Can an OVP........
 

prove to be faulty without blowing a fuse?

on two of my cars, the answer is yes.

pull it out and shake it... if you hear the slightest rattle, it is likely a goner.

Yes they can!! I had the one on m car that was bad when i got he car and the fuse was good and then a used one that i got off of a parts car did the same.

I've read here that they can rattle and still be good. Mine rattles.

A place to buy is (MBV Parts) Dave Walton Spares in Oz or perhaps ******** in the US?

http://www.***************/search/product.aspx?sid=stm4at55ynakaa453bvocoiz&makeid=800016@Mercedes&modelid=1193105@260E&year=1989&cid= relay@relay&gid=4593@Overload%20Protection%20Relay

They all rattle. It's just the PCB in the mounting slots.

my new ones didn't rattle.

the bad ones did not have blown fuses

True tell symtoms of bad OVP would be Skin Rash, Migraine Headache, Overcast Weather, Fading Paint, Poor Radio Reception, Dirty Dishes, and Poor Credit.
The list is endless... , but these are the more common factors..........

Spot on Arthur.

It was skin rash!

Yeah, "Da OVP Rash "..we call it...very common ..

If you go to the Archieves , you will see that OVP has been blamed for just about everything..so goes my post..:)

.and in acuality, it ranks high in causing many electrical gremlins....
,,but to answer your queation, the fuse is feed for ECU power and ABS module, [ ABS will light w/blown fuse], but most OVP relay malfuntions are circuit board poor solder conection or blown zenier diodes. The OVP circuit section is a spike arrestor through the zeniers to ground to protect the ECU circuits from spike/over-voltage, but when they go, they also effect many electrical feeds.
The early ones were notorious for faults, but the modifed/new ones are much better/robust.
..so , a blown fuse does not mean a bad OVP, or a good fuse does not cancel out a bad OVP diagnosis.............

Thanks for the comprehensive reply Arthur.

You've saved me a trip to the dermatologist!

Forgot to add the OVP self explanitory meaning..

O.V.P. relay = "Over-Voltage Protection " relay.......................

Matter of fact, a blown OVP fuse would rarely indicate the OVP is bad either... The fuse will blow if the alternator/battery source voltage goes too high, of if there is an excessive load on the circuits the OVP supplies. OVP caused problems usually result from poor internal connections forcing the output voltage to be erratic, which confuses the engine management circuits.

Steve

best and most logical explanation i have heard about a bad OVP

Thanks to all for your responses, but maybe I'm barking up the wrong tree.

My 260e will crank but won't start and I was hoping the OVP may be the cause.

However I did a fuel pressure test yesterday and with KOEO the pressure was 25psi.When i cranked it the pressure went up to around 80-90 psi.but fell almost immediately back to 25psi.with ignition off.Is this right?

My apologies in advance for my limited mechanical knowledge.