What engine and year is your SL?

Probably could do with a good service of all filters, clean of throttle body, replacement of vacuum hoses etc.

 

Hi thanks for the reply

1991 300sl 24 with 104.981 engine. Waiting for parts at the moment. Have put new spark plugs in ..rotor and dust cover are on order. Distributwr cap is near new. Fuel filter/air filter oil and filter and power steering filter in the same order. Looks like a three week wait before I can get all the parts in the car and start it. Fingers crossed.

attacking the plastics and seat repairs for now. When done I have the soft top seals.

 

vickana writes "Car has rough idle on D at lights etc with the occasional shudder but not stalling" .

My 1998 SL500 does exactly the same thing but only when stopped and in D. I realize we are talking about two very different cars but the description got my attention. I've had the car about 10 years and have used a scanner that presents real-time graph data and nothing I measure reflects the shudder, which occurs about every 17 seconds, when it's in the "shudder mode" which is about 1/4 of the time.

I look forward to the suggestions and possible solution to the problem.

 

fwiw -- while my car was in its resting season this winter and my front bumper cover was out being redone, I replaced my valve cover gaskets including all the breather hoses and connector. I've only driven the car twice since but noticed that the idle is now smooth when stopped. It was never 'rough' to the point where it could vibrate something off the engine cover, but as most have experienced, that little shudder -- and basically there since I bought the car 6+ years and 55k miles ago. During that time I changed plugs and wires, engine mounts, and kept regular care of all fluids and filters, yet have always had that just short of perfect idle. The only stalling and rough start issue I've ever had was solved with a CPS replacement.

 

Traced fuel smell in the garage to fuel dripping out of the electrical connector on the bottom pump. Definitely not comming from the fuel lines and connections. Dripping from the + electric connector- at the base to be precise.Tried to tighten the connector but doesn’t seem to do anything.
Wondering if it’s safe to drive the car to a mechanic in this condition.

 

Have a fire extinguisher handy if you must drive it.

 

Don’t feel confident driving it to the mechanic now. Will have to tackle the pump replacement.

A pain to get under the car to work on them so many bolts and crush washers!! I feel it must-be easier to remove the whole assembly out to work on the replacements rather than doing it the car.

Will try to get the exact bosch part number for the fuel pumps tomorrow and run a order. Two week wait to get parts here. :-(

 

I feel it must-be easier to remove the whole assembly out to work on the replacements rather than doing it the car.

It definitely is easier to take the whole assembly out. Get a fuel line clamp or vicegrips and clamp off the fuel line. Disconnect the fuel line coming from the tank and the one coming from the filter. Disconnect the electrical connections from the pumps. The whole assembly hangs from rubber hangers that are easy to undo. Oh yeah, remove the plastic cover first! Pelican Parts has a good writeup on pump replacement. Don't disconnect the line from the tank where they show. Disconnect it BEFORE the T fitting where the small line from the regulator connects. Also, TAKE PICTURES when it's out and on your work bench!!!! Voice of experience here. After putting mine back together, I realized after I was under the car that I had put everything back in the bracket backwards! Pictures are your friend!

 

Super !! thanks for the write up. Make sense the remove it before the T and the connections are so fragile and it’s better to tackle them on a bench rather than lying upside under the car with little clearance. I have read the write up from pelican parts where I bought all the parts and a few YouTube videos. I bought some screwtype clamps to do the hose but they seem to be rock solid trying to squeeze with hand. Hopefully it won’t crack when I put the clamps. Will post how I go when the pumps get here to NZ from the US..

 

There is no need to remove the pump assembly.
You see, that one way or another, you must pinch the fuel lines.
The way you are right now you are set, for fire.

The moment that the pump wires are disconnected. Leaking fuel.
For spark, you just need the ign switch on. Wire touches the ground....

Start by disconnecting the battery.
Get two good hose pitchers.
Use two 17mm wrenches, one on the pump check valve the other on the cap nut.
Have a container, loosen the cap nut wait for the fuel to stop.
The rest is easy.

While there replace the fuel filter, you must replace the copper crush washers....

Regards,
aam.

 

Thanks a lot for the advice. I disconnected the battery before I raised the car as soon as I saw drips from the plastic cover. Will try what you suggested when I get the new pumps got a new filter already.

 

Update 1

Fuel leak fixed with two new Bosch pumps and new fuel filter. Thanks to all the advice I got really helped me tackle this job.

It was easier to take the assembly out. Decided not to use hose clamps due to the rubber hose from the tank being rock hard and there was a good chance of it cracking. Ended up pumping the fuel out of the tank and the last 4 liters drained out into a pan underneath.

swapping out the new pumps and filter was easy. Sprayed wd40 on the bolts the night before so removing the tightened bolts definitely helped.


Few more service items changed while waiting for the pumps

New air filter
New air temp sensor
New thermostat
New rubber grommet seal for the air filter to intake housing.
Vacuum line from fuel pressure regulator to intake replaced.
New set of spark plugs
Oil and filter.
Finally charged battery and ran the car. Idled okay. Took the car for a long drive drove okay much better than before.

Second day drove out in the cold evening and noticed car was not running as great and noticed the idle getting rough when coming to a stop. If I managed to slow down to a stop smoothly then the idle was okay but when I had to stop at an intersection suddenly the car stalled once. Started back up again without issue although the long crank problem still exists.

SRS light flickers from time to time, rollbar light now flickers on the dash and in the button itself. Rollbar works fine.

Checked battery voltage without starting the car..12.6v so it should be okay.I will check it again with the car running tomorrow to see if it drops below 10v during starting and reading with ALT charging. Previous owners installed an atlasbx battery which is roughy 4 months old from the receipts. It’s a 68ah 570CCA unit which is only 60% size of the battery tray. I suspect that it could be an underrated battery for this car. Most suggestions on the forums are 95ah 800CCA. Not sure if this could cause the flickering dash warning lights. Apparently pre 96 models don’t have seat mat sensor which also causes the srs light flickering so buying a srs seat emulator has been ruled out.

Driver’s seat has now stopped going back. Have ordered the black plastic gears from eBay. This puppy is definitely testing my patience compared to all the other Ws I have owned. Going to add fuel injector cleaner to the tank after the alternator test and see if the injectors could be the culprit without taking them out of the car. Don’t have the courage to twist the nuts on those skinny lines.☹

 

vickana,
If you haven't already, you really need to purchased the correct battery size. Battery size and condition effects the entire operating system and will eventually effect the soft top mechanism.

 

Hi all.

new battery in..95ah with 900CCA.
SRSflickering light gone. However the rollbar light comes up occasionally. Noticed right rollbar sensor arm broken. Possible cause will have to source a replacement. Also got myself a pulse code reader.Maybe a reset ?

On a positive note. Car ran great on a two hour drive with good idling at stops. Idle is perfect at cold starts but could do better at warm temp. No stalling at stops now.

injector cleaner and the long drive could have improved the overall running.

 

I don't know which R129 you have, but the rough idle and shudder from lights (if this is an M119) might be the vacuum hoses. The 119 has lots of them, and if there's a leak, that's the symptoms you'll get, just as I did. A set of new hoses and bam, smooth idle and power from the lights.