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Old 09-05-2000, 01:59 AM
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I am trying to solve a lingering hard start problem on my '86 300E. I believe the air flow sensor plate may need adjustment.
Here goes. There is a gap furthest from the fuel distributor which is larger than anywhere else on the plate. My understanding after reading Probsts' FI book is that the gap should be uniform around the plate and its zero position be even with the top of the vertical face.
So, do I adjust the plate downward (the large gap would disappear, but the plate might rest too far down in the vertical face.
Or, adjust the plate upward and re-center it. And to top it off, the guide pin is flush with the sensor housing so I am paraniod I might drive it into the intake manifold if I try to adjust downward.
Has anyone been through this procedure before? Thanks in advance.

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Old 09-05-2000, 07:56 PM
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To begin with, adjusting the air glow sensor is a very differcult thing to do. I would advise replacing it. Those potentiometers are very critical in their adjustment.

Check OVP (overload protection relay), make sure its not black, the black ones have cold soldier joints and can cause starting problems, especially cold. Red are OK.

Aslo the fuel pump relays are updated and improve starting.

If the problem is warm, it may be injectors leaking down, or fuel distributer center shaft seal leaking.

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Old 09-05-2000, 08:48 PM
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Join Date: Mar 1999
Location: Suwanee, GA, USA
Posts: 4,712
Ian has a point on where to start. The newer fuel pump relays do have different programing for the cold start valve.

I have adjusted many of these plates. You will not get it to sit even. You should have no more than 2mm of play when LIGHTLY pushing inward on the plate (stopping when you fill the resistance). If there is more than 2mm, you have to drive the pin to the left of the tower down with a punch...IF you go too far, you have to take it apart and start over. YOU MUST RESET FUEL MIXTURE (LAMBDA) AFTER DOING THIS.

Donnie Drummonds
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