FYI Fuel Pump and Hose Replacement Info with part numbers (Was: Fuel leak while running)

[gerryvz]

With the exception of MB-branded hoses, when still available, I have been using the highest quality aftermarket fuel-rated hoses for fuel lines over the past couple of years. Aftermarket junk hoses (even formerly decent name brands like Cohline and Conti) are not worth risking a vehicle for this critical part.

Fortunately good quality fuel lines are easily avaialble. I am strongly considering buying a hose end crimper so that I can manufacture my own lines. I need to look further into the prices for these.

 

[rayhennig]

Bit of an old thread but we've just replaced the entire pump(s) pack at the rear of the 300CE-24. This followed a few pump noises, several hesitations and one stall.

2 Pierburg pumps, MB filter, Bosch accumulator and ALL MB hoses. I did have a Trucktec low pressure hose in reserve as it was tricky to track down the MB one. Got one in the end.

Now we come to the strange bit. Before the work, cold starts were instantaneous. Hot starts also fine. But, after the work, cold starts may involve 2 seconds' churning. Why?

Someone reminded me that my new (2017) fuel distributor did not come with a new filter. So I installed a new MB filter and no change.

To recap, after the work overall performance from idle through to spritied driving and hot/warm restarts is as new. Very satisfying. I know it's subjective but I'm convinced that overall performance is now better. So much so that I am now using the "E" setting on the 5 speed box and it seems to have better low revs torque.

But now, after the super new pump pack installation, all is well aside from <2 second cranking for cold start.

Faulty check valve on new pump? Symptoms suggest pressure is dropping overnight.

Leaks - no, we've checked twice, not a trace of a leak.

Any ideas chaps?

Best to all.

RayH
PS: Just prior to final alignment and tightening:

 

[gerryvz]

You need to attach a fuel pressure meter to the car's fuel distributor and check how much the pressure goes down vs. spec. MB has published a chart that shows how much fuel system pressure leakdown is acceptable at various time intervals. If you are out of spec here, that will definitely tell you whether you have a fuel pressure problem, or not.

Do the Pierburg pumps come with a fuel pressure valve installed on one (outlet) end of them, like the Bosch pumps do? This valve helps maintain system pressure when the car is off, in conjunction with the main fuel pressure regulator (diaphragm pressure regulator on Bosch KE-Jet cars). Assuming you also replaced the fuel accumulator per the photo above (assuming your car is a KE-Jet M104 car).

Also, did you replace the diaphragm pressure regulator (main fuel pressure regulator) underhood? These can and do go bad, although the testing I mention above will help determine whether you have a pressure problem, or not.

I know the LH-Jet M119s and the HFM-based M104s which use the dual Bosch pumps, do have and require the pressure check valves at the pumps. Not sure about the KE-based M104. I'm pretty sure my KE-Jet M117 also employs the check valves on its dual Bosch pumps (same fuel pumps as the M119 LH).

 

[rayhennig]

You need to attach a fuel pressure meter to the car's fuel distributor and check how much the pressure goes down vs. spec. MB has published a chart that shows how much fuel system pressure leakdown is acceptable at various time intervals. If you are out of spec here, that will definitely tell you whether you have a fuel pressure problem, or not.

Do the Pierburg pumps come with a fuel pressure valve installed on one (outlet) end of them, like the Bosch pumps do? This valve helps maintain system pressure when the car is off, in conjunction with the main fuel pressure regulator (diaphragm pressure regulator on Bosch KE-Jet cars). Assuming you also replaced the fuel accumulator per the photo above (assuming your car is a KE-Jet M104 car).

Also, did you replace the diaphragm pressure regulator (main fuel pressure regulator) underhood? These can and do go bad, although the testing I mention above will help determine whether you have a pressure problem, or not.

I know the LH-Jet M119s and the HFM-based M104s which use the dual Bosch pumps, do have and require the pressure check valves at the pumps. Not sure about the KE-based M104. I'm pretty sure my KE-Jet M117 also employs the check valves on its dual Bosch pumps (same fuel pumps as the M119 LH).

Thanks for your response.

Under hood (bonnet???) fuel pressure regulator brand new and working perfectly before the pumps job. Starts immediate after that.

Pierburg pumps identical to Bosch except for rubber surround. Check valves on both.

Accumulator brand new.

As said, the only changes are the pumps, accumulator, filter and tubes.

Still baffled although recent starts have been a little quicker. Weather's hotter - higher pressure???

Thanks again.

R

 

[gerryvz]

Please attach a gauge and monitor fuel system pressure leakdown vs. MB spec and see if there is an issue there. That's the starting point as far as fuel pressure is concerned.

 

[rayhennig]

Please attach a gauge

Love to do that but we have no such gauge.

Interesting update. Grilling weather here and car in the sun. Hasn't been started for 48+ hours.

Instant start.

I wonder what that tells us, if anything?

R

 

[ALL500]

Starting up with a weak battery, after sitting for some time and I have fuel pouring out of the pump/filter (I’ll have to check which, or both).
Would this be due to the pump not getting enough juice, or perhaps it’s time to replace?
It happened once, then on another start with a fresh battery, the leak stopped after running for a min or so. On a further attempt the leak is back. Will not attempt to run the car in this condition certainly.

