You need to get your fuel system pressures (upper and lower chamber in order) by using a fuel pressure gauge. I went thru this whole mess when I adjusted my EHA. If you forget where the EHA adjustment screw was originally positioned you're in for a hell of time without gauges.

System pressure (lower chamber) should be 5.3-5.5 bar measured with fuel pump relay removed and contacts 7 and 8 jumpered.


Upper chamber pressure is measured at the cold start valve connection on the fuel distributor (just follow line from valve to distributor). This is what your EHA has adjusted and it should be .4 to .5 bar below your system pressure (4.9 to 5.0).

Your EHA may be leaking because you have the pressure too high. I'm guessing it's running very rich. Get it within spec and it should idle and run fine and then you can adjust the lambda to fine tune it some more.

Good Luck

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-Paul-
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi

I'm in Kirkland, WA.

Yikes... this is going way beyond my capabilities :-( I certainly don't have any pressure gauges.
One thing I did notice is that white vapor would occasionally puff out of the intake when I cranked the engine over (filter box was removed for adjustment). Would this be an indication of a rich or lean condition?
Mika

If it is rich, which way does the EHA set screw need to be turned to lean out the mixture?
Mika

It seems that little adjustment screw passes over a chamber in the middle of the screw bore, so depending on where the screw is will determine which way you need to turn it to lean/richen the mixture.

If it's screwed all the way down then it's too rich, so counter clockwise from there to lean it out.

If I recall correctly, mine is positioned approximately 5 turns up from the very bottom. You may just want to replace the EHA as mentioned above.

Here's one on Ebay incorrectly labeled as a FPR:

EHA

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-Paul-
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi

Do all W124 cars use the same EHA part?
Mika

I don't know if they all do but that EHA for a 190 2.3 is the same part # for the 124.

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-Paul-
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi

Mika, mail-order the new EHA valve and install it yourself. From my experience the plastic body is probably cracked. You'll need a Torx bit for the 2 bolts.

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Fred Hoelzle

I'm leaning towards this approach.
Thanks for all the input.
Mika

yes it is. I just replaced mine - an absolutely trivial exercise. there is absolutely nothing to adjust. If this part leaks. as mine did, you HAVE to replace it .... it can't be fixed. Mine cost about CDN$ 300 or 350 or something close to that. After replacement, I passed emissions, as well the car accelerated MUCH better (no stumbling and lag) and is getting significantly improved milage. Best money I spend on the car. There is only two or three bolts holding it..... nothing to it.

cheers, guenter

Thanks again! I think I'll buy a used one from a forum member who is parting out his car. The EHA is a recent replacement, so it should be in good shape. I hope that solves the problem.
Mika

I assure you there is an important adjustment on the EHA. It's on the face that bolts up against the fuel distributor. There's a brass screw there that, when removed, reveals an allen screw (2mm IIRC) that sets the pressure in the fuel distributor. you may have lucked out and gotten a new one that was adjusted right for your car. No guarantee that anyone else will.

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Norm in NJ
Next oil change at 230,000miles

Are you sure EHAs are not calibrated by the mfg? Does the FSM suggest adjustment of all replacement EHAs?

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'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E

I sure hope they are calibrated at the factory. I've heard from several individuals that new EHAs were drop-in plug 'n play parts...
Mika

Unless you fuel distributor is way out of whack it should be able to adjust within the proper range when a new one is dropped in. The adjustment on the unit is to of course compensate for older units and to get the EHA back into the proper range so it can control and maintain proper air/fuel mixture throughout the rev band!

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~Jamie
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2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's.

1986 190E 2.3 Black, Auto, Mods to come soon.....