OK so you came here hoping for tips on replacing that electric fuel pump in your R230 / SL500 Mercedes, right? Maybe like me you didn’t find any full-length instructions here on MBWorld, or YouTube videos online about it?



THIS POST IS FOR YOU



First question: Can an average DIY guy/gal do this job? Yeah sure, maybe. I am going to assume you are reasonably mechanical and equipped. I presume you have some skills and at least a garage. What follows are reasonably comprehensive meta-steps. I’ve included minimum tools suggestions, and a few “gotcha/watch outs” that might make your life easier. And I’m assuming that you deeply respect gasoline and understand just how explosive it really is…liquid AND vapor.



If you don’t believe gasoline can explode and horribly burn and kill you, don’t attempt this repair.



GETTING TO THE PUMP. Naturally, you will have to raise your car up enough to get under it and work. A lift is best, but not absolutely required. I did mine with the car up on ramps under all four wheels. If you have a lift, please email my wife and tell her why I need a lift too. J (This R230 is her car, not mine) No, you can’t do it with a jack on the differential, or only jacked up in the back…but who would ever get under a car with only a jack on the differential anyway…Right? For a little extra clearance, you can make sure to raise the car up with the ride height gadget even more.

SPECIAL CIRCUMSTANCES: Besides the correct replacement fuel pump and the tools I’m about to list, you will need either a completely empty fuel tank (not always easy to achieve) or a .595" diameter fuel line plug and a screw type hose clamp that will go between 21 and 26 mm. I found that a standard ½” male air chuck quick disconnect (the bigger one, not the typical one you have on your regular shop tools) is exactly .595 diameter. That has ¼” male NPT threads on the other end, so a ¼” NPT pipe cap works well to make an improvised but secure fuel line plug. Just make sure whatever you have is .595” O.D. and you’ll be fine.

Along with the fuel line plug, you need a fuel line pinch-off tool, or a set of small long nose Vise Grips. If you use the Vise Grips, they need to be specially prepared not to cut into the rubber in your tank to pump fuel line. I did that by simply shrinking three layers of shrink tubing over the jaws. You could also slip some vacuum hose or fuel line, or even just wrap the jaws with electrical tape…but DO NOT clamp those jaws right on the fuel line or you will damage it. I’m always leery of pinching lines, but Mercedes leaves us little choice in this case. If the tank is full of fuel (which is almost always when a fuel pump fails, for some diabolical reason J) you can either siphon it mostly empty or drain it out the bottom by disconnecting the line. Either way, you will need a LARGE catch pan for spilled fuel, because you will most likely spill a fair amount of highly flammable and explosive vapor creating GASOLINE.



WARNING: If you can’t be bothered to siphon the tank, and don’t want to pinch off your fuel line, then you better have at least 22 gallons of “somewhere to catch and put that fuel real quick too – gas cans, another car’s tank, etc. If you don’t pinch the hose, the gas will flow out really really fast. It can be done, but I predict pulling it off un-pinched and trying to plug the line “real quick” will spill about 1-2 quarts of gasoline, minimum. YOU HAVE BEEN WARNED:



Tools and Stuff



· Of course, you need a good and appropriately sized and typed FIRE EXTINGUISHER.



· Also, don't forget your FIRE EXTINGUISHER. Did I mention that already?



· Cell phone for pictures and the 911 call if fire starts



· Fire Extinguisher Helper / 911 caller



· You will need and I recommend special "clic-clamp" European style line clamp releasing pliers - available from Lisle Corp. About $17 on Amazon. The Lisle tool is a nice tool. Better than the Chinese knock offs on Amazon, IMO.



· Also, get a Lisle fuel line separator/spreader tool. Made in USA. Nice tool for $13 bucks.



· A hook shaped hose pick (a small one, for fuel lines) I recommend a 90º version



· Long shank wide blade flat screwdriver



· ¼” drive ratchet



· 10MM socket



· A 10” x ¼” extension



· 6”-8” flexible shaft driver for your ratchet (goes around curves and obstructions)



· An LED headlamp



· A face shield and/or safety glasses to minimize fuel splash into your eyes



· Heavy duty blue nitrile gloves



· Rags, drysorb, a broom and dustpan to immediately pick up gas-soaked drysorb



· A 20” or similar box fan



· A creeper is really nice. So is my air-conditioned garage. I would call them almost mandatory, but that’s just me.



· If you use beer to help you perform this kind of work, I estimate this to be a two beer job.



· IMPORTANT: If you elect to use a battery powered drill driver to take off your 10mm nuts instead of a hand ratchet, remember that battery powered drill drivers have BRUSHES which make SPARKS inside the motor, which can ignite GASOLINE VAPORS which are EXPLOSIVE. Just a word to the wise



Step 1. After preparing your tools, workspace, elevating the car onto the ramps, etc. and examining the area above the differential where the fuel pump and filter assembly lives, grab your ratchet, extension, flex shaft and 10mm socket and remove the two 10mm plastic nuts that retain the fuel pump vibration isolation bracket. (above the pump, on studs that protrude from the underbody of the car) When they are loose, you can pull the pump down lower where you can access the work a little easier.



