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Old 03-28-2012, 07:37 PM
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Join Date: Jan 2009
Location: N.W. In.
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sluggish 85 300 SD

Do'nt know what happened a while back I took notice my plastic line from back of intake to the boost switch on other side of engine was unhooked so I got proper stud and washer hooked it up and could not believe the differance it made on get up and go seemed it lasted a little couple of months and now back to no pick up again. I took the line off at both ends and made sure it was open but still no go it is like the Turbo is not kicking in. What does that line do? Does pressure from the spinning turbo somehow add more fuel to the IP for the go. Or is the turbo just adding more air to the engine or does it do both at the same time. I do have my kick down switch under gas pedal unhooked as it seems to shift better with it unhooked and I thought this should have no effect on the boost. What can I check to get my pick up or boost back as it is kind of slow pulling out onto high speed road or for passing ability.

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Old 03-28-2012, 08:19 PM
PowerstrokeJoe's Avatar
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Join Date: Nov 2011
Posts: 29
Thats the line to the ALDA which limits fuel until you have boost. You might try taking the banjo bolt out of the intake manifold that the line attaches to and clean that up as it has been known to clog. That would be where I would start.
2008 Ford F-250 6.4 Power Stroke Diesel Lariat 4X4
2000 Dodge Ram 2500 Quad Cab 8.0 V10 4X4
1990 Toyota Pickup OM617 Turbo 5spd
1987 Suzuki Samurai
1985 Porsche 944
1983 Mercedes 300D Turbo (parts car)
1982 Mercedes 300D Turbo 322k and counting.
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Old 03-28-2012, 08:27 PM
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Location: Atlanta, GA
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You might just need a new switchover valve. I replaced the original on my 81 300SD about two years ago. Got the supply lines mixed up and could not get over 30mph; switched the lines and have good pickup and power again. If it is not working or is clogged, your SD will be a slug - and it does not need to be. Remember one of the intakes is merely a vent and does not get capped off.
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Old 03-28-2012, 10:11 PM
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Location: Middle TN
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Measure your boost. You need to be driving under load to boost. My switchover valve is bypassed but max boost is only ~ 7#. I need to make sure waste gate is working and adjust. There is much information on the site.
85SD 240K & stopped counting getting paint. 84SD 180,000. Probably up for sale in the fall 2020. 85TD beginning to repair to DD status.
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Old 03-29-2012, 09:06 AM
toomany MBZ's Avatar
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Location: central Va
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Temporarily bypass the switchover valve, any difference?

83 SD

84 CD
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