Flushing the Fuel Distributor - PeachParts Mercedes-Benz Forum

bostonmish · #1 01-28-2010, 03:04 AM

Question First: Does anyone know the thread size of the FD output lines? I need a bolt to plug the outlet.

I want to plug 7 of the 8 FD outlets (leaving one empty at a time) to flush the FD, one port at a time.

Project:

1979 Mercedes 450SLC. After diagnosing and fixing several components, I am attempting to cleanout a spare Fuel Distributor by filling it up with Yamaha Carburetor Cleaner - widely used in motorcycle fuel systems due to its effectiveness in dissolving fuel varnish while NOT attacking any of the rubber or plastic components.

My method of filling the FD was to:

1) remove FD from car

2) remove fuel line outlet filters

3) inject Y-Cleaner into the threaded towers (empty of fuel lines) on top of FD

4) slowly extend the plunger until the fluid is drawn in (this of course is possible only when the plunger exceeds its normal range of travel)

5) even more slowly move the plunger to the very top position, avoiding pressurizing the interior and ejecting cleaner

6) repeat the injection / plunger operation 3 or 4 times until the unit is full of cleaner

7) leave alone to soak for as long as practical (Yamaha Cleaner is so effective in undiluted form it would act in as little as 30 minutes)

Next I plan to install this FD on the car and flush it using the car's own fuel delivery system. I plan on connecting the high pressure and return hoses and capping the rest of the outlets, except one (at a time) of the FD-to-injector lines. The WUR control and return lines will be plugged by a spare WUR. The Cold Start valve, by a spare CSV.

I am a bit in the dark about the FD-to-injector output lines. I hope someone can help me properly ID the size of the bolt with which these ports can be plugged. All I know is that the thread pitch is 1.0mm.

Back to the FD cleanout: I would like to flush the FD chambers one by one, mostly to observe what comes out. I am under no illusions that if serious contamination (rust) is present, that it would flush out, but I know from years of experience that all of the fuel varnish will certainly be gone.

I would appreciate any comments and especially if someone can help me to ID the correct thread size.

Bostonmish

PS I have restored a completely plugged WUR, back to 100% spec. by injecting it with the Yamaha Cleaner and drawing it from the inlet to the return ports by alternating vacuum and pressure with a mityvac. At first the unit was plugged completely with fuel varnish. I filled the inlet cup and the fluid stayed there. No amount of vacuum (within reason) would draw the fluid in. After about 20 minutes (at room temp) I was able to transfer some pressure from the outlet and observe an air bubble in the fluid on the other side. I applied a bit more vac/pressure over the next few minutes. After 1 hour the fluid appeared in the output side and the level equalized between both ports. I knew the diaphragm was now covered. 12 hours later the unit was transferred to the vehicle and confirmed to be 100% in spec, from absolute cold through the warm up cycle and beyond. Keep in mind, the unit was completely gummed up when I started!

bostonmish · #2 01-28-2010, 04:00 PM

Some photos to document the process:

Photo1 - FD with output filters removed

Photo2 - MityVac used to inject Yamaha Cleaner in a controlled way ...(almost) no mess

Photo3 - FD filled up with cleaner. After this the plunger movement draws the cleaner inward. Repeat this step 3 or 4 times.

TnBob · #3 01-28-2010, 11:14 PM

Those Mityvac vacuum hand pumps are a serious tool that is designed to just work as bostonmish's excellent thread shows.

Very clear good explanation of an easy fix to a perplexing issue !

bostonmish · #4 01-29-2010, 02:37 AM

Just a bit of a follow up:

3 topics covered here:

(1) Solution to plugging the FD outlet ports

(2) Observations on cleaner interaction

(3) Next steps & general comments

1. Plugging the FD ports was accomplished by utilizing the hardware on the backup M117 intake manifold and the BMW motorcycle calipers and hoses. The MB intake contributed one of the thermo-vacuum switches, which happened to have an identical thread as on the FD injector line ports.

The BMW calipers (good to have spares) each supplied a brake line and a brake hose. Both ends of the brake line and one end of the hose had the required thread size/pitch for my FD plugging needs. Each brake line was cut in two and then folded shut in a vice; the brake hose was cut and plugged with a nail, secured with piano wire. I am pretty sure the nail plugs will withstand 80PSI.

What can I say? This is improvising with what’s on hand, but for me it beats an uncertain drive to hardware stores. Also, this sort of exercise becomes a fine validation to why certain amount of junk is good to have in your basement.

