W124 cold start woes

[Farmbenz]

Hi, I'm having trouble with starting a W124 300TE. Sometimes it will not cold start or run without throttle. When it starts it is rich. After a few minutes it suddenly clears up and is fine. On some days it is fine and starts as it should.
Does anyone have any good ideas or similar experiences? (and solutions!)
Thanks in anticipation.
Farmbenz.

 

[lynall]

Maybe temperature sensor.



Lynall

 

[Farmbenz]

Thanks lynall, I have checked all connections on temp sensors and this seems good. I guess I was after more specifics. Which sensor does what? which ones go intermittant?
Farmbenz

 

[grober]

OVP relay ??---- feeds ECU, ABS and fast idle bypass unit. Does your ABS light come on at all?

 

[Farmbenz]

Well...funny you should mention that. The SRS light does come on when the key is in position 1 but at no other time. What does this mean?
Also, after seeing mention of the OVP relay (Over Valued & Priced?!) I removed this and opened it up to find that some of the solder joints were a bit dodgy. Re-soldering this has so far fixed the cold start problem but it was an intermittant problem before so I will wait before I can say it is a fix.
Farmbenz

 

[grober]

SRS different from ABS

The SRS system is concerned with the airbag/s (if fitted) and seatbelt tensioner systems. It should light up when the ignition is switched on and disappear after a brief delay showing the system has passed it's self checks. Only time to worry is if it stays on!! It has nothing to do with the ABS anti-lock brake system. If there is a fault with the OVP there is often a voltage drop across it. The ABS system has an operating "voltage threshold" If the supply voltage from the OVP drops because its faulty the ABS fault light (red) sometimes comes on altho there is nothing wrong with the ABS system itself but does point towards a faulty OVP. While you are in "soldering mode" it might be worth checking the fuel pump relay also. Its located beside the ECU like the OVP its usually marked kickdown and 6 zyl I have a feeling the cold start injection valve is powered thro part of this relay so might be woth checking out?

 

[Farmbenz]

Hi Grober,
Well yes, excuse my complete misreading of your post, of course you are right!
Anyhow your suggestion of the OVP relay was spot on. I removed this, opened it up to find some dodgy looking solder joints. De soldering and re soldering these and cleaning fuse contacts has fixed the problem. (about 14 days and 56 starts later).
Total cost of repair - 15 minutes & 2 inches of good quality solder & an embarrassing admission of misreading.
Thanks!
Farmbenz

 

[grober]

Glad you got it sorted. These are great cars since you can literally repair them with a soldering iron as you say. Try that with the integrated digital systems of today!