# 1996 Jetta difficult start and wont stay running....Sensor problem?



## argdnam0 (Nov 19, 2007)

Hi,
I have a 1996 Jetta with 120,000 miles on it. It just recently got a new clutch and about a week after that it started having problems.
At first it wouldn't start, I replaced the fuel pump and the fuel pump relay, then after a lot of cranking it finally started but when I went to drive it it seemed to randomly shut itself down. I could never get further than a block and it would do this. It idles great and when I wasn't moving the engine would rev up no problem
Then I changed the fuel filter thinking that it was restricting the fuel flow and now it starts,(very hard and a lot of cranking,) once idling it is fine, but when I suddenly give it gas it dies, a relay clicks and it takes about 2 minutes of cranking to start it again. If I gradually accelerate it works fine. I was wondering if maybe a sensor could be to blame or if you all have any ideas.
The other thing is that while I am trying to start it it seems to fire very breifly every time just as I release the the key to give the starter motor a rest. It's not enough to start the engine but I can hear at least one cylinder fire. Thanks for any help.Hi,
I have a 1996 Jetta with 120,000 miles on it. It just recently got a new clutch and about a week after that it started having problems.
At first it wouldn't start, I replaced the fuel pump and the fuel pump relay, then after a lot of cranking it finally started but when I went to drive it it seemed to randomly shut itself down. I could never get further than a block and it would do this. It idles great and when I wasn't moving the engine would rev up no problem
Then I changed the fuel filter thinking that it was restricting the fuel flow and now it starts,(very hard and a lot of cranking,) once idling it is fine, but when I suddenly give it gas it dies, a relay clicks and it takes about 2 minutes of cranking to start it again. If I gradually accelerate it works fine. I was wondering if maybe a sensor could be to blame or if you all have any ideas.
The other thing is that while I am trying to start it it seems to fire very breifly every time just as I release the the key to give the starter motor a rest. It's not enough to start the engine but I can hear at least one cylinder fire. Thanks for any help.


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## Andromeda451 (Jan 6, 2006)

*Re: 1996 Jetta difficult start and wont stay running....Sensor problem? (argdnam0)*

Driver,
If you turn the key on and then jump the starter solenoid manually and the unit starts I'd suspect a failed key switch. Also check for good engine to tranny to body grounds. On the ECM equipped cars bad grounds will give one a headache.


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## Dubguy21 (Feb 14, 2007)

*Re: 1996 Jetta difficult start and wont stay running....Sensor problem? (Andromeda451)*

anyone else, I'm having similar problems


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## Andromeda451 (Jan 6, 2006)

*Re: 1996 Jetta difficult start and wont stay running....Sensor problem? (argdnam0)*

Arg,
This may be weird but check the load reduction relay. I have seen issues with Rabbits, Jettas and my Fox where the load reduction relay had failed and it made the car start very hard...


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## ABIMELECH (May 27, 2005)

*Re: 1996 Jetta difficult start and wont stay running....Sensor problem? (Andromeda451)*

This could verylikely be the cranckshaft sensor, you need to check for fault codes to see what you have, if you have something like, engine speed sensor implausible signal, I would replace the rpm and also know as cranckshaft sensor and see if it does start.


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## Space9888 (Mar 18, 2002)

*Re: 1996 Jetta difficult start and wont stay running....Sensor problem? (ABIMELECH)*


_Quote, originally posted by *ABIMELECH* »_This could verylikely be the cranckshaft sensor, you need to check for fault codes to see what you have, if you have something like, engine speed sensor implausible signal, I would replace the rpm and also know as cranckshaft sensor and see if it does start.









thats not a bad point, but if the engine starts then stalls, or doesnt start due to other reason.... you get that fault as well. 
check for vaccume leaks, throttle clamp, maf sensor clamps 
also could be weak battery, or lack of charge, coolant temp sensor, loose maf clamp, or throttle clamp
also as someone else stated could be the ign switch or load reduction relay, could certainly cause this. 



_Modified by Space9888 at 4:43 PM 1-23-2008_


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## ABIMELECH (May 27, 2005)

(1) after a lot of cranking it finally started but when I went to drive it it seemed to randomly shut itself down. This one sounds to me based on my experience a defective hall sender also known as crankshaft sensor or rpm sensor if this sensor is bad the car shuts off due to the following reason, the sensor goes internally into an open circuit. (2) ,(very hard and a lot of cranking,) once idling it is fine, but when I suddenly give it gas it dies. here you need to remove the fuel rail and look through the injectors port down to the intake valves to see if there is any carbon build up, If there is carbon buil up around the intake valves, this will not allow the valve to seal properly therefore you get no compression and that will give you a lot of cranking. (3) If The crankshaft sensor is defective or bad as I describe in (#1) then the (ECM) will not know in wich position is the cranck shaft and it will not fire up. (4) the most important thing here is to check for fault codes first to see then steps ( 2 and 1) if in 2 everthing is ok I'll stick to (1) and see what happens.


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## jasonsp6 (Sep 8, 2003)

I vote the crankshaft sensor. Depending on the temperature/vibration the windings are opening up inside the sensor.
Chances are you will not see any error code for this.


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## jasonsp6 (Sep 8, 2003)

To clarify:
The camshaft sensor is a hall effect sensor. Usually the motor will run with a damaged one.
The crankshaft sensor is a VR or variable reluctance type. The motor will not start/run if this is damaged/open.


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## Space9888 (Mar 18, 2002)

*Re: (jasonsp6)*


_Quote, originally posted by *jasonsp6* »_To clarify:
The camshaft sensor is a hall effect sensor. Usually the motor will run with a damaged one.
The crankshaft sensor is a VR or variable reluctance type. The motor will not start/run if this is damaged/open.

to test it you could use a dvom and check to see how many milivolts a/c it produces as you crank it, through the signal wire pins. the bently should tell you the target voltage generally .3 a/c volts or 300mv(very cold)-1.2-1.8v or 1200mv or 1800mv(room temp). 
you can also check how many ohms the coil is producing in the crank sensor through the pins on the connector generally 800ohms to 1000ohms, this will effect the a/c voltage the sensor produces. the bently manual should have exact specs for that relative to ambiant temp and a cold motor. 
the hall sensor could be checked too by backprobing the signal circuit and ground with a dvom, backprobing is necessary due to the fact that the sensor needs a low voltage supply (cranking engine, with ecm supplies (B+) to the sensor), 
also you could use vag com and while driving find the fp relay adress word and see if it shuts off,
you could also watch the rpm adress words and see if the rpms jump around or cut out since you would be viewing the ecms perspective of the rpm signal
there is also adress words for battery voltage, this could indicate chargning abilities of the alternator and relay cutout
rpm signal keeps fp relay alive (ecm shutting off due to engine speed sensor cutout)
but if the car just cuts out, its bound to be a connection somwheres probably a ground , perhaps the engine harness connector near the trans. 
it could be very complicated or very simple. get your ecm scanned. that will tell you something especially if there is a bunch of ground faults. 



_Modified by Space9888 at 9:56 PM 1-25-2008_


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## TRUEBELIEVER (Apr 7, 2005)

*Re: (Space9888)*

I would backtrack what you did when you installed the new clutch. MAybe your ground isnt tight or you bumped into or damaged something.


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