190E...A few questions

Others may have another idea but I suggest you consider checking the car's "Overvoltage Protection Relay."

This devil has a fuse on its top.

Suggest you begin with the OVP relay, then, if the hard start persists, check the "cold start system" of sensors, cold start fuel injector etc.

Don't give up, you'll figure it out - and fix it.

EHA valve would be worth checking to see if it leaks, on the back of the intake, a rectangular black plastic block with fuel lines going in and out

- it regulates the fuel pressure and they leak - mine did and caused similar but not identical symptoms.

cheers. guenter

Mr. Lambach,

Thanks so much. I always look forward to your response.

In my 190E I have a Siemens OVP (12V - 10A) - Here is what I can verify.

- fuse is ok

- test between pins 87E and 87L reads 0 ohms (not open) anything else that could be wrong with it that isnt exposed in these test?

As far as the cold start/fast idle, here is what I've done (or know to be true)

- replace all 6 plugs and plug wires

- replace cap and rotor

- idle circuit tests at .55-.6 amps at idle

- ignition system test found 45kv at the cap

- fuel pressure is holding at 3.2Bar

Thanks again for taking the time to respond.

Roger H.

Guenter,

Thanks for responding.

Do you know of any recommended test for the EHA? I know where it is located, just unsure how to test it.

Thanks Roger

just check around the seams to see if it is leaking gas, if not you are very likely OK

cheers

Roger,

There is an excellent website, 190Revolution.net

that is an excellent resource for anyone owning a late 80's early 90's Mercedes 190. Check it out. John Mc

I'm most familiar with the older diesels and know generally about gas engines, but not specifically their various permutations and combinations of parts so read this as general guidance rather than specific repair instructions.

Suggest you create a new post specifically about the Over Voltage Relay

- what it does, exactly, and specifically how one can test it.

With respect to the cold start system, basically, there is an engine temp. sensor, a time/temperature relay and an electric valve that sprays fuel into the intake manifold. You engine may differ in its parts but the idea is:

1. if the engine is below a specific temp. (I believe its about 20 degrees C.) then
2. power is sent to a time / temperature relay (or similar) which is ON for a brief period, longer when colder.
3. The electric cold start valve sprays fuel into the intake for about 5 or 10 seconds - just long enough to get the motor running.

You've changed to usual ignition parts but not touched the cold start system. Since you're good with a test light try the plug to the cold start valve when the engine is cold and someone briefly cranks the starter. There should be power to that plug, if only briefly.

I hope this helps you.

Tom

In the course of my "travels" on Usenet a kind soul posted this explanation of the OVP relay. I don't know enough about electronics to opine on its truth but you may.

The OVP relay protects the sensitive electronic circuits, i.e. your ECU from high voltages.

It basically consists of a fuse, followed by a relay energized by a small circuit, which has a zener diode built-in. This relay feeds the the SRS, ECU and ABS (any others?). If the voltage goes too high, the zener conducts, and shunts the circuit to ground, cutting out the relay, and if very high, blows the fuse.

These relays get tired, as basically, it has to activate continuously when the engine is running. 10 years ± is about the lifetime.

When it cuts out, your engine reverts to "dumb" mode, and won't compensate for temp, O2, timing, etc.

SRS, ECU and ABS, that's all. And depending on model and/or # of systems that are protected, there are different versions of OVP relay, between 5 - 9 pins, and 1 or 2 fuses.

A cross-cable during a jump start can easily kill this relay.