N/A D24 loses power nearing max revs, brown black grey smoke

[245d6]

So I have this 245 D6, 300.000 km's, 1983, which runs quite well (i suppose, only used to air-cooled gasoline engines so I try not to worry to much about some ticking, valve noises etc.). It starts okay, seems like it has one bad glow plug. It starts immediately but makes a bit of a noise for the first 10 seconds and smokes a bit for about 30 seconds. But this isn't my biggest concern, something quite simple to fix it seems.

The biggest issue is that it won't go over 110 km/h, especially when giving it full throttle it eventually goes slower, starts to smoke brown/grey/black. If i let go of the gas it gets better and eventually i can get it a bit above 110 on the counter. Up until 100 no issues at all.

Some background:

Car had been sitting since 1999 (from the papers I got, never spoke the old owner). No idea about maintenance, but when I got it it was hard starting, lots of white smoke for the first 2 minutes.

Changed the timing belt and IP belt ''according to procedures'': Built my own tools for the pulleys and found a cheap euro VW diesel tool set that contained the little tool for the camshaft position, dial indicator & locking pin for the IP gear. One difference with the ''real'' volvo tools: putting a .2mm feeler guage between surface didn't really do anything, still bit of play on the locking tool. However it became much better, easier to start, less smoke and less noise. I don't remember exactly what I set the pump to, but I think .85mm.

After welding the car back together, redoing the suspension and brakes i finally managed to get it through the technical check in order to get it road legal again and was able to really drive it for the first time.

Some things I noticed:

Fuel pump seems to make a bit of a zooming? noise when idling, goes away when i touch the throttle a tiny bit (don't know if this is problematic, maybe belt is a bit too tight?) Sounds like a bearing with a tight belt, but I thought i read that the pump doesn't have any roller bearings.

Spews quite a bit of vapour / oil from the crankcase breather, so much that the entire intake is full of black ''grease''. This was already when I got the car, and I still need to remove the intake and clean everything. Planning on rerouting the crankcase breather into a catch can. In the first 500km's the dipstick went from full to reading 3/4, when I take of the breather tube I think i know where the oil is going... I don't really mind at the moment, maybe pull the engine out next year and rebuild it but for now I would like to just drive it for a bit.

injector at the rear of the engine is a bit sweaty, was leaking last week but magically solved itself, now the 3rd injector has started leaking. Not too bad, no diesel under the car but they're wet. Is on my list to fix.

No clue if the cold start device is working, it was disconnected when I got. I suppose it is in ''warm'' mode but have no clue on how to check, could be a reason for my issues maybe.. Car always starts, even with bad battery and -10 celcius weather (despite some smoke at those temperatures)

When replacing the brake lines I noticed the fuels lines under the car are quite corroded, didn't replace yet but maybe this is part of the problem i'm having.

Bit of a ticking noise sometimes, sounds like valves which I still need to adjust, is on my list and I don't think it has anything to do with my problems. Old engines make a bit more noise (what i've learned)

Here is a youtube link to a short video of the issue:

https://www.youtube.com/shorts/WCDEUbljOyk

Too bad my friend decided to film me rather than the disgusting stuff coming out of the exhaust of my car but i think you can make out the noise it starts to make as it revs up and see at least some of the smoke coming out of my leaking exhaust. I didn't want to unnecessarily rev it to redline again.

So the problem is not a ''power'' problem i suppose, it does the same thing in neutral when revved to max, same thing in 1st, same in 2nd (pulls to 60 km/h, then slows down to 50 km/h as it starts to smoke), 3rd and eventually 4th (it's 4-speed with OD but OD isn't working yet, problem for later).

Trying to come up with a plan at the moment:

1. Replace fuel line from hard line to pump with a clear line to see if there is air in the system. I'm not sure if this is the issue as it smokes black / brown / blue but figured I might check as it's easy.

2. Clean air intake, reroute crankcase vent tube into catch can. My theory: As car starts to rev up, more pressure builds up, more oil gets thrown out in to the intake system which is then introduced into the combustion chambers, making the engine run ''rich'' on diesel / oil / air mixture?

So far no runaway situation so can't be too much, but maybe this could be the problem?

3. Recheck pump timing, maybe i screwed up somewhere and it's off, resulting in too much fuel at max revs? Don't know if this could lead to the engine bogging down and losing some power.

To be honest, I don't mind not driving over 100 km/h / 60mph, but would prefer the engine to be as ''healthy'' as possible, considering its age and me having no idea about how it has ever been maintained. Also no idea about d24's, maybe 100km/h is it's top speed with only 4 gears? It is slow..