300SEL 3.5, engine started after 2 years

[Tomguy]

Where are you reading manifold vac from? Best place: Disconnect the vac line for the locking system & use that. The distributor uses throttle venturi vacuum - totally different & won't help. If measuring from here takes a while for vac to build up and the door locks arent "T"ed still but you are directly in this system, check your booster; it should hold vac (maybe lose it slowly, but drop no more than 10" per half hour I'd think).

Only 10" of manifold vac is indicative of a major leak somewhere. Plug the line to the trans (or see if it somehow became disconnected like mine was). Replace your 8 "Lower" injector seals - the uppers are retainers, not seals; you don't need to replace these. Spray carb cleaner or another aerosol around the manifold half seals, aka "Donuts". They might be toast. Plug the booster line if it's questionable. You should be seeing well over 10" on a warm idle.

[GGR]

Originally Posted by werminghausen

GGT: I have a 33PSI reading of fuel pressure at the cold start valve (20PSI after engine shut down.
Can I now adjust the 'box' to maximum engine speed by turning the screw up or down?

You should first eliminate the gas leak and then reduce fuel pressure to 30psi at idle via the Fuel Pressure Regulator. This is a bell shaped device with three fuel ports at the top back of the engine in the center, connected to the fuel circuit. Don't confuse it with the one next to it with only two ports. To reduce the fuel pressure you unscrew the bolt on top of the FPR until you reach 30 psi. Then you can start playing with the richness at idle.

Regarding vacuum leaks I also heared of people spraying propane or butane in the manifold area as well as under it, at idle. If the idle goes down, then you have a vacuum leak in that area(the engine sucks the gaz in resulting in a drop of idle speed). Then I guess you can try to narrow down by spraying different places at a time.

[werminghausen]

Originally Posted by Tomguy

Where are you reading manifold vac from? Best place: Disconnect the vac line for the locking system & use that. The distributor uses throttle venturi vacuum - totally different & won't help. If measuring from here takes a while for vac to build up and the door locks arent "T"ed still but you are directly in this system, check your booster; it should hold vac (maybe lose it slowly, but drop no more than 10" per half hour I'd think).

Only 10" of manifold vac is indicative of a major leak somewhere. Plug the line to the trans (or see if it somehow became disconnected like mine was). Replace your 8 "Lower" injector seals - the uppers are retainers, not seals; you don't need to replace these. Spray carb cleaner or another aerosol around the manifold half seals, aka "Donuts". They might be toast. Plug the booster line if it's questionable. You should be seeing well over 10" on a warm idle.

Thanks Tomguy, very helpful
I was first reading vacuum at the distributor line first but switched to the door lock port then reading first 10"Hg 2 days before , then yesterday I had the engine on for a while and it went up to 14-15" after warming up.
I was testing if I could 'kill' the engine at idle if I screw the idle screw in..and yes easily...the engine stalls. The other thing I experienced is: at idle if I completely block the intake of the airfilter, the 2" diameter hole, it has almost no effect on the idle speed, engine won't stall. This means air is leaking in somewhere?
I'll test the booster lines as you mentioned first, then test the vacuum line to the trans/modulator- is this line another port at the intake manifold or t-ed to the door lock?
Replace Lower injector seals: are these lower seals visible from the outside?
Is it an 'easy' job or a pain? Any part number?
Spray carb cleaner or brake cleaner at manifold halves/donuts. I need to figure out what these halves/donuts are. By spraying brake cleaner ..it would be sucked in an increase engine speed?
Ah..there was one thing that concerned me yesterday: when starting the engine it was 'pinging' the first seconds. Not sure what this was.
Martin

[werminghausen]

Originally Posted by GGR

You should first eliminate the gas leak and then reduce fuel pressure to 30psi at idle via the Fuel Pressure Regulator. This is a bell shaped device with three fuel ports at the top back of the engine in the center, connected to the fuel circuit. Don't confuse it with the one next to it with only two ports. To reduce the fuel pressure you unscrew the bolt on top of the FPR until you reach 30 psi. Then you can start playing with the richness at idle.

Regarding vacuum leaks I also heared of people spraying propane or butane in the manifold area as well as under it, at idle. If the idle goes down, then you have a vacuum leak in that area(the engine sucks the gaz in resulting in a drop of idle speed). Then I guess you can try to narrow down by spraying different places at a time.

Thanks GGR
I'll reduce the fuel pressure then accordingly to 30 PSI.
I'll hunt for the air leaks in the manifold. Maybe exchanging the injector lower seals etc. or manifold halves. When I have good intake vacuum I'll adjust the
'box' ECU? for rich/lean mixture. (I was doing this last night trying to find the fastest idle by screwing the plastic thing in/out with 33PSI fuel pressure and I was unclear at what position speed was optimal- sometimes the speed is dropping abruptly from 750- 650 staying there and then after some minutes coming back- I have no idea what this is)
Ah- the other thing concerned me:there was a noise when I started the engine last night. It was like if the engine was pinging, just the first 30 seconds, then this sound was gone. Not a nice sound if the engine is pinging.
Any idea what this is?

[werminghausen]

Originally Posted by werminghausen

throttle linkage adjustment: For the WOT adjustment with 1mm before butterfly is fully open I don't know how this can work.
I think with my adjustments 78 and 114 (both measured from center to center - balls or rubber donut) the rod connecting to the butterfly I can reduce but then the idle position gets more difficult. I guess in order to do what you are saying ( 1mm before stop screw at kick down) the linkage wouldn't allow the accelerator pedal to go fully back to idle stop position.
i don't see how to reduce the travel of butterfly relative to the accelerator pedal travel. The ball heads are all metal and in ok shape i think.

regulating lever: I guess this is the 3 ball lever where the transmission rod is connected. yes what you are saying is actually happening. the pin in the fork is resting against the idle side of the 'fork' and the transmission rod is at its stop position pushed inward.

