1969 280sl starting issues

[edwardburak@erols.com]

1969 280sl automatic USA version

I have installed the motor in my car after a long restoration. I have all the wiring completed (at least I think so) apart from the radio/ antenna fuses beside the radiator overflow reservoir. I also need to finish some of the connections underneath the dash.

Radiator is installed, oil in engine, 10 gallons of hi-test gasoline. Engine was purchased from buds benz as rebuilt and detailed; it ran. I have all new stainless fuel lines, and new rubber lines by the injector and fuel pump.

This morning I went to start the car for the first time and it would run on a prime, but not on its own. This was fixed with cleaning fuse #4, cleaning the ground connection behind the driver's seat and sending direct 12v to the pump and lightly hitting it with a hammer. After this "boost" the pump functions with the turn of the key.

One question, does the pump ever shut off after it builds pressure? Or does it continuously recirculate the fuel back to the tank? Mine keeps running. I have 10-15 psi fuel pressure at the cold start injector.

After this fix, the engine runs at higher RPM , but won't idle. The venturi closes entirely, so I need to install the gas pedal and adjust everything.

The engine will not start on its own.

When I crank the engine, the Cold Start injector (on the side of the intake) does not get power. That black wire has continuity with pole #87 on the CSV relay harness and continuity with fuse #6.

The engine will start if I run a seperate jumper lead to the cold start injector (tapping it a couple of times during starting). Then the engine runs fine (except the mentioned idle maladjustment). When cranking normally (no jumper wire to cold start injector), neither the CSV relay or the Cold start injector "click" as I think they should. I do not think either of them are getting the power they need.

Next, I tested the CSV relay according to https://www.sl113.org/forums/index.php?topic=825.0

I sent positive 12v to prong #86 and negative ground to prong #85. This "clicked" the relay and I had continuity between prongs #87 and #30. I then concluded my relay as functionable.

When cranking, prong #30 has 10.6 volts. I tested this by half inserting the relay into its connector.

I have not tested if Prong #86 receives any power when cranking. The relay does not "click" when cranking, so there is no continuity between prong #87 and #30.

Prong #86 has continuity with W on the thermo time switch, and #85 has continuity with G. I think my thermo time switch is good, but do not know how to test it. I do not think it is my problem, as I have tried to start the engine both with the TTS disconnected and with a copper wire connecting the two wires. 

I have not checked the wiring from CSV relay and ignition switch, is that my next move?

what do you recomend?
thanks

[Fonzi]

I would think the pump should run continuously.  It sounds like you know more than me about these cars though. 

It sounds like you’ve discovered yours needs more fuel to run.  Is that right?

I’m working on a 1969 280se and someone sent me an injector pump, and I need to give it more air to run (disconnected the linkage from the FIP). 

It sounds like there are a lot of adjustments.  Is the linkage sitting on the throttle stop in front of the cold start injector?  If not, maybe it’s getting too much air.  Could there be vacuum leaks?

[edwardburak@erols.com]

Yes, I think I need more fuel to run, as the cold start injector is designed, to create a richer mixture for start up.

You are correct, the throttle stop is not screwed out enough to raise the idle. I have not yet delved into the linkage adjustments, I have heard that there are many "hack-job" ways to do it, and I need to do some more research first.
thanks

[Fonzi]

I just watched this one and am glad I did.  The first 16 minutes were very helpful, but I watched all the way to the end looking to learn more.  https://youtu.be/F6sxlOFmoYw

[Cees Klumper]

The throttle stop screw is only used to get the butterfly valve as closed as possible, just shy of binding. Idle mixture is controlled by the large screw on the back of the FI pump + the air screw on top of the air intake manifold. Do watch the video, your warm running device may be stuck in its bore from non-activity. Lots of info in the linkage tour in the tech manual.  The fuel pump is always on when the ignition is turned on.

[Benz Dr.]

The throttle stop screw is only used to get the butterfly valve as closed as possible, just shy of binding. Idle mixture is controlled by the large screw on the back of the FI pump + the air screw on top of the air intake manifold. Do watch the video, your warm running device may be stuck in its bore from non-activity. Lots of info in the linkage tour in the tech manual.  The fuel pump is always on when the ignition is turned on.

Pretty close. Idle speed is obtained with three separate parameters:

fuel
air
ignition timing

[edwardburak@erols.com]

Ok, I watched that video, I will check the throttle stop screw and adjust the idle accordingly (using the large screw at the back of the FIP). I may have an issue in my warm running device, timing, etc..

