Ahhh TDI help? PD Jetta

[wolf_walker]

I'm out of ideas (and it didn't take long since it don't have a VE pump ), but my buddys last year made A4 Jetta PD suddenly quit the other day.
We did the t-belt not too long ago, few months, and it's intact, it cranks over evenly so I tend to not think mechanical.  The lift pump wasn't lifting much, so it's replaced.  It will occasionally, at random, start and run fine for a few seconds, but mostly nothing.  The glow plugs work, it had no codes per vagcom right after it died.  Flow while cranking from teh return line is low compared to the lift pump's feed ability. 
My last thought and coming from the occasional starting briefly is fuel pressure.  Tandom pump?
It was replaced under warranty awhile back, there is a little ick on the vacuum side fitting but not a ton.  I see the test spec is at 1500rpm, can it even be tested below that via the pressure port?  I have not had a chance to poke through vagcom for missing input signals, but I'm bout out of ideas, I don't do newer cars other than 986/996 Porsche stuff.  Thoughts?

 

[Vincent Waldon]

So it's not throwing any codes??  Scanned with VCDS?

[wolf_walker]

He checked it first off with vcds, yes, nada for codes.  I know on newer german gassers they will not always toss a code for a fault that will stop it from running, I just don't know this system.  I thought I saw a crank sensor on the lower drivers front of the block, I told him to look for a signal from stuff such as that when cranking tomorrow.

[cyrus #1]

We had a crank sensor go bad on our PD a few years ago.  It would turn over quickly pretty much indefinitely without starting.  It was accompanied by a check engine light and a rather startling beep during cranking though...

[the caveman]

I would also guess the crank sensor. same problem will also sometimes not show a code on a gasser.

[BigVWman]

I thought crank sensor DOES throw code? Within first 6 seconds of cranking i was told

[the caveman]

I thought crank sensor DOES throw code? Within first 6 seconds of cranking i was told

Yes you could be right, but on the gassers, if it doesn't start, and the problem is the crank sensor, it won't . It will only show an intermittent failure while running, which is counter intuitive, because if there are no hard codes or other issues [bad fule pump, coil etc] the only thing that will keep it from firing is the crank sensor

[Vincent Waldon]

Is it quite cold where you are??  I vagly remember a cold-starting TSB for the PD engine...TDIclub is down right now or I would check.

You might find it with a big of googling...iirc it was glow plug related and so disconnecting the coolant sensor might be something to try.

[wolf_walker]

I told him to look for a readout of the crank sensor output while cranking the other day, don't know if he got back to it or not yet.

And it was in the 60's the other day when I was there with it, especially with the catching and running for a second or two, I think that would have done it if it was glowplugs.  It's an extremly well maintained and cared for car fwiw.  Will report back on the crank sensor stuff.

[Vincent Waldon]

And it was in the 60's the other day

Yup... probably ain't glowplugs then....

[myke_w]

I thought crank sensor DOES throw code? Within first 6 seconds of cranking i was told

Not always, I've seen dozens that never did, not that that's at all conclusive.

How about  109 relay?

Getting power to the ecu when this happens?

Verified flowing out of filter (for sure?) when key is turned forward?

[wolf_walker]

I assume ECU has juice as it talks to vcds without complaint.  He says inj qty is 0 on all 4 while cranking, no answer on crank sens output yet.

[wolf_walker]

Small phone-in update.  There is cranking RPM showing, I would assume that indicates good crank sensor?

He measured the injector resistance on the plug on the head and didn't get what the guys on TDI club said he should.
Does the harness in the head to the injectors crap out on these?

[wolf_walker]

well he got it back home(trailered) and I looked it over some this evening.  I swear it sounds like fuel, the way it will try to catch now and again.  Everything I can find in vcds looks ok, cranking rpm, cam and crank sensor, etc, etc.  I finally got him to pull the test port plug on the tandem pump, and while cranking there is a very, very leisurely flow of fuel from the plug.  The book says something like 50psi at idle or 1500rpm, I forget which, but no cranking spec.  Anyone have any idea?  I was expecting a vigorous spurt of fuel from a rotary pump like that, but nada.  Flow to filter with the lift pump (new) is good.  Thoughts?

[rallydiesel]

Anti-shudder valve could be stuck closed.