W124 E300d Fuel Lines

[spock500]

I would also replace the seals around the IP face plate, they usually go around the same time -

I also removed the clear plastic piping and replaced it with 8mm ID rubber, the orginal pipe puts a strain at the joints sometimes pushing them at an angle

 

[compress ignite]

R+R Delivery Valve "O" rings(seals)

7h is the rubber "O"ring (We are going to "Viton" rings now to eliminate any
problems with Ultra Low Sulfur Diesel's lack of Lubricity)

BUT, and here is the problem in many replacements:
7i The delivery valve spring is best replaced at the same time.
Along with
7f Which is a "One time Only Use" Copper (crushable) washer used for
sealing the Pressure Valve Holder 7 to the Pressure Valve Carrier 7g.

The other trick is to make sure 7g does not rotate in the process,Nor
should 7k be allowed to rotate in the process.(7k, 7g, and the body
of the Injection Pump have established an almost "Lapped" relationship
to each other by virtue of long standing friction.)

Absolutely Fanatical Adherence to cleanliness standards far surpassing
those in use in a surgical suite will reward the "Do It Yourself"er for
many , many miles.
Also check the FSM for correct tightening torques AND sequence for
your model engine.

I believe "Parrot of Doom" has established a complete "How To" for the
entire procedure.

 

[SilverSaloon]

I hope i'm not speaking too soon, but i think i've cured the starting issue (and the leak).

Last night i shone a torch on one of the pipes and noticed that every 20 seconds or so, a very small air bubble would rise up the pipe. i then looked at the connector (which i had fitted a new o-ring to) and noticed it wasnt clamped on very tight. so i took the pipe off and crimped the connector with a pair of plyers and re-fitted it so it was nice and tight.

thismorning, car started 1st turn of the key

so, make sure if you have any leaks, check those connectors and crimp them as i guess they work themselves loose over time. i also noticed there are a few other connectors that arnt very tight but i'm going to tackle all this again next week but atleast the main starting issue seems to be sorted now!!

i actually have already ordered a new set of clear pipes so will be fitting these anyway.

thanks

Derek

 

[SilverSaloon]

i now have the new clear fuel lines i ordered from MB.

They seem to have discontinued the older metal clip type and replaced with a white plastic horseshoe connector as seen on a few W210 images posted here occasionally.

hopefully this was to fix the crimping/loose issue i mentioned above.

i will fit these and see how it goes

at the same time, i also ordered a new fuel pre-filter O-ring (which is larger than the others) as this seems to be considered generally as a main source of starting/airleak problems.

 

[bolide]

The old 606 / 605 starting problem threads keep rumbling along

My local diesel specialist (Brian at Auto Marine Diesel in Brighton) pulled a serious rabbit out of the hat the other day. Presented with a 606-engined car that had air in the fuel lines he decided that the aluminium fuel filter housing had gone porous. There was (I'm sure) much sucking of teeth and disbelieving comments when he said that but, when the new housing was fitted, the air leak went away

The old Sherlock Holmes analysis - "We must fall back upon the old axiom that when all other contingencies fail, whatever remains, however improbable, must be the truth" - springs to mind. Or to his mind anyway

Nick Froome
www.w124.co.uk

 

[SilverSaloon]

it started again today

so looks like the starting issue has now been fixed (by crimping that connector).

i went to fit 2 new clear pipes in last night - one went in fine, the other went in and i thought was all well, so i started the car and then fuel was just pi$$ing out of the connector. i shut off and disconnected it (and broke a thin bit of plastic when getting it off again) and the new o-ring had split. i guess this must have happened when i seated the connector onto the engine. i fitted the old one back on again as i didnt have time to glue the think bit of plastic on the connector back together. i'll do this next week i expect.

these clear fuel lines seem to ask for trouble - even the new ones when seated dont seem as secure as my old ones once i'd crimped them.

as stated in the "veg oil" thread, the fuel filter housing (or maybe the bolt) seems to be leaking slightly aswell - this is very minor so i'll probably just leave it for now i think.

saying all this, my other W124 is completely dry - no leaks anywhere!! long may it continue!!

 

[spock500]

Even with new O rings from MB mine still were a very poor fir and continued to let in air -

The plastic pipe doesnt help as it can put strain on the joins - I replaced this with rubber diesel fuel pipe, easy and quick to do but found the only way to get them to fit properly was PTFE tape -

Bit of a knack to this as well, first wrap tape around without O ring maybe 5 times or so then put O ring on and do same again - this will give you a very snug fit

 

[Dieselman]

Presented with a 606-engined car that had air in the fuel lines he decided that the aluminium fuel filter housing had gone porous. There was (I'm sure) much sucking of teeth and disbelieving comments when he said that but, when the new housing was fitted, the air leak went away

Changed mine a few years ago due to this although not convinced it was the fix as there was still some air.
I think it may have just been pipe fit exacerbated by the tank strainer gradually blocking.

