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2 issues, 1 major 1 minor. both irritating!

2K views 13 replies 3 participants last post by  HawaiianLandYacht 
#1 ·
Hey guys,
FUEL PUMP
So ive been dealing with this fuel pump issue since i bought the car almost two years ago. the guy before me nig rigged the fuel pump assembley. I still havent figured it out but its eaten two of my fuel pumps now. I know the fittings on the pump arent correct because it leaks gas intermittently. recently it has been leaking significantly, especially if i sit idle for a few minutes then the vehicle will die out and i cant start it for a while. A mechanic said "its all wrong" but never told me exactly. well, i drove it for almost a year with little issues. then the pump died. bought a new one and installed, but its buzzing really loud like the other two and gets louder throughout the day. i didnt have the correct fitting again so i used the same set up, a worm clamp on the fuel feed line coming off the filter ( thats where it leaks). it looks like a male nipple should be on there but i dont have the fitting. also it runs fine most of the time, then recently it dies and leaks. I havent been able to find the correct mercedes screw clamps for the fuel lines anywhere. any help would be appreciated. will post pix later tonight.
COOLANT LEAK
i have found out where the slow drip leak is coming from (see pic). I dont know where this leads to though. its right at the firewall behind the fuse box. it also leaks a little sometimes at the resevoir fill tank hose, but there is a clamp on it too so i dont know how its leaking. It never overheats. always at 80c-83c. hottest it ever gets is 90c with the a/c blasting in stop and go traffic middle of the hottest part of the day. I have to refill the fluid, from correctly full to dash indicator light on, every 3-4 weeks daily driven 25-40 miles a day multiple stops. do you think there is pressure building up in the coolant lines or radiator that is squeezing fluid droplets out, or is it just old fittings that need replacing?
 

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#2 ·
The fuel pump shouldn't leak under any circumstances. If you're getting air into the system the pump could be cavitating, which would certainly account for the noise.

If the pump produces the proper pressure and volume for the application, it shouldn't matter.

I noticed that you're missing the rubber sleeve that goes between the pump and the strap that supports it. As a result it will transmit noise from the pump right into the body of the car.

And where is the screw that goes in the middle of the pump/filter clamp assembly? What is hold them in place?

As for your coolant leak, other than tightening fittings I wouldn't worry about it. I would be more concerned about the leaks at the fuel pump, as those are a serious safety hazard.

Dan
 
#3 ·
ya youre right about the set up. that was an old pic before the most recent pump swap but it looks practically the same. I dont know where to get the pump and filter bracket and especially the fuel hose screw clamp pictured on the left of the fuel pump. notice the one on the right is a perforated worm clamp. i thought maybe it is damaging or hindering the fuel flow and by that reason causing the fuel pump to work harder, making the progressively louder buzzing noise throughout the day. and i realized the reason why they nig rigged the bracket. the fuel pump that came with the car was bigger than the OEM so it didnt fit! so they removed the rubber bracket rest and stretched the bracket so it did. and it rattled around like two soup cans in a shoebox so they glued it. now i rerigged it, but its still not correct.
as for air getting inside... maybe. it does have a stumbling idle sometimes that catches itself but not enought to throw a code. i have no check engine light on.
only other thing i can think of is a partially blocked fuel catch screen at the fuel inlet line at the base of the tank.
 
#4 ·
The other thing that can make a pump noisy and indicate potential failure is crud getting into it from the tank. Have you checked the filter and seen if there is anything nasty coming out of it?

I have seen cars with tanks that got rusty from sitting for long periods of time without being full of fuel that will create enough junk that it will clog the filter and even get past it.

The screw clamps shouldn't matter as long as they're not over tightened and cutting the hose. If the hose is too big for the fitting, you need to get smaller hose or a larger fitting.

Dan
 
#5 ·
i was brainstorming and had an epiphany. i think you are on to something about the crud of the gas tank. it has a catch screen which can allow fairly large particles to get thru. okay. the fuel filter is pretty new and after running it for about a year the same problems from before are coming back. so maybe it IS rust and crumbs from the tank. I also have to admit that I run it on E pretty frequently as this is my way of reducing the amount of miles i drive. And i noticed that last time it did this i was running it on E for a few days, then I put it to quarter tank and it stopped bothering me for a while and i made it a point to always have atleast a quarter tank. then I started runnin it on E again. Now its acting up again and leaking. I filled half tank but now, I assume, its already blocked at the filter so its too late.
things to confirm my hypothesis;
-clamp hoses and remove filter and drain into a bowl. see if there are large particles.
-buy another filter and install. see if car runs well for a while.
-keep car filled to full tank all the time and change filter regularly and see if problems come back.

on another note, i remember now that the hose for the fuel pump did not fit on the fuel filter (too big) so i had to clamp it down tight with a worm clamp, but it did not leak for a while until, i assume, the filter got plugged again and started blowin fuel out at the line. now i need the correct hose diameter and the nipple to the fuel pump that screws in, rather than a larger hose that got forced over the fuel pump fitting (thats supposed to be a screw in type) and is too big for the fuel filter nipple. make sense? its possible that this may actually be a cheap fix.
 
