Help confirm possible OVP failure on 89 300E - PeachParts Mercedes-Benz Forum

Douge · #1 12-01-2009, 10:24 AM

Just about to roll over 140K. I have a very lumpy idle, but anything off idle it purrs and pulls strongly. In addition, I have a sporadic ABS warning light. I replaced the plugs with copper cores as PO had used platinum. Wires, rotor and cap replaced 9K miles ago. Other than the poor idle, there are no other drivability issues.

I pulled the OVP and visually inspected, it has a single 10a fuse on top which is intact. I sprayed the socket and terminals with electrical contact cleaner with no change in condition, in fact the ABS light is more frequent after I cleaned the connections.

Sounds like a likely culprit. Overall the car is in excellent condition and runs very well. If not the OVP, I think possible fuel filter, pump, accumulator or maybe the ICV?

TIA

Doug

PS, I have the single fuse relay now, can I put the double fuse relay in as a replacement? It is part #2015403745

ps2cho · #2 12-01-2009, 11:33 AM

ABS light is the ticket towards the OVP. Its almost guaranteed .

big dog 2 · #3 12-01-2009, 11:59 AM

Replace it! I did and everything is fine now on my 1989 300E. Had the same issues as your car too. I ordered my replacement part online for a reasonable price.

Now if I can find an easy fix or a leaking rear main seal! Hint: I don't think one exists!

mak · #4 12-01-2009, 12:53 PM

around this mileage and age sure letdowns are the fuel and OVP relays. I opened my OVP relay and found a cold joint at the Zener junction,resoldered it and all operations fine.
The fuel pump relay was soldered next when the stalls became more frequent.
rectified that too!
mak
300se

Douge · #5 12-01-2009, 01:17 PM

Thank you gentlemen. I found an OVP at the pick and pull for $6 and she is purring again!

ps2cho · #6 12-01-2009, 03:38 PM

Quote:

Originally Posted by Douge

Thank you gentlemen. I found an OVP at the pick and pull for $6 and she is purring again!

Another happy OVP replacement

300holst · #7 12-01-2009, 04:42 PM

If the substitute OVP continues to work, fine, however I had a new OVP relay replacement that started giving the same idle and ABS light symptoms after a few weeks with the new OVP. Eventually I found the the contacts in the OVP socket were loose. When I pulled the relay and replaced it, all would be well for a week or two then the symptoms would return.

I decided that the relay was subject to shaking and vibration which, over time, would loosen the relay in its socket and give intermittant contact. I fixed the problem by:

1. remove battery to give room to work
2. unbolt the relay assembly to allow access to the underside where the wires are connected to the relay socket contacts.
3. clean the OVP contacts with spray cleaner
4. install the OVP relay, turn the relay assembly over, push each contact on the socket firmly onto the relay pins using a small pick or screwdriver.
5. loop a Zip-tie through the relay assembly and around the OVP, pulling it tight so the relay is firmly held. Now it won't vibrate loose.
6. reinstall the relay assembly and battery and you're good to go.

Douge · #8 12-01-2009, 07:02 PM

Well I spoke to soon. Took the car golfing and ran it about 30 miles each direction and the lumpy idle is back, however the abs light is NOT coming on.

ps2cho · #9 12-01-2009, 07:06 PM

Quote:

Originally Posted by Douge

Well I spoke to soon. Took the car golfing and ran it about 30 miles each direction and the lumpy idle is back, however the abs light is NOT coming on.

You don't know if the one you got has problems too...Its best to just buy a new one. I consider the OVP a tune up item if you have no history of replacement. Its about $45 new. It is also a good idea to have a spare in the trunk...so buy a new one and keep that one in the trunk.

Ferdman · #10 12-02-2009, 06:47 AM

Doug, pull the distributor cap and check the condition of the cap internals and the rotor end. Clean/replace both, as required.

Douge · #11 12-02-2009, 01:46 PM

Quote:

Originally Posted by Ferdman

Doug, pull the distributor cap and check the condition of the cap internals and the rotor end. Clean/replace both, as required.

Done, it was ok but I had a spare (new) set and installed them. Still lumpy. Need to find a KNOWN good OVP to try.

dhjenkins · #12 12-02-2009, 01:55 PM

Quote:

Originally Posted by Douge

Done, it was ok but I had a spare (new) set and installed them. Still lumpy. Need to find a KNOWN good OVP to try.

Why not jumper the OVP completely and see if that gets rid of the problem. If it doesn't, it's probably not the OVP - though that doesn't rule out connections, wires, etc...