230sl M127engine without idling

[dnadanny1]

hi guys. Since the morning first cold-starting of my 1966 230sl is bad, and it is ok at/after second starting, I had sent my fuel injection pump for rebuild recently. However, when I got back my pump and install it to my car according specification, the first cold-start is ok, but it has no idling that when I  decelerate, the engine stalls.
Does anyone have any idea what would be the problem?
Any comment is appreciated.

Thanks a lot.

Danny   

[dnadanny1]

BTW, does anyone know how much CO level is considered correct?
 Thanks

[Cees Klumper]

Does the engine idle ok once fully warmed up? It may be the warm running device on the injection pump.
From memory I want to say the CO can be up to 5% but check the Technical Manual here, it should be listed there.

[Pawel66]

Is it not the old story of checking several things (including the WRD), adjusting and going through the linkage tour?

Something changed in the FIP during the rebuild and now you may just have to adjust the whole lot.

[ja17]

Yes, set your engine linkages and learn how to perform the "split linkage test" so you will know if your fuel mixture is correct.

[mrfatboy]

Here is the CO info.

Idle       
750-800   RPM CO  3.5 - 4.5  =  AFR 12.80 - 13.20

Lower partial   
1500      RPM CO  1.5 - 3.0  =  AFR  13.40 - 13.95
3000+  RPM CO  0.2 - 1.5  =  AFR  13.95 - 14.50

Full load   
3000+  RPM CO  2.0 - 4.0  =  AFR  12.85 - 13.20

[dnadanny1]

Thank you for all your idea and the CO data.
Can I know more details about "split linkage test"?
I am sure I have set linkage correctly.
The problem is that when the engine is before warm up, the fast idle is 1400rpm. And, when warm up for several minutes, the engine stall.

No matter how I adjust, I can not get the idle below 1000rpm. Whenever it goes below1000, it instantly stall and drop to 0 rpm.

I have concerned that the fuel injection pump may be the problem. However, the rebuild professional has been on this field for more than40 to 50 years. He said the pump was on specification when sending back to me. And, he suggested me to check other parts.

And  now, after performing every tests I can think of, it does not conclude anything yet. That's why I want your help to see where my blind spot is.

Thanks a lot. Appreciate all your help.

Danny

[Garry]

Danny,


As a full member you have access to the Full Member only content here.


https://www.sl113.org/wiki/


Have you watched the linkage tour by Joe Alexander.   If not i suggest you do that.


Garry

[dnadanny1]

Thanks all for your help.

I have performed the checking and setting of the following.
1. Cyclinder pressure
2. Valve clearance
3. Valve timing
4. Injection pump timing
5. Electronic fuel pump flow rate
6. Electronic fuel pump pressure
7. Cold start valve leakage test
8. Injectors open pressure
9. Injectors leakage test
10. Intake connecting rods linkage adjustment
11. Intake butterfly adjustment
12. Air idle valve adjustment
13. Ignition timing adjustment

After performing the above tasks, I still cannot come up with the root cause of the problem. So I still believe  it has to do with the A/F. The car idling is too high and CO unstable. After I adjusted the CO to 3.5-4.5 and constantly accelerate to 2,000rpm, the CO does not drop as it should. In contrary, it increases to 8.9% or above. This is very strange.

Also, I have no confidence that the upcoming replacement of 6 injectors will bring any improvement to the car, given the previous injector test stated in the above list.

Is that sufficient to indicate the problem happening in the pump?

Thanks a lot.

[mrfatboy]

When testing/setting your CO, is the car at full operating temperature?

What are you using to test the CO?

Have you verified that the WRD is working properly? When engine is cold,  remove the small air filter on FIP. Start engine.  You should hear loud air suction sound. As the engine warms to full temp the suction will diminish to almost nothing.

Put a test light on the CSV and verify that it is NOT getting power constantly when engine is running.

Just to be clear, at full operating temperature what is your RPM and CO numbers at idle?

[dnadanny1]

Thanks for your advice. These are the data I got.


Engine   Engine temperature   RPM   Fuel Pressure   CO   Idling Time
IGN ON    25oC                      0      1 - 1.1 bar         0        0
OFF          25oC                     0        0 bar                0        0

After ignition on, I block the electric fuel pump rear pipe and switch off, and the fuel pressure is dropped down to 0.

After ignition on, I block the return hose to the fuel tank and switch off. And, the fuel pressure dropped to 0.5 bar at first, and constantly dropped to 0 bar.