I'll remove again the airfilter housing and try adjusting throttle according your manual (WOT butterfly 1mm before end stop of wide open throttle).
Thanks so much, very helpful

I did adjust rod 3 connected to butterfly, lengthened it from 73mm to 77 mm in steps, now the axial movement (at WOT) of the throttle shaft is gone.

[GGR]

That pinging noise may be the timing chain rattling until oil pressure builds in the tensioner. It's more prone of doing so when restarting a warm engine after it sat for half an hour for example, as oil is more fluid. Did you change the tensioner when you replaced the chain?

If you can stall your engine at idle by screwing the idle speed screw and if your richness at idle is not completely off, then I wouldn't jump into changing injector seals and donuts for now. It won't hurt but they may not be the cause of your current problem and it's quite some job (you should consider doing it anyway for peace of mind, but may be at a later stage if they are not the source of the problem now). Typically, the symptom of vacuum leaks is a high idle that cannot be reduced as leaks are admitting more air than the engine needs for idling. If you can get a correct idle then the engine is sucking the correct amount of air it needs for idling, being through the idle air circuit and may be some also via some leaks, but the amount is correct. The vacuum should then also be correct.

Did you take your engine compressions? I guess low compressions can translate in low vacuum. Take them engine warm, all plugs off and cranking the engine WOT 8 to 10 times

[have mercy]

Get some carb cleaner for newer car It is not suppose to hurt your sensors, spray 1 little area at a time when idel changes that where your leak is.
the smaller the area you spray the easer it is to find leak

[werminghausen]

Originally Posted by GGR

That pinging noise may be the timing chain rattling until oil pressure builds in the tensioner. It's more prone of doing so when restarting a warm engine after it sat for half an hour for example, as oil is more fluid. Did you change the tensioner when you replaced the chain?

If you can stall your engine at idle by screwing the idle speed screw and if your richness at idle is not completely off, then I wouldn't jump into changing injector seals and donuts for now. It won't hurt but they may not be the cause of your current problem and it's quite some job (you should consider doing it anyway for peace of mind, but may be at a later stage if they are not the source of the problem now). Typically, the symptom of vacuum leaks is a high idle that cannot be reduced as leaks are admitting more air than the engine needs for idling. If you can get a correct idle then the engine is sucking the correct amount of air it needs for idling, being through the idle air circuit and may be some also via some leaks, but the amount is correct. The vacuum should then also be correct.

Did you take your engine compressions? I guess low compressions can translate in low vacuum. Take them engine warm, all plugs off and cranking the engine WOT 8 to 10 times

I didn't do the compression test yet. Maybe a good idea in order to get a sense in what condition the engine/pump might be? I should do the test.
Do I need to disengage the fuel injectors for this exercise? Need to look for the pressure gauge in the spark plug hole. Would you warm up the engine and then remove plugs, then doing the test?
Rattling chain/pinging: I did change the tensioner along with the chain. oil pressure gauge in the dash says 20-25...in the scale of 45 (is this 4.5bar?) at idle with engine warm...not sure what this pressure readings means. It goes up though when I rev the engine. pressure might be too low? When I start the engine cold the pressure is at a max at idle.

[werminghausen]

Originally Posted by have mercy

Get some carb cleaner for newer car It is not suppose to hurt your sensors, spray 1 little area at a time when idel changes that where your leak is.
the smaller the area you spray the easer it is to find leak

I'll get the carb cleaner then and try out.

[GGR]

Originally Posted by werminghausen

Do I need to disengage the fuel injectors for this exercise?

Yes, it is preferable so that you don't fool the engine. You can do that by disconnecting the fuel pump or by pulling out the fuel pump relay.

Originally Posted by werminghausen

Would you warm up the engine and then remove plugs, then doing the test?

Yes

Originally Posted by werminghausen

oil pressure gauge in the dash says 20-25...in the scale of 45 at idle with engine warm... It goes up though when I rev the engine. When I start the engine cold the pressure is at a max at idle.

That's very good. Scale is in psi.

[werminghausen]

Originally Posted by GGR

Yes, it is preferable so that you don't fool the engine. You can do that by disconnecting the fuel pump or by pulling out the fuel pump relay.

Which one is easier? the realy sounds easy..but where do I find the fuel pump relay?

[GGR]

Originally Posted by werminghausen

Which one is easier? the realy sounds easy..but where do I find the fuel pump relay?

That's the problem. On your car it is burried somewhere under the ECU and access is not that easy. It may be easier to just undo one of the wires at the pump.

[Tomguy]

I always just unplugged the trigger points & CSV.

[GGR]

Originally Posted by Tomguy

I always just unplugged the trigger points & CSV.

That's indeed another way to go

[werminghausen]

Originally Posted by Tomguy

I always just unplugged the trigger points & CSV.

For the compression test and preventing the injectors from fueling the engine...

What/Where are the trigger points and CSV to unplug?

I looked up some posts: trigger points are breaker points/distributor, correct?
'Unplugging' means pull the main lead to distributor and connect to ground?
Does this stop the injectors from firing?
Second measure is CSV =Cold Start Valve? Unplug this thing/wire and it will stop the cold start injector from firing?