2. After soaking for several days (while previously filled to tops of FD ports with cleaner & stored outdoors in 20-40F temperature), without any plunger movement, I observed the level of cleaner move down in all ports. I interpret this as evidence of the cleaner insinuating itself deeper into the FD, from the upper chamber to the lower, probably by slowly displacing air, while also dissolving varnish.

This required a refill, which immediately revealed that two chambers had more empty space (see the photo). I interpret this as evidence to support that at the initial fill up, each port drew up as much cleaner as it was capable of, in its contaminated state, and that some ports had less contamination in them than others (and hence filled up nearly completely right away). Once the cleaning and settling continued over a few days, the ports which originally had greater contamination and blocked passageways to the lower chamber now allowed the first dose of cleaner to flow down leaving more room at the second fill up.

This is theory and I welcome other interpretations, if anyone detects faulty reasoning in my summary.

3. What’s next? Now that the backup FD is completely full of very potent cleaner AND I have figured out how to plug the ports, it will be transferred to the 450SLC. The existing FD – suspected of being significantly contaminated – will be removed. The replacement will be installed on the AFM. Its Cold Start Valve line will be connected to a spare CSV and the WUR control and return lines connected to a spare WUR, (with both left loose). 7 of the injector line ports will remain plugged (see photo), with the remaining one connected to a fuel line w/o an injector on the end. The line will go into a clear container to catch fuel.

Ignition”ON” then the FP safety switch on the AFM comes off to energize the FP. At this point, assuming no leaks appear, I will depress the AFM plate and generate a stream out of FD into the container. The active line will then be moved to the next port on the FD, with the former plugged until all are flushed. I can’t wait to see what comes out of the FD !

If all goes well, once all 8 ports are flushed, the FD micro filters will go back in, followed by the correct fuel lines. I expect the car to run, at that point, but will conduct the system and control pressure tests, since the current settings of the primary pressure regulator (in the replacement FD) is unknown. I expect to only need to adjust the PPR shims in order to reach correct settings.

As background, if you are still here, the relatively low mileage 450SLC (87K) was not run for the last 6 years. It has a new: F. Tank Strainer, FP, Filter, Acumulator & Pressure Release Valve. Its current system pressure is 76-80 PSI. The control pressure is 12PSI at 10C, rising to 55PSI when motor is fully warmed up. The Auxiliary Air Valve is operational (piston retracted when cold & comes up as the motor warms up). I am assuming the Cold Start Valve and the Thermo-Time Switch are functional, but haven’t gotten to testing them.

The car will start and attempt to go into high idle, but the motor will die after 3-4 seconds, unless the AFM plate is depressed about ¼”. As long as the manual override is applied to the AFM plate (increasing the amount of fuel) the motor will run, but will die as soon as the AFM plate is released. This condition will be constant, even after the motor is fully warmed up. I interpret this as evidence of a partially blocked FD. Yes, there is some reason to suspect that one or more injectors are at least somewhat contaminated, but the FD is my primary suspect right now.

What do you think?

Ferdman · #5 01-29-2010, 08:20 AM

bostonmish, your approach makes sense to me. Let us know if cleaning the fuel distributor allows your 450SLC to idle properly without intervention.

Ivanerrol · #6 01-29-2010, 06:08 PM

Here is an interesting article on rebuilding a fuel distributor.

http://www.porsche928forums.com/download/manuals/CISRebuild.pdf

One day when I have a spare FD I'm going to have a go at this.

tinypanzer · #7 01-29-2010, 08:43 PM

According to my indie, who is an MB and German car specialist, the main problem FDs get with age is that the diaphragm stretches to the point where it actually can block the fuel outlet on the upper chamber. If this happens, you'll have one or more cylinders that just won't get any gas under certain conditions. This is what happened on my 560SEL, and is why he replaced it with one from a car he had out back. He didn't even charge me for it (wow!) so I know he's not BSing me.

mak · #8 01-29-2010, 10:00 PM

The FD rubber diaphragm is not available in a kit or any other form as a spare so the FD has to be replaced ?
mak

bostonmish · #9 01-30-2010, 03:09 AM

Latest Update:

Removed the old FD

Installed the new one (with the cleaner still in it)

…checked the AFM roller – where the tip of the plunger rests – confirmed it was free to roll – it was a bit stiff – and lubricated the roller and the pivot with Aerokroil.

Connected the FD to the mounted WUR (I originally planned on connecting it to a spare, during the flush, but did not have one of the lines with me)

Connected the Cold Start Valve line to a spare CSV

Connected the empty FD port – first one to be flushed - to a spare Injector Line which was bent to reach a plastic container

Ignition on, AFM FP safety plug off – fuel pump presurizes the system; detected several leaks – turns out the BMW metal brake line fittings did not make a very good seal, although the leakage was relatively minor; lots of shop rags to absorb the seepage

Proceeded to flush the first port (system under pressure, depress AFM plate, eject a few ounces of fuel). Then, proceeded to do the same for the rest of the ports.

