Car dies immediately at idle, and more....

[rogerh113]

Hello,

Sorry this will be a bit long, but the problem is odd.  1966 230SL.  Drove yesterday for about 1.5 hours, with 3 stops.  Car ran flawlessly until after the last stop.  When trying to start up, the car was reluctant (usually starts up immediately), and then ran rough.  Felt almost like running on 5 instead of 6.  Got only a block, and then died at idle.  I could start it again, but not for long and then after a minute or two couldn't start it at all.  The stop was fairly long, so the car was pretty much cold when all of this started.  Indignity of a tow home.

I figured it was a bad plug, so replaced the plugs this morning.  Car started immediately and idled nicely as normal.  Thought I was lucky this time.  Then I took the car for a short drive.  Started up again fine, ran fine for about 4 blocks, then died immediately at idle.  I was able to start it up again and get home.  Seems to run OK at speed, at least in the short time I was driving it, but don't know how long that would last.

Final background.  Recently had my fuel pump stop on me, but that was seeming resolved, and it was buzzing away this morning.  Also not sure why the car would run at speed and not idle if it was the fuel pump??

This has me stumped at the moment, so any suggestions on what to try or test would be appreciated.  Perhaps one of the cold start aids went out, but the engine is INSTANTLY off below 2K rpm, and I assume the loss of one of the cold start aids would cause it to stumble down instead of die immediately.... maybe not.

Thanks -- Roger

[mcama]

Roger,

With you saying that the motor is "INSTANTLY off below 2K rpm" I would suspect there may be an intake leak. Do you hear any unusual sucking noise in the engine bay? Examine your brake booster vacuum supply line. The check valve in these is often fragile and can break. A vacuum leak from this line or with the same magnitude can cause you symptom. The line runs from the booster to the intake manifold.

Does the car start easier with the accelerator pushed down part-way?


Best regards,

Mathieu J. Cama
Lawrenceville, GA
1970 280sl 4 speed w/ 56k miles

Old World Automotive

High Caliber Repair and Mechanical Restoration of Vintage Mercedes Benz
www.oldworldauto.com

1961 404s, 1965 190c, 1967 250s, 1970 280se, 1971 280se (5 speed), 1978 280slc, 1982 280te, 1983 409d, 1983 R80RT, 1985 500sel, 1986 2.3-16

[merrill]

check your dwell,  I had my car 66 230 sl serviced and it ran great, the as I got closer to home it died twice at different stop lights.

both times it started right up,  got home and it died in the garage.

checked the dewll and it was 18 degrees not 38.  I reset mine today to 36 and the car is happy.  I plan to mess with it more later to get the dwell closer to 39.

matt

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[hands_aus]

The rubbing block of the points is probably worn.
I suggest that you replace them and set the dwell.

The car will jump off the floor when you start it.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[Dwilly]

Hi guys

New to the forum and my problem is very similar to that of the OP which is why I'm tagging along here.

Ours is a 1970 280 SL auto, bought about 2 months ago. Everything seemed to be fine apart from a troublesome cutting out issue. After about a week it started to cut out when put in either '2' or 'R'. Then it started to cut out at traffic lights, roundabouts, etc. With various attempts to restart we ended up flooding the engine and having it towed back to where we bought it.  

Back at the garage they cleaned out the fuel tank, putting the cutting out problem down to me running the petrol tank too low and possibility of grit getting into the fuel pump. A new fuel pump and fuel filter were fitted and took the car home. It all seemed fine but still was cutting out at lights, on cold starts etc. When back at the garage they adjusted the constant speed solenoid to allow for more revs and this seemed to do the trick at least initially.

It was back to it's old self yesterday unfortunately and I couldn't even get it out of the driveway.

I'm due to bring it back tomorrow but if there was anything in your collective experience I could bring with me it would help a lot as I don't think this guy is a Pagoda expert.

Thanks in advance

[rogerh113]

Hello,

I did a visual of the vacuum hoses from the intake manifold to the brake servo and the cold start air line from the injection pump.  Both seem fine, although the run from the servo to the manifold is seemingly the original hose so I will replace that anyways. The check valve also seems whole and fine.  I was able to start the car pretty as normal (and I do give it a bit of gas from the pedal always).  Idled about 900 vs 1000 cold, so a little slow.  Checked for air leaks, and all I heard was the cold start air intake on the injection pump.  Car warmed up, with it just barely idling at 550 vs 750 normal.

I am running a Pertronix in the car, and the dwell measured out at 18 on my crummy old dwell meter.  Not sure what it is supposed be, but it is current low on my suspect list.

Finally, the fuel pump seems to be going dodgy on my again, as I had to tap it to get it started.  I will be fixing this, but will address in another post, since it may be off topic in this.  Not sure how the car could rev but not idle if it was the fuel pump, but I guess anything is possible....

Any other suggestions would be appreciated.  I am going to replace the vacuum hose and address the fuel pump, and then go after it again.....

Regards -- Roger