.

I feel stuck, like I suck, and I really need some direction so any help would be greatly appericated. The car only cost me $800 and $300 for the alternator it needed. Im really not trying to sink a ton of money into this car, so I really dont want to tow it to some hack job shop around here and get FU*KED for $500.
 
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#2 ·
Sounds like the crank sensor is most likely causing this. The resistance of the crank sensor should be 500-700 ohms. Which would also make sense when you say the car started easier when it was cold. Crank sensor problems usually first appear when you try to restart the engine while it's still hot. The heat directly affects the resistance. When heat goes up, resistance goes up.
 
#5 ·
The fuel pump kicks on and I have pressure at the rail, but most importantally I'm not getting spark so I dont really see it being the fuel pump, and the injectors failure to fire.

I feel an electrical problem here,
Everything points to the crank sensor, but I just put one in two days ago and nothing, nothing at all :facepalm:

Should I try a differnent one>?

REALLY CONFUSED
 
#15 ·
not really, everything seems to be point to the ecu, but in talking to some people the idea of cam sensor came up. Is it true that the car will not even crank if the cam sensor is bad?
How can I test this sensor, anyone know what the resistance should be in this sensor?
 
#16 · (Edited)
No that's not true. The cam sensor is not necessary for cranking or even running for that matter. And the cam sensor is a different animal all together from the crank sensor. The crank sensor is a pulse generator so it has a coil inside you can measure the resistance of. The cam sensor is a Hall effect sensor and has no coil to check for resistance. The bentley outlines a function check using an L.E.D. to check for switching. Essentially, the cam sensor only helps to give a more accurate TDC position for ignition and fuel injection timing.
 
#26 ·
OP: have you had any luck figuring it out? i had a previous car do this as well and it ended up being the dumbest thing. a couple wires were loose at the big connector on the right hand side (facing the engine from the front of the car). i simply disconnected it and reconnected and it started/ran soooo much better.
 
#27 ·
silmilar thing happen to a friend, something went wrong with his ignition switch (wiring) and the car would crank but not start. it would start occasionaly. he found out that if he put pressure downward while turning key it would start everytime. thats y i mention switch :thumbup:
 
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