Rebuilt engine - no power

[nag]

Hi,
I have just installed a reconditioned engine out of a 1969 280SE with a R20Y FIP in my 1965 230sl. The engine starts, warms up (WRD excess air shuts off when warm),  idles and revs fine.
However when attempting to drive off there was no power whatsoever. It would not pull away from my yard! 
A 123ignition and new coil have been installed and as far as I can tell the advance curve is working ok (the inlet manifold w/ vacuum advance is from the original engine. The 123 ign is programmed accordingly).
The fuel supply pump worked fine before the engine swap and a new filter has been fitted.

I had adjusted the linkage so that throttle valve and IP throttle arm both closed at the same time. The length of the link to the IP throttle arm is shorter then the length refered to in the tech manual seen on this site. I suppose that could be because the origiginal linkage system might be slightly out for the SE engine/ FIP.
Lengthening the linkage arm down to the FIP (lifted the arm off the stop on the FIP) got the car running, but still no power when trying to accelerate. I suppose playing with the linkage arm gets the 3D cam out of sync and actually didn't solve the power problem only enrichening the AF ratio.

Can someone pls advice me of the best way to proceed.

Thank you
erik

[69280sl]

Clutch or transmission problem?

Gus

[w113dude]

Agree, If the car is automatic could be low on transmission fluid.

[nag]

Thanks for your comments.

The car has a manual 4 speed transmission. As I tried to mention I got the car running adjusting the link down to the FIP (ie giving gas without opening the butterfly valve). The more I adjusted the richer the AF mix got, but never at any point of adjustment did I get any power when trying to accelerate.

I was thinking it may need adjusting of the full range screw (FIP), but that would that mess up the ideling?

erik

[ja17]

Check to make sure the rack in the injection pump is not stuck. The small rubber cover on the front of the IP can be removed to check the rack for movement. Sometimes IP racks on stored cars or engines, can get stuck. Also if the ignition timing is way off, the engine may not accelerate.

[twistedtree]

Injection pump timing?  With a freshly rebuilt and reassembled engine, I'd be looking first at things that might have been assembled incorrectly.  Injection pump alignment, ignition timing, valve timing, linkage adjustment, etc.

Don't rule out the 123 distributor either.  Do you have a vacuum advance or vacuum retard throttle body (they are ported differently), and are you sure the 123 is set accordingly.  I've been having a lot of trouble with a 123 on a non-MB car where I have discovered that they have the vacuum advance/retard programming backwards in the 123 and it makes a real mess of things.  I'm now going to test and confirm the advance programming on the 123 in my '64 230SL and not take their word for it.  123 won't tell you what their advance curves look like, so you need to either take their word for it, which I've proven to be unreliable, or test it all for yourself which is a PITA.  One thing you might try is to disconnect and plug the vacuum line to the disti.  That will disable the vacuum advance/retard and at least ensure that it's not working against you as it was with the other car I was working on.  It will also let you confirm that the "mechanical" advance is set and working properly.

[nag]

Thanks for some very good comments.

I have already checked valves and injection pump timing. It will probably be an idea to take the IP off again to check the rack movement. I seem to remember having read that it is suppose to move a total of 18mm or so. At the same time I will look for the rack adjustment screw as I couldn't locate it behind it's cover with the pump installed in the car.
I will also double check timing advance, also with the vacuum hose disconnected as suggested. The intake manifold is for a vacuum advance distributor and I programmed the 123 ign to #6 as mentioned in the manual.

