Thanks for the part info!

Yesterday I was able to test the pressure at the IP with both fuels and they seemed to be the same. It seems that the pressure does not remain constant the gauge is very erratic going from 0 to over 1 bar very fast. Is that normal? both straight diesel and the 50% svo gave the same readings.

I even tried hooking up an electric fuel pump both before and after the fuel pump with no change to my problem. The PSI from the electric fuel pump was supposed to be 14 but it only read about 5. Could that mean that the pressure release bolt is bad on the back of the IP? How much fuel pressure should there be in the IP and should it be constant?. Another question is the pressure released through the injector return lines?

It just doesn't make any sense based on whats happening. I think its a problem with the linkage on the inside of the IP.

Just to recap my problem... I'm able to start the engine and idle the engine and have it run normally on a 50% svo mix, but when it runs for awhile and gets warm the engine will not go back to and idle it wants to increase rpms even with the linkage set at normal idle. I have to hit the stop several times to get it back to idle (as per the video I posted). When its on straight diesel it will not start without some help with starter fluid or wd40. Once running it will not idle and when its running at a good rpm say 2000 or more if you hold the linkage in one place the engine will eventually die as if it were shut off.

Its weird that there is are opposite reactions with just a fuel mix of 50% svo.

Now I'm trying to remove the IP and replace it with a non tubo 617 engine's IP I have on an engine stand. I set both engines with #1 exhaust cam pointing straight up, so that both IP's should be timed exactly the same. I removed the three nuts that are on the front. Any suggestions on how to get the nut off the bottom back of the IP (the one in the car). Its about to make me think its just not worth it.

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83 300SD
80 300D