As soon as each port was flushed, I installed the mini-filter and then the fuel injector line.

After several cylinders were done, this allowed me to switch the FD port plugs which seeped with the now free ones which did not. Consequently, each successive port took a shorter time to flush, but the difference was 10 seconds instead of 20 (estimated).

Eventually I was done with all eight FD ports, not realizing I was close to ruining the motor…

But first, what emerged from the FD?

In 7 of the ports what emerged was some gasoline along with some dissolved contaminant. The dissolved contaminant was heavier than gasoline and would pool into the corner of the catch container and form a separate somewhat murky glob which would easily break up if shaken, but would congeal again quickly if allowed to settle.

When poured through a paper towel the contaminated residue appeared to be microscopic – I could find no evidence of any debris, however, the contaminant, if allowed to flow through the FD outlet filters and also through the Injector internal filter, could conceivably clog them. Then again, perhaps with enough Techron or B44 or Seafoam in the tank, this sort of contaminant might get dissolved and flushed away completely. Who knows.
One thing is certain, there was some residue in the FD which got dissolved and now ejected.

One of the ports seemed to produce some rusty fuel, but I am not 100% this was not rust from the threads or the old fuel line fitting. There is a possibility that one port has rust inside.

When I was done with all ports and all lines were connected (Injector, WUR, CSV, FD pressure & Return), I went to start the motor.

The starter tried to turn the motor, but the battery seemed weak. The starter would engage, but the motor would not even begin to turn over. I tried a portable booster. Same. I tried the shop charger. Identical response.

Then the hair on the back of my neck stood up.

I ran over to the motor and pulled out all spark plugs. Then I fitted an evacuation canister to the MityVac and slipped the collector tube into the first cylinder whose FD port was flushed. Gave the pump a go and …several ounces of fuel emerged.

Three cylinders had enough gasoline in them to be picked up by the mityvac, with two of them filled up almost completely.

Crestfallen, but still considering myself lucky, I put the tools away and went home.

Tomorrow, the day will start with a fogging oil injection into each of the cylinders, then some cranking, then a spark plug reinstall, then I will see if the motor will run. Stay tuned…

Bostonmish

Mike D · #10 01-30-2010, 09:07 AM

Yup. A buddy of mine, an excellent Indie Mercedes tech, refers to this as "fire-hosing". I went through all you did on my '85 500 SEL. Same results as yours. Mine was only one cylinder but the same "no-crank" situation. My car would actually run if I pulled the offending cylinder's spark plug.

I pissed about with it for a couple of weeks before I called it quits. Either get the distributor rebuilt, try a known good, used unit or bite the bullet and get a rebuilt distributor (ouch!).

I'm actually going the Megasquirt conversion route using Ford 19lb. injectors but that's 'cause I'm not smart enough to leave "well enough" alone.

bostonmish · #11 01-31-2010, 03:05 AM

Here is how it went:

Sprayed Fogging oil into spark plug holes – used a double length straw to reach into the cylinders.
Waited 30 minutes

Turned motor over with the starter. The motor ejected some gasoline, mostly on the left bank, whose FD ports were the first to be flushed yesterday.

Waited 1 more hour to air the cylinders out further.

Installed Spark Plugs. ………………and then:

I started the motor which immediately went into a very satisfying high idle and DID NOT peter out in several seconds.

I observed the AFM plate move down to reveal an air gap. This immediately confirmed my diagnosis of the previous FD being bad. With the old one, the AFM plate did not depress by the action of the motor, causing it to die in 3-4 seconds, unless the AFM plate was depressed by hand.

The motor now ran through its warm up cycle, but started to stumble and eventually died after 2-3 minutes (at about 50F ambient temp). [ This warm up time is consistent with the 056 WUR I now have installed, it is calibrated for a shorter warm up period; I’ll write another dissertation on the WUR in another thread…]

I interpreted this behaviour as fuel starvation – something completely within the realm of reason since the transplanted FD was sitting on the AFM with mixture settings that were not necessarily correct now.

I let the car cool down a bit to induce the warm up circuit into action once more. Removed the mixture plug and turned the mixture adjustment screw right (clockwise) by a ¼ turn.

Started motor, observed the operation …the motor came off the warm up cycle within a few seconds (it was still sufficiently warm) and settled into the low idle and did NOT die.

Lean condition is confirmed!

