IP idle adjuster engaged

[pagoden]

The IP idle adjustment knob on my 1969 280sl manual shift car has become very difficult to disengage from the adjustment screw-slot in the pump.  That is, it doesn't want to spin freely when not pushed in for adjustment: it 'clicks' when turned, without having been pushed in.  I can sometimes free it up with extended fiddling but am never quite sure just how I managed it.  It seems as if the adjustment screw inside has become screwed out so far that it's too close to reliably avoid contact.  (Adjustment 'clicks' feel same as previously.)  I'm loathe to start the thing with that device in such an iffy condition; when I got the car the idle mix screw was solidly jammed in to the full rich position, apparently from an attempt to adjust with engine running --- or maybe it arose from a condition similar to the one I have now. ??)

The only response that I've been able to come up with is to count the clicks all the way (clockwise) to the bottom of the adjustment screw's travel, then come back to what seems a sort of mid-point and start searching for the idle mix sweet spot again.  (I've put that off 'til tomorrow; that sequence of 36 or 42 or whatever clicks will cause me pain before it's over -- oh yeah, and then back out for a while, too.  Mine has both solenoids hung on the IP's backside.)

Is this reasonable?    What is the approximate 'click count' to get back out from bottomed to operating range?    What the heck causes such a situation (seems spontaneous) and how to prevent recurrence please?

Denny  

[Tonys113]

Denny,
I had the very same condition on my 69 280 and I believe you are correct that the adjusting screw is simply backed out all the way. If you can engage it and turn it clockwise start turning.
I had to turn mine what seemed for ever but it was definitely backed out too far from someone previously adjusting without the correct knowledge of how it works. You will find that once you find the mid point (+/- 16 click clockwise) that adjustment of the idle air screw will be required to bring idle rpm's in line.

There are numerous posts here n the subject.
Hope this helps

Tony

[jeffc280sl]

The idle adjusting screw has an effective range of less than 64 clicks.  At 64 CCW clicks from the CW stop the idle screw is partially out of the spring clips that create the click feel.   The idle adjusting screw has a short pin on the opposite end from the screw driver slot.  This pin inserts into a washer of sorts that presses against the idle spring itself.  If the idle screw has been turned CCW enough the pin on the idle screw can become disengaged from the washer.  If this happens simply turning the screw CW may not align the the pin and washer which could mess up spring tension and idle adjustment.

If you are at 64 CCW clicks out from the stop the idle thumb knob can be pushed in about 1/8 of and inch before engaging the idle screw.

Suggest you consider removing the rear pump cover and doing a visual inspection to see how far the idle screw has backed out CCW.

[ja17]

Hello Denny,

Yes, it sounds like it is out almost all the way.  Try turning it back in and see if it starts acting normal.
Removing the back of the IP for inpection, is a good suggestion. You may need a good right angle slotted screwdriver to unfasten some of the screws.

[pagoden]

Yikes, and thank you, gents.  Jeff raises an unwelcome possibility; at the risk of sounding like a wimp, I don't relish even the chore of winding that lil' bugger in for the five or six dozen clicks and back out for ~ 1/2 that, much less opening up the IP's rear works.  I sometimes wonder if I'm missing something, as 2 or 3 clicks are about all I can manage in one go; it's just such a contortion to get there, and then resistance and knob's configuration combine to 'tenderize' the fingertips in pretty short order.

I'll try turning it in and then back out to get some sanity into the situation, hoping for the best.

Looking ahead to the possible necessity of opening up the rear cover, I don't see how I could manage not to fumble small bits with the pump still mounted in the engine bay.  If I didn't lose track of the washer(s?) early on, then the prospect of re-assembly  of that many adjuster screws against their respective spring-loaded actuators --with washers for each, or just the one?-- without being able to see much of what I'm doing just sounds like a bad day laying in wait.  And do I want to R&R the pump so as to do it on the bench? No, I'm hard to please; that seems like a lot of hassle as well.  So how did I get into this situation?  I definitely did not crank that adjuster out to such an extreme as it appears to be in.  And if they engage while the engine is running they spin in clockwise and jam at the bottom end of their travel, don't they?  So if I can wiggle out of this one, how to prevent its recurrence?

Thanks, Tony, Jeff and Joe.  I'll come back with an update after the next 96 clicks or so.

Denny

[ja17]

Hello Denny,

First of all, you might want to determine what your mixture is. Make sure all your linkages are correct first of all. Use the "split linkage CO2 test" to find out if the engine is running rich only when cold or exactly when. If it is running rich only when cold, removal of some oval shims will lean the cold mixture. Removal of a BC shim or rack adj.  could solve your rich mixture if rich at all speed ranges. Then you may actually be able to wind the click screw in and leave it there, solving your porblem without removing the rear cover of the IP.

[jeffc280sl]

The solenoids are a pain to work around.  An alternative is to remove the bracket that holds the idle thumb screw.  Using a good light and mirrow you can inspect the idle screw to see if it is backed out too far.

[pagoden]

Well, it turned out well in the end, so that all that remains to concern me is how it got into that condition in the first place.  When purchased, the idle screw was spun all the way in and jammed.  In my inexperience, all I was certain of was that it was immobile, so that when the source of much of the exhaust smoke was traced to exhaust valve adjuster seals, I had that sorted as well.  But I didn't learn how many clicks they settled on, and now I have a much better idea of what's reasonable -- a hard-earned one.

