Starting - 560sl 1988

[ssientile]

Hi all,

i've posted before to no avail. I picked up my 560 about 3 months ago 56,000 miles and is maintained well. There are no MD Service dealers where i live on the island of Kauai in HI. SO ANY assistance or guidance would be greatly appreciated.

First got the car it would start with some difficultly. As in turn over time, 3 seconds to 30 seconds. I replaced the plugs (NGK) wires cap and rotor (Bosch). It did show a great improvement, turning over the engine till it fired was kept under 3 to 4 seconds. That was about 6 weeks ago, howvever, it has become increasly more difficult to start (fire). It doesnt really mater if the engine is cold or hot. It has become a beast, I can now hear the battery beginning to strain as it turns over.

Im gonna change the plugs again today (champion) and see if this helps in any way. PLEASE any comments wil be great.

 

[talbir]

There are a few potential causes :

(1) Air fuel mixture - if this is incorrect, hard starting will occur both hot and cold engine. This needs to be adjusted using the correct meters, i.e CO meter. The CO range is specified on the white sticker on the air filter cover and can be adjusted through the small hole in the air filter cover using a long reach 3mm allen key. Do NOT adjust this without the correct meters to hand - your local car garage should have a CO reading machine and should be able to adjust this. Turn clockwise to richen mixture, CCW to lean. But even VERY small adjustments make a big difference.

(2) Air metering plate - remove air filter and check air metering plate in intake. Press down with finger and release slowly - it should rise up without making any contact with the side walls of the intake. If it's making contact, it will cause VERY hard starting, as the plate jams against the walls when trying to lower on start-up. If required, re-centre the plate by removing the retaining bar at the top of the intake and slightly loosening the 10mm bolt securing the air plate and adjusting, so that there is equal spacing all round the plate.

(3) Loss of fuel pressure - fuel system needs to have strong residual pressure to ensure quick starting, especially on a warm engine. Approx 30 mins after switching the engine off, press the plate down - if you do not feel a slight resistance then you are losing fuel pressure. This could be through any of the following :

- leaky fuel injectors
- leaky fuel pressure regulator
- bad fuel pump check valves
- bad fuel accumulator

(4) Ignition coil- this may be weak. Have this tested by a lcoal garage or auto - electrician. Could well be the cause of yourhard starting.

(5) Fuel injectors - if your car has done more than 70,000 miles, your injectors could well be bad. They may not have a good strong spray pattern anymore. New injectors will provide a stronger and equal spray pattern. And so called fuel injection system cleaners will NOT clean these up. Only new ones from Bosch will suffice.

(6) Plug gaps - ideally the plugs on the 560 117.945 engine should be gapped at 0.04" or even 0.045" for a good start and idle. Also, use Bosch WR9DC for best results.

A step-by-step diagnosis is what's really required - simply replacing items will turn out very costly.

Hope this helps.

 

[talbir]

Hi,

There are a few potential causes :

(1) Incorrect air/fuel mixture. This needs to be spot on and if it isn't you'll get hard starting hot and cold. This really needs to be set with the correct meters to hand, i.e. CO meter to ensure the CO is within the right range. Your local garage should have one and be able to set this - the CO range is specified on the white sticker on the air filter cover. And there is a small hole in the air filter cover, through which the mixture is adjusted with a long reach 3mm allen key. Turn Clockwise to richen mixture, counter CW to lean out. But do NOT play with this without the meters to hand. Only a small adjustment makes a massive difference.


(2) Incorrectly centered air metering plate - remove the air filter and you'll see the air intake. Press down the air metering plate inside the intake and release - it should rise back up without making any contact with the intake walls. You should not hear any noise when it rises - I have seen several cars where this air metering plate is not centered and causes very prolonged hard starting, as the air metering plate jams and cannot move down as it needs to when starting. If it's not centered, with an equal spacing all the way round it, remove the retaining bar at the top of the intake, which is held down at both ends with two bolts and then loosen the 10mm bolt holding down the air plate - just loosen a few threads, allowing you to centre the air plate before re-tightening.

(3) Again, with the air plate, about 30 minutes after switching the engine off, try depressing the air plate. If it goes down easily with no resistance, then you are losing fuel pressure. The fuel system needs to have strong residual pressure to ensure quick starting. If the air plate shows a subtle resistance when pushing it down with your finger, then fuel pressure is being held. If not, fuel pressure is being lost - it could be through the following :

- leaky injectors (and leaky cold start injector)
- fuel pressure regulator (on side of distributor)
- fuel pump check valves
- fuel accumulator

Next time you go to start the car, try this : turn the key to position two, dash lights on and you should hear whirring of fuel pumps - when whirring stops, turn key back to zero and then back to position two again. Repeat this 3-4 times and then start the car - if it starts quicker than before, it's a sign that you're losing fuel pressure. Proceed to check the above items.

