Starting Solenoid On Back of Injector Pump (IP)

[JPMOSE]

I have read through a lot of threads but I am still a bit "challenged" on the subject matter.  For whom it may concern, the IP has a solenoid on the back.  In the case of late 250SL and forward, there are two (the other being a "Fuel Shutoff Solenoid").    The starting solenoid is the upper one.  I know that the IP thermostat adjust the mixture as it moves (or warms up), along with cutting off the extra intake air for increased idle speed.  

On that note, when does the Starting Solenoid operate and why is it necessary if the IP Thermostat adjusts the mixture?

What controls the Starting Solenoid (I know it's electrical)?  

What symptoms if it malfunctions?

Is it adjustable?  An easy replacement?

Best Regards,

J. P. Mose
1968 250SL

[A Dalton]

This sol. simply moves the rack to full foward position for secondary starting aid regardless of coolant temp. So, unlike the warm up thermo and the CSV, it is not temp dependent and always works when starter circuit is energized.
 Later  modified ball check valve replaced the R18 pump cones valves and it was found the rack foward posistion was no longer needed as the new ball checks held line pressure for starts.
R18Y pump were the last of this series. along with being the last of oil res/dip stick lube system.
New check balls can be added to these pumps.
 You can check your rack sol by using a 4mm test screw on rack at test port/plug.  Archieves has these test procedures.

[JPMOSE]

A Dalton...you stated in another posting that the 250SL has a separate relay for the Mixture Solenoid?  I performed the light test on my Mixture Solenoid this past weekend on a cold engine.  When I engaged the starter I didn't get a light.  So, I want to check the relay.  Where is it located?  Thanks!  JP

Best Regards,

J. P. Mose
1968 250SL

[A Dalton]

Just behind CSV relay.
 Both CVS/Mix relays are the same , so the foward one is CSV.
 Next to paint code data plate, left fender rail.
 Secondary contacts are fed from fuse 6  and on to solinoid.  Make sure you are testing your 12v  test light on positive side of sol.
{ Blk]  , as brn is ground side.
 Relay Primary [coil side - 85/86] are  from ignition start sw and ground.

[JPMOSE]

Well I'm back to working on the car.  It turns out that ONLY the Black/Pink Stripe wire is hooked up.  The brown wire was disconnected and taped up for some reason.  I hooked the light up to both wires and engaged the starter...the light comes on.   Here is the strange part   --  I removed the solenoid from the back of the pump.  There is only one threaded fitting for a screw, which the black/pink stripe wire was hooked up to.  On the other side there is no thread for the brown wire.  I also have a Fuel Shut Off Solenoid and it only has a black/green stripe wire to it and no hook up either for a second wire.  [:0]

I wish I have a digital camera to show you.  I did run 12V to the stripe side and attempted to ground the solenoid...engaging the starter didn't activate the solenoid (perhaps it is dead).

Does anyone have a photo to show me where the ground wire should hook up?  

Also...how do I hook up the solenoid to see if it works (I though I knew this procedure but may not). :oops:

Best Regards,

J. P. Mose
1968 250SL

[JPMOSE]

A Dalton...the more I look into this, the more I'm convinced that only a pos. wire should be going to each solenoid.  Are you sure the solenoids don't self ground via the injector pump?   My '68 250SL is a very early '68 -- S/N 003010 (I believe this is the 11th built '68 model).  This is right after the switch to having a pump with a fuel shutoff solenoid.  I see that the wire for the fuel shutoff solenoid was added into the harness.  My car has a few peculiar items because the '68 model year just started.  I'll bet the earlier models had two wires while the later models have one.  I wouldn't be surprised if my wire harness is the same as a '67 250SL so the extra wire for the fuel shutoff solenoid had to be added on mine.  This would also explain why it has a brown wire that is taped up because the self grounding unit wouldn't need it?  

My owners manual is a '67 probably because the '68 manual wasn't available yet.  My heater blower knob looks like the later one but has a hole in it and the blower switch does have a light in it (this was supposedly drop in the '68 model year).

I think my mixture solenoid is dead.  If I apply 12V to the connection and ground the unit with a wire (both wires hooked directly to the battery), the solenoid doesn't react.  Am I doing this right?

Best Regards,

J. P. Mose
1968 250SL

[A Dalton]

<<A Dalton...the more I look into this, the more I'm convinced that only a pos. wire should be going to each solenoid. Are you sure the solenoids don't self ground via the injector pump? >>

 Not according to my schematics and info.

