Problem starting and what does the E.H.A. unit do? - PeachParts Mercedes-Benz Forum

tino · #1 03-07-2008, 08:58 PM

I am re-posting my car headache again with updates to the problem.

I finally got my 1986 300E to run perfect and decided to further improve it but it seems that I broke it. What I did was check vac hoses and clean contacts and apply electro grease. I also removed the E.H.A unit at the side of the fuel distr. cleaned it and refited it. BUT now the car wont start. When I pour a bit of gas into the Fuel Dist it starts and runs for a few seconds indicating that it has spark - I cant hear the fuel pump for all the other buzzers etc in the car but to test it I disconnected the fuel line placed the end in a small water bottle and when I crank the engine gas does squirt out and half filled the bottle. There is also approx 4.5V at the E.H.A. contacts when the key is in the on position. I re and re the EHA valve just to make certain it was properly fitted but still not even a hint of trying to start. ----- What could be the problem?

Update: I removed and re-inserted most relays - and also disconnected and reconnected the battery -- and the car did start.

I spoke too soon -- the car is dead again........it just cranks.

After I again .... checked and cleaned all the relays I could find and switched fuses around not knowing what else to do .... I bought and installed a new fuel pump but the car still wouldn't start. In desperation I retraced my steps again and think that the trouble began when I removed and cleaned the EHA unit which is a black unit mounted near the top of the fuel distributor. In desperation I gave it a few whacks with the back of my pliers and ... ta daaaa... turned the key and the car started. Was this a coincidence or not ? What does this unit do? At this point I don't trust to venture too far with this car.

Just finished a google search and found the following explanation re EHA-------------The EHA "controls" the fuel distributer by varying the pressure in its chambers. Something to that effect anyway Power to the EHA is directly provided by the OVP relay, so if the OVP is acting up it will effect the EHA and the ICV. Check the OVP first.

OK .....now what and where is this OVP - could it be Over Voltage protection? If yes I did remove and give a few taps on a relay that had a 10A fuse on top of it - when I shook it there seemed to be something loose in it - is this normal?
Also what and where is the ICV let me quess Internal Control Valve ? Whatever it is where is it?

Found more info by google that may be of help to others ----- The OVP is very important and can cause a lot of problems - it also controls the ABS system - I read that the solder joints inside this relay do fail and an easy fix is to open the relay and re-solder the joints. Of course spending some cash and buying a new one is simpler. Does anyone reading this post have a good relay for sale??

UPDATE: I have removed the outer casing of the OVP and found that the some soldered connections to the printed board were badly pitted and oxidized. Using a tooth brush dipped in alcohol I carefully cleaned the connections and very carefully re-soldered them. Re installed this relay and the car started right away and all seems to work fine again. I most likely wasted my time and money by installing a new fuel pump but I feel that I could have spend a lot more money if I had the car towed to a garage and had to pay for them to troubleshoot. At least this way I know I have a new fuel pump.

pawoSD · #2 03-08-2008, 12:17 AM

The ICV is the Idle Control Valve....if its malfunctioning the engine will either will not start or will stall. The rav4 in my sig has this issue and I don't want to pay $200 for a new one....so I've been "fixing" it when it happens.

I think you're on the right track by replacing the OVP...it can cause a lot of problems. If the ICV is not working right that could cause problems too.

RBYCC · #3 03-08-2008, 11:22 AM

The OVP relay is located behind the battery.
It may have two fuses mounted on top of it.
Check to see if the fuses are intact.
This may have been your initial problem.
You may have created a problem by removing and banging on your EHA.
Better to leave things alone if you do not know how they work and how much it will cost to replace it.
EHA is not an inexpensive part and is a critical element in the CIS-E system.

tino · #4 03-08-2008, 11:23 AM

Quote:

Originally Posted by pawoSD

The ICV is the Idle Control Valve....if its malfunctioning the engine will either will not start or will stall. The rav4 in my sig has this issue and I don't want to pay $200 for a new one....so I've been "fixing" it when it happens.

I think you're on the right track by replacing the OVP...it can cause a lot of problems. If the ICV is not working right that could cause problems too.

This may sound dumb to mechanics - but please tell me - how does this Idle Control Valve look and where is it in an 1986 300E.

tino · #5 03-08-2008, 11:28 AM

Quote:

Originally Posted by RBYCC

The OVP relay is located behind the battery.
It may have two fuses mounted on top of it.
Check to see if the fuses are intact.
This may have been your initial problem.
You may have created a problem by removing and banging on your EHA.
Better to leave things alone if you do not know how they work and how much it will cost to replace it.
EHA is not an inexpensive part and is a critical element in the CIS-E system.

You are so right - it is better to leave things alone if they work especially if one doesn't know what their doing. - BUT I again didn't follow this advise and I removed and re-soldered the connections in the OVP - HOWEVER this time with good results. See the update to my original posting.