230SL Hot Start Difficulty

[mistertj]

Like others that I have read here on the site, had difficulty starting the car once the engine was hot. So, I've wired a momentary switch that activates the cold start solenoid. Works great as a workaround but doesn't solve the problem on the fuel mixture being too lean to support a hot start. I'm curious as to what the "real" solution is to fixing the problem. I've read about shimming the injector pump barometric compensator and also about adjusting the rack but would not really know what I was doing if attempting that.
Soliciting inputs please.
p.s. When the engine is all warmed up the choke is fully closed (no air is being sucked in).

[Pawel66]

I am not a mechanic, but can say that my hot start problems vanished when I replaced Thermo Time Switch, that activates Cold Start Valve. I know that theoretically it is supposed  to be working during cold start, but it works with warm engine too, just shorter time. Try to connect the switch you have for solenoid to CSV relay and switch it on for a second as you turn the starter. Or just check the TTS if it gives ground for a brief moment when engine is warm and check the relay.

The new TTS I have activates CSV when the engine is warm for maybe 0.5 second when really warm to maybe 1 second when it colled down a bit - but it helps the warm engine start.

I am assuming that all the spark plugs/ignition related topics are taken into account already. I am not advising on those as I do not know enough, I am sharing my observation on TTS working/not working and the hot start quality.

[franjo_66]

Easiest solution is to give it a bit of throttle !
Works every time 

[mistertj]

That's interesting.  I have thought about putting a jumper across the thermo switch to essentially bypass it and thus keeping the cold start solenoid induced fuel coming into the engine on starting. I'm still thinking that would be a work-around though and not fixing the problem...what ever that is.
On just giving it some gas, that has not worked but click the CSV a couple times and she starts right up.

[Pawel66]

The CSV role during hot start was a bit of a discovery to me when I was learning about it and then when I replaced it. Properly working TTS+relay+CSV help the hotstart as well - at least they did in my case.

If the TTS is broken - that is a bit of a trouble. Very expensive. In the US you can have it refurbished by Classic center for ca $600. Before that I saw listings on ebay for $1000! There are replacements, all this is on this forum.

[ja17]

You can solve this problem.  There are four different starting versions on the Pagoda engine (versions II, III, IV, V).  Version II is only used on some of the very early 230SLs. If yours is this early version  you will have an additional sensor (time switch) on the engine.  Most likely yours is version III. In any case you should identify which is yours. Review the "Starting  Tour" so you know what version it is.
First check to see if the CSV gets power (12v) during cold starts. If not jump the "W" (larger screw) to ground (earth). This will tell you if the TTS is bad. Try a cold start again with this jumper in place. Check to see if the CSV activates this time. It should activate with every start when this jumper is in place.  If the CSV is not getting activated then the CSV relay is not  working, or the "one second" relay is not working. Let us know what you find and we can move on to the fix. 

[mistertj]

Believe that I have a Version II from what I read.
The CSV works the way it should. The car starts great when it's cold or just getting warmed up. Once it's up to temperature (hot), it will no longer start. That's why I installed a button just under the dash so I can activate the CSV a couple of short bursts and then the engine starts immediately. Just giving the engine gas via the gas pedal does nothing.
It was always embarrassing to stop for a red light and if the engine died be stuck until I opened the hood and activated the CSV to give the engine some gas. Now I have the little button under the dash, so no more embarrassing moments. Although the button solution works great, it is a workaround and I'd like to find what the "real" cause is and fix that.

[Pawel66]

To me it looks like TTS (Thermo Time Switch) is not providing the impulse to relay  and then to CSV when the engine is hot. I think you should check the TTS. If it is not working properly, you will need to replace it. The original is very expensive, but there are replacements. All in this forum.

I am assuming it is TTS not relay or CSV because you say cold start is ok. You also say that when you activate CSV it starts. I would start from checking the CSV.

[mistertj]

So, you are saying that the CSV should be activating even when the engine is hot but perhaps for a shorter duration as determined by the TTS. Hmmmm!

