Well after the last thing my 1981 300Sd has pulled I am wondering what to do. I have changed and replaced and adjusted almost everthing chasing a rocking, missing motor. It seemed like #3 cylinder was the culprit. Then I fixed the pressure line to the ALDA valve and it came alive. The motor has 175k on a broken odometer. It looks super clean and when at 2-3 thousand RPMs it is so smooth and noise free. But it has a rock at idle. Then it started to get worse. I climb a 5 mile grade that gets me to 2500ft. My first 5-10 trips to work(25 miles one way) it pulled the hill at 65 mph. Then it started to slow. It started to also seem to not want to go over 4k and would not shift to high gear from there even on flat ground. It felt like it hit the governor and would not go higher than 4k even in neutral. The last trip up the hill it slowed even further to 3500rpm and 35 miles and hour. The engine starts a little rough cold then warms and runs great with tons of horsepower for a few miles, but soon fades with a high rev or warm engine. After the 35mph trip up the hill I nursed it home starting out with a power check and it pulled great cold. I drove it home and was easy on it the whole way. It ran normal. I stopped at my automatic gate and waited for it to open.

All of the sudden the engine starts to shake like it's running out of fuel with large amounts of white smoke out the tailpipe. This thing is shaking so bad my instinct was to get out, it was going to blow up. I have never felt an engine shake so bad, worse than even a Cessna startup or when I blew half of a clutch pressure plate out of a International 60 series. Then it started to smooth enough to get it to my shop. I wanted to see if the lift pump was working and I wanted to see if I could find the problem while it occured. The engine started to smooth and the smoke got better but it would rev to 4500rpm the fade back to 3500 in neutral like a governor stepped in. I pulled the cigar return line and it had a 4 inch jet of fuel at 2k. Then I filled a 5 gallon can in about 10 minutes with a section of fuel line. Volume seemed more than enough but pressure was unknown but would not blow a unclamped hose off when it was plugged with my thumb.

Does this sound like an injector pump problem, lift pump, blown motor or what?

Some other things: Blowby in it's current state will not blow off a plastic cap. The car sat for six years. I currently have full synthetic oil in it. It does not lose oil on the dipstick, no oil in cooling system or water in oil. And a new gold RD bolt.

I have a known good 84 IP on another spare engine. Would it be worth checking out the 1981 IJ pump or swapping the 84 into the 1981?

I am really tired at this time so I may have things off on the post, sorry.

Check your fuel filters, a clogged filter can cause a host of issues. also check your Air filter. Same reason

I failed to mention that i changed all the filters and checked the tank screen. It seems as though heating up the engine or high rpms start all the problems. I would think once a filter or tank screen plugs it would not unplug. I also ran with the fuel tank cap off with no change. The engine does not overheat(85). If I let it idle it idle and cool down it will start to run much better but not perfect. It seems to rock worse now. I searched for injector pump failure and found one post that seemed like what I'm dealing with. I am running out of items to check or replace.

If you have a Parts Fuel Injection Pump you can swap one at a time (so you can tell which one helped) the Fuel Pressure Relief/Overflow Valve and the Fuel Supply/Lift Pump.
The above assumes that both of the Fuel Injection Pumps are the same model.

Fuel pressure relief valve adjustment, overflow valve
Fuel pressure relief valve adjustment - PeachParts Mercedes ShopForum

A problem with your Linkages to the IP Throttle that would keep the IP Throttle Lever from going all the way to full Fuel could cause your symptoms.

A clogged or restricted Crankcase Breather could cause the Crankcase Pressure to build up and that would push your Vacuum Shutoff Valve into the shut off direction.

Tight Valve clearences get even tighter when the Engine is hot. You might want to check the Valve Adjustment.

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84 300D, 82 Volvo 244Gl Diesel

The shutoff valve seems logical and for sure the pressure relief spring will be checked. Can you have sufficient volume but not enough pressure? I don't think it's anywhere close to 14 pounds. Last time I plugged the return line on my other 126 it blew the line off and I got a diesel bath. This one can be plugged with my finger and no fuel will get by with little pressure and no clamp on the return line(new hose).

Have you checked your turbo?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I checked the check ball and nothing out of the ordinary, spring was 26mm. I did notice lots of air coming out of the pump with no air going in, none. Where would this air be coming from? Blow by? Internal pump leak? It was mainly at high RPM. The bubbles moved very fast. I will search for bubbles in the return line. Turbo got re-sealed after this started. It looked good while it was apart. I did nothing to the wastegate. I was reading the thread by bonedoctor?? and the shutoff valve being blown closed by crankcase pressure, this seems like what mine is doing.

I cleaned and re-sealed the turbo but the problem had started before this. I noticed it would not shift out of 3rd to 4th and would hold at 4k. I would lift the throttle and it would shift. Then start pulling hard again with over 10 pounds of boost. When it would stick at 4k it would only give 7 pounds of boost.

I have to also say this seems to have started with an oil change to 10/40 synthetic. The oil is at the highest mark on the dipstick. I also switched dipsticks because of a broken plastic ring. I wonder if the oil is sloshing or foaming plugging the crank vent system? I also seemed to notice the smoke out the back after stopping hard. Can oil ride the chain up while braking and overload the case vent if there is too much in the pan?

There should be no air bubbles at any time in the fuel system. Where were the air?? Out of the lift pump? IP return? Both?

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

PROBLEM FOUND!!! Thanks to Boneheaddoctor's long thread I checked out my blowby problem. I started by getting the motor to start shutting down which it was slowing to 3k rpms in neutral with motor sealed the way I had been running it. Then I pulled the valve cover cap off with a big pssst! HUMMM...put a rag over the hole and 4500rpm on the governor and it held. Put the cap back on and pulled the egr line off the airfilter. All it would do it 3500rpm! Pulled the egr line off the valve cover and 4500rpm. Then I discoverd the whole assembly caused back pressure and took it apart piece by piece until I found out what I had done wrong. The attached picture shows the adaptor pipe that caused back pressure. I can't believe it would cause the problem but it did. I replaced it with some steel heater pipe that would not crush with the hose clamp. What I also discovered is you should almost have no pressure in the engine when you pop your cap or pull the egr line. It should not hiss or blow off pressure, the egr vent line should handle almost all of the pressure volume. This has solved the trans flair, smoking, and it's got tons of smooth power! Still has a bit of rocking but not much. At least I can attempt a tune without the engine trying to blow itself up with blowby pressure! WOW! Thanks to all!

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The Hand Primer can be a source of an Air Leak and due to the Plastic Lift Pump Outlet to Filter Tubing getting discolored you may not see the Air going out of the Lift Pump.

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84 300D, 82 Volvo 244Gl Diesel

Also, if your vacuum pump has a bad diaphragm, it will cause oil to be sucked into the intake, thus causing white smoke. Also the bolt that hold the diaphragm on, can come out and cause a lot of horrible noise problems. Another thing I have learned, is if the car has been sitting for some time, you need to get it out on the open road and blow the hell out of it....lots of stuff can build up...but before that, check your radiator....if its an auto, the transmission cooler is in the bottom...sitting for a long time can cause rust...rusted out transmission cooler, will not be fun...waiting on my new radiator...

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