Warm running start issue, steps to follow

[Marrs]

So I read some posts on people with similar warm start problems and it seems the most likely culprits are one of these four issues:

• Vacuum lines split or leaking
• Cold Start Valve leaking
• Leaky injector(s)
• Accumulator

Are folks referring to the fuel accumulator near the fuel pump or is there a different type under the hood?
I'm gonna start with checking and replacing vacuum lines since they are cheapest and easiest, but after that what should I do next, start with the most common causes and work from there?


Here's a quick recap of what I'm experiencing if it sheds any light on which repair I should attempt first.
Cold starts just fine, no issues. After driving for a while, doesn't seem to matter if it's 10-minutes or an hour, as long as the engine is warm and I shut her down she will crank and crank before turning over. If I were to let the car sit for several hours it would start up again usually but anything less and it will crank a lot before starting. So far it has always started eventually but literally after several tries and maybe 20-30 seconds of intermittent cranking. I sometimes push the throttle 1/4 to start when warm but in these cases I usually end up flooring it before it will start, but I don't know if that is just coincidental or if that actually makes it finally start up. I do definitely get gas in my oil and do oil changes much more often in the meantime because of this.


Also, if anyone has any starting tips in the meantime I'm all ears.


In the case of the CSV and injectors, would I end up having these rebuilt or do I replace them? Any general idea on the cost to have these done at an indie? I'm still new to vintage MB's so please forgive my ignorance on the topic.

[meltedpanda]

check the CSV to make sure it is not staying open . Injectors that are not closing will also do this
Injectors can be refurbished , I used Witchhunters WitchHunter Performance - Injector Cleaning & Flow Testing Services they are good and fast.
you did not tell us miles or service history, but with gas in the oil sure sounds like an injector /CSV issue

[sjefke]

Gas in oil means major fuel oversupply somewhere and you should definitely check for a leak from either one or more stuck injectors or so. If one or more is flooding the engine, you should feel it while driving too because one or more cylinders will not fire well (sluggish driving and idling).

Pull the plugs and see which one(s) are black. They need to be brownish.

Bert

[wbain5280]

His car has Mechanical Fuel Injection. It uses a different kind of injector, not the electric ones we are all so used to now.

There is no accumulator, of any kind.

His Cold Start valve can leak. See Welcome - Mercedes Benz 230SL, 250SL, 280SL Pagoda Group technical section, fuel and the CSV overhaul is in there.

Hard starting is usually caused because the solenoid on the injection pump is not energized when the engine is cranking. Use a test light on the connections and check it.

If it's not on, there is a small cylindrical can mounted on the firewall. It has a small bi-metallic switch inside that needs to be adjusted. Take it off and disconnect it. The top is crimped on, so uncrimp it. There is a small screw adjustment inside and it needs to be slightly adjusted. Plug it back in and make sure it does not short. Make sure your test light is still connected to the solenoid on the injection pump. Turn the screw clockwise 1/8 turn. Have your assistant turn the key and you observe the light.

Keep making slight adjustments.

Its function is to provide a ground for the relay that controls the solenoid. When the contacts are open there is no ground. When they are closed there is a ground and current flows through the bi-metallic switch and it heats up after a short time, heating up and opening the switch breaking the ground. The keeps the engine from flooding.

Flooding can also be caused by the cold start valve on the intake manifold leaking and that needs to be checked too. Check the SL113 site.

The can looking Time Switch can be bypassed to always work and in fact later models, 250SE and 280SE engines did away with it completely.

Do some testing and tell is what happened.

The intake manifold mounted CSV needs a small O-Ring to seal it. Get some from the Classic Center.

[meltedpanda]

1962 220SE W111 Coupe MFI
Duh... my mistake , thanks Warren

[wbain5280]

One more thing to check with the warm up regulator. Unscrew the little air filter you replaced and start the engine cold. If the warm up regulator on the injection pump, the thermostat in the housing, is working properly, as the engine warms up, the suction in the hole will decrease and cut out at slightly less than 180, the operating temperature. If there is vacuum/suction at 180 F, the plunger operating the air cut off is stuck or the thermostat is bad.

You can take the thermostat out and heat it with water in a cooking pot and the meat thermostat. As it gets hotter, the little plunger sticking out of the bottom gets longer. If you don't have the service manual or CD, I'll have to look up the numbers.

Do not under any circumstances, push in the knurled knob at the back of the injection pump while the engine is running. The internal bits will be hopelessly messed up and you will have to send the injection pump in for adjustment.

Do not adjust the idle by adjusting the throttle linkage stops on the venturi or injection pump. Idle is adjusted by the idle air bypass screw on the intake manifold, somewhere. The locations has changed over the years. Consult the manual. That knurled knob at the rear of the injection pump is moved a click or two either way with the ENGINE OFF, and the air bypass screw adjusted until the correct idle speed is attained.

You will need a timing light and dwell/RPM meter, both are available at various places including SEARS.

Welcome - Mercedes Benz 230SL, 250SL, 280SL Pagoda Group is your friend. The International M-100 Group is also friendly since the 6.3 and W113 use the same type of injection system.

[TommyMacDaddy]

First off, I can assure you that I am not an expert on this topic. I'm certain others know more about this then I do.

I had an issue with my W108 250SE which was also difficult to restart. It turned out that the solenoid on the fuel distributor (Bosch Pump) was getting power as it should, so I looked elsewhere for the issue. I went in circles for a while trying to figure it out.
It turned out that the solenoid was simply stuck. I carefully cleaned up the sliding device in the solenoid (had to remove it to do so) with carb cleaner and it has been working properly for at least 2 years. Hot restarts, even on hot days, are great now.

