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1993 Bosch rotary idle adjustment

Old 06-20-2003, 07:20 PM
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1993 Bosch rotary idle adjustment

I have a 1st gen 5.9 with the rotary injection pump. The idle speed adjustment screw appears to be between the injection pump and the cylinder head. It appears to be almost impossible to get to. Is this the correct screw I am looking at? I am familar with adjusting the idle on the "inline" pump. It is much easier to get to. Unfortunatly, I have the VE rotary pump instead, which I am not as familar with. The reason for this post is my idle is too slow (about 500 rpm). I need to set it up because it stalls in hot weather at an idle. Other than that, the 5.9 runs fine. ;D
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Old 06-20-2003, 07:32 PM
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Re:1993 Bosch rotary idle adjustment

thats the right screw. you need a long screwdriver/punch to break the lock nut from the top. Then a small screwdriver to adjust it. It is a pain but its not that bad.<br>DM01
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Old 06-20-2003, 07:36 PM
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Re:1993 Bosch rotary idle adjustment

Be sure and check your lift pump pressure as well. The last 2 trucks that I diagnosed with a low idle problem have all come back to have a dead lift pump. 0psi at idle.<br><br>The idle screw is on the front of the pump closest to the engine. There is a lock nut on the idle screw that can be a real pain to get too. You can use a small 10mm (I think) gear ratchet and get to the lock nut and move the nut just enough. Or you can do like most folks and use a chisel or a big flat head screw driver and tap the lock nut loose while hitting the screw driver with a hammer.
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Old 06-21-2003, 12:12 PM
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Re:1993 Bosch rotary idle adjustment

If you have several different brands of the 12 pt box end wrench that fits the nut you may be able to loosen the nut by switching wrenches consecutively. Different brands usually have slightly different handle orientation and that worked for me. It is definitely an SOB.
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Old 06-21-2003, 12:45 PM
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Re:1993 Bosch rotary idle adjustment

It definitely is a bit of a pain to loosen the lock-nut. On my truck I was able to loosen it with a punch. I tried this on a friends truck and it wouldn't move, so I took a cheap 10 mm wrench and customized it with a bench grinder which then gave enough clearance to loosen the nut.<br>---<br>Al
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