Unidentified 4th Relay-'69 sl

[awolff280sl]

A 4th relay that hangs from an L-bracket near the brake booster does not seem to be a one-second time switch that I assumed it was. When power is jumpered to socket 87 on this relay's plug, the FUEL PUMP is activated; the CSV solenoid is not activated. I do not understand the purpose of this because the fuel pump is turned on anyway when the key is in position 2.
I have identified the other 3 relays near the brake booster from back to front: 1)wiper 2)FIP solenoid 3)CSV solenoid. This 4th relay's electric socket is plugged piggyback-style into the socket of the CSV relay. The 4th relay is of the same shape and size as the FIP & CSV relays. I have seen this L-bracket 4th relay in some other '69sl's in pictures posted on the forum. Do I have a short or is there some other purpose for this relay?

[awolff280sl]

A possible explanation: if the fuel pump is activated only with the ignition key in the "run" position, then this relay would be needed to activate the fuel pump in the "start" position.

[jeffc280sl]

Andy,

remove fuse #4 and put power on pin #87 as before.  Does the fuel pump run?

If yes, there would appear to be a short between pin #87 and the feed wire from fuse #4 to the fuel pump.

If no, then there is a power feedback short from an electrical component on fuse 2, 3, 5 or 6.  

If you think of power running in one direction, one side of fuses 2,3,4,5,6 is connected to the same originating power source in a chain. The outgoing side of the fuse routes power to the electrical components.  In truth without going through a diode power will go in any direction.  What I mean by power feedback is that a power short in the wiring coming from an electrical device is being routed back to the fuse.  Because the fuses are chained together on the feed side power can come back through the fuse and then out to another device through one of the chained fuses.  

If the answer is no I suspect from our earlier conversation that there is a power short through one of the electrical components fed by fuse #6.  Put fuse #4 back in place and remove fuse #6.  Apply power to pin #87 as before.  If the fuel pump runs there is a power feedback short in one of the components fed by fuse #6.  Fuse #6 controls the cigar lighter,  as well as the starter valve relay and the rich mixture relay.

These steps should help isolate the problem.  I suspect the relay wiring from out ealier conversation.

[awolff280sl]

Jeff,
Thanks again for helping me narrow this down. With fuse #4 removed there is no pump activity with power to 87 on the 4th relay. However, there IS pump activation with fuse #6 out and power to pin 87 (and fuse #4 in place). So...where do I hook up my voltmeter? Lots of different places, I presume.

[jeffc280sl]

That's interesting.  Well there is a power feedback problem.  It's just not in the fuse 6 circuit.

There is a wiring design problem with the brake fluid level sensor.  Maybe you have heard of it.  Unplug the connectors on top of the brake fluid tank.  Now try putting power on pin #87.  What happens to the fuel pump?

This problem is pretty well known and it is triggered when a circuit is completed by the low brake fluid sensor.  I have had my brake fluid topped off but the float on the brake sensor pin had fallen off.  It is held in place by a small rubber compression plug.  If this happens the sensor thinks the fluid level is low.  I remember opening the door would also turn the pump on.

Let me know what you find.

[awolff280sl]

Despite disconnecting the both brake fluid sensors, the fuel pump activates with power to 87 of the 4th relay.
I've read about the door light/brake sensor/fuel pump issue, but I've never had that problem myself.
Is it possible that, in the production period of my car, that in the "start" position of the ignition, power is supplied only to the starter (and its downstream relays) and the coil, thus leaving fuse #4 for the fuel pump out of the loop until in the "run" position. And because all of the starting aids require a flow of fuel, it was necessary to add a relay to power the pump during "start". Months ago, when I was tracing wires, I did ohm-out a connection that goes from the starter to this 4th relay (a purple wire at the relay).
Gernold has also seen this 4th relay and starter connection, but I think it was his impression that this relay functioned as a ballast resistor bypass during cranking by the "old style" starter.
I guess I could hook up a test light to the fuel pump, disconnect the 4th relay, and check for the light during cranking. Somewhat cumbersome (like everything else). There must be someone on the forum with this relay who knows what it is.

[jeffc280sl]

We know the power feedback at the fuse box is coming from the circuit that includes pin #87 of the fourth relay.  We know that pin 87 of relay 4 is not connected to fuse #6.  In general pin 87 is used to provide power from #30 to the device after #85 and #86 are energized.  Seems to me that somewhere in the circuit pin #87 on the fourth relay is wired to pin #30 on another relay connector.  This may be by design, I'm not sure.

We need some more data points.  Do the fuel pump test using pin 87 of the fouth relay while removing one at a time fuse 5 then 3 then 2.  This will tell us what fuse circuit the feed back is coming from.  We know its not fuse 6 or 4.  This will at least tell us what other electric devices are connected to pin 87 of the fourth relay.

We tried to do this once before but the only other thing I can think to do is for you to draw a wiring diagram with colors to indicate the relationship of the various relay connectors.  ie. what color wire goes from pin to pin.