 

[spock500]

Does anyone know the ID of the braided rubber leak off pipes for C250D, W202 - I thought I would buy a meter and cut it to size myself.

 

[Dieselman]

It's either 3mm or 4mm, but just buy leak off pipe, it's all a standard size.

Best place to buy from is a local diesel fitters, they generally use better stuff than a parts shop sells.

Regarding O ring replacements, are people doing all the O rings including the stop solenoid and lift pump inner ones.?

BTW. It comes by the meter from the dealers anyway, just twice the price.

 

[Number_Cruncher]

>>the stop solenoid

There's no stop solenoid on a W124, it's a vacuum shut off.

 

[Dieselman]

>>the stop solenoid

There's no stop solenoid on a W124, it's a vacuum shut off.

Of course, thank you.

In that case it won't leak air in or fuel out when the O rings fail, will it..

I was talking generically but I'll rephrase for absolute accuracy.

The fuel shut-off device, be that electrically or vacuum operated...

still has all the same O rings.

 

[spock500]

It's either 3mm or 4mm, but just buy leak off pipe, it's all a standard size.

Best place to buy from is a local diesel fitters, they generally use better stuff than a parts shop sells.

Regarding O ring replacements, are people doing all the O rings including the stop solenoid and lift pump inner ones.?

BTW. It comes by the meter from the dealers anyway, just twice the price.

Yup, I did all the pipes but as mentioned above removed the plastic pipe from the black fittings which makes it so much easier to fit.

The Merc seals which I bought from MB dealer were rubbish, a very sloppy fit but other members have used viton seals from an indie supplier.

 

[Number_Cruncher]

>> In that case it won't leak air in or fuel out when the O rings fail, will it..

Well, as it happens, no, it won't. The vacuum shut off on a W124 does not interface directly with fuel. It works directly onto the fuel rack, and so, has engine oil on the other side of the seal, not fuel.

 

[Dieselman]

You are correct, I was forgetting it just releases the rack to the stop position. Is there no hydraulic actuator at all then.

My reference was really to spocks picture in post #21.

You can see the fuel port.

http://www.mbclub.co.uk/forums/showpost.php?p=533733&postcount=21

An electrically controlled pump also releases the rack to the stop position but has a stop solenoid as well for surety.

 

[spock500]

Maybe I can help out here as I had one or two problems with the solenoid in that I couldn't prime the whole fuel system without the ignition being on (and glow plugs).

The fuel cut off solenoid had two valves, one to allow fuel to enter the main filter and lift pump the second allows fuel into the IP.

They are on the same linear pole switch, I just bypassed the first one.

Circled in blue is where the solenoid plugs into the IP which as a large O ring.

 

[Number_Cruncher]

The engineering of the stop system on a W124 is one of those things that I'm not sure you would get away with on a modern car.

There is the vacuum capsule which moves the rack, but, it needs vacuum to be applied to stop the engine - so, if there's a vacuum system failure, the engine won't stop!

This is in contrast to most engines which need a wire to remain live for the engine to keep running, and so, in the case of electrical failure, the engine stops automatically.

So, as a backup, there's also a stop valve on top of the fuel filter. I think most people would never read the owners manual in sufficient detail to know about the stop valve.

One of the odd side effects of the vacuum operated stop valve is that on the other side of the diaphragm is crankcase pressure - so, if you have a very worn engine with a lot of blowby, or if the crankcase ventilation gets blocked, the buildup of crankcase pressure can move the diaphragm, and stop the engine!

 

[Dieselman]

Thanks spock. I know, I was just forgetting that the mechanical controlled pumps don't have a fuel shutoff at all, they just drop the rack.

Could be dodgy if the return spring ever broke, the engine would run away, at least with fuel shut off you would switch off and kill the supply.

My comment earlier regarding lift pump O rings is because the lift pump leads into the IP chamber.
Any oil leaking into the lift pump could cause a problem but more likely is oil dilution from fuel leaking out of the lift pump into the IP as that is fed from the engine oil and returns there as well.

Worth doing, I was meant to be doing mine today, but didn't get round to it...

 

[SilverSaloon]

I would also replace the seals around the IP face plate, they usually go around the same time -

I also removed the clear plastic piping and replaced it with 8mm ID rubber, the orginal pipe puts a strain at the joints sometimes pushing them at an angle

Hi

i have tracked my leak down to here now. Spock - i have sent you a PM with a few questions.

Basically i want to remove the plate and fit a new seal - what can i expect when i unscrew it? will oil come out or fuel? if so how much can i expect etc.

i am hoping to do this from under the car reaching upwards.

thanks

derek

 

[Dieselman]

Oil will come out, not fuel.
Silversaloon, just take the manifold off, it's going to be sooooo much easier and you can see a lot more.