 

[gsxr]

Replacement time! The O-ring seal between the pump body and end plate has shrunk and is leaking under pressure. This will not fix itself.

Buy new OEM Bosch pumps only. If the high pressure hose from filter outlet to chassis pipe is old or not OE, replace that with new OE/Genuine while you're in there (don't buy aftermarket to save $100, you'll be leaking and repeating the job in a couple of years). Check the other fuel hoses while you're in there... feed hose from the tank, vent valve/hoses on the driver side too. All the information you need including part numbers are in this thread (scroll up, start at post #1).

Note - merged threads on same topic.

 

[emerydc8]

I’ve owned three 400E/E420s over the past 28 years and at one time or another I’ve had to replace the high-pressure fuel lines on all of them. I’m referring to the one with the banjo bolts (#89) in the link diagram). In fact, I’m putting this hose on the list for my next parts order. Hopefully they really do have them in stock. It’s a show-stopper when they fail.

1954-1999 Mercedes-Benz Line 129-470-06-64 | MB OEM Parts

1954-1999 Mercedes-Benz part # 129-470-06-64 - Line

www.mboemparts.com

 

[gsxr]

Jon, you mean this one, correct? I've not yet had this pipe assembly fail, but I did buy a couple new ones to have on the shelf for when they do fail.

AFAICT these are indeed still available new, relatively cheap insurance at $50 when installing new pumps!

Mercedes-Benz Classic Parts Search.

Browse through the Mercedes-Benz Classic Parts Search to see the availability of parts, promotional and newly manufactured parts and order them online (only in Germany).

partssearch.mercedes-benz-classic.com

 

[emerydc8]

Is that a metal hard line? It’s not the one I’m referring to. This was a rubber hose about 16 inches long (attached pics). Looking at the diagram I thought it had banjo bolts but it doesn’t.

 

[gsxr]

Is that a metal hard line? It’s not the one I’m referring to. This was a rubber hose about 16 inches long (attached pics). Looking at the diagram I thought it had banjo bolts but it doesn’t.

Jon, that is the high pressure hose which is DEFINITELY a common failure. In one case years ago I believe it was responsible for a fourm member's car burning to the ground. I've had to replace this hose on pretty much every one of my vehicles.

This hose must be OE/Genuine only ($117 list, ~$90 discount). The aftermarket ones have sadly been cracking badly as seen in your photos within a couple of years after installation (see post #48 in this thread). Years ago Cohline used to be $20-$25, but is now $50-$60, so there's definitely no incentive to buy the short-lived Cohline instead of Genuine MB.

Full details and photos are in post #8, click here.

 

[gerryvz]

I had the equivalent hose fail on my G-wagen some years ago, and it was NLA from MB. So I had a local hose shop make me an identical replacement with same connectors, out of fuel-rated hose. I think it's in the G-wagen forum here.

Yes, it is not a banjo fitting.

 

[ALL500]

Replacement time! The O-ring seal between the pump body and end plate has shrunk and is leaking under pressure. This will not fix itself.

Buy new OEM Bosch pumps only. If the high pressure hose from filter outlet to chassis pipe is old or not OE, replace that with new OE/Genuine while you're in there (don't buy aftermarket to save $100, you'll be leaking and repeating the job in a couple of years). Check the other fuel hoses while you're in there... feed hose from the tank, vent valve/hoses on the driver side too. All the information you need including part numbers are in this thread (scroll up, start at post #1).

Note - merged threads on same topic.

Thanks, the OEM Bosch pumps would be a dealer only item?

 

[gsxr]

Thanks, the OEM Bosch pumps would be a dealer only item?

Nope, Bosch pumps are available from aftermarket vendors. The dealer pumps should be identical but priced slightly higher.

Be careful though, there are counterfeit Bosch parts on the market. Only buy from a reputable, authorised Bosch reseller (Amazon, FCP, RME, AHAZ, etc).

 

[dreaming.haze]

Nope, Bosch pumps are available from aftermarket vendors. The dealer pumps should be identical but priced slightly higher.

Be careful though, there are counterfeit Bosch parts on the market. Only buy from a reputable, authorised Bosch reseller (Amazon, FCP, RME, AHAZ, etc).

I've ordered from FCPeuro / Amazon for Bosch pumps before - on the packaging they include a counterfeit checker code that you can see if things are actual Bosch parts.

 

[gerryvz]

Thanks, the OEM Bosch pumps would be a dealer only item?

No, the Bosch pumps are easily available via Amazon and many other vendors. I believe the correct part you want to look for is Bosch 69608. You will need two of them.

