ALDA screw destroyed housing threads!

[83mercedes]

When adjusting my ALDA set screw to make the mixture a little less rich--despite my efforts at being gentle--it popped up a little suddenly, ripping probably 70% of the upper threads out of the ALDA housing. Now, the only way I can get the screw in is to push it down and screw it into the bottom remaining threads (which causes the engine to not get enough fuel to go above 700rpms).
When I tried driving it with the screw out completely, the transmission shifts approximately 500rpms higher than it should, making it drive ridiculously and the fuel/air mixture is absurdly rich unless I floor it.

I can't drive it because I don't want to hurt the trannsmission, and it is pretty embarassing, so does anyone know where/if I could get just the ALDA housing? I'm afraid the magnitude of this problem may be horrific. I can't just have a machine shop rethread it, because then the screw would no longer fit.

[Brian Carlton]

Originally Posted by 83mercedes

I can't just have a machine shop rethread it, because then the screw would no longer fit.

You can.


The machine shop can use a metric helicoil insert and it will be as good as new. You will need to take the ALDA apart, however, so no chips get inside the unit.

[83mercedes]

Using crazy glue I attached the nut/washer to the ALDA housing, so now the screw can just be screwed through and adjusted as before, but without a lockdown nut, which is no big deal, since it is not inclined to move around anyways.

So, problem 1 solved, but now my adjustment seems all screwed up. If I turn the screw in much at all, the engine has the problem of not revving up high enough. Then, turning the screw out, that problem ends and this one begins. My shift points are too high, the engine lacks low end acceleration, and the shifts are incredibly rough. Furthermore, the shift points seem to vary depending on how I use the accelerator.

Is one of these problems clearly too lean and the other too rich? Is there some tiny middle ground I am missing here?

[Brian Carlton]

You have encountered the delicate balancing act of fuel/transmission response.

If you provide the engine with more fuel in part throttle conditions, you need less pedal to make the vehicle go. So, it shifts sooner due to reduced pull on the Bowden cable. Additionally, it shifts smoother because of increased vacuum created by the fact that you are using less pedal.

With reduced fuel, the opposite occurs. You need more pedal, resulting in more pull on the Bowden cable, later shifts, and lower vacuum which results in firmer shifts.

You can't do anything to the fuel on a diesel engine without affecting everything else. So, this is generally why it is recommeded to leave the ALDA alone.

In your case, you need to decide the proper position for the ALDA (by watching for visual smoke) and then adjust the Bowden cable and vacuum accordingly. It's not for the faint of heart and requires quite a bit of patience with very small adjustments and quite a few drives between adjustments.

Last autumn I had gathered from numberous searching on this forum to follow the same sequence that Brian describes. And it worked after several iterations.

First ALDA, then Bowden cable and vacuum modulator. It will eventually workout. I enjoy my power and transmission response very well and it seems to function like it probably should. Find a good smoke balance with the ALDA and then leave it alone and adjust the others for smooth shifts that occur when you want them to.

You are probably on the right track.

--CD

[psfred]

You can also change the shim under the ALDA rather than messing with the screw -- this is how it's adjusted at the injection shop. This will avoid messing up the internals or stripping the screw.

Shift points are unaffected by the ALDA adjustment other than what it does to boost pressure, so check the boost lines and make sure you have a good boost signal to the transmission modulator amplifier AND that the vac lines at the modulator control box are good, etc.

Peter

[Johnhef]

You might have luck just getting a whole unit from a junkyard. I had to swap out the one on my 603 last winter. The one from a blown 617 motor I had worked perfectly. Didn't even have to adjust it any.

[83mercedes]

[QUOTE=Brian Carlton] With reduced fuel, the opposite occurs. You need more pedal, resulting in more pull on the Bowden cable, later shifts, and lower vacuum which results in firmer shifts. [QUOTE]

Yes, these are the exact symptoms I am experiencing......but with the ALDA screw turned very far out. That's what I was trying to communicate earlier...the only transition I get when adjusting is going from the the non-revving situation to the situation described above. After that I can turn the screw all day to no effect, just the above problem.

I'm beginning to think it would probably just be easier to get a new unit; anyone have any experience in this, whether it would be worth it to pay dealer price for a new one and how to install it?

[Brian Carlton]

I don't think you can get a new ALDA from the dealer.

If you could, you would need smelling salts when you heard the price.

See if one of the forum members has a spare that they would be willing to part with. Or, see if you can find an IP, cheap, on e-bay and get the ALDA off that.

It's not difficult to install. There is one nut on the bottom of it that secures it to the IP.

[Johnhef]

I'd still go the junkyard route...

You can't get the ALDA from a dealer, I tried. They can only get it on a whole injection pump.

[engatwork]

I priced one out at the local Bosch shop within the past year and it was around $375 new..
Let me know if you need it and I have a good unmolested one I will sell. PM me if interested.