[Peter van Es]

Is it the Relay for Mixture Control (Relay #21 at http://www.sl113.org/wiki/pmwiki.php?n=Electrical.WiringDiagram). If you are a full member you can look at the colour wiring diagrams in the Technical Manual and figure out very easily what's what if you know the colours of the wires going to the connectors on the relay.

Peter

[awolff280sl]

Peter,
Thanks for your input. Looking at the Legend for the descriptions of the various electrical components, I find the following relays:
    #17-Relay for Wiper Motor (obvious)
    #21-Relay for Mixture Control (on 280 SL)-                  I think this refers to the FIP solenoid control
    #20-Relay for automatic starting aid (on 280SL)-
            I think this refers to the CSV solenoid control.
I cannot find a 4th relay for the 280SL identified in the Legend.

[awolff280sl]

Jeff,
Here is a drawing of the wiring, as best as I can tell. Please note that pin 86 of my CSV relay only has 2 wires, whereas the published schematic shows three. Because I cannot make out the colors too well, I am uncertain if one of these 2 wires goes to FIP relay 86 or to the starter/ignition.
Pin 30 of both the CSV and 4th relay go to fuse 6, which I guess would explain why the fuel pump activates when power is applied to 87 of the 4th relay.
I cannot make sense of the function of the 4th relay from this setup!

Download Attachment: 4th relay.jpg
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[jeffc280sl]

Andy,

Your sketch indicates the 4th relay is being used to bypass the the ballast resistor.  

I assume the brown wire of this relay is a ground.  Can you check this to be sure?

I need to understand the operation of the TTS a little better.  I think when the engine is cold terminal W on the TTS is grounded. I know pin G is fed from the ignition during cranking. As the TTS warms up does power pass from pin G to pin W?  

If you put the 4th relay out of the picture for now you can see that while you crank a cold engine, ground is provided to pin 85 of the CSV relay(from the TTS) and power from the start position of the key is provided to pin 86.  This causes the relay to close and power is sent via pin 30 to pin 87 and on to the CSV solenoid and a mist of gas is injected into the intake manifold.  As the TTS warms up ( 12 seconds or so) the ground is removed from pin W of the TTS and the CSV will not operate.  This completes the operation of the CSV relay.

The fourth relay- If the brown wire is a ground and the TTS/engine is cold nothing will happen with this relay.  The way your car is wired the ballast resistor will be bypassed only after the TTS is warm and power passes from pin G to W.  When this occurs power from pin 30 will be connected to pin 87 and +12V is sent to the coil to make a hot spark.  This only happens when the TTS is warm.  As mentioned earlier when the TTS is cold nothing happens with the 4th relay and the ballast resistor is not bypassed.

My questions:
When cold does pin W of the TTS see ground. When warm does pin W see power from pin G?

As I look at other wiring diagrams it looks to me like the wiring on the 4th relay is a a mixture of concepts.  I look at the relay and part of it looks like the time circuit for operating the CSV when starting a warm engine. Then I see it is connected to the coil which is the ballast bypass function.  Maybe someone just really got confused with this one.

What about the 3rd relay?  Not the wiper relay.

More to come.

[Peter van Es]

quote:Originally posted by AWOLFF280SL

I cannot find a 4th relay for the 280SL identified in the Legend.

Looking at the wiring diagram in the Technical Manual(http://www.sl113.org/wiki/uploads/Electrical/280sl_bw.jpg) and comparing it to your sketch, the ballast resistor should not be connected to any relays...

The CSV relay is #20 on the wiring diagram... tracing the wire from lead 30 appears to go only to fuse 6. So it does appear your relay is a non-standard addition...

Sorry, I can't help any further

Peter

[al_lieffring]

quote:Originally posted by AWOLFF280SL

A 4th relay that hangs from an L-bracket near the brake booster does not seem to be a one-second time switch that I assumed it was. When power is jumpered to socket 87 on this relay's plug, the FUEL PUMP is activated; the CSV solenoid is not activated. I do not understand the purpose of this because the fuel pump is turned on anyway when the key is in position 2.
I have identified the other 3 relays near the brake booster from back to front: 1)wiper 2)FIP solenoid 3)CSV solenoid. This 4th relay's electric socket is plugged piggyback-style into the socket of the CSV relay. The 4th relay is of the same shape and size as the FIP & CSV relays. I have seen this L-bracket 4th relay in some other '69sl's in pictures posted on the forum. Do I have a short or is there some other purpose for this relay?

This extra relay has been added to the system (previous owner?) to increase the primary voltage of the ignition coil when the starter is engaged.
The fuel punp running when the relay is bypassed is a feed back through the resistor back through the igniton switch eventually to the fuel pump. That is the reason why the relay is there, to isolate the circuit and prevent the feed back.

If the original starter has been replaced with a Bosch SR59X (it most likely has) this bypass function is built into the starter solenoid, the lager of the two screw terminals can be wired directly to the coil side of the ballast resistor. I ran a wire along the battery cable from the starter up to to the +(15) termilal on the coil.

If your starter only has one screw terminal it is still the original style and the relay is needed to keep this "extra spark when cranking" function.

