1.8t died on highway, now won't start

[flip240]

I haven't had a chance to diagnose this much besides what I could manage on the side of the road. The car died while my dad was driving it, and he pulled over to the shoulder. When you put the key in and put it to ON, the lights come on like normal and don't dim when you start it. Problem is when you start it, it will catch for maybe 1 cycle, then immediately die. Very similar problem to the one in this thread: Can't keep it running

I tried unplugging the MAFS to see if that could be causing it, but no change. I've had a bad MAFS on this car before, and unplugging the MAFS caused it to run like crap, but it at least started and ran in limp mode. I've also replaced the engine speed sensor (crankshaft pos. sensor) before; but the symptoms of that one failing were intermittent no-starts. Those never caused the engine to die before, but it's possible? Any ideas?

I work all day Friday and won't have a chance to look at it till Saturday so I'd appreciate any ideas you guys can bounce off me so I can get a better attack come the weekend.

[Smileybug]

Timing belt?

[D2Beetle]

I'm not certain it is the timing belt, could be but I doubt it because the OP said it will catch then die. Unless they got really lucky and the belt slipped one maybe two teeth.

Off the top of my head, something electronic; throttle body, maf, cam, crank, knock, O2 sensors, or coil packs or any combination. Perhaps a vacuum loss.

[simonsi]

I'd suspect the fuel pump or pressure regulator but it could be a number of things. If you can scan it that may save you lots of time and $.

[O 16581 72452 5]

Just something that's not going to be able to be diagnosed through a forum. Best advise i can give you is scan the ECU to start with.

[O 16581 72452 5]

Originally Posted by D2Beetle

I'm not certain it is the timing belt, could be but I doubt it because the OP said it will catch then die. Unless they got really lucky and the belt slipped one maybe two teeth.

Off the top of my head, something electronic; throttle body, maf, cam, crank, knock, O2 sensors, or coil packs or any combination. Perhaps a vacuum loss.

Throttle Body (TPS), Cam, Knock, and O2s won't cause a car not to start. MAF is possible, but usually the car will just run bad. You'd have to have 4 bad coil-packs to even think about not running at all...believe me, i lost two on my Audi and it still gimped me home.

Crank is about the only realistic possibility.

[alexvilla]

Scan it with VAGCOM

[simonsi]

Originally Posted by O 16581 72452 5

Crank is about the only realistic possibility.

My money is on its a fuel pressure problem, pump or regulator. As you say most ignition faults on these will still get you home.

A scan will tell....

[O 16581 72452 5]

Originally Posted by simonsi

My money is on its a fuel pressure problem, pump or regulator. As you say most ignition faults on these will still get you home.

A scan will tell....

That is a possibility too.

[flip240]

thanks for the posts guys, i'll give it all a try tonight. I left work early so I could get the problem diagnosed before Saturday night. I did scan the ECU, but just with a generic scanner, I have a vag-com but my friend borrowed it and i'm going to have to get it back today.

I changed the timing belt 30k miles ago, now at 110k. It was repeatedly cranking like it wanted to start, no metal noises so I doubt it snapped.

[D2Beetle]

Originally Posted by flip240

... It was repeatedly cranking like it wanted to start...

Like this...

[O 16581 72452 5]

Originally Posted by D2Beetle

Like this...

That doesn't sound like it wants to start. :P

[flip240]

You guys were right, I pulled one of the plugs after trying to start it, and it did not smell of fuel. I also tried cranking it with the plug out, and still did not smell fuel coming out of the cylinder. I went behind the seat and unplugged the fuel pump harness and tested the voltage on pins 1 & 4, it registers 12 volts when I crank the engine, but the pump isn't making any noise when I plug it back in.. I guess the pump just up and died all at once??

[simonsi]

Originally Posted by flip240

I guess the pump just up and died all at once??

They can do that... glad you've found it quickly! Hope not too many $...

[O 16581 72452 5]

The fuel pump gets it's voltage from the MAF sensor. You won't get voltage to the pump unless you're cranking the engine or the car is actually running.

Safety thing so if you wreck, the pump shuts off, some cars use oil pressure.

[72SuperBeetle]

When the fuel pump on my mk4 Jetta went out it left me stranded. I lifted the rear seat and tapped on the fuel pump cover with a rubber mallet while starting the car and it fired right up... It was enough to get the car home.--- It's worth a try.

-Good luck!

[simonsi]

Originally Posted by O 16581 72452 5

The fuel pump gets it's voltage from the MAF sensor. You won't get voltage to the pump unless you're cranking the engine or the car is actually running.

Safety thing so if you wreck, the pump shuts off, some cars use oil pressure.

Hmmm, but when you open the drivers door the pump primes - you can hear it clearly, no engine running or cranking then...as with most cars if the ECU doesn´t detect pressure from the pump then it will shut off, running engine or not as it assumes a leak is occuring. The OP did state he was getting voltage while cranking though so his diagnosis looks good whichever of us is right

[O 16581 72452 5]

Originally Posted by simonsi

Hmmm, but when you open the drivers door the pump primes - you can hear it clearly, no engine running or cranking then...as with most cars if the ECU doesn´t detect pressure from the pump then it will shut off, running engine or not as it assumes a leak is occuring. The OP did state he was getting voltage while cranking though so his diagnosis looks good whichever of us is right

Yeah, i didn't remember reading that part, maybe he went back and edited it in...or i was drunk and looked it over. :P

I haven't owned a gas Beetle, but all of my MK3s never primed the pump, it would only flow fuel when cranking or running. I was going to drain the fuel tank by rolling the key over with a disconnected fuel line and found out it only spit fuel when cranking. But like you said, either way, sounds like his issue has been found.

[simonsi]

Originally Posted by O 16581 72452 5

I was going to drain the fuel tank by rolling the key over with a disconnected fuel line

That is, to the ECU, a leak and it will shut the pump off, AFAIK on Mk3's too - most injected engines have had this for many years as a safety feature.

[O 16581 72452 5]

Originally Posted by simonsi

That is, to the ECU, a leak and it will shut the pump off, AFAIK on Mk3's too - most injected engines have had this for many years as a safety feature.

It worked while cranking *shrug*