2003 Volkswagen Jetta start issue - Please help

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Hello,

My mothers 2003 Volkswagon is giving us some major problems; here's a brief history.

Almost 2 weeks ago, one night after work, my mom's Jetta wouldn't start. We brought it to a shop, but when they looked at it the next day, it started right up. It seemed to work well for about 36 hours but then wouldn't start again. We got it towed to the shop once more (using our last AAA tow) and they looked at it over the following week. They said it didn't start for them at first, but they got it to somehow, and a code came up for the "crank" impulse sensor. They replaced it, and all seemed well. 24 hours later (similar to the amount of time we had it before), we were stranded in a parking lot for the third time; it wouldn't start. That was earlier this afternoon and we are going to have it towed to the shop again tomorrow morning.

Some specifics:

- The engine cranks fine, but won't start
- The battery is only a month old, and tested fine. We did notice an annoying humming sound coming from the back of the car (on the inside) though that wasn't there before, around the time the battery was changed. Correlation is not causation, but it did appear at the same time, and sounds like the area the fuel pump would be. The humming changes in pitch when we use the electricity (rolling up windows, turning on lights, air, etc)
- According to the shop owner, however, the fuel pump is fine. I wonder though, could a fuel pump fail in this manner, where it works fine sometimes and is dead during others? It seems like something is working for a day or so, and then "dying out" or something.
- I'm not sure about spark plugs, but I'm hoping my mechanic checked them.
- After trying to start the car, I hear a strange high pitched electrical buzz/whine coming from the engine. Is this normal, could this mean an electrical issue?
- The car drives fine once it starts. No stuttering or loss of power. It's all or nothing at all.

We're concerned because it doesn't seem like the shop can figure out what is wrong with it, and since it starts intermittently, but then fails a day later, the issue is difficult to pinpoint. What issue would cause the car to not start at all, and then, like magic, start up no problem after resting for a day or two, and then drive perfectly? We can't keep affording tows and rental cars, and we would REALLY appreciate some outside help or insights.

thanks so much!
 
They need to do a better job diagnosing this car. Electric fuel pumps fail for a variety of reasons some will disable the car immediately others will cause other problems before total failure.

The noise from the fuel pump area is a clue, there might be an issue with the pump and there may be a pump relay in the engine compartment causing the buzzing noise.
A fuel pump pressure and flow test should be performed when this happens as well as the electrical circuit.
It could be anything from just a failing relay to a pump or wiring or some other problem.

Find another garage, this one seems to be lacking the diagnostic skills.
 
I agree, if it's a 2.0 liter then it's most likely the fuel delivery unit (in-tank fuel pump) that's causing the trouble.

It's a fairly simple system with the following components:

fuel delivery unit: P/N 1J0 919 087 J and can be had for $95
a simple 15amp fuse in the panel on the left side of dash panel
a 50amp fuse on top of the battery: P/N N 104 249 03 $1
and a relay under the steering wheel area: P/N 1J0 906 383 C. This thing costs about $21.

Since the issue is intermittent then don't fool with the fuses. Go straight to the in-tank pump and the relay. Because you have a variance in audible note from the pump then I'd lay my money on that bet. It's a simple R&R item accessed through the trunk access panel. Access it, clean areas, replace pump, replace all gaskets/seals, close it up and drive on. Change the in-line fuel filter while you're down there too. In good VW fashion, clear codes and test drive.
 
I know on the tdi's they will not start if cranking speed is too low. Just wont try.
 
The high pitch electrical buzz/whine is the DBW throttle body. You only noticing it because of the failed start otherwise you'd never know it is there.

I agree fuel pump is more than likely the culprit. They can certainly fail occasionally. Mine did in-tank did in the TDI. It worked once a week until I heard no noise.

However mine is not required to drive as I have another engine driven low pressure pump. It was basically just the helper pump.
 
Originally Posted By: Thermo1223

However mine is not required to drive as I have another engine driven low pressure pump. It was basically just the helper pump.

I thought that when the in tank pump in a diesel failed, the distributor pump had to work extra hard, and could fail quickly.

But maybe that only applies to the 1998-2002 Cummins 24V Dodge Ram.
 
I would recommend having a VW shop look at the immobilizer and ignition keys. There is little correlation between a crank sensor and a fuel pump. I suspect the fuel pressure will test good. I was a service writer at a VW dealer back in 2001. The techs had difficulties over these kinds of problems even though they had the actual VW diagnostic tools. Without such tools, it becomes an expensive guessing game. The engineering of the electronics on these cars is not known for being good.
 
Originally Posted By: artificialist
Originally Posted By: Thermo1223

However mine is not required to drive as I have another engine driven low pressure pump. It was basically just the helper pump.

I thought that when the in tank pump in a diesel failed, the distributor pump had to work extra hard, and could fail quickly.

But maybe that only applies to the 1998-2002 Cummins 24V Dodge Ram.


I think if it were a bigger engine like a Cummins than I agree. It wasn't a long run from the fuel tank to the engine. The worst thing going for PD VW TDI's was that depending on the year you could get a pump with or without the checkvalve. If you had the checkvalve then you had no fuel flow without a working lift pump. Otherwise the tandem pump on the engine could easily still pull fuel as long as it never lost prime.
 
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