Way too lean with new FI pump (0.5% CO2)

[jameshoward]

Of the many threads I've read on the rich/lean subject the vast majority struggle to get the readings down and lean out the mix. I have the opposite problem and would appreciate advice on how to tackle it. I've just put a rebuilt FI pump back on having asked the guy to lean it out a lot.

The idle varies from about 750 - 850 rpm when warm unless I close the air idle screw, then it's better. The car shudders a little at speeds and at lower revs than before.

I've put it on a calibrated Bosch all singing/dancing tester at a service centre today. The mix is just under 0.5% CO2 at idle with the idle air screw a little open. I've put 15 clicks clockwise on the FI pump idle screw. I feel I need to make the mix richer thoughout the range. My question is how best to do this? Do I mess about with shims on the WRD, do I go with Merrills tuna can washers (which I don't understand, as we're about 200ft above sea level and since barametric pressure fluctuates and I don't live in the mountains I can't see how it would change much but do intend to see what washers I have there) or do I go to the full load screw at the back of the pump?

The Bosch machine found that the tappet clearance on cyl 1, 2 & 3 was also wrong, which is odd coz they were set about 300 miles ago. So I'll redo them tomorrow. Dwell was 40 degrees.

It's a '66 230SL, manual.

Thanks.

James

[hands_aus]

quote:Originally posted by jameshoward

Of the many threads I've read on the rich/lean subject the vast majority struggle to get the readings down and lean out the mix. I have the opposite problem and would appreciate advice on how to tackle it. I've just put a rebuilt FI pump back on having asked the guy to lean it out a lot.

The idle varies from about 750 - 850 rpm when warm unless I close the air idle screw, then it's better. The car shudders a little at speeds and at lower revs than before.

I've put it on a calibrated Bosch all singing/dancing tester at a service centre today. The mix is just under 0.5% CO2 at idle with the idle air screw a little open. I've put 15 clicks clockwise on the FI pump idle screw. I feel I need to make the mix richer thoughout the range. My question is how best to do this? Do I mess about with shims on the WRD, do I go with Merrills tuna can washers (which I don't understand, as we're about 200ft above sea level and since barametric pressure fluctuates and I don't live in the mountains I can't see how it would change much but do intend to see what washers I have there) or do I go to the full load screw at the back of the pump?

The Bosch machine found that the tappet clearance on cyl 1, 2 & 3 was also wrong, which is odd coz they were set about 300 miles ago. So I'll redo them tomorrow. Dwell was 40 degrees.

It's a '66 230SL, manual.

Thanks.

James

James,
The shims under the WRD are removed to 'LEAN' the air/fuel mixture in the whole range.
Usually there are 3 shims of different sizes. There would be no problems adding extras.
They are used on sedans so maybe you can find some used ones to experiment with.

Was the Inj pump thermostat replaced with the rebuild?
Are all the components in place where the Inj pump water housing/thermostat sits on the WRD housing
see pic
Download Attachment: IPWarmUpDeviceParts_3.jpg
25.99 KB

If that collar is missing the whole thermostat housing will push the WRD plunger deeper than normal and make it impossible to adjust for correct mixture.

OR

On the new Thermostat that i bought there is a brass washer type collar that was too large for the aluminium collar. I had to drill out the aluminium collar to allow the thermostat to sit at correct height. This made the air/fuel mix too rich.

The collar could be missing....worth a look

I wouldn't play with the barometric 'can' washers because when you go to the hills you will have problems.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[merrill]

james
so, bob offers some good advice,

when the car is cold is the air filter at the inj pump thermostat letting air in?  then when the car gets warm does it shut off?

per me thread, when I increased my inj pump 11 clicks hans at H&R said that was too much,  when we pulled the tuna can there was only a .5mm shim, after increasing the shim to 2mm and backing off the pump 11 clicks everything worked better.

one thing I noticed is when the pump is rich the idle rpms react to a change in the inj pump air idle screw, when the co is closer to 4.5% the reaction to changing the idle air screw is much less.

I assume your fuel filter is ok and the pressure is good?

I doubt the appet clearance will cause your co2 to be off 4%. check the valves and the other stuff and let us know what you find.



Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[jameshoward]

OK, Bob: I haven't pulled apart the WRD yet. I very much doubt it was touched as part of the FI pump rebuild (!). (A long story). I don't have a readily available supply of shims, but assume I can make some if needed. I think that the rest of the thermo will be OK as it hasn't been messed about with.

Matt - That tuna can; still can't figure that out since pressure changes with the weather. The FI pump filter is new; it lets air in on warm up. Just before about 180 deg F it shuts off at which point it starts to run rough. (Fluctuates). Agreed about the tappet clearance; that was just something the Bosch machine happened to throw up as another job. Fuel filter should be OK, and certainly the pressure is very good.

Does anyone have a view on using the full load screw to adjust the mix?

Bob, Mat, keep 'em coming! I've read all your posts and tried pretty much all of it. I need to get radical hence request for a view on anyone who's richened the mix across the range.

JH

[merrill]

james,
sounds like your wrd works,

as far as the tuna can, yep it deos change but when my pump was rebuilt it had a .5mm shim and seemed to work ok, then it did not.

after trying to richen the mixture 11 clicks hans had me increase the shim to 2mm and back off the mixture 11 clicks.  it works ok now.

I have no explanation but the tuna cans are rather old, maybe they are something we need to learn to live with?

is your fuel pressure at least 15 psi at the cold start selenoid?

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[ja17]

Hello James,

Yes, the adjustment of the full load screw on the rack is the other way to change the mixture at all ranges without messing up the shimmed adjustment on the "tuna can" or the "WRD".  I do not usually suggest this. Normally something else on the engine causes the poor running.

Anyway, this adjustment is the opposit of the idle mixture screw. Clockwise turning leans the mixture. Counterclockwise richens it.



Joe Alexander
Blacklick, Ohio

[jameshoward]

Joe,

Thanks. Taking your point about an unrecommended activity, is there anything else at all I could check before going to the screw? Would it be better to add shims/washers etc rather than use the screw? I am as sure as I can be that everything else is pretty much OK (less the tappets, which I'm off to do now).

James

[jameshoward]

In this post Ray has a similar problem to me, albeit that he's coming at it from the opposite angle: trying to go lean, I think.

http://index.php?topic=6945

Can I temporarily adjust the linkage as discussed by Joe in this post to see what that does and make the car run richer? If so, is it just a case of lengthening the rod to the FI pump, accepting it will screw up the idle?

Also, having not seen a WRD shim, and not having any laying around, is it the sort of thing one can adapt from a washer, or is there a place I can get some if the advice is to add a shim or 3 to richen the whole range? (Or if anyone has any they're not using and wants a good home for them). Neither SLS or Niemoeller know what I'm talking about, and they're about the best bet for parts in Germany that I know of.

Thanks,

James

[ja17]

Hello James,

Make certain you installed the injection pump correctly on time. You can be 180 degrees off and the car will still run fairly well. The idle will not act right. 20 degrees after top dead center on number one (both front camlobes upward 10 o'clack and 2 o'clock roughly).

I have a good selection of the oval WRD shims if you need a couple.

Joe Alexander
Blacklick, Ohio

[Raymond]

James,
My problem was solved without adjusting the full load screw. At Blacklick, Joe laid hands on her and she was cured.  

Actually, I had the linkage just right, I replaced the FI thermostat (which required drilling out the collar) and guessed the lucky number of shims, just before the trip to Blacklick.  The idle issues I had were because I was just too timid with the adjustments on the FI thumbscrew.  (Hans' influence.)  My car was close but between Joe and Pete and two more clicks the day after I left, I adjusted the FI pump 10 clicks to rich.  The idle air screw on the intake is much more effective now.  

My advice is enrich the mixture with WRD shims and ignore Hans.  Turn the thumbscrew in four, then two click increments, until you can get the performace you want with the air screw.  Use a tach and vacuum gauge to get the ideal balance.