Here is what I had previously read. "The original thermal time switch, as well as this replacement switch, are designed to deliver extra fuel through the Cold Start Valve for 9.5sec at 20deg C, this time drops until the coolant reaches 35 Degrees C (95 Degrees F) at which point the internal contact will stay open and will no longer deliver extra fuel through the Cold Start Valve".

[Pawel66]

Yes, I know all this - read it. What you also see in the starting aid section, is that MB were struggling a bit with hot start and were modifying it along the years, including the last modifications on version III (early and late) of staritng aid, which is to give 1 second impulse to CSV above 35 degrees. At some stage the solenoid on FIP was helping, then it was gone, something had to take its role when hot.

The modern Bosch TTS replacement (unfortunately looks different than original) has electronics inside and gives impulse even at high temperature. Works perfect. Anyway, it is all activated when the ignition key is turned on.

Look, I am not qualified enough to argue the point. I am just sharing my own experience. If your TTS works properly (which is easy to check) - then it is fine. Please do not take any cost involving action if you are not convinced. It may be something completely different (air buffles in fuel lines? caused by too high temperature?). I am assuming that you have all other things (ignition, mixture, linkage and valves related) under control. Are you using the proper spark plugs? Are they in god condition? I guess these are the usual suspects...

I just thought: if you are saying thet the trouble is there when you immediately try to start after engine stopped (traffic lights) then maybe indeed I am on a wrong track. If you leave the car even 5 minutes - it cools down a bit, not much, but  a bit. Disregard it then, it must be something else.

[Pawel66]

Just keep thinking about your case...

I am sure you will get better/more educated advise from fellow Members, but before that, just for speculation...

You have to assume that some basics are correct, e.g. you have correct well working spark plugs, properly gapped, etc. But let's assume your car is running too lean when warm. No problem with cold start. You may not feel it when driving other than the usual symptoms (the look of spark plugs, exhaust, temperature, etc.). Then when hot it may be more difficult to start the engine perhaps. Unless you inject more activating CSV. Just thinking loud.

[mistertj]

I have checked just about everything...linkage, timing...dwell..new plugs...pop tested all the relatively new injectors (they fire nicely at about 265 - 275 psi with no dripping)...fuel pressure at filter...fuel flow back to the tank...CSV...TTS...and on. The engine just isn't getting enough fuel for a hot start without activating the CSV. The plugs after a nice run are pretty darn clean and I don't believe that the run mixture is to lean given that there is no backfire popping upon acceleration. The engine revs up nicely.
So after hearing the suggestions I double checked everything and it's as it was before. What I have just done is turned the rack adjustment screw 4 clicks counterclockwise. Right now I am waiting for some parts to rebuild the shift mechanism and once I get those installed later in the week...I'll get to see what the rack adjustment has done. Will let you all know.

[Pawel66]

Remind me please - rack adjustment counterclockwise - you made it more rich? Rack adjustment is tha main screw, correct? Not the idle?

[mistertj]

Yes, I am making it more rich. It is the adjustment inside the pump. The idle adjustment you turn clockwise to make richer. It is the adjustment on the outside of the pump. As you turn the idle screw clockwise, the weights inside the case move closer to the center. Beyond that...I know nothing.

[Pawel66]

That reflects my knowledge too, I just wanted to confirm if I remember correctly. Thank you.

[rgafitanu@gmail.com]

First to eliminate something:
I am assuming that you are trying to hot start it with the throttle open, right. When the engine was switched off there is a lot of gas left in the intake chamber that if the throttle is not open to let the air in it may flood the engine (info from this forum).
Did you check the air fuel mixture at idle hot with the split linkage method?
On of the main cause of hot start problems is injection lines: gasoline may vaporize in the lines due to heat rendering the injection atomizing ineffective. The gas pressure must be around 10PSI to keep gas below boiling point. This pressure must also be maintained in order to have an immediate start and not have to crank for several seconds until you fill the lines again. You have the injectors at one end the and the IP check valves at the other end of the injection lines that are keeping the pressure up. You verified the injectors so check that the IP check valves are not leaking. Loss of pressure in the lines is usually indicated by start in 2 or 3 cylinders with the others joining in after a few seconds.