(4) What is the mileage on your car ? If it's done more than 70,000 miles, it may be a good time to change the injectors. Fuel injectors have a lifetime off approx 70,000 miles. New fuel injectors will deliver the correct spray pattern and of course deliver better starting, if the old injectors are bad and worn.

(5) On the 560 M117.045 engine, the spark plugs really ought to be Bosch WR9 DC. More importantly however, the gap needs to be a little bigger than other V8's to provide a better start and idle. The ideal gap is 0.04" or even 0.045". I'd stick with Bosch plugs and gap them correctly.

(6) Finally, ignition coil maybe weak and not delivering a good spark. Have this tested at your local garage if possible.

I would recccomend you go through a step-by-step diagnosis if possible, rather than replacing items as this will be very costly.

Hope this helps.

 

[ssientile]

talbir,

THANK YOU!

You have given hope to where there was none. I will do the things that I can and bring the car to a local garage if need be with the information you've provided me with. But having this information is greatly appreciated. Its a great help to know there are people like you out there

Thanks Again!

 

[talbir]

No problem - anytime.

Sorry for posting up twice - I was just about to post my first message and I lost it somewhere and ended up rewriting....and then it reappeared, so it ended up going twice. Although my second message is more detailed...!

Ah well, never mind.

cheers

 

[ssientile]

You second post is extremely helfull. When I change the plugs 6 weeks ago I set the gap to the manuals recommendations of .032". I regapped them to 0.43" and ordered the correct Bosch plugs. I believe it must be the fuel system. There was no resistance on the plate after 30 minutes as your mentioned in your post. So if you agree it must be the fuel. I double checked all the connections to the fuel injectors and none were loose. I'm leaning towards the check valves or the resorvoir. The car has sat for awhile prior to me picking it up. I want to try to eleminate all the things I can prior to bring it to a local garage, as there are no MB Dealers on this island.

AGAIN thank you, if you ever get to HI let me know i'll buy you a beer

 

[talbir]

Hi,

I don't drink beer or any form of alchohol, so it'll have to be an orange juice, if you insist...

Yes, you are losing fuel pressure if plate shows no resistance. Does it show some resistance after 1 minute, or five minutes. The resistance should be very slight - but the plate shouldn't just fall down under the slightest nudge from your finger. If you have to apply some minor force and actually 'push' the plate down, then you have fuel pressure - otherwise not.

The fuel pump check valves is a good place to start - I'd recccommend changing the fuel filter whilst your down there. I'm sure your 560 has 2 fuel pumps, and the check valves are approx 10gbp each, so fairly cheap. It'll be easier if you remove the entire fuel pump assembly at the rear - clamp off the main fuel line, disconnect from primary fuel pump, disconnect hose from fuel accumulator and disconnect flexible hose on fuel filter (17mm). Then remove the 4 10mm bolts holding up the assembly and remove the entire unit.

I doubt the fuel accumulator is the problem - that's usually the culprit on warm start problems.

Check the fuel pressure regulator too, on the side of the fuel distributor. There is a plastic hose coming into it at one end - disconnect and check to see if you can see any fuel drops. If so, then regulator is hot and that's where you are losing fuel pressure.

Hope the check valves sort it.

 

[ssientile]

Hi,

Thank s in advance for those of you that respond to my inquiry. As you've read above theres been a difficult time starting the merc when it sat for more than 20 minutes. Ok..on the side of the fuel distributor there is a small black part that is leaking onto the engine. The leak is not a major one, but the dripping is appartent. IT is bolted on the side of the fuel distributor with 2 screws and has 2 electrical conections to it.(approx size is 1"x1"x1-1/2") I tried to look up the part number (bosche 2437020007) but to no avail. Can someone please tell me what this is so another can be ordered.
Steve

 

[ssientile]

Any suggestions will be greatly appreciated

 

[kenjava]

Hi All,

I equally have an issue with the part number (bosche 2437020007) which i am currently searching for a replacement. I am not so experiencd in this matters and have searched for a replacement part for my 1984 benz 190E to no avail.
Can anyone tell me what that part is called and where I can find the part to order?

Merci,

Kenjava

Hi,

Thank s in advance for those of you that respond to my inquiry. As you've read above theres been a difficult time starting the merc when it sat for more than 20 minutes. Ok..on the side of the fuel distributor there is a small black part that is leaking onto the engine. The leak is not a major one, but the dripping is appartent. IT is bolted on the side of the fuel distributor with 2 screws and has 2 electrical conections to it.(approx size is 1"x1"x1-1/2") I tried to look up the part number (bosche 2437020007) but to no avail. Can someone please tell me what this is so another can be ordered.
Steve

 

[talbir]

That part is the fuel EHA valve, sometimes referred to as the 'fuel guvnor'.

There is also a seal that is availabel seperately for it from MB.

Seal is probably less than £10, but the EHA valve is approx £150.


Talbir