Ray
'68 280SL 4-spd Coupe

[glennard]

Here's my take--.  1. Make sure the butterfly is closed at rest.  2. Run engine until at normal temp.  3. Free up rods to the butterfly and FI pump.  Note rpms- should be 750-800.  4. Slightly open butterfly- rpms should go up 50- then engine will stall as you add more air. Close butter fly.  5. Adjust idle air screw to highest rpm attainable.  6. If it is over 800, stop engine and turn FI knob CCW a couple clicks(1 click for every 100 rpm over 800 up to 3 clicks). 7. Restart engine- repeat  5 and 6 until the engine idles at 800.  Turn in(reduce air) the idle air screw until the rpms drop 50 to 750 rpm.  8. Reconnect rods.   The objective is to have the engine idle at 750-800 with the minimum fuel flow and its associated air flow necessary for 775 rpm.  MB recommends the 50 rpm fuel rich mode adjustment.  This idle adjustment assumes all other air/fuel sources are zero- i.e. the CSV is not leaking, the air slide is closed, etc.

[al_lieffring]

James

As far as I am concerned, adding or taking away shims from the cold start thermostat and the barometric compensator are a half-@$$ way to adjust the pump. The main rack screw on a 230sl is more difficult to get at than the 250 and 280 pumps, but it adjusts in the same manner, The biggest problem is usually getting out the slot head acess plug, this behind and below the cold start solenoid. Often it takes a 3/8 impact with a screw driver socket to get it loose.

Next problem on a 230Sl pump is that the starting solenoid's acting arm inside the pump is blocking access to the adjustment screw head, There is a 14mm bolt head near the return spring of the throttle linkage arm


This screw head is the fulcrum that the arm pivots on. backing out this screw will move the arm clear of the adjusting screw, Turning the screw more than the the 2 or 3 mm needed to get clearance for your screwdriver will cause the arm to fall off the pivot, so be careful not to turn the screw too far.

Now a screw driver can be inserted in the main rack screw, one click here is a much larger adjustment than on the idle thumb screw and it works in the opposite direction,

Any time the motor is restarted the pivot bolt needs to be returned to its original position, This is a lot of back and forth work getting the mixture adjusted this way, but I think you will get much better results.

Good Luck

(BTW) this procedure is for 6.3 pumps too

Al Lieffring
66 230Sl
Jones'n for a new gas tank

[jameshoward]

Gentlemen,

Many thanks for your illuminating posts. Lots of different advice and ways to skin the cat. Joe, thank you for the kind offer of shims. I'll let you know how it goes.

I lengthened the FI pump rod about 6-8mm last night just to see what difference it made to how the car ran. The idle smoothed out a little and I was able to open the idle air screw without the rpm bouncing up and down. When driving the car, the hesitation between 2-3000 rpm was gone. The car would motor along happily in 4th at 30mph without shuddering. So it would seem that I have confirmed I'm very lean.

I may revisit the FI pump timing as Joe has suggested, but the auto gasket stuff that's at the union between pump and block will be a pain to redo. I am pretty sure, though, that it went on properly. I remember reading the BBB which talks about cylinder 6, and then Joe's posts that talk about cyl 1 at 20 deg. I went with Joe (and the Haynes manual said the same thing).

I re-did the valve clearances the other day. They were off a little as picked up by the Bosch machine at the tuning shop. Oddly enough, the car now runs worse and I've a sort of ticking noise coming from the engine. That's annoying.

I've been grabbing a few moments with the car after work. I need to get stuck in again this weekend and put into practice all the top tips that have been posted here.

Thank you again.

JH

[glennard]

James, Opening the idle air screw(engine at 750 rpm and warmed up) should result in 1, 50 rpm increase for first little bit of opening, then 2, a progressive decrease in rpm as the mix is leaned out- until it stalls.   Anything other than this, something else is amiss.

[merrill]

james,
the gasket stuff at the inj pump mount should not be a big deal.

once the pump is off there is a spacer that soemtimes has sealer on it.

when I re installed my pump I put a new paper gasket between the block and spacer with a thin coating of sealer.

the biggest pain is getting the lower inner bolt off that secures the inj pump to the block.  I usually get to this from underneath the car



Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[al_lieffring]

James

If you are going to remove the pump to recheck the injection timing, while the pump is off and the main rack adjustment is more easily accesable, go ahead and open up the main rack adjustment two clicks counter clockwise (richer), then reinstall the acess plug finger tight, if it needs more adjustment after the car is going again it will be easier to do.

Al Lieffring
66 230Sl
New blue top just arrived
new gas tank on order