Radu

[mistertj]

Once hot (operating temperature) and trying to start throttle or no throttle the engine will crank forever and not start. With two clicks of the CSV, starts immediately.

On the split linkage, I have done it several times as has my mechanic. He is the one that recommended that I richen the rack by turning the adjusting screw 4 turns counterclockwise.

On the check valves, my pump has been modified with the ball check valves versus the cones. Pressure is maintained for days and days. All one has to do is loosen any of the lines and you get a strong spray.

Will know more in a couple days when I get to drive the car again. Right now I am waiting for shift mechanism rebuild parts. I had the shift lever drop through the floor and rub on the drive shaft. Not a good sound or feeling.

[mistertj]

A happy ending!  Parts came today for the shift rebuild so that's done.

Took the car out for a test run and to get it "hot". Got back home and turned the engine off and immediately tried to restart. It started each and every time! So, adjusting the rack to richen the mix worked. Now...if 4 "clicks" was the right amount or a little too much. That remains to be seen.

I did the split linkage test and moving the injector pump rod would cause the engine to stall. Moving the air intake rod a little made the engine rev and then any further movement caused a stall. So I will adjust the idle mixture to lean it out some.

Now I need to find out why my speedometer only reads about half of the MPH that it should be showing?

[ja17]

Keep us informed on your starting.  To see if the CSV is getting power during hot starts, simply hook up a test light or volt meter to confirm that it is being activated.
Concerning the speedometer check to see if the needle rises during de-acceleration, then falls during acceleration. Do this during a test drive in a forward gear.

[Pawel66]

If on split linkage test adding air made the engine rev up 100-200rpm only, maybe you are there. But you will probably check it with a proper meter. Then if the mixture is correct and hot start does not work, I would turn my attention back to CSV.

[rgafitanu@gmail.com]

I agree with Pawel. Many posts here suggest the mixture to be on the rich side, my engine as well. As stated by Pawel, the split linkage is qualitative at best, you need a AFR tester to get it right.

[ja17]

Did you check to see if the CSV activates during your hot starts?  If it does not you need to fix this first. If it does you need to check the fuel spray of the CSV. The fine fuel filter screen in the intake fitting of the CSV gets clogged and reduces fuel spray. Also one or both of the fuel spray jets of the CSV can be plugged. Remove the CSV and watch the fuel spray qty and pattern during operation. You can leave it hooked-up externally for the test.

[Pawel66]

I cannot express how happy I am that someone as experienced as Joe or Radu kind of agrees with my suggestion! 

[Bonnyboy]

I just have to repeat myself - when checking the cold start valve operation make sure you have a fire extinguisher close by  - even though I put the valve in a plastic bag to check it, fuel spilled out and started a fire - not a big one but it was still a fire with gasoline and could have been real bad had it jumped to the bag.   

In my case my hot start problems were solved by a cleaning of my cold start valve - check valve was stuck open  -  and the advance plate in the distributor losing a screw and going wonky didn't help but I expect that my CSV was not operating correctly for a few years before I caught it.   Losing the screw in the distributor just made me check everything closely.  My car was a real B^&ch to start when hot - now its fine.

[mistertj]

Comment from Joe Alexander:"Keep us informed on your starting.  To see if the CSV is getting power during hot starts, simply hook up a test light or volt meter to confirm that it is being activated.
Concerning the speedometer check to see if the needle rises during de-acceleration, then falls during acceleration. Do this during a test drive in a forward gear."

Just returned from a test run...car engine hot. Car restarted without any problem. Voltage, although small, measured across the CSV. Success although I was surprised to see voltage. Thought for sure after thermal switch opened, there would be no voltage on starting at the CSV...but there was. Thank you for the enlightenment.
On speedometer...at about estimated 65mph, needle hunts between between 45 and 55mph. Really didn't do much noticable between acceleration and deceleration but at about 30mph, needle goes to 20mph upon acceleration and then on deceleration...jumps to 40mph. It would do that consistently. So, what might that indicate and how to fix?