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2002 Jetta TDI Won't Start When Engine is Hot

Hey everyone,

I’ve got a 2002 Jetta TDI that’s been playing stump the mechanic for the past two weeks. I’ve had about $800 worth of work (most of which had error codes and were necessary), but given that the next suggestion is to replace the fuel pump at a cost of ~$2k, I figured it was time to get some additional opinions.

When the car is completely cold, the engine typically turns over a few times before starting up. Sometimes a few turns into seven or eight, but I’ve never had it not start. The problem comes when I’ve driven it somewhere (like to the grocery store, yoga class, or to get gas, to name a few) and try to restart it after my task is done. The warmer the engine, the lower the chance it will start. In it’s most extreme, the car will not start at all, and I have had it stall out on me at stoplights if I do manage to get it started.

The car has had a history of intermittent hard starts in the four years I’ve had it, but nothing at all like this.

In the past two weeks, my mechanic has replaced the coolant temperature sensor, thermostat and seal ring, serpentine belt tensioner and serpentine belt, power supply relay, fuel pressure regulator and seal rings and the crank sensor. They’ve also been able to see that something is off about the fuel pump since they can see air bubbles in the fuel line, but thought I could push the car for a while without having to replace the pump.

Thoughts? Anyone agree or disagree with my mechanics? Anything else I should tell them to check for? Given that the blue book for the car is only $3800, should I be thinking about a new one?

Thanks in advance!

Your ignition relay is shorting out. One of the contacts is shorting against the metal case of the relay. For some reason the relay expands just enough to where there is a short. Happened on our 87 Jettas (we had 2) and especially dangerous on the freeway driving 70, middlelanes. .

Relay on our 87Jetta was in the cabin, under the dash, left of steering, Square metal rectangle, It is a plug in part- was a cheap part. GL

Has anyone checked the fuel filter on this car?? Diesels are very sencitive about dirty filters as they are also water seperators.

I find it hard to believe a good mechanic can’t fix this, if he has seen it happen.
Does he, by chance, own a boat or a house on a tropical island someplace?

As a follow up a Diesel motor is very basic when it comes to running as there is no ignition system… ALL you need is Fuel and Compression… The issue as you are finding out is there are a few reasons for poor fuel pressure. One can be the pump, but like I said above make sure someone has checked those filters. This is more true if they have not been changed…

OP, We even had the computer module changed. It is the relay.

Check the new relay to insure there is enough clearance. You will see it.

It sounds like your mechanic is on the case. Those are all the thing’s I’d have thought of. I probsablyu wouldn’t have changed them out until they were proved to be not working, but that’s a judgement call.

Pay att’n to what @longprime is saying, seem sto be speaking from experience. If it’s not that, I’d guess next to check the fuel pump relay, O2 sensors (if you have them on a diesel), or the fuel injector pump.

$2K for a fuel pump! That’s high even for a diesel. I’d certainly follow up on the relay possibility and before you give the OK on the fuel pump make sure the mechanic checks the fuel line pressure.

How many miles on your Jetta? It should go at least 250K before needing replacement.

There absolutely must be no air bubbles in the fuel line of a VW diesel, TDI or IDI. Get that air leak fixed first. Then post on if you still have the starting problem. Many more diesel experts and owners there.

it I remember, Our Gas Jetta, had 2 pumps. and yes we changed the gas tank pump.

The fuel filter was the first to be changed.