Step 2. Grab your specially prepared vice grips. Set them to a jaw gap width of about 3/8” and clamp them onto the rubber tank to pump intake line. Set the squeeze of the grips to the minimum amount of crush required to barely pinch off the line. Do NOT over-pinch or crush the hose. Even pinching it off a little is somewhat abusive, but if you are careful, you’ll probably be o.k. This compromise is better than a massive uncontrolled shower out of a ½ inch I.D. hole in the bottom of a 22 gallon tank full of explosive gasoline.



Step 3. After pinching it off, you are now ready to remove the fuel pump intake line. Using Lisle Clic-R Clamp pliers, unclip LARGE clip to fuel pump intake. The intake points to the passenger side of the car It is very tight quarters. Be prepared to be patient. Dropping the pump down, in step 2, makes it a little easier for some folks.



IMPORTANT PREP MOMENT. Once you have the Clic-R Clamp off, and BEFORE you do anything else, HAVE YOUR .595" diameter fuel line plug nearby and READY and have your catch pan READY and have your FIRE EXTINGUISHER ready, pin out and a helper standing by to operate it. (Did I mention you would need a FIRE EXTINGUISHER HELPER?) Make sure your helper is a calm person, has a cell phone and understands that in case of fire, and after immediately using the fire extinguisher, he/she is to dial 911 if a fire breaks out. Double-check your details. Make sure you have eliminated all sources of vapor combustion -Compressor motors, AC powered droplights, battery drill motor brushes - anything that can make a spark that can ignite gasoline vapors. Make sure doors/windows etc. are open to vent out any gasoline fumes. Have mop-up rags handy, in case of a spill. Run the box fan to help dissipate the fumes. Oh, and KNOW FOR SURE ABOUT HOW MUCH GAS IS IN YOUR TANK. If you were to experience a sudden and unstoppable stream of gasoline into your catch basin, where will you put it all? How would you catch it, and into what edifice would that catch occur?



Step 4. After making these preparations, plus anything else safety related that you can think of – and after positioning your catch basin in the right spot, and pinching off the line with the modified Vise Grips, and removing the fuel pump intake line Clic-R Clamp, now use the hook tool to work the big line loose from the input neck of the fuel pump. Once you get it loosened up a bit, use fuel line spreader tool, and remove the fuel pump supply line. As it slides off, be ready to stick your thumb over it at first, in case there is some minor leakage past the Vise Grip clamp. If you don’t use the Vise Grips, ALL THE FUEL IN YOUR TANK WILL COME SPILLING OUT LIKE A BAT OUT OF HELL. Either way, QUICKLY plug the LINE (not the pump – whatever is in the pump will just have to spill a little, hopefully into your catch basin and not all over your face…but wear your face shield or safety glasses just in case.



REMINDER: The line you are about to disconnect is a big hole connected RIGHT TO THE BOTTOM of your fuel tank! Double check your pinch-off. Have your .595” diameter plug ready. Once you have this stabilized and not leaking, and have cleaned up the gasoline that sloshed and splattered everywhere, and vented your work area, and washed your hands, and cussed and stuff, you are ready for the next step. This is where it gets fun.



Step 5. UNMOUNT fuel pump bracket from the pump. Since you have the bracket off and the intake fuel line off, you can now actually slide off the two rubber band vibration isolators from around the pump and slip the whole fuel pump bracket out from under the car. You’ll be glad you did in the next step



Step 6. Now, with pump free and shifted towards the driver side, you can more easily disconnect the wiring harness from the pump itself. Two squeeze clips, vertically oriented - one on either side of the black plastic clip. Squeeze clips in and pull black plug straight off. It is not too hard, but can be a PIA. IMPORTANT – If your fuel pump was leaking at the pump, this means the connector is wet with gasoline. This means the neoprene seal in the wiring connector is SWOLLEN. This will haunt you later, but the solution is easy. More to come on that…just note if your pump is leaky and wet at the output end.



Step 7. Once pump is electrically disconnected, use your 10mm socket and remove the two nuts retaining the fuel filter assembly. It is located on the DRIVER side above the differential (near the fuel pump) Unbolting it drops it down enough so you can get your Lisle Clic-R Clamp pliers on it. Now, take off the FRONT-MOST of the two Clic-R Clamps attached to the filter. Use your flat blade screwdriver to scoot the line away from the fuel filter a little. Once you do that, you can get your fuel line spreader pliers in between the hose and filter body to force the fuel line off the filter's fron't input pipe. Be prepared, as more gasoline will spill out here, so keep your catch pan handy AND YOUR FIRE EXTINGUISHER and FIRE EXTINGUISHER HELPER, etc. As soon as you have the line free, push the filter back up higher where it usually sits. This will stop or minimize fuel spill from the filter.