Engine   Engine temperature   RPM        Fuel Pressure   CO           Idling Time
Running   24 oC                   1400        1 -1.1 bar           8%          30 sec.
Running   24 oC                   1200        1 -1.1 bar           6.5%      120 sec.
Died         24 oC                 1400        1 -1.1 bar          0.75%     180 sec.
               

After the engine died, I restarted the car.
Then, I adjusted air screw, and the car had 1200 RPM.

Engine   Engine temperature   RPM        Fuel Pressure   CO            Idling Time
Running   65.5 oC                   1200        1 -1.1 bar       2.4%    720 sec.
               
I think the engine is too hot, then I adjust down the RPM by air screw.
But, the RPM didn’t go down, and CO went up to 5.5%.
When the idling time was 1140 sec. I adjusted the air screw to complete close, the RPM is 1000, CO 6%.
When the idling time was 1800 sec, the RPM is 1000, CO 7.3%.
Finally, I stopped running the engine, because I think the data will not change further.

And I wait 30 minutes after the shutdown, it is very difficult to start.
And, I try to press the pedal to help the start-up, and it works.
But, I have to keep pressing the pedal, if I don’t, the engine died.
 

[mrfatboy]

It seems you are trying to adjust RPM and CO by only the idle air screw.  I have read nothing about you adjusting the FIP idle mixture. This is the small knurled knob on back of FIP.

You must adjust both FIP idle mixture screw and the idle air screw together to get proper RPM.

Never adjust the FIP idle mixture knob while engine is running. Very bad.

Only worry about final rpm/co numbers at full operating temperature.

Verify that the WRD is operating correctly.

Read about the FIP adjustments  in the tech manual.

Once you verify the above questions come back and we can help you make final adjustments 👍

[mrfatboy]

Here is an CO analysis of my 280sl.  You should be similar.

[dnadanny1]

I am really appreciate and thank you for your graph and your help.

First, sorry I didnt mention about the small knurled knob on back of FIP. Actually, I have adjusted both air screw and the small knurled knob on back of FIP for a warm idle that I dont need to keep my foot pressing the pedal, CO about 3.5, rpm about 800, when the engine stops. However, it never happened. Also, I have used smoke machine to test the leaking at intake system, and the intake system turns out having no leak.

Second, I dont know how to verify the WRD. Can you give me the relevant information ? Thank you.

Third, It is a good fast idling(1400rpm) before first 3 mins, the CO 6.5 - 8%.

After 3 mins,engine start to slow until it stalls. Then I restart, the engine will stalls if I dont keep pressing the pedal. Therefore, when the engine stalls, I adjust many time the air screw and the small knurled knob on back of FIP for a higher rpm until the engine can keep its idling without my foot pressing the pedal.

After 12 minutes from the first start, I check co/rpm number, CO 2.4%, rpm1200. And I keep it running idle for 20 mins, the engine temperature is 180F and the rpm unchanged but the CO is 5.5%, I think the rpm and CO too high. Then I  adjust air screw and adjust the the small knurled knob on back of FIP for leaner mixture. The lowest level I can adjust is 1000rpm and CO6%. After 10mins, the rpm unchanged but the Co goes to 7.3% and the engine stalls.

BTW, it is strange to me that before the engine stall, I slowly and constantly accelerate for 10sec. to 2200 rpm, the CO is abnormally 8.9%.

Thank you very much.

Regards,
Danny

[mrfatboy]

See post #9 on how to test the WRD.  Also much has been written about it. Use the search function for more info.

If I'm understanding you correctly it seems there are at least two problems going on.

1. It's sounds like the WRD is leaning out the pump too much.  Adding oval shims under the WRD will help fix this.  Are there any oval shims under the WRD now?  How many? What thicknesses?

2.It also sounds like you are getting more fuel over time.  Leaking CSV? Leaky fuel injectors?

Do one thing at a time.

1. Verify the WRD is working properly.  There should no air suction from the FIP air filter at full operating temperature. Report back.

2. Get best CO/rpm you can by adjusting air idle screw and FIP idle screw at full operating temperature. Report back. Don't adjust any more.

Once we get that info we can tackle the WRD.

[dnadanny1]

Thanks for your reply.

1. If there is no air suction from the FIP air filter at full operating temperature means WRD is working properly. Then, my WRD is working properly.

2. the best CO and rpm I can get at full operating temperature is after 12 minutes with CO 2.4%, rpm 1200.