[awolff280sl]

Jeff & Al, thanks for helping me solve this. The brown wire is a ground. I'll test the TTS function once I get my valve cover towers. Jeff, the other relay (not the wiper) tests out to be the FIP mixture relay (87 works the upper FIP solenoid).
I do have the SR59X, and I have also run a wire from from the larger screw to the coil side of the ballast. I guess my next step would be to disconnect this 4th relay.
My impression is that this relay, while not mentioned in any MB wiring diagrams or supplements that I have seen, was in some way "standard" during a period of production, and not unique to my car from a previous owner. I say this based upon the use of an original relay & connector, but especially because I have seen it under the hood in pictures posted by a few other memebers of this forum.

[jeffc280sl]

Andy,

Sounds like Al has some very good tips. Especially the power feedback.

FYI, according to the Haynes wiring dagram the fuel enrichment relay and the CSV real share power on pins 86 from the ignition switch. They also share power on pin 30 from fuse 6.

Can you read a part number on the 4th realy?  I think the piggy back style connector circuit was designed by MB as a starting aid for the one second burst of fuel to the CSV when the engine is warm.  Haynes calls it at time switch with part # 0015451624.  It appears like   somehow in the past it was rewired as the ballast resistor bypass relay.  Maybe the time switch failed at some point and was replaced with regular Bosch relay and converted to the bypass circuit.  Hence my question.

[jeffc280sl]

Andy and Al,

I think this diagram and writeup explains how the time switch should be wired.  Comments?

Download Attachment: andyrelay1.jpg
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[al_lieffring]

quote:Originally posted by jeffc280sl

Andy and Al,

I think this diagram and writeup explains how the time switch should be wired.  Comments?

Download Attachment: andyrelay1.jpg
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I just got the June, 2008 Pagoda Notes, with Joe's tour of the starting aids (an excellent article BTW).

According to Joe's charts the version III wiring in Jeff's diagram would be for a late 230sl with the enrichment solenoid and the cold start injector wired in parallel.

A 1969 280SL (version IV) would have the injection pump enrichment solenoid activated any time the starter is engaged (possibly the original function of the mystery 4th relay) and the cold start injector operated by the thermo time switch and the one second timer via another relay.

So everything in Jeff's diagram would be correct for the version IV cold start injector but terminal 87 would not "T" off to the pump enrichment solenoid.

A USA model 1969 injection pump should have both an enrichment and shut off solenoid. Make sure when you re-route the 87 lead from the 4th relay you connect it to the start enrichment (upper) solenoid.

Several times I have had cars towed in to my shop from another shop with the start enrichment wire connected to the shut off solenoid after a new motor or injection pump had been installed.

I am currently not using the type III wiring on my 66 230sl cold start. Explaining why would only make this post even more confusing, but I too have 4 relays on the safety latch bracket. But not wired like any of the 5 standard versions, because of a starting problem peculiar to my vehicle.

[jeffc280sl]

Al,

Thanks for the input. It is very helpful and much appreciated.

[awolff280sl]

I can't read any part number on the 4th relay.
I don't want to beat this horse to death, especially because I'm getting confused.
Al writes "A 1969 280SL (version IV) would have the injection pump enrichment solenoid activated any time the starter is engaged (possibly the original function of the mystery 4th relay)". I don't get this because the FIP starting relay (relay #1) already performs this function at any temp, any time the starter is engaged.
Jeff, if I understand correctly, theorizes that the 4th relay may have originally been a 1-second time switch that was replaced by a Bosch relay. Pictures of the 1-second time switch show it to be a round device, Bosch relays are box-like. The problem I have with this theory is that there are other '69sl's out there with 4th Bosch relays hanging from L-brackets. Perhaps my 4th relay was re-wired, but I'd sure like to learn the intended original function of this relay.
One last request to those with this 4th relay to help out.

[jeffc280sl]

Hi Andy,

I think this stuff can be confusing especially when we try to understand why or what was done to your car in the past.

Lets just stick with the knowns.  You have a fuel enrichment relay that appears to be wired and operating correctly.  You also have a CSV relay that is wired correctly and operating as designed.  Same can be said for the wiper relay.  The issue comes down to the 4th relay, its purpose and if there is a better implementation.  I didn't realize until I read Joe's explanation in the Pagoda Notes that the time relay was discontinued in production sometime after 1965.  An after factory modification kit could be added to the post 1965 through late 1970 production cars if needed.  You can decide if you want to add this kit to your car.  I think we also know the purpose of the 4th relay as wired in your car is to bypass the ballast resistor.  There appears to be a better way to wire it up and I suggest you consider that.

I think you can also take steps to try and determine why your battery discharges after long periods.  This may or may not be related to the relay wiring.

[awolff280sl]

Maybe this picture will help.
A 4th relay in this part of the engine bay is found during a production interval of the 1969 280sl. It is wired to one of the other relays by means of a connector that is piggybacked onto the other relay's connector. The sequence of the relays may vary from car to car. The wiper, FIP, and CSV relays have been thoroughly discussed on the forum. But a 4th relay of this shape, in this location, using a piggyback connection has not been decribed, to my knowlege.
I am trying to find out the intended function of this relay.
Thanks.

Download Attachment: 4TH RELAY.jpg
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