Fuel System Contaminated -- Need some Input - PeachParts Mercedes-Benz Forum

ps2cho · #1 06-28-2011, 09:10 PM

Starting new thread to sum everything up and start fresh:
Original thread: Ideas as to huge MPG drop since overheating?

Problem:
-Used to get 21-22mpg, now get 12-13mpg
-Figured out rust in system, possible filter split.
-Replaced injectors about 100mi before found rust (possibly clogged?)
-Power is sluggish and seems to hit a wall with power @ ~4500rpm. It'll go higher, but it seems to just stop producing power and I can feel a possible knock (so I stopped).

Items replaced/done
-Fuel Tank flushed (have not removed though)
-Fuel Filter Replaced
-Fuel Distributor + EHA Brand New
-Ran pump into jar before putting new distrib in....No rust found. Gas was clean.

So now...

Pulled injectors and found some dirt...No way dirt should be there. I'm guessing before I found the rust, it contaminated the injectors.

This is what I found: (KEEP IN MIND, These injectors have < 100mi on them!! They are practically BRAND NEW)

[1] -- SINCE they are practically brand new....anyway I can clean them successfully? I have put them in a bottle full of B2 Chemtool overnight....think it'll clean them enough or will I need to do more?
Is there a way to successfully backflush them? Since these are mechanical, is there a way to somehow open the nozzle?

[2] -- Plan to flow test system at distributor (injectors disconnected, lines on) into plastic bottles to ensure a) double check no rust b) double check strainer is not blocked. Sound a good idea?

Any thoughts or ideas for approach to solve this? Car hasn't been driven in 9months....Just moved house to somewhere I can work on my car now, so time to get her back on the road!

oldsinner111 · #2 06-29-2011, 06:19 AM

I would drain fuel and filter it,with paint filter.

ps2cho · #3 06-29-2011, 01:05 PM

I was doing some more research and reading (in my Bosch Injection and Fuel Management book by Probst) and it mentions this:

Quote:

"For KE Systems, measure delivery at the return line from the system-pressure regulator. Measure where the flexible line meets the steel tubing. Disconnect the return line and attach a test hose.

You're measuring pump delivery at the return line instead of the input to the fuel distributor because fuel delivery is specified at system pressure, against the force of the system-pressure regulator, and would be different if measured at an open supply line."

Looks like I did it the wrong way a few months ago. I read it, but did it wrong anyways LOL. I just didn't think about it requiring force against the FPR. Live and learn!

Quote:

Originally Posted by ps2cho

So....According to FSM it states 1L in 40seconds....so I am getting 2.24L/min == 1.68L/40sec.

Only thing is that it mentions testing it at the fuel return line at regulator, not where I tested it. I assume I should be OK where I tested it right since the distributor is new, there will be no restrictions there.

I will redo the test -- Maybe its not the injectors then! (although they should be cleaned again now) Let's see what the fuel pump delivery test reveals now!

Since the car starts and idles perfectly, its just possible full load flow is hindered somewhere upstream (pumps or strainer), hence WOT power is lifeless and high end rpm gets a knock. Makes sense to me logically.

ps2cho · #4 06-29-2011, 09:39 PM

Flow tested injector line from distributor, did 3 videos as illustration...

MB specs:
Idle Speed: 3cm^3/min
Partial Load: 30cm^3/min
Full Load: 100cm^3/min

My readings: (each water bottle 10g, so 10g has already been subtracted from each number)
Idle // Partial // Load(WOT)
1: 21g // 83g // 98g
2: 21g // 85g // 98g
3: 21g // 84g // 100g
4: 21g // 84g // 100g
5: 22g // 85g // 98g
6: 21g // 83g // 94g

EDIT: Videos:
Idle: http://www.youtube.com/watch?v=NyqTNyl99ZQ
Partial: http://www.youtube.com/watch?v=BWG4QWSsT2Q
Full: http://www.youtube.com/watch?v=uVQWB_LjYL8

Need help with converting....How can I convert since gasoline is not 1:1 grams to cm^3???
Density of gasoline is 0.68g/cm^3

EDIT2: Check my calculations here....but:
D=M/V
0.68g/cm^3 = 21g / V
...
V(0.68g/cm^3) = 21g
...
V = 21g/0.68g/cm^3)
V = 30cm^3
So that would give me:

Idle: 30cm^3
Partial: 125cm^3
Load: 147cm^3

So what exactly does that mean? Am I running heavily rich or are the factory specs a MINIMUM amount of fuel required?
If I am running rich, why would that be if my fuel pressures are within spec?
Kinda lost at this point now...

sptt · #5 06-29-2011, 11:06 PM

I wish I knew the answer for you. FWIW...I did replace both of my Fuel Pumps, Filter, and Accumulator at the same time and pressure was a lot stronger after letting it sit plus, when I opened my gas tank, it held more pressure than before after running and sitting where it would lose it after about 10min of sitting with no vacuum held in the tank. Now I struggle a bit to get the cap off. Has to be a simple answer there somewhere for ya...