Amazon: https://www.amazon.com/Bosch-69608-Original-Equipment-Replacement/dp/B000BZIDP8/ref=sr_1_1
FCP Yurro: Mercedes Electric Fuel Pump - Bosch 0580254950
AutohauZ: Bosch In-Line Fuel Pump, Electric 69608 Mercedes Benz E320 R129 SL500 560SL 190E
RM Yurropean: Mercedes-Benz E500 Sedan 124.036 5.0L V8 Fuel Pump (New)

 

[wvhamme]

Hi, are these part numbers the same for 500E, E500 and E500 limited? Thx

 

[gsxr]

Hi, are these part numbers the same for 500E, E500 and E500 limited? Thx

It depends on the build date. The last few months of production of E500 (both Limited and non-Limited) may have a single fuel pump which is not the same, and also does not have the same hose from pump to chassis fuel pipe. See post #32 here. Check your VIN, if it's anywhere near the cutoff point, visually confirm what is on your car... sometimes the EPC break points are incorrect.

The vent hoses on the driver side, and fuel tank feed hose, are the same for all years of production.

 

[ChrisH]

Crap! I noticed a fuel smell emanating from the right rear of my E420 the last couple of days and turned to the forum as I always do and found this thread. being an old fart as I am without a hoist this would be something I would farm out, but It appears that the NLA monster has struck again..
When I built my Hot Rod, I used a lot of Russell braided flexible fuel lines. You can bend and conte into any number of positions and perhaps could be used for some of the NLA lines? It’s too bad somebody doesn’t put together a kit with all the parts and pieces that we all appear will need inevitably,to do this repair.

 

[gsxr]

Crap! I noticed a fuel smell emanating from the right rear of my E420 the last couple of days and turned to the forum as I always do and found this thread. being an old fart as I am without a hoist this would be something I would farm out, but It appears that the NLA monster has struck again..
When I built my Hot Rod, I used a lot of Russell braided flexible fuel lines. You can bend and conte into any number of positions and perhaps could be used for some of the NLA lines? It’s too bad somebody doesn’t put together a kit with all the parts and pieces that we all appear will need inevitably,to do this repair.

Which part is NLA that you are trying to replicate? The only one which had been NLA is the 90° molded hose at the tank return (rarely leaks) and there are alternative part numbers available (see post #30). AFAIK everything else is still available new.

Have you identified the leak source yet? It's almost always the high pressure hose from filter to chassis hard pipe.

 

[emerydc8]

If it’s this hose it’s still available. I just got one from MB Laredo for $85.20.
124 470 80 75

https://www.mbpartsource.com/oem-parts/mercedes-benz-fuel-hose-1244708075

 

[gsxr]

Uncle Kent is offering an LH-SFI "Injection Delivery System Overhaul Kit"... does not include the vent valve or return hoses, just the "supply" side. Unfortunately the aftermarket Cohline high pressure hose is poor quality, and has a relatively short lifespan (see photos in post #48 in this thread for details).

More importantly, the tank-to-pump supply hose is flat out a bad solution for the 124 (not sure if this could work for the 140). MercedesSource is supplying bulk hose for the tank-to-pump hose, not an OE formed/molded hose (specific to each chassis, 124 vs 140). And, he offers no splice/connector to attach a short section of original/old tank hose to his new bulk hose. The listing just says "fitting at tank not supplied" but there's no explanation how you are supposed to attach the bulk hose to the tank!

M119 V8 w/ LH-Jetronic Fuel Injection Delivery System Overhaul Kit | Product | MercedesSource.com

mercedessource Product - For 1992 to 1995 W140 and C140, 1994 to 1995 E420, E500 and SL500 - ONLY V8 engines with ELECTRONIC fuel injection! PLEASE do not order in error! Check your engine first with the cover off. It should look exactly like the one you see in the picture below. LH-Jetronic...

mercedessource.com

Since these components are now 30+ years old, we recommend you replace all the wear parts so you will not get stranded in the future. This is the most complete kit available anywhere in the world.

• Two Bosch OEM fuel pumps with wiring hardware.
• New filter of copper sealing rings [Huh?]
• 4 correct copper rings to complete pump installation (at the check valves)
• 4 new rubber mounts
• Long high-pressure hose from filter outlet to feed line to the engine [Cohline aftemarket, not OE]
• Short pump-to-pump high-pressure hose [OE/Genuine]
• 1/2 meter (14mm I.D.) smooth rubber hose to make tank outlet hose, fitting at tank not included [BULK HOSE!]

Buying all OE/Genuine Mercedes parts will cost more than the kit below, but it is worth the extra cost to get quality components which fit correctly.

 

[ChrisH]

It was indeed the high pressure hose! New filter and O rings ,no more leak

 

[ALL500]

Turns out it was the high pressure fuel hose for me also. It was leaking like one of those garden soaker hoses you place on your lawn. Easy replacement as directed on this thread.

 

[jnes]

I just rebuild my fuel pump package. One photo from the starting point. Hoses are OE Mercedes and pumps from Bosch, filter&spacer is from Mercedes.

I was able to source proper hose clamps from Switzerland (NLA from the dealer).

 

[dboz]

My Cohline replacement rotted as well, they're using POS material. I didn't want to buy another one so I cut the crimp ferrules off at both ends, discarded the rotten hose, bought 2 feet of 5/16 fuel injection (100psi) rated hose from Autozone, used double high pressure screw clamps at either end and it's working perfectly so far. Watching it (and smelling) often, so time will tell if it's a good fix.