In my 40 years, I have never seen one with internal ground..as a matter of fact, that is one thing that Benz is known for .. separate ground wires for each component vs chassis grounds.
If I am reading your post correctly, you are saying that you have the two terminals, but the ground side is not tapped for a terminal screw ??
Possibly a replacement sol...I will do some further checking, but , do this  simple ohm/continuity test below and you will know for sure

 Just put an Ohm meter on each terminal and check for  continuity
to the case and that will tell you. Also do a coil ohm spec reading across both terminals. I will get that resistance spec.
Or , as stated in my earlier post, screw a test bolt into the rack test port and watch for rack foward position when 12v is applied to the terminals.

[ja17]

Hello,
I believe at least some of the later models did not have the ground wire attachment on the solenoid. Check page 00-74/6 of the BBB (Fig. 00-74/7).  I suspect that the ground wire was just left taped to the harness in these cases.

Note that the intake cold start solenoid on the intake manifold has only a positive wire going to it also.

It does sound like your starting solenoid is dead. It should activate when a hot wire is touched to the terminal. This starting solenoid moves the injection pump "rack" to full rich when the starter is engaged.

Joe Alexander
Blacklick, Ohio

[JPMOSE]

So it appears that the later IP units self ground.  My solenoid is definately dead.  Well there goes another $100+.  

Today I will check the Fuel Shutoff Solenoid and see if it works.  In fact I may just disconnect it and see if this could be the reason my engine shuts off suddenly after 20-30 minutes (as Joe Alexander knows, I have examined everything else and it is definately fuel related).

Thanks for all the help!

Best Regards,

J. P. Mose
1968 250SL

[A Dalton]

If you have brought 12v + over to it from the battery, then I agree it is open if it is a case grounded unit. [ you will hear the rack move]
 I do see the later 130 eng did use a case ground replacement .. But if it is not case ground, it will not work w/o a ground. That is what the ohm meter will tell you.
 The specs. I have read on two units here [ both early/late 250's] is 1.1 and 1.2 ohm . These are both  original 2 wire units.
 B/c both the brown ground wire is there and on the schematic, it is possible the sol was changed to the later unit and the Br wire taped
off. Either should work.
 I would Ohm it before buying a new one, then you will know for sure..
 

[JPMOSE]

I performed the Ohm test and it is 1.1.  I also discovered the relay didn't work.  I took it apart and cleaned the contact with emory and it now works.  

The solenoid is dead...I think they are around $150 new, so I called H&R to see if they have a clean used one...we will see.  If they don't, I'll spring for a new one.

Are the Mixture (Starting) solenoid and Fuel Shut Off solenoids the same part?  They look the same...

Best Regards,

J. P. Mose
1968 250SL

[rwmastel]

quote:Originally posted by JPMOSE

.... so I called H&R to see if they have a clean used one...we will see.  If they don't, I'll spring for a new one.

You could call Pacific Fuel Injection to see if they have a used one as well.  Might as well try both the "big players" before giving up.  There's a lot of other resources to try if you want to spend the time shopping around.  Companies like S&S Imports, SL Tech, etc.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[JPMOSE]

Rodd..thanks for the suggestions.  I actually ordered the part on line today for $62.79 new (Bosch P/N 0330101012).  Mercedes wanted around $170!   I did a search on Google and found I could order it on Rockauto.com.  Almost seems to good to be true.  We shall see.  Thanks for all the help.

Best Regards,

J. P. Mose
1968 250SL

[JPMOSE]

Well this had a happy ending.  The Starting solenoid now works.  I had received an e-mail from Rockauto that this p/n was on backorder from Bosch, so they cancel the order.  My fear was the low pricing would go way up.  I called Bosch and they didn't have any idea when more would be available.  MB wants $220 retail/$160 wholesale.  I spoke with Hans at H&R and he said he could rebuild one for me.  I guess he has done this many times, as the earlier starting solenoid with two wire hookups is no longer available.  

Last night, a neighbor came over to my garage while I was under the hood.  He asked me about the solenoid I complained about and was interested in its function.  So I explained and happened to try a hot wire on it again...IT WORKED!  I tried it several more times, including with the ignition switch and all is well.  The relay wasn't working until I cleaned it on Sunday.  I'll bet the solenoid and relay haven't worked for many many years.

Again -- the Bosch part number for this solenoid is 0 330 101 012 - self grounding model.

The Fuel Cut Off Solenoid p/n is 0 330 101 013 or 016.  I think the 013 was replaced quickly with the 016 as a mod. in dimensions was required to work with the 6.3L engine.  The Fuel Cut Off Solenoid started with late 250SLs and was only offered in a self grounding (one wire hookup) model.

If anyone wants to add the P/N(s) for the earlier starting solenoid with two wire hookups, it may benefit future readers of this post.  Also the MB part numbers would be useful.  Thanks for all the help.

Best Regards,

J. P. Mose
1968 250SL