On my 89 300E, I took the fuel distributor plunger out to check the seal. It was OK. I put it back together and now anytime the fuel pump is running it sprays fuel from all the injectors as if the plunger is fully depressed. I have adjusted the plunger height to every possible position and no change whatsoever. What did I mess up?

You forgot the O rings, or you messed up putting it back together.

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Fun, fun, fun

Oi, Cap'n...

You just made me lose my nerve!

I was gonna do that!

Anyone know whazzup with the Capn's FD?

I put the seal back in just like it came out, at least I THINK I did. The plunger isn't sticking, it just appears that whatever cuts off the flow of fuel isn't working.

The fuel is metered by the size of the slit open by the plunger position. However the metered fuel flow is thru a path covered by the O rings. If the rings are leaking then you would see the symptom you describe.

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Fun, fun, fun

At the time the constant spray started, I had not taken the FD apart. All I had done was to remove and replace the plunger seal. No O-rings had even been seen at the time.

Seems like control pressure is not pushing against the plunger, hence, even with no deflection of the air flow plate, the plunger is not returning to rest.

My 2 cents.

Just because the plunger could be removed the way you did it doesn't mean that you removed it in the proper sequence - or more important, that you replaced it in the correct sequence. I.e., it might not be step 20 of a 20-step procedure. It might be step 4.

I think it is time to do a complete teardown and find out what happened. There are photos if you search that show o-rings that seal around the six ports, and they may have become dislodged or damaged by removing the plunger. They appear to install with the entire assembly apart.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7

Cap'n

Didn't remove the o-rings before?

I thought I saw a post where you had photos of your o-rings and one of them was like slightly out of shape?

So I'm guessing that you toredown your FD before?

Then you must have had a good inspection of the internals for rust, pitting, etc?

The O-rings do not seal against the plunger itself. They seal the plunger chamber where the upper and lower housings mate. I did end up taking the distributor apart and putting it back together, but the constant spray problem was there before I took it apart. All the orings were intact when I did separate the two halves. There was no trash or obvious signs of wear it the distributor. As a matter of fact, I was surprized at how clean it was. Any trash that was there seemed to have made it's way to the injectors.

Did you try basic adjustment?

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

I tried adjustment of the plunger screw, the one that holds the seal, through the entire range of the locknut. Is there another adjustment?

I am refering to the main metering adjustment between the airhorn and the distributor. The 3mm allen wrench one.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

The fuel distributor is separted from the airhorn and the fuel lines and injectors still connected. There is no pressure on the distributor plunger at all, since it is't connected. When terminal 7 & 8 are bridged, fuel sprays from the injectors as if the plunger was completly depressed, as it would be by the airflow meter palte arm.

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What would affect the flow from the fuel distributor ports if you have no restriction in the outlets? The way you have it rigged, pressure will be nil in the plastic tubes, and the differential pressure valves likely can't regulate that. The fuel distributor is not designed to shut down fuel flow, but to regulate the pressure at low flow rates - and just below the 40-50 psi of the injector check valve is as low as it needs function.

If you connect the injectors, you should be able to build back-pressure, and maybe trapped air will be purged from the unit.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7