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1989 190e 2.6
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16 Posts
Discussion Starter #1
Hi guys,
I have been lurking on the forum soaking all your guys' knowledge dealing with the stalling issues related to our cars.

I have just bought a 1989 2.6l 190e project car which starts and dies. The car sat for 4 years in my mechanics' back yard, had a 1/4 in layer of dust. The good news is there is no rust with the exception of the battery metal tray.

I ordered basic maintenance items to install: spark plugs, rotor, cap, fuel filter, o-rings for the leaking EHA, valve cover gasket etc. Oil change and fuel drain will follow right away.

The most common failure point of these cars seems to be the OVP relay which, if that 10amp fuse is not blown, provides unreliable variable voltage to:
- ABS computer
- to fuel computer
- to idle speed control valve

The car's electronics rely on a good 12V power source to properly operate. I am a big fan of the Ford starter solenoids/Bosch relays and install them on all my vehicles to make starting procedures easier (1967 Chevy - remote starter solenoid, 280z Datsun - the same setup to by-pass the weak ignition starter wiring). The same was done to the headlights circuits.

What do you think of installing a 30/40 amp Bosch relay with a good 12V battery hook-up (10 amp inline fuse) which will be positioned between the OVP relay and those 3 aforementioned circuits? The idea is to re-use old OVP relay base and solder the Bosch relay wires there to avoid any wire cutting as much as possible. The great thing about these Bosch relays is that even a small 5V+ feed will trigger the relay's magnet thus providing the solid 12V+ from the battery. So even if the OVP relay is failing, we still enjoy 12V+ supply.

I am attaching a basic diagram. Please let me know what you think.

Thanks,
Den
 

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'87--190E 2.3-16v(being rebuilt), '99--C230 Kompressor
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3,488 Posts
if the 10 amp fuse it blown it means replace the ovp relay...they were built like crap and need to be replaced with new OEM parts ($50)...sub parts have a tendancy to fail

as for your plan you want to install a relay inbetween the ovp and the ovp base? and your going to tie all 5 wires into "85" and then out of "87"? if you did 5 individual relays one for each circuit i could see the possibilities albeit redundant...but all into one? i don't think it will work...but go for it anyways and see what happens...just don't be surprised if you fry 1/2 your electrical systems.
 

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1989 190e 2.6
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16 Posts
Discussion Starter #3
By default on the OVP relay there are already 3 circuits sitting on one bus (87E, 87E, and 87L). If there is weak voltage going to all 3 circuits, 3 car parts start to exhibit unstable performance.

But, yes, 3 in, and 3 out via that Bosch 30 amp relay. The overvoltage part is still being taken care by the original OVP relay (10 amp fuse), so logically, it should prevent electronics from being fried.

Good point about splitting the circuits. I will need to identify which one draws more amps: ABS or the idle valve.

Here is the updated diagram.

Also, if we are looking for redundancy, we can hard wire (bridge) posts 85 and 87 on both relays, thus allowing the current to flow even if both relays fail.
 

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