Temperamental 230SL After New IP Installed

[captainslow]

So I installed a spare rebuilt IP in my 1966 230SL. I opted to rebuild/replace due to the car having sat for a while and having a tough time running off idle until warm. It would start and idle great but any toe in on the throttle would cause it to stumble and die. I figured it was the WRD and didn’t want to down the car for a long period if I took it apart and it wasn’t the WRD. The car ran rich at idle no matter what I did but above 1700 it was snappy never smoked and didn’t smell gassy.

Long story short, everything worked and it ran although a little rich, hot start was also fine. Fast forward, I installed the new pump and I can’t get the sucker to run hardly at all. Sadly I didn’t follow the scientific method and replaced all 6 injectors, did plugs and new wires as well as cleaning and relapping the CSV at the same time as the pump swap.

I’ve checked that the CSV isn’t leaking, but this car seems to just run RICH at all rpms now. I took all the relays apart and cleaned them. Interestingly each relay looked spotless and brand new on the inside. The round relay was interesting because the contacts were touching which I found odd… I figured they would close rather than open when activated.

I can get the car to run with everything hooked up when the engine is completely cold. It will fire pretty quick but not catch, then recrank and it will idle very low until I give it some gas and it will creeeeeep up in RPM. Once it hits 2000ish rpm it takes off like a scalded cheetah and runs great and smooth. The longer I let it run at that rpm the more it starts to bog down. The rpm’s will start to drop and if I let it fall too low it will drop down shut off and refuse to start until the engine is cold. I’ve pulled the plugs and they smell like gas and cylinders 1 and 4 are black. I’ve checked the CSV solenoid with the key on to make sure it’s not energizing and flooding the intake. I will have an assistant tomorrow to check to make sure the relays are timing out correctly but I’m kind of at a loss.

The symptoms to me sound like it’s running rich, but I can’t get it to start hot even with a fresh dry set of spark plugs. The only wiring I’m not 100% on is the enrichment solenoid. I unhooked it but didn’t take a picture. I’m not sure the hot vs ground side matter. I hooked the brown ground up to the RH side of the IP solenoid (side closest to the block). Is it possible the rack is just going full enrich all the time?

Any support even if just emotional is appreciated.

[ja17]

Make sure your engine linkages are adjusted correctly first. Learn the split linkage test and you will be able to see if it running rich. Plan on rotating a fresh set of plugs in the car even if the others are new.

[captainslow]

Linkages are good, they were adjusted on the old pump (per your excellent guide!) and this one required minor modification to get it to all sync up. Went through the starting aids today and everything appears to be working correctly. IP solenoid triggers for 1ish sec at crank with the starter; the solenoid on the intake manifold stayed powered for about 5-7 seconds during cold start then shut off.

We played around with some extremes today, turned the IP all the way in and all the way out. Full rich on the IP with the idle bleed screw closed actually gave the best idle I’ve seen yet. We could keep the car running around 800 rpm by gently working the throttle. This made us think vacuum leak. Brake booster is solid, rubber hose going to the WRD is tight, air fitting on the CSV is tight. New o ring on both the CSV body and solenoid.

As the car warmed up it became more difficult to keep things running and then eventually started back firing out the intake. Once the car is warm ish 120-150 degrees-ish. It won’t start again without a jumper wire going from the battery to the CSV to give it an extra shot of gas. I can’t keep it running at that point but at least it will fire. All signs point to not enough fuel or too much air. WRD is the next logical thing to investigate since it handles both fuel and air.

Spark plugs have been black but I kind of attribute that to them never coming up to operating temp. Haven’t hit 180 yet. I’ve been burning them back down with some map gas and they seem to work great on a cold engine or with the CSV manually activated.

As an aside the electric fuel pump was replaced about 2 months before I purchased the car in 2020. I got under it today and had my assistant key on. It produced enough pressure on the pump exit for me to feel it there as well as all the way to the rubber line going to the fuel damper. When triggered off it quickly goes soft indicating to me the return and supply are free of blockages.

Ignition system should be good too! I replaced the points with a pertronix unit and matching coil when I bought it and just put new 1kohm spark plug wires on at the same time I did the IP (I verified they are 1kohm, as Ronald Reagan said “Trust but verify”).

[captainslow]

I have new information! I tested the fuel system today. It bypasses about 1 liter every 13 seconds on the return line. One thing I did find troublesome is that when my assistant keyed the car off the fuel continued to siphon at a fairly high rate. I attached my hose to the hardline on the exit of the fuel damper. I assumed that the little fitting on the forward inboard side coming out of the injection pump was a relief valve. To be clear this is the one that goes from the injection pump to the inlet of the fuel damper. Could this be by problem? It should have arrested any siphon action by only breaking open at 15 psi. As soon as I got the hose above the tank the siphon broke. How is my IP building any pressure if it’s going straight through? I’ll report back with fuel pressure at the CSV but need a hose to fit over it I can clamp down.