1. For checking the oval shims under the WRD, frankly speaking, I am not familiar with the theory of the injection pump, and I have no data or equipment to measure or adjust. Therefore, I had send the pump to an expert a few weeks ago for rebuild who have been on this field for more than 40+ years.And, when I get back my pump, the problem emerged. This is what he replies to me "The fuel flow was on specifications when the pump left my shop. I have adjusted hundreds of pumps in the same way.".As he is the expert, I have no way but to trust him. And, i am lack of confidence to check the oval shims, because it may affect the setting or adjustment the expert had made.

2. There is no leaking CSV and no leaking fuel injectors.

Thanks a lot.

Regards,
Danny

[mrfatboy]

So it seems your WRD is working properly👍

The oval shims under the WRD affect fuel mixture ONLY during warm up. Adding shims erichens warm up mixture. Removing shims leans FIP.  See pic.  You would need to remove the two screws holding the WRD on and lift up to see how many shims if any are there.

Your FIP expert most likely only can test the pump as if it was running at normal operating temperature. The WRD is separate. You verified it's working but not adjusted properly. Check oval shims.  See the tech manual.


Finally, 2.5%CO  at 1200rpm seems.like an odd ratio. Try reducing idle air screw to raise CO and lower idle. Maybe somebody else can chime in?

What tool are you using to determine CO?

[dnadanny1]

Thanks fatboy for his proactive and consistent guidance.

After his consistent help in whatsapp for 2 days,
my mechanic starts to concern about the engine drag being the cause of problem.

It is because he mis-filled the coolant before that there is no sufficient coolant to the water pump, and he mistakenly started and run the car until overheating. Without coolant, it is possible that the the pistons rubs the cylinder wall because of overheating cause engine drag.

Is any one know whether engine drag will cause no idle? How to check there is potential engine drag?

BTW, will an engine with 175psi compression also affect the idling setting

Thanks a lot.

Regards,
Danny

[ja17]

I have only seen engine drag caused by bad crankshaft bearings.  Not a likely cause. If so your oil pressure would be low. Sounds like the engine is rich when hot. Try disconnecting the engine linkage at the intake. As the engine warms and begins to stall open the intake venturi lever slightly. Leave the linkage going to the IP at rest. Report back with the results.

[dnadanny1]

BTW, what is the easiest and the most accurate way to test blown cylinder head gasket?

Thanks a lot.

[dnadanny1]

HI ja17. I have tried disconnecting the engine linkage at the intake butterfly as the engine warms. Within 3 minutes of warming-up, the CO from 7.5% drops to 1.9%, and when it begins to stall, and I open the intake venturi lever slightly, but it doesnt help, the engine died anyway.

What should we do next?

Thanks for your help.

Regards,
Danny


 

[dnadanny1]

BTW, I have removed all 6 spark plugs out. Please refer to the attachment. The color on each of the spark plugs are different. Since I had already replaced 6 new spark plugs, is it gonna help if I replace with 6 new injectors? 

Thanks a lot.

Regards,
Danny

[mrfatboy]

HI ja17. I have tried disconnecting the engine linkage at the intake butterfly as the engine warms. Within 3 minutes of warming-up, the CO from 7.5% drops to 1.9%, and when it begins to stall, and I open the intake venturi lever slightly, but it doesnt help, the engine died anyway.

What should we do next?

Thanks for your help.

Regards,
Danny

Danny, 

I believe your CO dipping to 1.5% during warm up is normal. Please review the chart I posted above.  If the WRD is operating normally the CO will rise again when the WRD completely closes the air slide valve. 

When the air slide valve closes there is no suction coming from the FIP air filter.  You have already stated you have checked this and there is no suction when the car is at normal operating temperature.

Now,  going back to when the engine died during warm-up at CO 1.5% and you opened up the throttle body air flap you let more air in and made the CO even leaner which it then stalled.

The CO data that you posted several days ago states that your CO dropped to .75% during the warm up phase which stalls your engine.

But your main problem when the car is at normal operating temp sounds like its too rich.  JA17 wanted you to open up the throttle body air flap (linkage disconnected ) at normal operating temp and report back. However,  from our conversations we already know your car is running rich (like JA17 suggested).

Concentrate getting the engine to run at normal operating temperature first before adjusting any shims on the WRD.

[ja17]

Just to confirm our thoughts.... this time split the linkage as before and as engine warms and begins to stall, leave the intake linkage at rest and move the linkage to the IP slightly open.

[perry113]

Have you verified your point gap and ignition timing are spot on?
Just saying.