Cold start valve voltage

[djenka018]

Strange.

Can you check if both the terminals on CSV are measuring short to one or other terminal on TTSW

What year and market and model is your W116?

There could be, indeed, wires mixup

[bolbol]

Hi revilla,

It seems to me, as djenka018 stated,  TTSW should ground CSV at "cold" temperatures, . My question, did you check TTSW when you made your tests or just fuel pump and CSV ? TTSW should energize "ground" CSV when cold and for various durations per ambient temperatures (Max around 12 seconds when temp is -25C ). Both CSV and TTSW should be in the same wiring loom.

Some models came with both A/C starter relay and Fuel pump relay ? do you have both ? one,, or possibly none ? Location : Fuse Box.
One thing that ties all this together specially that P and N is not a go but R and D is; neutral safety switch.

This is all brainstorming after a long day.

bolbol

[revilla]

Hi guys,

Thx a lot.

car is a 1977, europe spec, 280 sel.

CSV has 2 wires (pink/blue and brown/blue) and same colors for TTSW plug. when car is cold, or TTSW placed in cold water there's continuity between  the 2 terminals (G W) of TTSW indicating circuit is closed.  There's also continuity at CSV connector terminals under these conditions (TTSW closed). 

I did another 20 cycles test but this time measuring voltages at CSV connector and observing fuel flow/spray at CSV nozzle.

Ignition SW turned to pos 3 (engine crank)

1 crank for each of the following changing the probes location each time. 

Voltmeter red and black probes connected to:

pink/blue and chassis ground          P= 10.2V      N= 10.2V      R= 11.6V

brown/blue and chassis ground       P= 10.2V      N= 10.2V       R= 0V

pink/blue and brown/blue                P= 0.03V      N= 0.03V       R= 11.6V

In all cases CSV always sprayed while in R and never while in P/N

Regarding the other questions by bolbol , I only checked voltages at CSV.  I see 3 relays inside fusebox. 

Thanks guys.

Robert

[koan]

Thermo time switch has three connections, W, G and ground through screw threads.

G is heating coil to ground, W is switch, open if hot, connected to ground when cold.

+12V from cranking circuit to G which continues on to Cold start valve

Other terminal Cold start valve connects to W of Thermo time switch, this grounds and activates Cold start valve.

Bridging terminals of TTSW as a test does nothing as that's not the way it works.

Cold start circuit is powered from start position of ignition switch via PRNDL start switch.

Looking into Cold start valve connector, one terminal should +12V only when cranking and 0V otherwise. Measure Voltage from battery negative terminal to connector pin

Other terminal of Cold start valve connector should be open circuit to ground if engine over 15C, or short circuit to ground if below 15C. Measure Ohms from battery negative terminal to connector pin, but only with ignition off.

Thermo time switch needs to cool down between tests.

[djenka018]

What Koan said is what I would say anyway... thanks.

I would like to ask is when you measured 12V at pink/blue, was it at W terminal on TTSW or at the cold start valve?

When key is OFF, does it measure short pink/blue on CSV to pink/blue on TTSW W terminal?

Disconnect the blue plug on MAF meter throat and do the same test as earlier. Check the volts between the WUR wires and observe the fuel pump running when key is in RUN position.
This is to point towards any potential wiring issues at fuel pump relay

[revilla]

Hi guys,

All good now    CSV works well.

After reading/digesting the last posts I realized what was missing.  Thanks for the help.

This time, I again placed the TTSW in cold water, but this time I connected a wire from TTSW thread to chassis ground.  Before I cranked I double checked W terminal had continuity to ground, it had so switch was confirmed to be closed.  I then cranked and voila !!!!  CSV sprayed when cranking in P and N as it should.  That rules out CSV and TTSW as the root cause(s) of my cold start difficulties.  This realization doesn't solve my problem but at least it confirmed it's not related to CSV and TTSW. 

Just one last question.  When I disconnected the plug of the TTSW and bridged the 2 female terminals, leaving the plug disconnected from the TTSW, isn't that effectively sending the signal to the CSV to spray?  My assumption was that this procedure simulated TTSW closed as if it was cold allowing me to test just the CSV.  That's the only piece of the puzzle still unclear to me.

