Idle speed way too high

[Gromit]

AAZ transplanted from 95 Golf to Kubvan:

It idles at ~2000rpm. I backed out the minimum idle speed stop screw all the way, I backed out the idle speed adjusting screw till it came out, loosened that screw on the lever to move the, uh, sub-lever so that the idle speed adjusting screw can now move the idle lever toward lower idle speed without falling out.

Now the idle is slowed all it can be, the lever is against the aluminum where the minimum idle speed stop screws. Accelerator lever stops against the residual fuel volume adjusting screw.

Why does it idle so high (after warming up)? It idled normally when it was in the Golf.

Does that idle speed lever work on the governor, does the governor control the idle speed? Or does the idle lever just control the amount of fuel injected when at idle? If the former, I can't imagine why the change, nor what to do. (Pump internal pressure problem?)

If that lever affects the amount of fuel injected at idle, maybe there's a change in the load on the engine. It no longer has a power steering pump, and I went from poly-rib to v-belt to drive the alternator. And I have the injection timing at .89mm, was .74mm, and the cam timing was way off in the Golf, it's dead-on now. In the Golf, the pump had electronic control of the Injection start positioner, now that is disconnected.

What do I do?
Can I turn out the residual fuel volume adjusting screw until idle is right? What problems does that cause?

[CarlosA]

There will be some far better responses soon, but you are right, backing out the fuel screw will do it. On mine i`ve played with it a few times and had to adjust the idle to compensate afterward.

Editing to add the reason I had to adjust this was because the pump parts i`m using were from a different car... so it necessitated adjustments.

[Gromit]

Thanks CarlosA

I just read the Bentley residual fuel volume adjustment. I'll follow the procedure tomorrow.

Its a bit confusing, understanding what is going on in the pump would help me more than following directions; I'm trying to read between the lines in the manual: I get the impression that the lever on the back of the pump regulates the lowest setting on the governor, and the Residual fuel volume is to be not quite enough to raise the engine speed past the idle stop on the governor.

Not sure that I described my concept well, but tomorrow when I play with the Residual fuel volume I'll be able to test out my theory. I just remembered that that adjusting screw had no tamper-proofer on it, so someone must have raised it up to compensate for something wrong that I fixed in the transplantation.

Okay, feeling better now, not fearing the fuel volume adjustment. Will report tomorrow.

[libbybapa]

The idle speed is controlled by the play between the governor and the idle spring both pushing on the lever assembly that moves the control collar. If you cannot get the idle low enough through adjustment of the idle screw and residual pressure (the pressure described in that name has nothing to do with pump internal pressure, it is talking about the residual pressure of the main governor spring capsule acting on the control lever assembly), then your accelerator lever is not indexed to the correct spline of the accelerator shaft. Loosen the bolt and nut that hold the two parts of the lever together and the lever to the shaft. You then need to rotate the shaft CW and the lever CCW. You will then need to increase the max fuel screw and adjust the idle.

[Gromit]

That explanation is really helpful, thanks libbybapa.

[Gromit]

I turned out the residual fuel volume adjusting screw 6 turns. Moved the idle speed screw a little, it idles at 900 now. It wasn't obvious how much I should change the residual fuel vs idle screw; but it runs fine now (other than the noise- more in another thread). I'll play with it another time when the problems are all fixed, to figure out what it should be.

Now it idles 900, nice and smooth. Oil pressure is not even 10psi (engine warm) at idle- is that about normal for a fresh rebuild? It goes up to 30psi at 2000rpm.

Plenty of power, much less white smoke after climbing hills to set the rings. Still way too loud to take into town. Thanks to VWDieselparts.com for all the helpful information!

[Una]

Eh, I wouldn't dwell on the oil pressure too much. These engines didn't typically have an oil pressure gauge from the factory. It was just meant to be whatever it was, so long as the warning light was out.