2.8l tdi (inline 4) (Lt 46) 96 kw, 2001 - performance issues / questions

**RasmusRMT** · 17-12-2021,07:06 PM

Hi, hello everybody.

I am new here, first post, hope i am posting this in the right section. Also English is not my first language, so... I'l do my best.

A while back i got a good deal on a 2001 VW Lt 46 2.8 tdi. I has been sitting until just now when i found myself in need of a truck, and figured it was time to put it to work. Started with some maintenance, oil, filter, some work on the brakes, replaced a wheel bearing, all good so far. But then i took it for a longer drive than just around the neighborhood and realized it lacks a lot of power.

The engine seams to run fine (for an older vehicle, a bit noisy maybe), it just seams to lack about half its hp. Even with no load i am having trouble just maintaining speed, in 4th and 5th gear, if there is any kind of grade.

So far i have installed an aftermarket fuel press gauge pre IP, realized i had no fuel pressure at all, so i installed an aftermarket marine lift pump. I now have 6 psi steady before the IP. It now starts a little quicker, but small or no change when driving.

I also installed a boost gauge. At 2000-2500 rpm, in 4th or 5th gear, i can't get more than 0.2 -0.25 bar (like 3-4 psi). At lower gear and higher revs it goes a little higher but no more than 0.5 bar.

First real question(-s):

How much boost should there be? And how much can the motor handle by the way?

If the waste gate was stuck, it would be in closed position, and to high boost?

I am about to bypass the inter cooler to rule out any leaks there. Do i need a new turbo?

Next i am thinking compression (cylinder) / injectors / IP. Not sure what to do first. Leaning towards injectors.

That's the story so far, any input appreciated.
If you read this far, also thank you for your time.

/Rasmus

**Crasher** · 18-12-2021,04:13 AM

That is a Mercedes engine, you may get more help on a Merc Sprinter forum, I don’t work on them but I know they are prone to injector problems

**RasmusRMT** · 18-12-2021,09:33 AM

From what i have read, even if the Lt and sprinter share the same body, each company put their own engines in it. Also, i can't find a sprinter model with a 2.8 liter (2.7 or 2.9) or any reference of Mercedes ever making a 2.8 inline 4 tdi. And it says VW on the valve cover, might not say anything about the block...

Engine code for this particular 2.8 is ATA by the way.

**Crasher** · 18-12-2021,10:06 AM

Could you post the VIN?

**RasmusRMT** · 18-12-2021,10:12 AM

Vw1zzz2dzyh026313

**Crasher** · 18-12-2021,01:00 PM

It is too early for my ability home and I am not great on anything above the Transporter because we can’t get them in the door, too high.

**RasmusRMT** · 18-12-2021,07:40 PM

Still thank you for taking the time.

Next thing i tried was connecting individual return lines to the injectors to see if they "leaked" the same. No diesel at all. Realized i only used this method on common rails in the past. Is this normal for TDI engines?

**Crasher** · 18-12-2021,08:39 PM

I have only encountered leak off on common rail and obviously VW group were late to the party on this technology.

**RasmusRMT** · 20-12-2021,08:47 AM

So i spoke with a diesel mechanic (who specializes in turbos and IP's) and he told me to try adjusting the IP before i replace it. Sure enough there was an adjustment screw on the pump, just above the injector lines.

I should be able to screw it in until i see black smoke on full throttle, then back it out just a little. I was told 1 full turn should be plenty, start with half a turn and take it from there.

Well, i am at 3 full turns now, and finally starting to get reasonable power and boost (about 0.5 bar any time i hit full throttle). No black smoke or anything.

Assuming the waste gate is working, i reason that i should not be able to blow the motor with a stock turbo. So unless i see black smoke i am aiming for about 0.7 bar of boost.

Does anyone know how much boost that motor can handle?

So for now, conclusion is, IP was (is) the issue, the rest seams more or less fine. How ever... Since 3 full turns is way more adjusting than normal, the IP is most likely at the end of its lifespan, and if i want to keep using the truck, i will need to replace it or have it rebuilt in the near future.

**Crasher** · 20-12-2021,12:29 PM

Sounds to me like you should have the pump and injectors checked by a Bosch Diesel service centre, the manual says the boost should be tested on the road by driving at full throttle in 2nd gear at approx 2000 and 3000 rpm holding the vehicle on the brakes at approx; 40km/h where the boost should be between 0.9 and 1 Bar.