I'm currently looking into buying a wideband O2 sensor/ gauge to assit me checking the AFR as I drive the car. I have seen that Innovate sells such a sensor - MTX-L and also sells a clamp for the O2 sensor so that it can be secured to the exhaust tail pipe. The O2 sensor and clamp are a bit pricy, but I suppose if that could help me figure out where the problem is it would be worth it.
Anyone had any experience with an O2 sensor for tuning the car?

rgds
erik
 

[twistedtree]

The rack movement can be checked easily without removing the injection pump.  There is a cap on the front of the pump which might already be removed.  The rack shaft is behind the cap, and you can screw a small bolt (I think Joe said 8mm?) into the end of the shaft to give you something to push/pull on.  I think you'll know right away if it's stuck.  Personally, I'd avoid removing the IP if at all possible.  It's a pain in the butt to get it off and back on again, and even if it makes it easier to get to the main adjusting screw, you'll need to make the adjustment with it on the car anyway.  I've found that you really need to remove the upper solenoid (if you have one) to reach the rack screw.  It otherwise blocks access.  The good news is that the solenoid is easier to remove than the whole IP, and I've run the car with the solenoid removed and not had oil splash everywhere, so you can remove it, make your adjustments, then reinstall it.

[nag]

Hi again,

As suggested I have just checked out the rack movement. After removing the rubber cap at the front of the IP I screwed in a 5 mm bolt. The rack could easily be moved and quite a distance.
Measuring the movement from no to full throttle the rack only moved approx 2 mm. Doesn't seem a lot.  The measurements were done with the cold start assy removed. With the could start assy in place the rack will shift so the throttle start location would be different, one but shouldn't think that would affect the total movement from no to full throttle.
Anyone knows the distance the rack should move?

thanks

erik

[twistedtree]

Measuring the movement from no to full throttle the rack only moved approx 2 mm. Doesn't seem a lot.

Just to be sure I understand, 2mm is how much the rack moves when you move the FIP control lever from idle to full power, right?  But if you grab the bolt and move the rack directly it moves freely, and moves over a longer travel distance?

Now a caveat - I know just enough about these things to get myself in trouble, so if JA17 or BenzDr or other knowledgeable people say otherwise, believe them over me....

But if I'm understanding you correctly, I think all is well.  The rack movement is heavily influenced by the spinning counterweights in the rear section of the FIP, and that only takes effect when the engine is running and the weights are spinning.

Do you know when this engine and FIP last worked properly, or is it all new to you?  That might help provide a clue.

The easiest way to test for mixture problems is to play with the FIP linkage to cause the FIP lever to be ahead of or behind the throttle flap lever, rather than exactly in sync.  If the FIP lever is moving ahead of the throttle lever you will be enriching the mixture (more gas relative to air), and conversely if the FIP is trailing the throttle lever.  Such changes are for diagnostic purposes only as they will otherwise mess up idle mixture and possibly all sorts of other things, but it's a quick and easy way to experiment with the mixture while driving under load, which appears to be where your trouble is.

You might also want to double check the ignition timing.  Here's a quick check list:

- First, check to see if your crank pulley has two scales on it, and be sure you are using the correct one.  Otherwise you will be off by 30-40 degrees which might explain everything.

- With vacuum disconnected and plugged, set the idle timing.

- Rev the engine up and confirm that you are getting correct mechanical advance.

- Confirm that the manifold vacuum is ported for advance.  There should be no vacuum at idle, and an burst of vacuum when you goose the engine.  If it's ported for vacuum retard, it will be the opposite.

- Connect the vacuum line and see how it changes the timing.  For advance, which is what you believe you have, there should be no change to timing at idle, and when you goose the engine the timing should jump forward.

Checking all that will at least allow you to rule it out.

[nag]

Hi Peter,
thanks for your response.

I have just resently bought the engine/IP, so I don't know much about it.

I have remeasured the rack movement.

I can push/ pull the rack by hand a total of 15mm (measurements are done with a ruler, so not spot on). I have read that the distance should be between 18 and 18,5 mm, but not sure if that also holds true for the R20Y fitted to my 280 SE engine.
Rack movement when operating the gas lever on the pump is 4mm. (I mentioned 2mm in my previous posting, but it seems like the spring doesn't quite pull the rack fully back). This last measurement of 4mm was done with the linkage disconnected.