Gilly · #6 06-30-2011, 08:14 AM

I wonder if the crap is coming from the fuel distributor itself? I'd be more curious about solving the contamination problem before getting it running correctly. If it is too rich you can reset the mixture (test with on-off ratio or CO meter, on-off ratio being preferred). Are you sure it's rust, could it be rubber particles?

ps2cho · #7 06-30-2011, 10:35 AM

Quote:

Originally Posted by Gilly

I wonder if the crap is coming from the fuel distributor itself? I'd be more curious about solving the contamination problem before getting it running correctly. If it is too rich you can reset the mixture (test with on-off ratio or CO meter, on-off ratio being preferred). Are you sure it's rust, could it be rubber particles?

ps2cho · #8 06-30-2011, 01:23 PM

This morning I checked injector spray patterns, look good to me. All injectors are spraying like they should I believe.

Next I decided to turn the CO/Mixture screw counter-clockwise, as to lean up the mixture....then I flowed the injector lines again at WOT.....No difference! Weird?

Attached my fuel pressure gauges again. Pressures look to spec and its holding the 3.1bar with engine off, so accumulator is functioning.

Kinda lost on where to go

EDIT: So with this considered -- that brings the question, what regulates the fuel amount if the fuel pump is designed to pump more fuel than is actually needed?
Did some searching -- found this:

Quote:

The primary-pressure regulator maintains the pressure in the fuel system constant. The pressure regulator incorporated in the fuel-distributor housing maintains the delivery pressure (= primary pressure) at about 5 bar. Due to the fact that the fuel pump delivers more fuel than the engine needs, a plunger shifts in the pressure regulator and opens a port through which excess fuel can return to the fuel tank.

The pressure in the fuel system and the force exerted by the spring on the plunger in the pressure regulator balance each other out. If for instance, the fuel pump delivers slightly less fuel, the plunger is shifted by the spring into the corresponding new position and in doing so reduces the open section of the port through which excess fuel flows back to the tank. This means that less fuel leaves the system at this point, and as a result the primary pressure in the system increases to the specified value. When the engine is switched off, the fuel pump also stops running.

The primary pressure drops to below the injection-valve opening pressure. The pressure regulator closes the return-flow port and prevents further pressure reduction in the fuel system.

I wonder if the FPR is toast then although it is still keeping pressures at the specified 5.1 bar the system needs?

ps2cho · #9 06-30-2011, 02:38 PM

Just ran the fuel pump test at the fuel return off after the FPR...

Did NOT get the specified 1L/40sec. I think first steps then are replacement strainer, then fuel pumps and possibly accumulator.

YouTube - ‪M103 fuel pump test‬‏

sptt · #10 07-01-2011, 02:31 AM

You definitely have some fuel in that bottle. How long did you run it to get that much? Very interesting!!! I guess they had to do something due to the mechanical fuel injection system. Will keep monitoring the post for your findings.

sptt · #11 07-01-2011, 02:18 PM

By the way, I took my car in today to the "Transmeister" here in So. Cal (only works on Mercedes) to fix my tranny pan leak and I asked him about MPG in these cars. He said the best he ever got out of one of his new 300E, many years ago, was 24 MPG when he drove to Vegas and kept it under 80mph. Otherwise he said 18 to 21 average is normal for the w124.

ps2cho · #12 07-13-2011, 12:28 PM

Tank has no rust in it at all which is great:

Got a new strainer + ordered every single hose in the fuel system -- so that should eliminate any possible swelling, cracking or inner rubber disintegration if there is any. I'm "hoping" the pumps are ok, its just the lines that have swelling causing a loss in volume and not pressure. It makes sense, but who knows.

Its pointless replacing parts until the lines are done.

A big thanks to Phil for finding 3 special order hoses. (FPR to return line, Feed line to distrib + return line to tank)

ps2cho · #13 07-13-2011, 03:17 PM

I just took all pumps and accumulator out...

One of the pumps still had some of the old brown gasoline that I was having issues with before....
Why would there still be bad gas stuck in the pump if I have been running it recently and everything has been coming out clean?

Could this indicate anything about pump condition?

Debating replacing them anyway, but its the cost that hurts...

JohnM. · #14 07-13-2011, 05:31 PM

The fuel system needs to be surgically clean. The tank should have been removed first thing when you had crud issues and hot tanked / sealed.

If there was old gas in one pump, it would be safe to assume that fresh gas wasn't going through it (at pressure, nonetheless). Replace the pump(s), before chasing any of those engine rubber hoses.

K.I.S.S principle applies here.

ps2cho · #15 07-14-2011, 09:00 PM

Got all the hoses today in the mail and (2) brand new Bosch pumps on the way! I'm hoping by the end of next week everything should be back together and fingers crossed it will be normal again.

Can't wait!