Flushing the Fuel Distributor - Page 2 - PeachParts Mercedes-Benz Forum

bostonmish · #16 02-06-2010, 12:16 AM

I use the ACC-CARBC-LE-NR which came in a black bottle.

Now for the bad news:

My car, now with the transplanted, cleaned FD, is experiencing fuel delivery problems. These problems might still indicate a faulty FD. I have finally been able to testdrive the car, after a thorough cooling system flush and the problem made itself evident.

It's a strange problem: The motor will idle pretty well and for a long time ( during coolant flushing and tuning). It will rev up and sound very good, when stationary, however, after about a mile of driving the motor will gradually lose power, stumble and stall. If I let it rest for as little as two minutes, the car will start right up and run for another several. If I let the car rest for 20 or 30 minutes, I can drive it around the block before the bogging down comes back. The odd thing is that this condition only appeared after a 30 mile run, during the initial test. It now will set on within a mile or two. [...update: the more I consider it, the more this sounds like sediment & rust in the fuel tank problem ]

This behaviour will also happen with the gas tank cap off.

I'll start another thread to discuss the problem and possible solutions, but getting back to cleaning the FD:

I would not yet rule out it's potential. The FD I have been experimenting with came with unknown history. As a result of cleaning, I know some contaminant washed out, but for now that's the only conclusion I can make.

bostonmish

zhandax · #17 02-06-2010, 04:54 AM

Here is the good news if it really is the FD. Apparently the Porsche guys have had the same issues and have gone a bit further with tinkering as detailed in the link above by Ivanerrol. Elsewhere, Deltacom has posted a link to a guy on eBay who sells diaphrams for the FDs to allow rebuilding. I contacted him yesterday to ask if he offered the diaphram for the FD on a 300SL and he indicated that he would have them in a month. Check the pics on Deltacoms post. Your diaphram may look like the one on the right which appears to be the logical result of years in a highly-volatile hydrocarbon environment compounded by more recent exposure to an oxygenated solvent (i.e. ethanol) to which nitrile butyl has poor resistance (I am guessing the likely composition of the original).

Ivanerrol · #18 02-06-2010, 06:17 PM

I saw that listing for those FD diaphragms and sent an email off to the ebay seller also. He will also have diaphragms for 4 cylinder type KE FD's as well as 6 cylinder in a month or so.

bostonmish · #19 02-07-2010, 12:51 AM

zhandax, thanks for the comments.

...going further, like the Porsche guys, i.e. a complete FD teardown, was precicely what I wanted to avoid by devising a cleaning method.

The fuel deformed FD membrane is only possible on the later, light alloy FDs. The early, cast iron units (what my car has) have a stainless steel diaphragm.

As an update on my 1979 450SLC, with further analysis: considering the type of performance degradation the car experiences now, the new primary suspect is not the FD, but the (likely rusted and degrading) fuel tank.

The earlier work performed, however, was a methodical elimination of confirmed "bad" components, in the order of natural escalation up the food chain, taking into account MB CIS pressure and other tests and that the car sat for 6+ years. First the FFilter, then FP, then WUR, then the FD, etc.

Finally, the original FD was indeed confirmed to be gone, and the used + cleaned (per method described in the earlier posts) FD makes the car run.

For anyone following this thread, the possibility that a "bad" FD can be cleaned is still viable, although not 100% confirmed, at this stage.

bostonmish

zhandax · #20 03-20-2010, 06:13 PM

I just found the problem with mine. I finally got a day off, got the Yamaha cleaner, pulled the FD and started to fill the holes. When I turned it to fill the last two holes, I noticed that the part number on the FD ended with 012. This is the wrong FD. It fits a 300E. The 300SL takes either 0438101043 or 0438101044. I guess the PO took the car to a mechanic that didn't do his homework. Fortunately, a wrecker on eBay had the entire AFM assembly from a 1992 300CE w/ 98k miles for $279 and it is on the way.