I proceeded to adjust the now running motor (off the WU cycle) with about 1 ½ cumulative clockwise enrichment turns. The idle kept coming up and I kept adjusting it down with the Idle Adjustment screw.

Very satisfying to rediscover the motor at the point where it responds to “regular” adjustments.

Eventually, since I do not have a CO meter, I settled on a setting which was probably a bit too rich. The motor would diesel lightly when turned off. A ¼ turn in the lean direction fixed that problem.

In the interim, I had ample opportunity to rev the motor through its paces. The sound of a low mileage MB V8 revving it up was music to my ears all night long!!

So what have we learned? For one thing, the FDs CAN be flushed. With the right cleaner and method, they can be self injected (on the bench, using their own plunger), soaked, reinstalled and flushed with the car’s own fuel pump.

Unfortunately, since I received the replacement FD without knowing any of its history, I don’t know whether it was operational. I do know that it had some fuel varnish and residue which washed out from every port.

I intend to repeat the flush technique on the FD I just removed from the SLC. Since this one is confirmed “bad” the next test will be the one to watch.

What’s next for my ’79 450SLC?

[ Oil Change + Fuel Filter Change]

The very next thing I’ll do is perform the basic pressure test (system pressure). I do not know either the condition or the settings of the Primary Pressure Regulator in the replacement FD. It’s pointless to proceed with any further tuning without confirming (and adjusting into spec., if necessary) this, most basic setting.

Next will be a Control Pressure test, followed by a Leakdown test.

Next - the injectors. I have a spare set soaking in carb. cleaner in a small ultrasonic tester (the darn thing has auto shut off, so most of the cleaning is from the soaking action). I will rig up appropriate connections to our Motorvac machine which will allow me to power flush and also check the “crack” PSI, as well as the “leakage” if any.

The clean injectors will go in and then the remainder of the fine tuning be applied, of which the low hanging fruit – the replacement of the many rubber vacuum and molded hoses – is of primary importance.

bostonmish

Mike D · #12 01-31-2010, 07:54 AM

Congratulations! I'm glad it worked out for you. You can use an aerosol spray can of "brake cleaner" to clean the injectors. Spray "carb cleaner" won't work either due to a higher viscosity or a lower propellant pressure. The plastic spray tube fits tightly into the top of the injectors

zhandax · #13 02-04-2010, 07:00 AM

If one has a FD that is not gunked up that badly, could one remove the EHA, shoot carb cleaner in both chambers, and move the air flow diaphram repeatedly to allow the cleaner to penetrate the plunger cavity? This is with the hope that a sticking plunger on the FD is the root cause; mine is only blowing black smoke out the exhaust. I was searching for evidence of successful attempts of that effort when I found this post.

bostonmish · #14 02-04-2010, 12:58 PM

First, I did not say my FD was "that gunked up." I only set out to test if I can wash ANY residue out of an unknown condition FD.

I cleaned mine on the bench (off the car). In my tests the only way to draw sufficient quantity of Yamaha carburator cleaner - not spray brake cleaner - into the chambers was by extending the plunger far beyond where it can travel when mounted on the AFM.

If you spray and pulse the AFM plate (what you are calling diaphragm), you'll get _something_ in, but I would not rely on that method.

My test was successful in that it reached its objective - I was able to inject cleaner, and then to purge out some contaminant. Furthermore, the cleaned FD is now operational, in the car. However, I have yet to apply this method to a KNOWN bad FD. That test is planned but not yet scheduled.

bostonmish

zhandax · #15 02-05-2010, 06:27 AM

Sorry for the terminology, I am just happy that someone is seeing some results from exploring the rehab options available with the CIS FD which has previously been considered an 'untouchable' system. As mentioned, I found this post from a search based on a suspicion that there may be more options to rejuvenate these units than had been previously published.

I am not even certain, at this point, that this is my problem. From searching here for a few weeks though, it definitely points to the FD as a major suspect (1993 SL with 90K miles which appears to have mostly sat since 2005 and now blows black smoke out the exhaust). I have a new temp sensor which I will install first. If that makes enough difference to render the car drivable, I will mix 50/50 Seafoam and give it the proverbial 100 mile Italian tuneup.

I cynically suspect, though, that the end solution will be through the FD and I now see that the FD must be removed to extend the control plunger beyond its installed range of travel. That is no problem as soon I can get a weekend off work without being iced in at home (which has been the story so far this year....)

I do have one final question; is the Yamaha carb cleaner you mention the stuff offered by Amazon (Yamaha Carburetor Cleaner Dip 32oz ACC-CARBC-LE-NR) or the stuff available from boat dealers as ACC-CARBC-LE-NR? The abbreviation is the same but they are in differently-pictured bottles.