Author Topic: Engine sputter when hot.  (Read 5736 times)

Bob G ✝︎

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Engine sputter when hot.
« on: March 29, 2009, 01:31:12 »
After I changed the oil and  filter on my 1968 280SL . I took it out to PCH to give it a run. there are some places along the coast where you can open up the throttle and due 70MPH permitted traffic is not backed up. I stopped to get an rootbeer float at the tasty freeze and noticed after the car sat for 10 minutes the engine sputter like it was on three cylinders. I almost felt like I may not get  back home.

The gasoline gauge registered at 2/4 still have1/2  tank of fuel. the fuel filter was changed two years ago but no real miles have been put on the car. The engine finally cleared and began running on all six cylinders the temperature was 180 C  not hot. When I returned home I popped the hood to check for sings of loose hoses ,I also checked the spark plug connections and found one just a hair loose and popped it back tightly.

I am going to have the fuel changed again and wanted to know how to do  this it looks tricky. I suspect  that the engine needed a good tune up and the valves adjusted and the fuel  pump  adjusted it seems to run rich and foul plugs if not given an open gate to clear  them out.

I have heard these cars were not designed for traffic, this is  the first time the foulling has happened to me and I wonder if it is a sign  of  something to come?

Bob Geco
1968 280SL
11301201906
94988 miles I am sure the engine has been rebuilt.
« Last Edit: March 30, 2009, 04:52:24 by Bob G »

J. Huber

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Re: Engine sputter when hot.
« Reply #1 on: March 29, 2009, 15:02:50 »
Ahhh, PCH. I recall taking my car a few times down the coast when I lived in SB. I usually went only as far as Malibu but remember a few jams. The open road was great! Wish I'd snapped some pics for posterity (and to keep up with Rob Marks  :))...

Anyway, I'd say its true that traffic can sometimes cause the temperature to rise -- however if your car is properly maintained, it should be able to handle it. Do pay attention to the gauge though -- it is meant to make you pay attention.

And, if you are thinking of changing fuel filter, its not too difficult. Be sure you have the proper filter and the large rubber canister seal. The seal is not always included, so double check.

If you have no lift: what I do is, with an oil pan under the canister, loosen the bolt. Hold the can, and when its free, some fuel will spill out but into pan. Then carefully fish the can up and out. You will then need to get the rubber seal out of the housing on the car. It may fall right out, or will be wedged in. Comes out easily (Gravity!).

I look closely at the filter and to see if anything is in the can. Usually nothing. Wipe it clean, insert new filter. The tricky part now is getting the new seal to stay in its groove while you line up canister. Gravity again! I use a dab of vaseline on the seal, which buys you a few seconds while you get the can sandwiched on. Then line up and tighten the bolt.

Good luck.
James
63 230SL

graphic66

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Re: Engine sputter when hot.
« Reply #2 on: March 29, 2009, 16:47:36 »
Did you let it idle for 10 minutes? Sounds like you "loaded up" your engine, meaning you fouled your spark plugs with to much fuel. They will clean themselves up after running at higher RPM's. What spark plugs are you using and what gap? You could have a weak spark from ignition issues. Could be points, wires, cap, rotor etc. These cars run rich and getting loaded up is not to unusual if you let them idle for long periods. If you have resistance spark plugs that could be the biggest contributor to your problem.

Bob G ✝︎

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Re: Engine sputter when hot.
« Reply #3 on: March 29, 2009, 18:11:19 »
Mr. Huber:

Thank you for the information you provided on changing the fuel filter. Vaseline is a good suggestion to hold the o ring seal in place till I can line up the canister and get the bolt started. I ran the car on PCH and it ran very well. just a little bit of roughness  at idle.

The last time I changed the plugs I noticed oil around the threads on the head? I am suspicious of this and think I may need valve guides and the exhaust  valves replaced and the intake valves ground. I am over due for a good tune up point, rotor cap and valve adjustment as well as setting the mixture properly. These are thing I do not have any good back ground in, so I will have to send this to a good Mercedes-Benz technician who has experience with this model and year.

I am using factory Beru spark plug wires from Germany these are like new so I  suspect the tune up part of the engine adjustment will help cure some of these hesitation problems when sitting and restarting.

Thank you all for your help:

Bob Geco
« Last Edit: March 30, 2009, 04:51:33 by Bob G »

Ulf

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Re: Engine sputter when hot.
« Reply #4 on: March 30, 2009, 07:38:59 »
If I let my car idle for 10 minutes, it will show exactly the same symptoms as my fuel mixture is too rich (about to get it fixed). On the go, there is nothing wrong, but idling for more than a few minutes sometimes causes the engine to stop by itself...

Best regards

Ulf
1965 230 SL in silver (DB180)
1982 Land Rover Series III SWB
2008 Jaguar XF 3.0
2005 Mini Cooper

Bob G ✝︎

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Re: Engine sputter when hot.
« Reply #5 on: March 31, 2009, 04:36:54 »
Spark pluges are NKG BP6ES gap is I think 0.34? I had not removed them for a while prehaps I need to fine a cooler spark plug would that help?

Bob Geco
1968 280SL
« Last Edit: April 07, 2009, 01:31:25 by Bob G »

graphic66

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Re: Engine sputter when hot.
« Reply #6 on: March 31, 2009, 06:09:00 »
You probably want a hotter plug. I use the NGKBP5ES, the next hotter from the BP6ES. I gap them at .034 also with the "red" coil and stock ignition.