Step 8. Congratulations, you can now fish the pump out from above the differential housing, taking it out of the passenger side. It will come out easily, complete with the short section of fuel line you disconnected at the fuel filter. Once the fuel drips and leaks are minimized, and you have again wiped up the splatters sloshes and messes and cussed and stuff, re-empty your catch pan into a safe and distant container. NOTE: At all times, make sure to continuously ventilate your work area, and of course keep your FIRE EXTINGUISHER handy. No smoking, of course, no sparks, no grinding, welding, bar-b-que nearby, etc.



Step 9. With the fuel pump on your bench, carefully compare it to your replacement unit, Take pictures of hose orientation, etc. Verify all aspects of replacement part fitment. Length, diameter, wiring plug IDENTICAL, output ports in correct orientation, etc. If all is well, and using Clic-R Clamp pliers, remove the Clic-R Clamp from the OUTPUT port of the pump and recover the shaped fuel hose from pump output to fuel filter input (if you are reusing it.) Using your hands or the fuel line spreader tool, remove the fuel line from the fuel pump output. Reinstall the used line or put your new line on your new pump, observing correct orientation of the shaped hose by looking at the pictures you took. (You did take pictures, right?)



Once you're done with all this crap that was the result of Mercedes' stupidly selfish decision to locate a pump in such an unserviceable location, reverse the steps and put the new pump in.



IMO best order is;



1. Electrical Connector

2. Fuel filter supply FROM pump output line, at filter

3. Bolt up fuel filter

4. INSTALL PUMP ISOLATION BRACKET ONTO PUMP

5. Install pump intake hose and Clic-R Clamp

6. Bolt pump bracket back onto car





FINAL NOTES and TIPS:



Make certain that you get the routing of the wire and hose correct, and that you remember to do item #4 above (INSTALL PUMP BRACKET) before you put the hoses on…or you will be removing the fuel line and doing it again, because you cannot put the bracket on after the hoses are connected. J



As I mentioned earlier, if your car has been leaking fuel at the pump housing, like so many seem to do, this means the electrical connector (and the vibration isolation rubber ring) has been soaked with gasoline. These rubber pieces will be swollen, soft and mushy. Not a big deal EXCEPT for one last nightmarish and diabolical Mercedes/German obsession with tight tolerances!



Because of exposure to the ethanol in the gasoline, that little yellow neoprene seal in the fuel pump wiring harness electrical connector has now swollen up to twice it's normal thickness! When you pop the connector off the old pump you won’t notice it, but when you first try to clip it back in place on the new pump, IT PROBABLY WON'T CLIP IN. You will wonder why. You will fight, you will struggle…you will imagine special MB special fuel pump harness clamping tools. You will try and try, but no amount of ridiculous pressure will persuade the clip to engage, and you simply CANNOT get a tool up in this tight space to assist the clamping. What is wrong? What did I do? Is this the wrong pump? Yikes!



Relax, I have great news – There IS NO SPECIAL TOOL OR TRICK. The correct answer is beer and television. Simply walk away. Don’t fight it. Leave the plug hanging down, put a box fan under your car and wait 12 hours or so. The seal will vent off the gasoline and alcohol it absorbed and shrink back to it’s regular size. Odds are very very good that when you come back later tomorrow, the connector will clip on very easily, just as it is designed to do. This is proof that beer and television are essential components in repair and maintenance of an R230.



Testing for leaks. When you finally do get the new pump back in, the Clic-R Clamps and the various brackets back on, make sure to carefully double check for fuel leaks. Do this with the car RUNNING and up on the ramp or lift. As far as I can tell, no code resets are required when replacing a pump. It is a dumb pump. Two wires. +12V and ground.



Last step: Locate your 10mm socket and return it to the tool box. J



Postscript notes:



Regarding Clic-R Clamps. If you hate Clic-R Clamps, you can put screw clamps in place of the Clic-R Clamps. If you like them, you can reuse the Clic-R Clamps if you didn't screw them up getting them off. Mine went back on just fine.



Fuel lines: The reason my pump failed is because that OEM Pierburg pump was obviously NOT really built to function with ethanol-based fuels. It’s rubber seals swelled up internally at the crimp end of the pump, and then of course started leaking. So, moral is that my 2005 era R230 does not like ethanol based fuels. Your R230 may love them. Whatever…while you have the various rubber lines and pieces off, examine them carefully to see if any of them need to be replaced. Do it now, or kick yourself later.



Fuel Filter: If you are brave and patient, this might be a good time to replace that fuel filter too.



That’s it. Hope this helps someone.

 

This is how I syphoned my fuel. Hardly spilt a drop and the tank was all but empty when I finished.

 

Nice. Or Noice as we say here.

Safety always... remember the deadly consequences of an 'empty' tank with its fuel vapours is a potential explosive bomb should any ignition source be present.

 

Hence the cloths placed around the pipe in my pictures. :-)

 

hello my friends. what is the number of fuel pump??

 

Bit late, but just for future reference, I used Bosch #001-470-12-94, also known as #0-986-580-354. They are about $200 new. Sure there are cheap clones on Ebay for $50, but in my experience they rarely last long.

 

hey do you have a part number for the separator tool ? or what's the alternative?

 

gas pump part number 0014701294
fuel filter 0024773001