Perhaps this information will help you. Please let me know if there is any info that I could provide that would benefit your efforts.

[Marrs]

Hi all, thanks for the replies. I am currently following a step by step tutorial as graciously provided by another member but will report my findings as I progress and will let you all know what works and what doesn't. Lots of great info.

Wbain, is the time switch you're referring to also called the Thermo switch? Mine was recently replaced with new if so.

[Marrs]

So I just completed the tests for the CSV and it seems to check out as OK. To the member assisting me, thank you kindly, I wrote a PM but was having computer problems last night and had to resend it a couple of times, so not sure it went through. My sincere thanks.

I may have resolved the warm start issue rather by accident.
I followed a tip I found on the W113 wiki about giving some throttle on warm starts. I've been told, and seen it stated here before, that there should be no throttle for a MFI car but that isn't the case. I found statements in my original owner's manual saying that with a cold engine you need to turn key on for a few seconds before engaging starter, this is position 2 or "run", the position just before crank. Theoretically no throttle is needed for cold starts... but for a WARM START it states to turn the key to position 2 and leave it there for 5-6 seconds before cranking, then apply full throttle while cranking (but do not push far enough to engage the kickdown switch). It also said do not release the key from crank position when it first fires but rather after it has fired definitively, maybe another second or so in my experience. This is quite a juggling act but after a couple of days it becomes more intuitive.

This backs up another post I read elsewhere where someone said they leave key in position 2 for 15-seconds before starting to purge vapors from the lines of a sort of "mild vapor lock," and claim they haven't had a warm start issue since. I use the manual's 6-second rule for expediency and use full throttle and in the three days since I began this procedure I have not had a warm start failure since. I am going to confirm my results further over the next week and report back.

I hate to say it, but I am starting to think that at least some of the hot start issues are simply out of ignorance about how the system works. I was certainly doing it wrong and I hope my admission of guilt will help others with this frustrating problem.

Please do let me know if this works for anyone else out there!

[Marrs]

Originally Posted by meltedpanda

you did not tell us miles or service history

Overlooked your question somehow.
Mileage is a verified 96,000 and service history is somewhat unknown. I know it has always been registered and was told that the original owner drove it about 500-miles a year for much of it's later life. The mileage relates to an average of 2,000 a year, so if they put 3-6k a year on when it was newer the miles make sense. This is a one-owner car prior to my purchase. I've had tons of work done over last few months ($5k) like new radiator, electrics, switches, lube, some suspension bits, steering box rebuilt, but my mechanic also told me that all hoses look new and the suspension had had some recent updates so I know it wasn't neglected. Seems most of what I'm running up against is purely age related.

[Palolo]

Originally Posted by Marrs

I found statements in my original owner's manual saying that with a cold engine you need to turn key on for a few seconds before engaging starter, this is position 2 or "run", the position just before crank. Theoretically no throttle is needed for cold starts... but for a WARM START it states to turn the key to position 2 and leave it there for 5-6 seconds before cranking, then apply full throttle while cranking (but do not push far enough to engage the kickdown switch). It also said do not release the key from crank position when it first fires but rather after it has fired definitively, maybe another second or so in my experience. This is quite a juggling act but after a couple of days it becomes more intuitive.

This backs up another post I read elsewhere where someone said they leave key in position 2 for 15-seconds before starting to purge vapors from the lines of a sort of "mild vapor lock," and claim they haven't had a warm start issue since. I use the manual's 6-second rule for expediency and use full throttle and in the three days since I began this procedure I have not had a warm start failure since. I am going to confirm my results further over the next week and report back.

I hate to say it, but I am starting to think that at least some of the hot start issues are simply out of ignorance about how the system works. I was certainly doing it wrong and I hope my admission of guilt will help others with this frustrating problem.

Please do let me know if this works for anyone else out there!

Ok, I tried it today, too, and it worked.

Let my car run for 20 minutes to get everything nice and toasty, then I shut it off, went inside to wash up (I was replacing fuel pump and filter) and simulate running in to 7-11 for something, and when i went out, I tried it. I let the pump run for one-one-thousand to ten-one-thousand, applied right foot til I felt the stop, and cranked her over.

Aaaand...it worked! Maybe a little too well... It caught and revved a little more enthusiastically than I would have liked, but it was warm, lubricated and ready to roll. In the future, I think I have to back off the loud pedal from "just kissing the kick down switch" to maybe 3/4.

Real test: when i take the car down the hill to meet the local MBCA chapter, and importantly, getting back up the hill and home.

[Marrs]

Originally Posted by Palolo

it worked!

Real test: when i take the car down the hill to meet the local MBCA chapter.

Great news! I was about to my car before I figured it out.
Just remember, it's getting back up the hill in these cars that's the hard part. I fine tuned when to let go of the key while cranking, hard to overcome years of letting it go immediately, but I got even better starts all day today so your starting should improve as you get more practice.

[Palolo]

Hey, I made it up the hill! I live in the back of a valley, and the road slopes gently uphill for a few miles, then the last 200 yards to my house are steep, as in L-gear-steep. Coming up the valley, the temp was even with the line above 175. As I got to the steep hill, the needle was one width above the line, and after hoofing it up the hill, when I parked, the needle was two needle-widths above the line. (Not sure if that is normal for a tough/spirited run)

After parking, I turned off the car, waited a little, then did the MB/Marrs warm start procedure. Vah-rooom!

So I attended the local chapter of MBCA's meeting. Mine was oldest there by something like 15 years. Hahaha!

I was hoping to chat with someone about the peculiarities of mechanical injection and the axle compensating spring, but nope... maybe next meeting some classic car owning members will appear.