However, should I not be getting power to the black wire connected to the cold start injector?
thanks

[Pawel66]

You should when cranking.

[edwardburak@erols.com]

Correct, and I am not.

[mrfatboy]

Check your TTS and relays to make sure they are working properly.

[edwardburak@erols.com]

The relays are good, as I tested them based on https://www.sl113.org/forums/index.php?topic=825.0.

I have not tested the TTS as described on https://www.sl113.org/wiki/Engine/ThermoTimeSwitch.

It mentions to certify that all the wiring is good, I will check all that I have not already tested (CSV relay to ignition switch)

[Pawel66]

Edward, you can just provide power to CSV manually during cranking to see if it helps starting. A lot of people have switches under dash to do that. When cranking and a second or two after.

[edwardburak@erols.com]

Yes, it will start consistently if I do that by running a jumper wire from the positive battery post to the Cold start relay

However, I would like it to function properly

[mnahon]

You're better off using the 'Alternative Test' in the technical manual, which is equivalent to using this procedure on page 2, issue 2, volume 2 of Pagoda Notes:
https://www.sl113.org/wiki/Restricted/PagodaNotes?action=download&upname=PNv2i2.pdf

[Pawel66]

Yes, it will start consistently if I do that by running a jumper wire from the positive battery post to the Cold start relay

However, I would like it to function properly

Then it may be the TTS, if you say relay is ok. Simple first step is to disconnect wires from TTS (at least the W wire) and check if there is ground on connector W in TTS when the engine is cold. If ground is not there, TTS is shot. Then you are into alternative as for its replacement.

But it can also be a power supply topic. Not sure how fluent you are in this, so if not for your benefit, then perhaps for others who will read it and need it...

Depending a bit on the year of car you have, but in essence: you may have two relays there on the relay bracket - one for CSV, one for mixture adjustment solenoid on the FIP. If you do not have that solenoid on FIP, you will still have the relay for it most likely, not hooked to anything.

Power comes from fuse 6 to both relays independently to pins 30/51. You should have power on both pins after ignition. When the relay is activated power from one relay goes to CSV, from the other to the solenoid on FIP. Power goes from pins 87. The relay you are after, the one to CSV, should have black/pink/white wire coming from pin 87 to CSV. The other relay, to solenoid on FIP, has black/red wire there.

The CSV relay is activated by:
- power from ignition switch delivered to pin 86 when the key is turned to cranking (not fused)
- ground from TTS delivered to pin 85 from W connector in TTS (that is why - if no ground on W with cold engine, CSV will not work)

The FIP solenoid relay is activated by:
- power from ignition switch delivered to pin 86 of the CSV relay, then to pin 86 of this, solenoid, relay (there is abridge there) when the key is turned to cranking (not fused)
- ground is permanent

So if power is not delivered to CSV, as you figured out, then either there is a break in the power supply fuse 6-relay-CSV or the relay is not activated, so either power from ignition switch is not reaching the relay or the ground is not coming from TTS.

[ja17]

I would hook a 12 volt test light to the intake cold starting valve (CSV) and another to the top solenoid on the back end of the injection pump (CSS). When attempting a cold start below 95 F coolant temperature, both lights should activate, momentarily
more or less.  Most likely your problem is lost contact in one of the relays. Each device has its own relay and they are both identical. Your car most likely has two relays for that year. Some years had more and later cars had less. You can try to identify your cold starting system in the charts and photos in the tech manual. These relays can be opened up, contacts cleaned and be operational again. Since the starting relays are identical, you can switch them around to help diagnose your starting system. Don't confuse the wiper relay (larger and more prongs for the plug) with the smaller starting relays. They all occupy the same area next to the brake booster. The thermo time switch can also be defective, but not likely in most cases. We can go to the next step after you perform these tests.

[Fonzi]

So did edwardburak@erols.com ever get it starting correctly?  I was following this one in an effort to learn the system on my parts car 1969 280se before tearing it apart and scrapping it.  I think I’m having the same intermittent CSV power issue.

[edwardburak@erols.com]

I have not figured it out yet. I have not been able to work on it as much as I hoped.
I did find if I disconnect the fuel mixture relay (the one that has a 2 connectors piggy-backed), the car starts fine.
I have tested the relay, and it is good. I have bench tested and swapped relays around, the relay is good.