Rotary pump fuel screw

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amaurer

amaurer

10 Year 15 Year
Joined
Sep 2, 2007
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Location
Longmont, CO
On the rotary pump, which way do you turn the screw to turn fuel DOWN? I'm trying to reduce smoke on my BJ73 which failed emissions last year.

I found the fuel screw that lynchmob pointed out in this thread, but when I loosened the locknut and turned the screw, it was ALL the way in. I can only screw it out.
 
lynchmob said:
Turn it in to reduce fuel.
Click to expand...

Well I'm fxxxed then. Why would the screw be all the way in already?

This pump was rebuilt by the PO some years ago, but I haven't touched anything on it since then - I had to cut the safety wire to adjust the screw.

Locked79 said:
IN = more fuel
OUT = less fuel

Back it off in 1/4 turn increments, adjust idle and test drive.
Click to expand...

Or maybe I'm OK?

Which is it? I checked the FSM, the adjustment procedure isn't clear on which way to turn it:

LvhoDzG.png
 
This is to clarify where some of the components are, and how to adjust your pump..

Below Pictured is the non turbo no altitude compensating pump

VEpump.webp

The major difference between this, and the turbo/altitude compensating pumps is the addition of the "LDA" on top as pictured below
Bosch_VE_LDA_Diagram.webp

The most common asked question is usually about turning the fuel up or down.. Adjusting the smoke screw so to speak.. This adjustment is pictured below.. If your pump has never been tampered with there will be a steel collar crimped over the threads.. Remove that collar by some manner and loosen the 10mm jamb nut.. Best method on the car is trial and error, typically a quarter turn at a time.. When you get close you may need to use eighth of a turn increments.. But this can vary pump to pump pending on wear and such..

Turning the screw clockwise increases the fuel injected over the entire rpm range.. Turning the screw counter clock wise reduces the fuel.. Keep in mind that when increasing the fuel you may need to decrease the idle, and when decreasing the fuel you may need to increase the idle..
VEpumpscrew.webp


Idle adjustment is pictured below, it's the screw closest the engine.. The screw that is further away from the engine is the max RPM adjusting screw.. Both of these adjustments are pretty self explanatory.

This info was taken from another forum.
 
OK, interesting, thanks.

I did pull the screw out 1/2 turn since I had no other choice. I have an EGT probe, so I figured nothing too awful would happen... voila, no smoke!
 
lynchmob said:
DOH I was wrong... I blame it on too much welding and the heat.

How in the world are you running with full fuel? Do you have a turbo or is there an HAC unit on the pump?
Click to expand...

No HAC and no turbo. I'm also at 5000' elevation.

I do have an EGT gauge and it will indeed make some hot exhaust, but nothing crazy. But like I said, it was indeed smokey, but very driveable.

I'm a little surprised the pump wasn't delivering more fuel, TBH. If I add a turbo it seems like there isn't much headroom there.
 
It's surprising with your altitude. If I drive at 5000 in my 75 it's hard to maintain hwy speed and easy to raise the egt
Good news is you can add a boost compensator and follow the same methods used to tune a 1hd-t
The boost compensator from a HD-t will fit your pump
 
Drew, do you still have the steel collar on your fuel screw? That would limit fuel increases (but not decreases). Not sure if the PO put another one on after the rebuild...

At Boulder elevation you should be blowing lots of black and pushing high EGTs on hills... Especially on Eisenhower or something like it...
 
lynchmob said:
It's surprising with your altitude. If I drive at 5000 in my 75 it's hard to maintain hwy speed and easy to raise the egt
Good news is you can add a boost compensator and follow the same methods used to tune a 1hd-t
The boost compensator from a HD-t will fit your pump
Click to expand...

Does the boost compensator do anything that manually turning the fuel screw doesn't?

I mean, I get it adjusts for changes automatically... but will it make it drive better at any given altitude?

BreckenridgeCruiser said:
Drew, do you still have the steel collar on your fuel screw? That would limit fuel increases (but not decreases). Not sure if the PO put another one on after the rebuild...

At Boulder elevation you should be blowing lots of black and pushing high EGTs on hills... Especially on Eisenhower or something like it...
Click to expand...

I haven't even tried going over I-70 yet. It'd be a slow ride.

As for the collar.... interesting, I don't know. I had a lock nut, of course, and a safety wire, but didn't notice a collar? I'll snap a pic tonight.
 
I still have mine too. That's the one.

Good to know you probably have a LOT more fuel you could dump in when you turbo. The smoke was probably just from the addition of 5000 feet to your base elevation.
 
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