[captainslow]

More news! I’m only getting 9.5 psi at the CSV. Plenty of flow on the return side to the tank though. I’m going to swap return restrictions valves from the old pump onto the new pump and report back. The amount of fuel that siphoned through should not have been that much if the restriction orifice is working. If it doesn’t fix the problem I have a new fuel supply and return line waiting in the wings. If that still doesn’t fix it, the “new” fuel pump is probably the issue.

[ja17]

You might be on the right track. Check to see if that check valve on the front inboard of the IP is stuck open. If so you will most likely have pressure loss. Below 11psi. you will have problems.

[captainslow]

I think the prognosis is in. Swapping back to the “old” return valve yielded a 1 psi increase in pressure at the CSV. I turned my attention to the pump. My “replaced” low pressure pump appears to have simply been painted… with the cover off you can clearly see they didn’t even take the dirt out of the grooves in the flathead screws before spraying it with paint. The filter sock on the pump had a good amount of rust in it (can’t see any in the tank through the sender hole) but I think the best option given the cost is to replace the tank with an aftermarket and get a new low pressure pump posthaste.

If Bob Youngman is patiently waiting for my issue to reveal itself to be the pump, I’m now in the market for one 😉.

As a final note, deadheading the pump on the return side only yielded a 19 psi static pressure from the old pump. I think I found an old forum post where the pump should be able to generate up to 30 psi.

[captainslow]

Defeated yet again… new pump, a new fuel supply line and a new return line back to a brand new tank. Still 9psi at the CSV. I took the restriction valve off the injection pump, took it apart and it looks virtually brand new. The little plastic bit seems good but to me the spring seems pretty weak, but I guess the area of the plastic is pretty small requiring only a little force. 

I did some playing around with the injection pump at this point since I can hear the fuel RIPPING through the pump now (the new pump is twice the flow of the original at 14 psi). I cracked the injection lines at the injectors and am getting a good flow of fuel from cylinders 4, 3, and 2 with the electric pump running. 6, 5, 1 are dry as a bone. Is that normal operation? I would have assumed no fuel would go to the injectors unless the IP was turning. I spun the engine over with the starter to see if maybe it was at a happy spot and the IP was in the partial compression stroke and that was why I was getting fuel, but the same cylinders were gushing fuel and the dry ones were still dry. Next step is maybe pull the injectors and see if I have a leaker affecting my running fuel pressure.

Any more advice is greatly welcome.

[captainslow]

No leaky injectors, I will try and stretch/shim the spring in the pressure relief valve and see if I can sneak some more pressure out before it starts to crack.

[captainslow]

By stretching the spring I got the system pressure up to 12.5. If I pinch off the return the pump has no problem hitting its 15 psi internal bypass. Still won’t run right. I can get it to run with the cold start aids working and then once it warms up no dice. It won’t operate anywhere below 1700 to do a split linkage test. I popped the bolt cap thing off the end of the rack and it’s sitting as far as it will go towards the front of the car. If you poke it aft it smoothly travels but then pushes itself back to the most forward position. I played with the old IP pump on the floor and it did not move unless it was moved from the end of the rack. I even took the WRD off the end of the IP on the floor and manually actuated its lever and that didn’t push the rack forward either.

Beginning to think this rebuild IP is a dud. 

[captainslow]

An interesting aside, I also determined the WRD nut on the side was twisted to the test position, disabling the air slide. I’m going to swap back to my old IP and see if the old girl fires right up and holds a higher line pressure.

[Cees Klumper]

As you are getting fuel to half the injectors with engine off but pump running, and not the other half, is it possible that (some of) the little pistons inside the FI pump are stuck? There is info here on freeing them. I don't know if this is normal or not though.

[Charles 230SL]

Hello Captain, there’s something wrong with that spare/rebuilt injection pump. You should be seeing fuel from all six injector lines when you crack the lines and spin the starter. Lack of fuel at #6, 5 and 1 is a good indication that three of the injection pump plungers are binding up or stuck.

[captainslow]

See but here’s the interesting thing. I’m seeing fuel WITHOUT spinning the starter on 4,3, and 2. And I mean it’s a TON of fuel. If I left the line cracked it would just keep pouring out as long as the electric pump is on. 6,5, and 1 definately have fuel coming out when it’s spun with the starter. The engine runs GREAT above 1700 rpm for about 4 minutes until things warm up. Doesn’t sound likes it’s missing or it’s running on three cylinders. It’s actually quite smooth.

