# Help! Jetta wont start in hot weather



## 82pickupguy (Feb 22, 2002)

I've got a 1996 Jetta that doesn't want to start now that the weather has warmed up out. It turns over just fine, just doesn't fire. Once it cools down at night it fires right up. I've replaced the mass air flow sensor, manifold temp sensor, fuel pressure regulator, checked to make sure the fuel pump is working. I am out of ideas what to do. Has anyone run into this before? It's got me stumped.


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## keganater (Apr 29, 2008)

I'm having the exact same problem!!! I know I'm losing fuel pressure in the heat and couldn't think of anything but the pump or the regulator, but if you have already replaced yours with no success, then I think I will hold off on mine. I replaced the fuel pump relay with no results (it was worth a shot for $5 shipped). I don't know if this helps or not but I have noticed that when it doesn't want to start, the pump does not run when the key is turned to the accessory position and there is no clicking coming from the relay.
Also, once I get the car to start, I have absolutely no problems...
I'm a student without a whole lot of money and I don't want to start shot-gunning parts at my car. Any help/direction would be very much appreciated 










_Modified by keganater at 2:41 PM 7-17-2008_


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## keganater (Apr 29, 2008)

could it be a bad temperature sensor somewhere??? 
I could really use some help, I need a car to get me to work and back =( ...


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## Blue2.0 (Jul 1, 2008)

*Re: (keganater)*

Engine coolant temp sensor? I've heard those things can produce very weird problems.


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## keganater (Apr 29, 2008)

Ok, so i pulled the connection off of my engine coolant temperature sensor and its got some liquid in there, (maybe coolant). Definitely doesn't look like it should have that. When I pull this sensor is coolant going to leak out everywhere?


_Modified by keganater at 7:49 PM 7-17-2008_


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## FL 2.0L (Aug 1, 2002)

A very small amount will come out if the engine is cold. Top off the reservoir with distilled water. It is always good to have a liter and a half of G12 on hand for these instances.


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## keganater (Apr 29, 2008)

haha well I guess my engine wasn't as cold as i thought. sensor looked ok after I pulled it. Any way to test it before I go buy one?


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## Pry (Nov 27, 2004)

*Re: (keganater)*

crank position sensor


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## MyFriendsCallMeWhiskers (Jun 5, 2008)

*Re: (keganater)*


_Quote, originally posted by *keganater* »_ Any way to test it before I go buy one?

Yeah, you can check the resistance accross the pins...there's a specified range of values a working sensor should fall between. The values are specified in the Bentley, and I've seen them posted before, some creative searching may lead you to those threads if you don't have a bentley. 
I don't know if the values on the sensor vary with make or sensor color (i.e. blue vs. green sensor).


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## 97VWJett (May 17, 2003)

*Re: (MyFriendsCallMeWhiskers)*

Resistance only tells 1/3 of the story. You have to also look at the sensor on either a DVOM or graphing meter like a Fluke 98 and interpret the signal. 
Can you scan for codes?


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## keganater (Apr 29, 2008)

Alright so I just replaced the sensor for $10, a lot easier than trying to test the old one. I also replaced all my vacuum hoses. Still experiencing the same problem. Any other ideas? Thanks


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## Pry (Nov 27, 2004)

*Re: (keganater)*


_Quote, originally posted by *keganater* »_Alright so I just replaced the sensor for $10, a lot easier than trying to test the old one. I also replaced all my vacuum hoses. Still experiencing the same problem. Any other ideas? Thanks

ya i got another idea, replace your engine speed sensor/crank position sensor.


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## keganater (Apr 29, 2008)

why would a "engine speed sensor/crank position sensor" have anything to do with it not starting in the heat? I don't want to just replace misc. parts in my car until i find the right one.


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## vwguru714 (Aug 23, 2007)

*Re: (keganater)*

you say the fuel pump does not run and the relay does not "click" with the ignition in on position when the problem occurs.... maybe check the ignition switch (electrical portion) to see if voltage is going to fuel pump relay


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## 97VWJett (May 17, 2003)

*Re: (keganater)*

We can guess all day and recommend to the OP that he replace this that and the other part. The car needs to be diagnosed!
If you are in the Bellevue area, send me an email or IM and I'll see what I can do for you.


_Modified by 97VWJett at 7:21 PM 7-21-2008_


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## Pry (Nov 27, 2004)

*Re: (97VWJett)*

if you are obd1 try changing your relay 109. its for ecm power and its cheap. if still no go then id get a bentley and learn how to properly test the CPS so you can be sure its bad before buying a new one. 
http://www.germanautoparts.com...364/1


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## bbrooks762us (Jul 25, 2008)

*Re: (Pry)*

Any other ideas out there? I'm still baffled by this thing. It's starting to drive me nuts.


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## dingo222 (May 27, 2006)

I'm having the same problem. 97 jetta won't start when it's either :
1) hot outside and the car has been in the sun,
2) I've been running it for a few hours and turn it off and try to restart it.
I replaced my coolant sensor also with no luck. There is plenty of spark going to the plugs, and air isn't an issue. IT really acts as if its not getting fuel. 
My mechanic is completely baffled. ANy ideas????


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## smokeymountaindub (Feb 26, 2007)

*Re: (dingo222)*

Test your ignition coil.
A small break in the coil windings might allow the car to start when cold, but when hot they expand..... making a small crack a big one.
I'm assuming you've checked for spark and aren't getting any.


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## arekay (Aug 6, 2008)

*Re: (dingo222)*

My Jetta is doing same thing. Seem to the heat inside the car causing the problem...most likely electrical. If I roll down the windows and let car cool out a bit, starter will turn over and I'll have no problems. Did you find a fix? Seems to be a common problem.


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