I have previously tried to adjust the length of the linkage down to the IP from very lean to too rich (checked sparkplugs). At no adjustment could I get power when trying to accelerate driving at around 2000 rev's. At too lean I couln't even drive the car, although it was ideling and reving quite happely at standstill.

I checked the TDC scale with the no 1 piston at top so the timing scale I use should be the right one.


I will recheck the timing when I get the opportunity. Hopefully in a couple of weeks.

Thanks again
erik

[twistedtree]

That's quite the puzzler.  Was there any difference in performance when you richened the mixture?  It sounds like it got worse when leaner, so if it improved when you made it richer, that is at least a clue.

I haven't run into this myself, but on the theory that the FIP isn't delivering enough fuel to do anything other than rev in neutral, here are a few things I've heard other people run into that you might check.

- The plungers/pistons inside the FIP might be stuck.  If their stroke is limited, it might explain what's going on.  Search this forum and you will find explanations of how to check and resolve this problem.

- The outlet fittings on the FIP might be too tight.  They must be tightened to the proper torque or they will restrict fuel flow.  This is not the nut that holds the delivery pipe in place, it's the fitting that screws into the FIP itself, and I believe needs to be removed anyway to check for full plunger movement.

Perhaps one of these will yield a simple fix.

[glenn]

Does it rev up(3-5000 or so) in neutral?

[nag]

Thanks for your comments,

I followed the advice to read up on all the comments regarding adjustment of the rack.
Rather than fiddeling with the rack adjustment screw itself, which I on my first and only attempt didn't locate, I decided to adjust the pump adding 14 mm ID shims to the barometric controller.
After a couple of attempts I ended up adding a 2 mm shim and I'm happy to say that the engine accelerates fine under load.
Pretty amazing it went from no power to normal power adding a 2mm shim.

I have followed the advice on the linkage adjustment, butterfly valve closed, throttle arm against stop and lined up against 10 mm hole in the manifold. With this configuration the linkage down to the pump only measures 225 mm, short of what is mentioned in the linkage tour.
When pushing the throttle arm from the FIP stop, in a very short movement of the throttle arm, the rack moves instantly approx 4 mm. After that further movement of the throttle arm to full throttle has no effect on the rack.
I suppose I therefore have to assume the 225 mm linkage down to the FIP is correct for the R20Y FIP.

When I recieve the O2 sensor/gauge and exhaust clamp I will see if I can fine tune the FIP further. I also need to bring down the ideling from 1000 rpm (up from +800 prior to adding the 2 mm shim).

rgds
erik
230 sl w/ 280 SE engine R20Y FIP

[Benz Dr.]

I think the correct measurement is 223mm so you're fairly close.

  I find that adjusting the compensator is easier than any other way to correct fuel ratios across the entire range. If that's all that's wrong with it then you should be OK.

[twistedtree]

And adjusting at the BC also adjusts idle fuel, so that's why your idle is up.  If you now adjust the idle mixture you should be able to get the idle back down to 800.  Sounds like you are getting close....

[nag]

I just recieved the clamp for the Innovate MTX-L oxygen sensor before leaving for work again. After fitting it to the the end of the exhaust I went of for a quick test drive.
The gauge/ sensor reading the AFR seems to work fine. On idle (too high at approx 1000 RPM) the AFR was very rich, around 11.5%, during acceleration it went very lean, around 17-18%, before settling down to between 14-15% when driving along at 2-3000 rpm's.
I tried to lean the idle by turning the idle screw on the FIP a total of 6 clicks CCW, with little effect. Idle AFR went up to about 12,5%, still very rich, and RPM  at idle went if anything up 100-200 RPM's. Not what I had hoped for.
It seems as the AFR readings are opposite to what they are supposed to.
The car drives ok, but I suppose with the correct set up should hopefully run better. Difficult to say as I haven't got another SL to compare it to.

Any ideas for what to do next?
I will start with re-checking the timing - have left it for this long as it is a pain to get the hood off and back on.
Don't know if it is possible to adjust the linkage to give the FIP a head start to the air valve in the suction manifold?

rgds
erik