1964 230SL All of a Sudden...Hard Starting

[mistertj]

My 230SL was always quick to start but two weeks ago I had to crank her for what seemed like forever. No response unless I held my foot all the way down on the accelerator. Then slowly it would start firing with the starter still engaged for at least a half minute before coming alive. Just like years and years ago when you accidentally flooded a carburetor and had to hold your foot all the way down on the accelerator to get it to start. Tried to start this past weekend and the same results. Then this morning, thought I'd disconnect the cold start solenoid in case that was getting stuck and flooding the intake. Same results...needed to hold the accelerator down to the floor to get any sign of life. Eventually, with the starter continuously engaged and foot to the floor, it would start to fire.

Any ideas on what's going on?

Thanks.

[707dieseldean]

I would start by checking fuel pump pressure and volume.

[badali]

Twist all the fuses.  Sometimes they get corroded.  I had the same problem and found it by accident while trouble shooting another problem.

[Ed Riefstahl]

Hi Mister TJ,
I had this issue a few years ago with my 230SL.
My advice is start with the simplest things first. If you haven't already done so, take a test light and touch the connection at the cold start injector, then have someone crank the car. The light should light as soon as you crank the engine.

If the test light doesn't light you are not getting power to the cold start valve. 
You can then do as Brad says, check all the fuses. I often take a test light and go right down the line of fuses and touch both ends of the fuses to know for sure I'm getting power in and out of every fuse.

If you're getting power to the cold start valve, I'd want to check the cold start valve out. Here is a quick test I use for that. I simply hook a small test wire with a clip to the positive side of the battery and touch the other end to the cold start valve and hit the key. If the valve is ok, It should fire up.

Going from memory - I think the cold start valve gets its power from the temp sensor on the head right behind the injector pump and not directly from the fuse box.

Hope I've been of some help. Good luck.

Ed Riefstahl
Erie, PA

1966 230SL (Ms Magoo)
1970 280S (Miss Daisy)
1989 300SE (Majestic)
1999 BMW Z3 5 speed
1991 BMW 318I 5 Speed
1997 Toyota Paseo Convertible - Red 5 speed (have you ever seen one?)
1997 Ford Ranger step side (Mater)
2023 Mazda CX 5

[rwmastel]

Ed,
Thanks for suggesting logical testing procedure.  We shouldn't just throw guesses at the problem.

Mistertj,
Here's a long thread about starting aid systems. Tons of info on how they work and how to troubleshoot.
https://www.sl113.org/forums/index.php?topic=27927.0

Also, you're a full member, so here's the tech manual entry.
https://www.sl113.org/wiki/Restricted/Engine-starting-aid-tour

I think between the two, you should be well educated and have good testing procedures to find and fix the real problem(s).  Let us know how you get along.

[Benz Dr.]

If your cold start valve isn't working you will crank a long time before your IP builds up enough pressure to start the injectors opening.

[mistertj]

Thanks everyone. Will check out what you all have suggested. Thought the engine was getting flooded and slow starting as a result but not getting enough fuel could cause the same symptoms. Got it!

The above was earlier today. Now for an update. I thought ok...not getting enough cold start fuel. Validated this by spraying starter fluid into the air intake. Kicked right over. So I checked the cold start valve power and it was getting 12 volts. Disconnected fuel input and and clothes pin clipped a small plastic bag over the end. Cranked the motor and yes...got fuel. Took the cold start assembly off and bench tested. Solenoid worked and I could blow air through...no obstructions. So, put it all back into the car. Turned the key...car started. Guess there was a gremlin in there that got chased away.

Thanks for all your inputs. It was definitely a not getting start fuel related issue.

[Ed Riefstahl]

Glad to hear you got it working and the car starts now. After reading you latest post, I got to wondering why all of a sudden you have cold start injector working again. Sounds like you never did detect cause.

These old cars do sit a lot and like Brad suggested, if you haven't already done so, give your fuses a twist every once in a while to make sure they are making good contact. I do this periodically when under the hood and think of it. I also touch a test light to both ends of the fuse periodically when I have the cover off.

That type of fuse does tend to oxidize on the contact surface. This is probably information you already know and stuff you have already done. But, I just got to wondering what your gremlin was.

Good luck,
Ed Riefstahl

[mistertj]

Ed - I have used the "spin the fuses" fix in the past. Usually it was the fuel pump. It wasn't this time though. Several years ago I installed a supplemental wire to the valve as a just in case. I had clicked it a few times when I was having the current problem but it did not help. It is a mystery but now gone so all is well.

[Ed Riefstahl]

Wow, now that's funny. A few years ago I had the same problem with my 66 and also installed a supplemental wire at the time. The wire is still there, but not being used. I never did figure out why I had no cold start for a while.

I thought maybe you could shine some light on the mystery for me.

Ed Riefstahl

[mistertj]

I had seen under Electrical and Instruments - Multiple Cranking Before Ignition a similar discussion. Received many helpful hints there as well. Unfortunately or fortunately as a result of my trouble shooting and moving stuff around, the problem went away. The last thing I did was try to trace the wiring from the #6 fuse to relay 21. That was before lunch. After lunch I gave the engine a crank, noticed that the test bulb hung on the cold start relay stayed lit and then the engine fired and started. Maybe the giggling of fuse #6 was the key but I had done that previously.

Anyway, was given a really great wiring diagram in color with numbers that are readable so as I get time I'm going to try to match the actual relays with the diagram and mark them. So, when someone says "sounds like Thermo Time Switch, I'll know which one it is.

Thanks for all the inputs.

[rwmastel]

I've also heard that relays can be intermittent.  Their contacts can be cleaned, I believe.  I've never done it, but something to search for in these forums.  Maybe you spun the fuse to just the right spot for fresh contact?

[glcg123]

I had a situation similar to yours, with the car starting great one day and all of a sudden not starting properly. In addition there was no cold high idle. You could get it to run after a minute of sputtering. We diagnosed that the warm running device piston was stuck in the down position or warm running position. As such none of the cold start devices were working. We removed the warm running device, freed up the piston and now the car starts perfectly, with a cold high idle, dropping down when the engine has warmed up. A big thanks to Dan Caron of the Benz Barn for his telephone assistance.

George 1965 230SL 4 spd