#7 ·
If the tank is left empty or near empty for an extended period of time, especially if it's in an area where there might be temperature and humidity extremes, condensation will form on the inside of the tank and it will rust. Period.

Once this occurs there's no fixing it short of removal, cleaning and coating.

No matter how many times you change the tank screen or filter, they're going to continue to get crudded up if the inside of the tank is corroded.

Not only that, but the garbage that gets past the screen and filter, and there will be stuff that does, will destroy the fuel pump.

If it were me I would start by pulling the trunk lining, removing the fuel gauge sender, and having a very careful look at the inside of the tank.

Anything else is just a temporary fix if this is the case.

Dan
 
#9 ·
If it were me I would start by pulling the trunk lining, removing the fuel gauge sender, and having a very careful look at the inside of the tank.

Anything else is just a temporary fix if this is the case.

Dan
I couldnt get into the tank, i was nervous about screwing around with gasoline at night with a drop light. Im not even sure what side of the trunk i would enter the tank from? I can try again tomorrow afternoon & see if there is rust around it or if the seal is corroded and letting air in.
 
#8 ·
okay so I got an indepth look at her today and i think the fuel pump is the culprit. I copped a new filter and swapped it out, then drained the fluid in a disposable cup. it was BLACK. I also attempted to blow air through it from the inlet side and it was like blowing thru a coffee straw. the new one was like blowing thru a mcdonalds straw. i checked the fuel relay (30 amp)and ran a 12v current to it and checked the ohms... it made the audible click and even had the same continuity as the other relay next to it (pink 50 amp) triple checked it. seemed to be fine.
connector wires on the pump was a tad loose so i tightened them just a bit, 1/10 of a rotation. started the car up and it ran all the way to operating temp... but i was skeptical so i waited- then it died again after 8 minutes. the pump usually makes a buzzing noise but it wasnt buzzing... it was noticably quiet with kind of a palpitation and turning off and on after a few minutes. oh ya, i adjusted the nig rigged foam insulation so the pump was no longer touching any of the metal bracket. but even when it wouldnt make any noise or vibrate the car still ran! for minutes! i even revved it hard just to see if the pump died and it was just surviving on the fuel left in the fuel lines, but it took a while for the vehicle to sputter to death. fricken wierd! put the key in, ignition at on position, got under her and checked the voltage at DC 20V- it read 20 v or so at the wire... then 15-16 at the threaded connector, then around 10-11 then finally stabilized at about 13-14 but it moved around A LOT for a couple of minutes. what the hell is that all about?
I think the fuel pump is jacked, but i thought that they just completely die rather than have irratic behavior like this... which makes me wonder if i checked the fuel pump relay improperly or if there is a bad connection somewhere. keep in mind there is NO check engine light on.
I just bought another fuel pump online from an O E dealer. I understand bosch doesnt make pumps anymore... they just box em under their name
 
#10 · (Edited)
The pump in the picture is the type of pump you see in older w140, the ones with 2 pumps. Your car should have the newer style pump which is smaller in diameter and longer compared to the one you have. I believe the later pump has a pressure equal to 2 older style pumps, and since your car has ONE of the older ones, it's not getting enough fuel pressure. I had one of the pumps fail in my older w140 and had a symptoms of no starting and diying.

I would find a whole assembly for newer w140 with the fittings and everything of eBay, or maybe contact Eddie here, and take it from there.

EDIT: Here are 2 pictures so you can compare the pumps. Also after taking a second look on that picture of yours, I believe it has the wrong filter too. The older models came with filters that have threaded fittings, while newer models have filters with regular inlets and outlets.
 

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#14 ·
I removed every bit of trunk linning possible and inspected everything... I do not believe there is a leak anywhere around the gas tank or corrosion that would cause an air leak.
I finally got a break in the rain and switched out the old fuel pump with the newer longer one pictured above. I put new fuel line between the pump and filter, and swapped the fuel hose clamps all around with non perforated screw clamps similiar to MB ones. I even clipped off the wire leads to the fuel pump, re stripped the wires and attatched new leads and crimped them like a pro. started the car up 5 times and checked 5 times for leaks and even floored the gas to 5000rpm... no leaks. pump even sounded nice with a perfect hum rather than the usual buzz and sputter noise.
Then I packed up everything in the darkness of night, started driving home after a quick dinner stop and guess what happened next????

Nothing. I made it home with no problems :wink
Thanks for the help dudes!

Next is the stupid radiator hoses.
 
#11 · (Edited)
its not the older style pump, i replaced it.
ur totally right tho, but unfortunetly i cant change out the filter as of now because i cant find the banjo bolt and rail that are used as the *pump to filter fuel line fitting anywhere. this is the set up for now. the filter is correct for the year, a double nipple that i had to put the worm clamp on both ends. it has the correct high pressure 80psi hose too. its not leaking as of last night and the new pump is on its way with expedited shipping. the pump is just like the one you pictured and i'll be able to use the correct sized fuel hose now.
 
#13 ·
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