cold start valve and relay

[n/a]

I have read many articles here on how to adjust your points in the relay box by removing the metal shield around it, but mine appears to be solid black plastic with a large harness going into the side, the Hanes manual also shows this (#5)unit but again does not look adjustable...I also do not see any of these for sale...Now on to the cold start valve, I see where people are removing these and cleaning them with some success, for a 71 is there any fuel pressure and can I just remove the two pipes going into this valve and clean the apparatus and reinstall ( these valves cost 800.$$$$$so I do not want to mess up here)...It takes approximately 10-12 seconds to cold start and it is a very bumpy affair...any incite would be appreciated. thanx

[Ben]

Cant answer re the relay..........never been there but for the valve itself I succesfully removed and cleaned mine and got it working by following the advice given here previously !

There will be some residual fuel pressure when you remove the fuel fitting, the one nearest the rad, but a rag around the pipe will sort it as you remove it !

I believe there is a small gauze filter here, dont loose it. I would first chgeck to see if this unit actually working electrically before removing and cleaning it. Check it with a test lamp at its connections and get someone to crank from cold. It should light momentarily. If not you need to check the relay and thermo time switch.

If it DOES light you can takje off the rubber air filter pipe and with a torch and mirror again get someone to crank while you observe a fine mist spray. If you see a trickle or nothing then it DOES need to be removed and clean carefully !

There are plenty of other posts so you could use the search feature for better results !

Regards,
Ben in Ireland.
'64 230SL 4sp.

[jeffc280sl]

The relay iteself is not adjustable.  There are contacts inside that can be cleaned.  The relay is a standard Bosch style that is readily available at most auto parts stores. The ones in the auto parts stores will require a new connector for our wire harness.   I have even seen some Bosch style relays with round pins that may plug right into our wiring harness.  

I would check it as Ben suggests before taking it apart.  Let me know if you need some help doing this.

Jeff C.
1970 280SL 4-speed

[Raymond]

Silly thought.  I hope you know by "torch", Ben meant a flashlight.  :mrgreen:

Ray
'68 280SL 4-spd Coupe

[ted280sl]

Ah yes; the cold start valve, csv. Many a line has been written on this site regarding the csv. There are two basic areas of concern regarding the CSV. Either it does not deliver any fuel, which is usually and electrical problem, or it leaks, which is usually a mechanical problem. Establishing where your problem lies is simple enough and can be done by a process of elimination.  
  A simple light attached to the CSV solenoid while the engine is cold will tell you if the solenoid is being activated. You can also run a line to the solenoid from the battery. Hav someone crank the engine and just touch the solenoid on the back of the CSV. If the engins starts right up you have an electrical problem which has nothing to do with the CSV.
  The second test is also rather simple. It is the CSV leak test. There is a small bolt on the side of the CSV. If you remove that bolt and turn the ignition to the on position nothing should happen at the CSV. The fuel pump should be pressurizing the fuel system and if the valve is functioning properly no fuel should be leaking out of the bolt hole. If it is leaking the CSV needs to be rebuilt. Mine was rebuilt for less than $100. I believe this would be a better investment  than a new one for $800. I suggest that the $700 you will save is better spent entertaining members of this club.
Ted 1969 280SL My CSV passes the leak test every time!

[Ben]

There is just one other area which may need attention and that is if all the checks as below are done but you are still not getting any spray then the nozzle may be blocked. These can be ultrasinically cleaned though some have had success poking very fine wire into the nozzle. The entire CSV need to be removed for this operation, obviously, and you may need a new sealing ring to refit !

Regards,
Ben in Ireland.
'64 230SL 4sp.

[hands_aus]

A little off topic but definitely related to CSV's

There are at least 2 different types of CSV used on these cars. The later CSV unit is a different diameter to the earlier unit...probably related to the different inlet manifolds.

Earlier models had a valve mechanism with a bronze valve and seat that can be lapped.
Later model cars had CSV with a 'ball and spring' valve mechanism.

I was told that the ball wears (goes out of round) and won't seal on the bronze housing. I am not sure if these can be repaired.
Maybe a new "ball and spring" valve can be added.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[rwmastel]

quote:Originally posted by Ben

I would first chgeck to see if this unit actually working electrically before removing and cleaning it. Check it with a test lamp at its connections and get someone to crank from cold. It should light momentarily.

A question from an avid reader, but a novice mechanic:

Must one obtain a test lamp at an autoparts store, or can a simple home light bulb and socket work?  Home bulbs are expecting 110 to 120 Volts here in the USA and the car is obvioulsy a 12 Volt system.

Thanks,

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

[hands_aus]

Rodd,
I went to an electronics store and bought small 12volt lamps for testing purposes. They are about the size of two match heads with wires about 150mm long and cost about $1.00 each ... probably less in the USA.

I use alligator clips on the wires to connect to whatever I am testing. Usually one end is connected to the chassis and the other to your current project eg CSV.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[mdsalemi]

Rodd--didn't you see Joe's lamp tester from Harbor Freight?  I think it is about $5.  It has a ground clamp, a long probe, and a clear handle with a 12 V bulb in it.  We used it to diagnose David Pease's CSV on Sunday.  Turns out the relay was not working.  David and his friend Mike took the relay apart and cleaned the contacts, now it works.

Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored

[rwmastel]

No, I missed that!  I wish I had been there to see that and the CSV cleaning.  I must have been off talking about something else with other people.

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

[mdsalemi]

quote:Originally posted by rwmastel

No, I missed that!  I wish I had been there to see that and the CSV cleaning.  I must have been off talking about something else with other people.

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

It was simple.

Ground the test lead, put the probe on the CSV's + connector, and crank the cold engine.  If it has power, your probe lights.  In David's case, it did not--no power=bad relay.  Put another relay in, and it did.  Now we isolated the problem to the relay.  Took the old relay out, removed the cover, used fine emery cloth on the contacts, put the cover back and resinstalled.  Voila, it works.

Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored

[hands_aus]

Recently there was an engine bay fuel smell around my early 250SL.

There was a film of fuel under the CSV housing on the solenoid end.
It turned out to be a leak from the small conical solenoid-to-housing seal.

To eliminate other possible problems, I tested with the 5mm bolt removed…. ignition on, engine not running…. there was no leak.

Spark Plugs look normal.

The CSV housing has a tapered recess that allows a seal to be compressed onto the small brass collar on the solenoid.

see pic below

I bought a couple each of fuel O-rings: 8.5x2mm, 8.5x1.5mm.

The 2mm O-ring was the correct thickness, although it was slightly smaller than the brass collar of the solenoid.
When re-assembling it was pushed over that collar by the housing.

Now there are no leaks and no smell.


Download Attachment: ColdStartValveDismantled_small.jpg
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Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto