OVP Relay

[jpskiller]

got a couple of glitches with car at moment so thought I would try and borrow a OVP to try to see if this helps, but when I went to change it noticed mine has 2 10a fuses in top not the normal 1 fuse, can anyone explain why it's different and has two, and does anyone else have the same type, spare I could maybe borrow.


oh and the problems I'm having are intermitent

1) 2k Idle speed on startup (normally when engine cold ie not started for a few hours) - getting more common.

2) Stalling - normally when turning a corner or braking to a stop - not often but a pain when it does it.

 

[jaymanek]

The two fuse one is for cars with ASR and other bits.. Im fairly certain you are ok to use the two fuse one in place of a one fuse, but not the other way around.

 

[jpskiller]

The two fuse one is for cars with ASR and other bits.. Im fairly certain you are ok to use the two fuse one in place of a one fuse, but not the other way around.

ok, but apart from ABS / Air Con / Cruise, my car dosent have anything else like ASR etc

 

[jaymanek]

I cant remember at the moment what the extra pins do... The two fused ones have 9 pins and the single fused ones have 7 or 5 I think..

Anyway, in either case you will need a two fused one... same as mine in the SEC..

 

[jpskiller]

Still looking for one of these if anyone has one...

 

[neilrr]

What's the part number?

Piccy?

 

[jpskiller]

What's the part number?

Piccy?

at work at min, will check later and post part-no. cheers

 

[jpskiller]

Just had a look and part no is : 201 540 37 45
top is orange with 2 blade 10a fuses.

 

[Dieselman]

The fault doesn't sound like OVP to me, it sounds like a gummed up throttle flap and maybe idle control valve, or at the worst a vacuum leak.
A spray with carb cleaner may give a fix.

 

[jpskiller]

The fault doesn't sound like OVP to me, it sounds like a gummed up throttle flap and maybe idle control valve, or at the worst a vacuum leak.
A spray with carb cleaner may give a fix.

cheers, had vaccum checked all OK no leaks that can detect. also when engine is at idle the economy needle is a 0, had throttle flap cleaned and idle control valve checked, they appear to be ok, but couldent hurt to spray a bit of carb cleaner in again!

also had new sparks (nothing fancy NGK I think ) and HT leads recent..., (not miss firing) but should I invest in some good spark plugs

ie
http://cgi.ebay.co.uk/MERCEDES-300E...hash=item230270582536&_trksid=p3286.m14.l1318

or are these any good and worth the money
http://cgi.ebay.co.uk/BOSCH-Super4-...hash=item120280854850&_trksid=p3286.m14.l1318

 

[grober]

Both the ABS and IDLE CONTROL VALVE and EHA may be driven from the OVP as I recall on the earlier cars. I believe someone had idle problems due to excessive voltage drop across the OVP leading to the fast idle control valve malfunctioning. Try taking it apart and soldering the pcb connections.

The fast idle control valve may be faulty or sticking--- don't know if its a rotary idle actuator or the older bimetal strip auxilliary air device ? Worth taking a look at to see if its jamming/ dirty .

 

[Ian B Walker]

Both the ABS and IDLE CONTROL VALVE may be driven from the OVP as I recall on the earlier cars. I believe someone had idle problems due to excessive voltage drop across the OVP leading to the fast idle control valve malfunctioning.

The fast idle control valve may be faulty or sticking--- don't know if its a rotary idle actuator or the older bimetal strip auxilliary air device ? Worth taking a look at to see if its jamming/ dirty .

Its the rotary idle actuator version. Its been out, tested, cleaned and replaced. So has the cold start valve. The throttle body has been cleaned and all vac lines have been checked with no leaks (including the gear box lines). A fuel pressure test has been conducted and meets Mercedes Specifications. One thing we have not looked at is the charcoal filter, that may have something to do with it but I am not convinced. OVP relay? possible but once again I am not sure.

 

[grober]

Unlikely to be the charcoal filter unless the line to it is letting air into the inlet manifold. Easy to block it off temporarily to test. The 9 pin relay with 2 fuses simply fuses the 2 outlets 87e and 87l separately whereas in the earlier relay both 87e and 87l shared a common fuse. I would definitely replace it since poor /high resistance connections can give rise to strange injection system faults. As a first step try resoldering the pcb contacts inside the relay can. Any friendly TV repair shop/ amateur wireless opo should be able to do this for you for a fiver if you aren't handy with a soldering iron. Worst comes to the worst just replace it.

 

[Dieselman]

Unlikely to be the charcoal filter unless the line to it is letting air into the inlet manifold. Easy to block it off temporarily to test.

Air leakage or sticking throttle/valve is still my No1 hit, it just sounds like it as it's after the over-run when they will be fully closed.

Do these cars have any base idle setting which the ECU then controls, if so it may be too low and the idle valve can't react quickly enough .
On Bosch Digifant systems if you disconnect the water temp sensor and rev up to force limp home mode (base settings) the idle compensator parks and the base idle is revealed. I wonder if the Motronic can do the same.?

Is the idle control actually working at all?
Try putting the engine under load and see if it resumes normal idle.

 

[Will]

I think JPS' car is Jetronic.

I'm with Grober here - it sounds like textbook OVP issues, certainly fits with the intermittant nature of the problem.

I reckon the OVP relay is failing due to poor solder joints, giving unreliable power to the idle control valve etc, hence causing it to stick in position - causing either high, or too low an idle (depending on where it's moved to when it loses power).

Could obviously be something completely different, but considering what has already been checked, how commonly the OVP relays fail and how easy/cheap they are to fit I would certainly want to rule it out.

Will

 

[Will]

BTW, is it worth checking what type of OVP relay is fitted to your 190? Could well be the same or compatible for testing purposes

Will

 

[Dieselman]

I think JPS' car is Jetronic.

Doh, of course it is, it's got an idle control valve, but doesn't that also mean it has a base setting for the throttle flap?

 

[Will]

Doh, of course it is, it's got an idle control valve, but doesn't that also mean it has a base setting for the throttle flap?

Presumably, although I've never had cause to adjust one so far.

I think many people ignore this and probably just use the idle adjustment instead.

Will

 

[Dieselman]

Presumably, although I've never had cause to adjust one so far.

I think many people ignore this and probably just use the idle adjustment instead.

Will

That's really what I meant, unless the throttle is closing too much, if that's possible.
What is the base idle setting and how is it achieved. Presumably via an air bleed port and screw.
If I had a car here I'd know but I don't.

The way to set it is to park the idle valve then set the idle to spec. I think all will be ok then.

I thought this car has KE-jetronic, in which case I think using the throttle flap is the way to do it.

 

[Will]

That's really what I meant, unless the throttle is closing too much, if that's possible.
What is the base idle setting and how is it achieved. Presumably via an air bleed port and screw.
If I had a car here I'd know but I don't.

The way to set it is to park the idle valve then set the idle to spec. I think all will be ok then.

I thought this car has KE-jetronic, in which case I think using the throttle flap is the way to do it.

I'd have thought it'd be the other way round. Ie, adjust the idle using the screw as low as it goes, then adjust the throttle to whatever engine speed you wanted, then adjust the idle speed back to spec.

I know there's a small screw to adjust the idle, I imagine that there is as way of adjusting how much the throttle closes to as well?

Will