97 Jetta GL - Hard Start when Cold

[LuvmyVW]

I noted some similar threads on this forum, but with slight variations. Figured I'd post to see if anyone could help.

When it's cold outside (below 20degF) my 97 Jetta GL 4 cyl, 2.0L automatic turns over and trys to start but has a hard time firing. The battery tests at full voltage, and the starter, coil, coil wires, cap and rotor have all been replaced. All of the battery and ignition contacts have been cleaned. Plugs and wires have been checked and they are good. It's almost like it doesn't get enough compression to start until it turns over enough times to warm up the system and then it'll start.

I'm careful that if it doesn't start right off to mat the gas pedal to engage the automatic shutoff of the fuel valve to prevent it from flooding. As soon as it starts to try and fire I release the pedal to allow fuel flow and it then typically starts.

All of this takes 5-10 minutes depending on how cold and I'm concerned with killing my starter or doing other damage. Is there anything else I can check that I haven't already?
Thanks for any help

[Trekker]

I have the same thing... isnt as bad after an oil change... Im thinking of replacing the oil pump

[LuvmyVW]

Thanks for info. If you do replace the pump let me know how it works out.

[pmartino]

I had a similar problem on a Plymouth Laser, lived with it for 2 years and then did some reading... turned out there is a sensor that tells the computer how rich the fuel mixture should be. The colder it is the richer this mixture needs to be. When this sensor (a variable resistor) was faulty the computer always thought is was warm out and took forever to start because the mixture was too lean.

It's called a coolant temperature sensor I believe... there should be 2 of them, 1 for the rad fan and one for the computer. You might be able to test it before you change it but I can't find the info in the Jetta Haynes book.

[LuvmyVW]

Thanks for this info. I know the system thermostat is good. Your suggestion makes sense since after I let it turn over a gazillion times it starts and then runs fine which make sense as the components are warmed up enough by then. I'll have the shop check for other sensor issues, O2 and other fuel mixture sensors. I'll post again if I get a resolution.

Anyone other suggestions are greatly appreciated.

[boschmann]

He's referring to the coolant temp sensor for the engine management. It's loacted in the plastic flange where the upper radiator hose goes into the cylinder head, the blue one. The sensor should read 2000-3000 Ohms cold (68F) and go down to 200-300 Ohms @ operating temp (190F). I don't know what it would be below 20F, but would expect 5000 Ohms or so.

[LuvmyVW]

Thanks for clarifying. I just had it checked and the coolant temp sensor tests out fine so that's not it. Bummer.
Boschmann, what do you know about putting an engine block heater on this vehicle. I have a friend with a 98 Jetta who has one and it works great. I'm thinking this may solve my problems for less money than continued diagnosis by the mechanic. The heater pump is relatively inexpensive and we can do the work ourselves. Any warnings or cautions for doing this

[boschmann]

I don't think it's a good solution to your problem, but I don't have a prblem with the aftermarket coolant heaters. I prefer the simple heating element type type that goes in place of a freeze plug to the ones that go in a hose & have a circulating pump. Anytime you start cutting & diverting the cooling hoses you can introduce a problem. When the car does start (after a hard start episode) does it run properly? Once warm does it restart easily after sitting for an hour ot two? Do you have access to a basic fuel pressure gauge?

[madbomber1]

I have exactly the same problem except my car is a 1998 jetta GL. I get the feeling that it is fuel pressure related. I too measured the temp. sensor and read about 2K ohms. Try turning on the key and wait for 30 seconds. My manual says to wait 30 seconds if it does not start?