I guess the solenoids are leaking oil, as my adjuster is always oily.  And some previous efforts have apparently left tool marks on the rim knob.  The combination is excruciating after 2 clicks, and I can only reach it effectively with my left hand, so that the clicks out toward lean are SO much more ergonomic than the clockwise ones toward my recent goal, full rich.  I took it in stages over the weekend, ended up with ~ 48 clicks to full stop.  I gave it half that back out into what I hoped was operating range.

When I discovered this situation I was fiddling with the barometric compensator shims.  It came with a 2.00 mm and an .250 mm only --- And was stuck at full rich idle --- And wouldn't run below 1400.  I made so bold as to remove the .250 shim some time ago when the whole thing was hugely over-rich.  Recently, I felt that all the rest of the adjustables were in reasonable enough shape to make a try at the overall mix and scrounged up a motley batch of discs in a variety of thicknesses to give a range from 2.00 to 4.00 mm.

The problem with the idle adjuster was discovered almost immediately.  I had moved it a bit since it was initially set by the shop (but nothing very ambitious) so that I had developed some sense of the feel and spacing.  I'm sure it was nowhere near as far out as it was last week when I went to it to compensate for the first trial set of BC shims and found that I couldn't disengage the external adjuster knob from the inner adjuster screw with sufficient confidence to risk starting the engine.  I wasn't at all sure what I was feeling, but I knew it wasn't good. 

Thanks to you gentlemen I gained the insight and confidence to make it right.  THANK YOU!

Aside from the relief at having avoided some unknown disaaster, the joy of this experience has been that my engine likes a BC shim pack of 3.00mm much better than what it has had.  (No, I'm sure it's not Right yet --probably nothing on it is 100% right yet-- but it's very much better, thank you --- rather nice, actually.)  Shim pack consists of one 14 gauge "machine bushing" and a 9/16 circlip, both from the local hardware store as I have yet to find where old BC shims go to die.

But what's to prevent a recurrence?  I'm pretty sure I understand that engaging the external adjuster with the internal adjuster whilst the engine runneth results in both being spun full in tight.  So this leaves what possible mechanism or sequence of              events to give the condition of (nearly) full out adjustment?                         

Joe - Yes, over the past months we've made great strides, starting at 233mm, refurbing ball ends, Split-link CO2ing and such,                                                                           ~97% of which I'd not have had a clue about if not for our Group with it's generous, hard-won, priceless wisdom.

Tony - You struck just the right note of encouragement and information from a fellow-sufferer who'd obviously been there before me.  At that point I still wasn't sure of the whole picture/how to interpret what my fingers were 'seeing'.  In that sorry condition your input was mighty welcome.

Jeff - Thanks for taking an interest in my plight.  I hope we can get our act near your level of inquiry one day.  Meantime, that suggestion to remove the external adjuster assembly was wizard.  And I really wanted to do that.  Still do.  Mine is based on a ~43mm hex cap, screwed (I have to suppose) onto the IP.  There is no clearance to swing a titmouse, let alone a cat or wrench in there.  A socket of such dimension has walls too thick to fit into place.  I'm thinking the only shot at it while the IP is in place will have to be when oil filter canister is off.  (I have an enormous 46 wrench which ought to crack it loose, but only if the flats happen to be where I can get on it -- and it'll take at least 50#s to budge.)

So:  what befell us (my 113 obsession and I) wasn't so great -- & seems at least unlikely.  How can it be avoided?


Thanks again,

Denny
           


 

[jeffc280sl]

Denny,

The fip has an oil feed directly from the engine in order to keep the parts lubricated.  The solenoids do not contain any oil so they are not leaking. 

The idle adjusting knob should never be adjusted while the engine is running.  Is that what you mean about preventing the problem?

[pagoden]

I'll get a screwdriver in there to see if I can snug them up at their bases.  But there is oil at the joint between metal case and  black plastic end cap, quite a ways from the flange at the base.  And I remember similar solenoids leaking petroleum liquids out through similar crimp joints in times of yore and yet remaining functional all the while.  I don't wish it to be the source, am just beginning to look for this leak and certainly welcome voices of experience with suggestions.  So far, all I know now is that, while plagued with a constantly-wet idle adjuster and exploring the vicinity rather closely for ways to bring tools to bear, there was that nice clean oil at the outer end of the lower solenoid, around the crimp joint.  (Not so sure about the other one.)  I'm definitely open to another source, just didn't see one while engaged in the other issue.

The ground rules for idle adjustment were among the first lessons I learned, what with the IP's idle mix adjuster frozen tight and 'way out of whack.  Seems the best way to put it in that condition would be to push it in with engine turning over.  I worked some of that out myself, which this forum and some local old-timers confirmed.  And things have been peaceful on that front until recently when, goaded by your recent offerings on IP mix adjustment and the fact that my engine's other adjustables have been coming together, I started to do a little rudimentary fiddling with the overall mix by way of the barometric compensator's shim pack.  And there it was: when I went to compensate the idle mix, there was an odd-feeling situation that felt like the internal adjuster was screwed 'way out 'in my face', so much so that I was afraid to trust the external to stay clear of the internal if I were to re-start the engine.  I didn't.  I asked for help and got it on several levels.  Whew.

Thing is, no, I didn't crank that idle adjustment 'way out into an unreasonable posture and can't think up a way for it to have happened during the normal course of operation, as we can with the opposite over-adjustment where it's spun all the way in.  So: what happens in that process? or how did it get that way?   And ultimately, how can it be prevented?