Hot Engine Starting / FI issues

[Andres G]

Hello All,

I wanted to check in with the experts here before going to the shop to have them work on the car for this. Here are the symptoms I'm experiencing:

1 - The engine takes a few turns to start from cold, but once it does, it idles at about 1500 RPMs until it warms up, then revs down to about 1000 RPMs. However, if I blip the throttle once the engine is warm, the revs come down to about 750/800. The same thing happens after some driving, when coming to a rest, the revs remain at about 1200 unless I blip the throttle again and they come down (roughly 750 - Halfway through the bottom of the rev counter and the 1000 RPM mark) if I do not touch the gas pedal, it will stay high in revs.

2 - (Now the tough one) After the engine is warm and I've ben driving for some time, say anywhere between 30 minutes to an hour and then shutting the engine off, it will immediately fire up if I turn the key within the following 15/20 minutes. However, the more time goes by after that, the harder it gets to start while the engine is still warm/hot. It can get to the point that it seems just too much cranking to start (sometimes more than three or four 5 second attempts)... I have resorted to pumping the gas pedal or hold it flat down to get the car to start, but it just seems wrong.

Any ideas on what these two things may be related to?

Thanks in advance.
Andres G 

[Peter van Es]

Re point 2: when the engine is hot, you are meant to start it and pump the accelerator at the same time. This behaviour is normal, and is described in the user manual.

Re point 1, Constant Speed Solenoid, Warm Running Device? Linkage ?

Peter

[J. Huber]

Not surprisingly, I think Peter! is right on the money. And while I have never messed with the WRD, I'd say the other two (linkage and CSS), you could tinker with yourself without necessarily sending the car to the shop. (Unless, you want to, of course. Some are more comfortable experimenting than others...and believe me, I have gradually become more "experimental" over the years -- and for many things, the mechanic is my first and only choice...Just be sure to find a trustworthy and 113-capable one.)

Anyhoo, my car has a similar habit of locking into a higher rev (not as high as yours but still higher than normal ~ 1100) only when I pull up from a drive and put it in park. Then if I give the throttle a slight nudge, it drops to my "happy" idle ~ 800-850. Then when I drop back into gear, it settles in near that same 800-850. Now, I have to add -- this happy zone is not without its trials and tribulations. The linkage must be set right -- without any slop at the bushings or ball sockets. And the CSS needs to do its thing. Then you can mess with the air and fuel mixture for idle if necessary. Always at my side for this is George Davis's brilliant Fuel Injection Linkage Basic Adjustment  now available to full-members in the Tech wiki. It really makes setting the idle very do-able for DYI ers.

As for warm starting. I have had times where I needed to give throttle -- but also when things are going well, the car will start without it -- cold or hot... Its a never-ending dance... but worth it. Good luck.

[psmith]

Hi Andres,

Mine does the same thing when it's cold, the revs stay up at idle.  Since I have an automatic, I attribute it to the Idle Speed Solenoid. 

As for starting, check the Starting Aid Tour in the Tech Manual.  Mine went suddenly from starting on the first crank to taking 4 or 5 tries to get it to catch.  I checked the Thermo Time Switch and Cold Start Solenoid and they were both working correctly.  It turned out I had a short in the wiring.  It would make sense that that is where the problem lies because your car is starting when warm, when that system is not needed.

[Benz Dr.]

Hold the throttle open a bit while starting when hot soaked.

 The different idle speeds are from worn distributor springs. Run the engine until hot and find the higher idle speed. Shut the engine off and then start it again without moving the throttle. If the idle speed is lower the springs are weak inside of the distributor.

[knockmacool]

Thanks, similar idle symptoms, so very helpful thread

[Andres G]

Thanks all for your replies.

I'm not very clear which is the Idle Speed Solenoid (Is this the diaphragm where the accelerator linkake rests when I let off the gas? - No wires attached?)... can anyone help with a picture? I'd like to know exactly which one this is to get my hands on it and see if it's working or not.

Dan was absolutely right on the distributor springs. I followed his suggestion and after the engine was hot and reving at a steady 1200 RPMs with my foot off the gas pedal, I turned it off and then on again and voila... the RPMs were now at bout 800.

Now I know I need to replace/refurbish the distributor. Is this something easy for a DIYer? I can always send it off to be refurbished by a pro, but I have read the maintenance history on the car and the distributor was worked on a few years back (in 02) when the car had about 5.000 kms less.

I'm definitely one to experiment, love to... as long as I'm able to deliver results after tinkering with whatever I've chosen for the occasion.

Thanks once more.
Andres G-

[psmith]

Here's mine...

[Andres G]

Hmmm... thanks for the picture Peter. My car does not have a solenoid in that location at all... there is a rod that connects to a small plate, that in turn rests on a vaccum type valve (only it's not connected to anything).

Does this have something to do with my car being manual?

Andres

[J. Huber]

Yes, it has everything to do with that! The manuals don't have the CSS. Guess we should have clarified that way back at the beginning!

[Andres G]

HHS! I guess then there is something else I need to be messing with...

I realized after reading Dan's post again, that the car is not doing what he mentioned. It's actually starting back up at the same RP Ms as when I turned the engine off (from the higher idle speed). I assume there has to be something related to the linkage here that I need to be checking.

Also, yesterday the hot starting issue occurred once more, it took almost 45 minutes waiting to get the car to start again... This time I noticed something interesting that may be related to this issue. Here's what happened:

- After the engine started, I drove back home (15/20 minute drive) and once home I decided to align my headlights so the car sat on the driveway with the engine idling while I was working the alignment. Some 15 minutes went by alternating high and low beams, as well as fogs, when the car started idling irregularly for a few of seconds until the engine eventually died. When I tried restarting, the battery off course, was RIP.
- I then connected the jump wires to my company car and left the two connected for about 10 minutes before attempting to restart the car. When I finally did, it came right back to life with only a 1/2 second crank time... incredibly fast and noticeably different from everyday start up.
- This time I also realized that the red warning light in the instrument cluster was on (engine running) but not with it's regular intensity... more like distantly faded. Any idea what this might mean?

I get the feeling this may be a charging/distribution problem.

Thoughts and comments are welcome.

Regards, Andres G

PS: Headlight adjustment results were great!

[Raymond]

The warning light comes on when the current from the alternator is low.  Most common guesses: either the belt is loose, the battery is nearing the end of life and not taking a charge well or the alternator is tired.  Those are the easy fixes. 

[Andres G]

Thanks Raymond,

In fact, the charging light issue turned out to be a combination of all of the above. I replaced the battery with a new one (the old one would not charge up, even with a battery tender set @2A for 18 hours), and I also took out the alternator and sent it in to have diodes replaced. I'll have it back today hopefully and will be able to get back to dealing with the starting issues.

Andres