I pulled the pump last night and something weird I found was the fittings on 4,3,2 on the injection pump were dry. 6,5,1 had a little puddle of fuel up to where the fuel lines had sat. It’s like there’s no check valve installed on 4,3,2.

The rack moves buttery smooth and self returns on this pump. Can you get a stuck piston and still have smooth rack return? I think the other big outstanding question is can you have pressure at the fuel injectors WITHOUT spinning the injection pump?

[Charles 230SL]

..I’m seeing fuel WITHOUT spinning the starter on 4,3, and 2. And I mean it’s a TON of fuel. If I left the line cracked it would just keep pouring out as long as the electric pump is on..

hmmm, that doesn't sound right - are you sure all (6) check valves are there? Remove one of the fittings (4, 3 or 2) and confirm the spring and cone-valve aren't missing. There's some pictures of the cone-valves here: https://www.sl113.org/forums/index.php?topic=24659.msg177150#msg177150

[captainslow]

hmmm, that doesn't sound right - are you sure all (6) check valves are there? Remove one of the fittings (4, 3 or 2) and confirm the spring and cone-valve aren't missing. There's some pictures of the cone-valves here: https://www.sl113.org/forums/index.php?topic=24659.msg177150#msg177150

Ding ding ding we have a winner!! The check valves on the offending cylinders are seized in there tighter than my little fingers can pry them out. The other ones come out freely with no issue. I tugged on it a little bit with a pliers with cloth under it and couldn’t get it to budge. Any suggestions? Sad this is like this on a brand new pump. I replaced the main fuel filter and fuel injection lines to prevent something like this happening.

-Joe

[captainslow]

Charles that post you linked to was everything that I needed and more.  I think these three valves are done for, maybe their seats as well.  I might look into doing the ball valve mod for this pump.  One valve was so stuck it ended up pulling the seat out of the pump.  The other two came out with some kroil and a little twisting.  If I had pulled straight out I have no doubt at least one of them would have also pulled a seat out of the pump.  Here are some pictures of the #2 cylinder that had the most issues. 

I think the best option is to put the old pump back in.  I feel that these check valves are just going to keep hanging up on the valve guides.  I noticed the one that pulled the valve seat out protruded ever so slightly below the bottom surface of the valve seat.  I had to hit it with a small drift to get it out and it still didn't want to give up without another whack halfway through the travel.  That valve had a visible mark about where it came through the bottom of the valve seat.  Unless I sand it down a little I'm not sure I won't randomly have this issue on the road.

I'm 99% sure my lean condition is coming from the valves being just slightly open and allowing a little bit of fuel through, maybe just enough to burn (again it didn't sound like a 3 cylinder!).  Here is a YouTube video of it running before I pulled the pump.  This was full enrichment on the idle adjust knob and almost no air bleed on the intake manifold so max richness below 1700.

https://youtube.com/shorts/lddgaeU1I4A?feature=share

[Charles 230SL]

...I think the best option is to put the old pump back in.  I feel that these check valves are just going to keep hanging up on the valve guides..

You might consider using 3 good cone-valves & seats from the other injection pump. 

[Charles 230SL]

hi Captain, hate to be nosy but I'm curious how it's going with your fuel injection pump. Did you install the old pump?

[captainslow]

Put it all back together the way it was, bled the injection lines and she fired right up! I even reinstalled the old lift pump and that seems to work fine. I’m going to put the fuel gauge back on and see if the failing check valves will cause a low pressure value at the CSV.

Admittedly it’s not “ready to rock and roll”. I freed the WRD up on my old pump and now I need to play around with the idle settings. It won’t hold an idle unless I slightly push on the throttle. I need to adjust timing first because I can never install the through bolt on the injection pump without loosening the PS reservoir bracket near the head, and that requires adjusting the dizzy and then resetting it to the mark on the dizzy housing. I think it’s a 5mm Allen, a clicky wheel, and a flat headed screw driver away from running well.

[Pawel66]

I wonder if you are aware of a simple check valves test (comes from BBB):

1. Clean the pressure fuel lines at FIP before unscrewing.
2. Blow the connectors after unscrewing the fuel lines with compressed air - I understand to get rid of potential dirt that might have dropped into the connectors during unscrewing and to blow out remains of fuel that may be there so that you can see fuel level raising inside the connectors in case the check valve is faulty.
3. Undo the fuel lines.
4. Push rack in to the back until it stops.
5. Switch on the ignition (fuel pump)

Fuel coming out through a valve - bad valve, not coming out - good valve.

[captainslow]

Ahhh I guess I should read the BBB more often!