Your help is appreciated.

Thanks again.

Robert

[revilla]

Never mind about that last question guys.  After seeing this pic it's clear.

http://www.hglmotors.co.uk/ts/tts.htm

[djenka018]

you will never forget how this circuit works now...

Usual issue with cold start issues is bad injectors and severe vacuum leak along the injector sleeves.

Injectors are ~$30 each and sleeves/seals are dirt cheap in US of A

I had the same cold start issue (long cranks left scars on starter motor) but after replacing the injectors and seals all went fine.
You may get lucky and get improvement with injector seals only

[revilla]

you're right about learning how the circuit works.   

I've been learning a lot since I own the car. sometimes even making mistakes along the way.  but it's all worth it.  the knowledge absorbed is priceless, it can be transferred to others and saves big $$$$.  Even simple things like  changing the oil, or replacing brake pads are so incredibly expensive here. They ask for 70-100 EUR to change oil/filter while I can do it for 45 EUR max. 

Considering injectors are not that expensive as you said, i might venture into that next.  Also I need to take a 2nd look at WUR for cold control adjustment.

I'll keep you all posted.

Have a great week.

Robert

[djenka018]

Start from cheap stuff. Leave WUR for the end. Chances are it is not terribly off.

Seal the vacuums. They plague this engine.

Standard engine (I assume, being in France) has simple externalvacuums but must not forget all those contoured hoses, seals (like the notorious injector grommets and O rings), and correct timing advance vac changeover valve.

I used cable tie around contoured hoses and some contact adhesive to seal it all during fault finding. Ended up later replacing them but it was cheap to confirm the leak existed.

AutohausAZ.com
bits4benz.com.au

[revilla]

Hi Guys,

Ordered injector's seals, plastic sleeves and o-rings.  Based on advice at the beginning of thread, when I apply full throttle things improve indicating air leaks.  I was surprised of low prices so I ordered, it doesn't hurt to change 37 years old rubber parts. 

Changing the seals around the injectors seems easy based on videos and prev posts (bracket removal, line disconnection, injector pulling, rubber seal removal).  No big deal. However, I couldn't find a whole lot about the plastic sleeve and its o-rings.  I understood this o-ring also gets harder with years and it's critical to prevent air ingestion. It seems possible to break the plastic (maybe brittle) while pulling/rotating.  Makes me nervous.   

How about DIY injector cleaning? Any home made method recommended?

Any advice is appreciated.

Thank you all.

Robert

[djenka018]

When you see the new mushroom injector seal and compare it to the old one, you will think you have a wrong part.
Nope.
As an elderly Merc service guy in Rosebank Mercedes said to me: "if you had something push you hard on top of your head for 20-30 years, you would assume another shape too..."

Try not to brake the o-rings or you will have to recover them from intake manifold. A hook may help pry them or keep them from falling if they become loose.

Use "rubber grease" or, I think, vaseline for assembling to make sure everything fits perfectly.

Correct your timing, idle 1/min and lambda=1 at idle afterwards. Get ready for shite loads of power.
On M116/M117, lambda will be close to 1 at idle when CO is approx 1-2%. Should be close for M110. There could be a label somewhere on top of the engine with CO, timing angle and idle rpm default settings

[daantjie]

Do not use Vaseline, it is petroleum based and will eat the rubber.
Silicone grease is best.

[revilla]

Thanks for all the advice guys.  parts ordered, work will be performed next weekend.  I also found a couple of rubber plugs that look/feel more like hard plastic now.  I'm pretty sure there is some serious leaking there.  I'm planing to replace those too.  I completed the first part of the job.  Removed plates, sleeves and injectors.  I understand there should be a tight fit but they were in fact easy to slide out with zero resistance.  That means the seals and o-rings were probably not really sealing from air ingestion.  We'll see the positive impact when the new ones are in place (using silicone grease and not vaseline .  I'll keep you all posted.