04 bew no start

I have an 2004 BEW tdi, 5 speed i just picked up for next to nothing that wont start and stay running.
Back ground information: Previous owner was driving down thw highway and car quit on him. Had it towed to a shop and they told him it needed an engine (for what reason he was not told) They swapped out the original engine (127k miles) for a junk yard motor with 100k miles. Installed new tb and set it in there. They could never get it running. Long story short he got the car towed to his house and its sat for at least 6 months till i just bought it two weeks ago with the original motor. Upon getting the car home it received a new battery, all 4 glow plugs were bad, in tank lift pump was bad and relay 109 was bad. The car cranks at normal speed. When you turn the key on, new pump cycles as it should, glow plug light comes and goes after 3 seconds or so, start the crank car instantly comes to life but wont stay running. Crank sensor is showing signal on vcds and torsion value for the split second the car is "running" looks to be in spec. The only thing out of the ordinary that i see on the laptop is all 4 injectors never show any change from 0 on the injector pulse. I have no codes and everything seems correct for the car to run. Tandem pump goes to 70 psi when the car attempt to atart and if i keep cranking past the initial burst it remains at 25-30 psi. Im thinkingim the the point of double checking all the grounds being clean and in place but just wanted everyones opinions

Thanks in advance

Get an immobilizer light?

Interesting that relay 109 was bad ... I thought that that was only an ALH problem?

Immobilizor is inactive. Its not tripped on the dash or on the laptop

And I've tried all 3 keys i have

If the immo is tripped, it will start right up and shut off. When you say it is "inactive" do you mean it has been electronically removed from the ECU? If this was an issue, it would set a DTC "engine start blocked by immobiliser" but that DTC will not show up with most generic (useless) scan tools FYI. VCDS will tag this, though.

The other possibility is the ignition switch, which will only let power through when in the crank position, but once it returns to the run position it loses it so the engine shuts back off.

Another possibility is stopped up catalyst (seen that before). It'll start and run for a second until the exhaust simply backs up back into the engine and won't let any more fresh air in and the engine stalls. A stuck shut intake throttle flap could do the same thing, but that should set a DTC.

Vcds shows immobilizor is not tripped and the throttle flap is working as it should. One other strange thing to build on about the exhaust being possibly blocked, i never get any smoke and once you stop cranking with the intake off air comes out the intake in burst like it is under pressure. Could that be the egr valve opening relieving thw back pressure?

Although I have little to add, I am interested in how this turns out. Oilhammer has some very good suggestions. What about the injector harness?

I'd take that downpipe loose at the turbo outlet and see if it starts up and runs. 5-10 min, 3 nuts, and you'll know if your catalyst is stopped up solid. I'd also reach in and check the turbo shaft with your finger.

Since you have the old engine, what does the turbo look like? Is the exhaust side all oily like it failed and filled the cat with oil? Or maybe they put the old turbo on the second engine in which case, you will need to pull the down pipe as mentioned and check for oil and if the turbo is loose. The turbo may be the root cause of the cat plugging up so if the turbo is really loose, be very, very careful starting it so you don't get a run-away.

I planned to check out harness with the meter and make sure its good and if its not swap harness off original motor over to see if that makes a difference. I'll pop the exhaust loose and see what happens and also check the turbo on the motor i have on the skid

Original turbo is tight and no signs of pushing oil

Since you're new, I have a tip- When you're lucky enough to get replies from Oilhammer and Whitedog, follow the advise to the letter.
Most of us on here, most replies, are from enthusiasts, those guys are experienced mechanics.

Thanks to the info. Popped egr pipe off and started right up. In all of my adventures if pushing wrenches in last 10 years never seen a cat shut a diesel vehicle down completely

Yep, I've only ever seen it happen a handful of times, and the only diesels I have ever seen it happen on were BEWs for some reason. And they pretty much did the same thing you described. It was when I noticed that no [normal] start-up puff was occurring from the car's hind end that I suspected the catalyst clogged up.

Nice find. So how do we go about checking out cat. converter? Will spirited driving keep it clear?

Please keep us updated on how it turns out. Great find Oilhammer. Maybe it would be best to just remove my cat so this can't happen. I live in a place where the goobermint doesn't get all up in my stuff.

So any other thoughts on why this happens? I'm with JB05 and want to know what kind of preventative driving/maintenance should be done. I'm getting kind of scared about mine since for the past few years, she rarely gets out of town.

Maybe driving conditions that make alot of soot? Maybe injectors failing and making alot of soot? Maybe a worn camshaft that is causing incomplete combustion? But if that was it, it would be more prevalent on BRMs, it seems.

Bonus for boisebiker is that you now have a spare BEW that probably has nothing wrong with it.

I added this under the Misc. no starts.

BTW, if anyone has any other misc. no start situations, regardless of engine, let me know.

I think driving like an old lady (or old man?) doesn't help. For every clogged BEW catalyst I have seen, I've seen 500 others just fine at 1/4 million+ miles, so I am not really sure I'd lose any sleep over it. Obviously if there was a turbo failure and the driver kept driving, maybe that was a contributor. The OP said the car "died" and the engine was "replaced". So there may be a key point to the story missing, but at this point we really don't know and it likely doesn't matter. If the engine that is in there now, and the turbo that is attached to that engine, seems to be in good order otherwise, and once a new catalyst is fitted the car starts and runs normally, I'd say problem solved and motor on.

This is very interesting. Same thing happened to my 2004 BEW. I was and another mechanic today who have lots of experience with TDI (Shout out to Griffen Motorwerks in Berkeley) who spent some time with me to see what I might have missed.

The car has been sitting at another shop (supposedly renowned for their VW knowledge, but they haven't been able to get it started either) so I'm gonna tow it out after they've had it for 3 months with ZERO results. The basically told me that I put gas into my TDi, which I guess is their job to doubt the user, but when they ran a bypass, same deal.

My next step was to pull injectors, but I'm gonna pull the EGR pipe to see if it starts.