Old pump is back in and the engine is timed. Starts up and runs good. Doesn’t smoke really. Idle is still super rich (why I started down this path). Applying the split linkage test I can support 1700 rpm with the fuel being supplied at idle when I have the clicky wheel turned out as far as it will go.

Any suggestions on why it’s that way? Barometric compensator tested good, CSV doesn’t leak a DROP, plugs are a nice tan color after some freeway driving; what gives!!? It does start awefully nice warm or cold tho. I’d love to sort out the idle!

-Joe

[rwmastel]

Captainslow,

You've done a lot of good work trying to figure this out and get it sorted.  More than most of us in this Group have experience with, including me.  This has been a good educational read.

Now, regarding this last post, when you say, "Applying the split linkage test I can support 1700 rpm ..." does that mean you can't get it below that rpm or the engine stalls?  Stalls when taking away the air supply?  There's no more fuel supply to take away in the test?  Sorry, just trying to understand details.  Then you add the condition, "... with the fuel being supplied at idle when I have the clicky wheel turned out as far as it will go."  Remind the novices (like me), is that a full lean adjustment of the rack?  So, if I understand correctly, the condition is that in split linkage test with minimum fuel supplied the rpm is still high, indicating that somehow too much fuel is being supplied from somewhere.  Do I have it?  That's why you said, "Idle is still super rich"?  But, not rich when driving because "plugs are a nice tan color after some freeway driving".

You've mentioned the WRD a couple times in this thread.  What's the status of the WRD on the currently installed pump?
- "I freed the WRD up on my old pump"
- "I also determined the WRD nut on the side was twisted to the test position, disabling the air slide."
- "I even took the WRD off the end of the IP on the floor and manually actuated its lever and that didn’t push the rack forward either."

[captainslow]

Captainslow,

You've done a lot of good work trying to figure this out and get it sorted.  More than most of us in this Group have experience with, including me.  This has been a good educational read.

Now, regarding this last post, when you say, "Applying the split linkage test I can support 1700 rpm ..." does that mean you can't get it below that rpm or the engine stalls?  Stalls when taking away the air supply?  There's no more fuel supply to take away in the test?  Sorry, just trying to understand details.  Then you add the condition, "... with the fuel being supplied at idle when I have the clicky wheel turned out as far as it will go."  Remind the novices (like me), is that a full lean adjustment of the rack?  So, if I understand correctly, the condition is that in split linkage test with minimum fuel supplied the rpm is still high, indicating that somehow too much fuel is being supplied from somewhere.  Do I have it?  That's why you said, "Idle is still super rich"?  But, not rich when driving because "plugs are a nice tan color after some freeway driving".

You've mentioned the WRD a couple times in this thread.  What's the status of the WRD on the currently installed pump?
- "I freed the WRD up on my old pump"
- "I also determined the WRD nut on the side was twisted to the test position, disabling the air slide."
- "I even took the WRD off the end of the IP on the floor and manually actuated its lever and that didn’t push the rack forward either."

Great questions,

By support 1700 rpm I mean there is enough fuel being supplied at idle (800 rpm ish) doing the split linkage test I can get the engine to go up to 1700 rpm before it starts to stumble when adding more air. If I could take away more fuel I would! I might pull the shim under the barometric comp but I’d hate to lean everything out based on my plug color. I suppose I could do the split linkage at a higher rpm and see if I’ve still got more fuel than I want being supplied.

Full lean is the clicky wheel all the way out. In my mind this is backwards from an idle jet on a carburetor which always messes me up!

The other somewhat odd thing is by twisting the air bleed screw out I can’t get it to support a higher rpm either. I backed it out what I would consider pretty far (4 rotations) and in this setup turning it out really has no affect. Turning it in and I mean really cranking it in will cause the rpm to drop. I would have assumed the rpm would have continued climbing until it met the amount of fuel being supplied. Another Mercedes mystery.

The WRD should be functional. It slides nicely. When I took mine apart (I didn’t remove the roll pin) I never found that internal spring I’ve seen in other peoples pictures. Not sure the R11 pump has that spring. The mechanism the WRD touches inside the pump to influence the rack moves freely and returns freely to the up position. It has some sort of internal spring that pushes itself back up. I installed the new thermostat from my new pump to make sure I was going to have a working t stat on this pump. It’s as goood as it’s going to get! I could take my spare pump apart now and see if there is a spring in that WRD. Also I was a dope and didn’t fully understand how little that the WRD mechanism moves the rack. If the rack isn’t in the full back position it gives the effect of the rack not moving.  I placed it in the full back position and I can feel it push forward. User error on that statement.

[rwmastel]

Thanks for the details.  And looping back on another point, the injection pump now on the engine has six known good valves with good seats & seals?