[W126 Coupe] W126 losing power

[Jonathan Hodgman]

Dick,

Tom is CIS, not CIS/E, so the procedures for out Gen II cars don't apply 
when it comes to EHA/VOHM etc, etc..

the fuel pressure gauges, yes, they are a must when tuning CIS.

Jono
On 7/30/2011 7:33 PM, Dick Spellman wrote:

> Hi Tom,

>

> Change the plugs to the prescribed NGK or Beru.  The OEM Bosch W7 or 

> 9DCO (I can't recall) may still be available at your local MB dealer.  

> All are single electrode plugs and offer the correct resistance for 

> the ignition system.  The Bosch Platinum +4's are NO GOOD on your 

> engine regardless of what the parts store may have said.  Presumably 

> you used OEM cap and rotor, not aftermarket.  Plug and coil wire leads 

> should be Karlynn or OEM.

>

> A quick check of the coil supply voltages as per the manual is a good 

> idea to rule out a weak coil.

>

> Fuel pressure gauges (StarProducts Lindhurst, NY $80~) would allow you 

> to check the system and differential pressures which should be 

> something like 5.3 bars system with a differential of 0.40.  Just as a 

> comment, a common tweak to the differential pressure is to adjust the 

> screw on the EHA so you get 0.45 diff. for improved performance.

>

> You could road test with a minimum 12ga. stranded (soldered tips)  

> jumper wire on the fuel pump relay socket to rule out an ailing FPR.  

> The jumper is needed in any case for the fuel pressure tests with 

> gauges.  A write-up on using the Star gauges for a 300se (same set-up 

> as your 380) is on Steve Nirvig's web pages.

>

> The gauges will also let you know if the system has any leaks such as 

> the control piston seal or accumulator.  You don't mention replacing 

> the fuel filter this could be fouled and restrict flow. What's the 

> age/mileage on the 380's single fuel pump?  This too could be weak.

>

> Of course, a VOHM meter preferably with dwell angle (Sears $30) 

> connected to thediagnostics outlet (see Dan Landiss's write-up) would 

> allow you to accurately tune the air/fuel mixture at idle and at 

> 2500rpm.  This critical setting cannot be done manually.  This same 

> meter will let you test the EHA's current once the engine has warmed 

> up.  Where the factory spec'd O2 is in place and new you should be 

> okay and not need to meter this in the passenger footwell.

>

> Have you disconnected and blocked off the air pump?

>

> Good luck,

> Dick

> diyr

>

>  On 7/30/2011 6:13 PM, Tom Brophy wrote:

>>

>> I  a have 1985 380se, with a 1984 500sec Engine. the compression is 

>> within 5lbs of the fuel filter.  factory spec on all cylinders.

>>

>> I have a loss of power under load [going uphill] or quick 

>> acceleration, otherwise car runs smooth at a constant speed, but 

>> dropped 4-5 mpg. failing smogou see if the system pressure is 

>> dropping misserably - CO emissions. replaced catalytic converter 2 

>> years ago.

>>

>> I'm fairly sure whatever is causing the power loss is at the root of 

>> my smog woes, the emissions are about 10x higher than 2 years ago.

>>

>>

>> What I have done --

>>

>> new spark plugs bosch platinum, [tested plug wires] new cap & rotor, 

>> new fuel injectors w/seals, new dir replacement bosch O2 sensor, 

>> checked timing adjusted fuel mixture [manually], cleaned idle control 

>> valve. replaced ECU [salvage] when nothing else worked.

>> even at a richer mix I still have a problem under load and the engine 

>> stalled on the dynamometer. someone suggested it might be the 

>> catalytic, and I loosened the exhaust to create a good leak before 

>> the catalytic and the engine still stalled when I put it under load 

>> by applying the brake and reving the engine slowly to about 1100 RPM.

>>

>>

>> Any suggetions?

>>

>>

>> Tom

>>

>>

>> The MB Coupes Website! W126 SEC Mailing List Postings remain property 

>> of MB Coupes, L.L.C.

>>

>>

>> The MB Coupes Website!

>> W126 SEC Mailing List

>> Postings remain property of MB Coupes, L.L.C.

>

>

> -- 

> The information contained in this e-mail and the attachments, if any, 

> is legally privileged and CONFIDENTIAL.  It is intended solely for the 

> use of the individual or entity to whom it is addressed and others 

> authorized to receive it.  If you are not the intended recipient you 

> are hereby notified that any disclosure, copying, distribution, or 

> taking action in reliance of the contents of this information is 

> strictly prohibited and may be unlawful

>

>

> The MB Coupes Website!

> W126 SEC Mailing List

> Postings remain property of MB Coupes, L.L.C.


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.pairlist.net/pipermail/mbcoupes/attachments/20110730/f09fd041/attachment-0001.htm>