560SEL fuel leak by EHA valve

[hbofinger]

I just redid the entire rear end fuel delivery, including fuel filter, accumulator, new line between the pumps, and new pump backflow valves. Everything hunky dory, but a after a few weeks I got a fuel smell coming from the front.

I discovered the leak: found dampness below the EHA valve by the fuel distributor. I have two questions:

1. Is this coincidence, or did my work in the back restore fuel pressure to a higher level, causing the leak in the front?

and

2. What is the likelihood that it is just the o rings underneath the EHA, and that I don't need to replace the entire valve? Car has about 130,000 miles on it.

Thanks!

[rayhennig]

Originally Posted by hbofinger

What is the likelihood that it is just the o rings underneath the EHA, and that I don't need to replace the entire valve?

Thanks!

Worth trying the o rings but it may be leaking in the valve.

RayH

[hbofinger]

Does not seem to be extreme, wiped it clean yesterday and smell hasn't returned yet after almost an hour of driving.

Will try o rings first and then go from there.

[Hit Man X]

Well the leak could be so small it could evaporate quick... that was how it was on my 560. The 300SEL leaked so much it puddled under the car.

Lost both EHA valves within a few weeks. 158k and 297k.

[hbofinger]

I'll still go with the o rings first, because they are so cheap. But I am now going to research on how to adjust a new EHA. Thanks!

[Frank Reiner]

Originally Posted by hbofinger

I'll still go with the o rings first, because they are so cheap. But I am now going to research on how to adjust a new EHA. Thanks!

Re: EHA adjustment

There is, to my knowledge, nothing in any service manuals, factory or aftermarket, that describes a process for adjusting the EHA. That said, one could make an adjustment of the actuator current after bringing the CO percentage into spec if the current were at that time out of spec. My understanding has been that the EHA is set by the manufacturer for a specific flow rate at a specific current; field adjustment is not anticipated, hence, no instructions in any manuals.

[MBeige]

My 190E 2.6 is under the same predicament.

Tried about 4 used EHA valves that my mechanic gave me a warranty on them for leaks. So far, 3 leaked (and caused high cold start idle speed), and the 1 that didn't leak and didn't cause a high cold start idle speed instead caused the car to run poorly it bogged down on take off - pretty dangerous when the guy behind is about to accelerate too.

So I put back the old leaking one (it's leaking from the body seams of the EHA unit itself), as well as in between the distributor and EHA housing. The power is back, no more bogging down on take off. Actually currently waiting on the new EHA ($266 for new one, with 2 O-rings included) to arrive this week.

My mechanic was right - small chance that the O-rings are bad.

[Elektri]

You might find more information on EHA theory of operation and adjustment by searching for the appropriate Bosch Jetronic technical information (K, KE).

It is my understanding that the EHA valve adjusts the engine for more rich or more lean based on information provided by the oxygen sensor.

And that a new EHA should be adjusted about right? That adjustment being in the "center" between rich or lean.

So the engine computer could send a + - electrical signal to the EHA and it would adjust more rich and more more rich if more current is sent. And the opposite, - + and it would adjust more lean.

Sort of like playing tennis. You hold the tennis racket out in front of you in the center. Then you are ready to swing to the left or to the right should the ball go either direction.