Fuel Pump Relay Location on 500SEC Euro? - PeachParts Mercedes-Benz Forum

#1 03-24-2007, 07:41 PM

Hello everyone,

I left my 500SEC in the garage for a couple days this winter when it was very cold (below 0) here in Wisconsin, as I usually do in winter, but this winter we didn't get much snow early on so I was driving it for a little bit while my van was in the shop. When I went out to start it after the weekend, it wouldn't go. So I figured gas line freeze, which is common out here, and forgot about it for the winter, seeing my van was fixed later that day.

Now that spring has rolled around I wanted to take the car for a spin and found that it still won't start. After some checking I realized it's not getting fuel, and it doesn't sound like the fuel pumps are kicking in. I had this problem with my old '86 560SEL and found a bad solder in the fuel pump relay to be one of the issues. So I thought this would be a good place to start looking, BUT I CAN'T FIND the fuel pump relay. In the 560SEL it was pretty much right next to the fuse box, but not in this SEC. I checked the Chilton manual and it doesn't show the location of the relay. Does anyone know where to find the fuel pump relay? Please note the car is a 1982 500SEC AMG European model, which seems to make good service information (or any information) hard to come by. Or does anyone have any advice on what else to check for to diagnose the problem, assuming both fuel pumps are good?

Any help would be greatly appreciated, as I'm just itchin' to get out of the minivan and into the AMG.

Thanks,
Dylan

jhodg5ck · #2 03-25-2007, 10:07 AM

It's hiding in the fuse box

If you need a new one let me know..they euro Gen I FPR's are different then the Euro.

Have fun getting her back on the road!

Jonathan

#3 03-25-2007, 03:25 PM

Thanks for the help Jonathan, it is very much appreciated. I thought that relay was the same as (or similar to) the fuel pump relay, but didn't think it was the fuel pump relay. For some reason I thought I recalled 2 of them in my 560SEL, one in the fuse box and one outside of it, (the one outside of the box being the FPR and the one inside being the kickdown, although my memory of it is definitely not vivid) so I passed it off and started to hunt for it's twin. I'm going to check it out later on this afternoon and I'll be back on to post the results of my findings. Thanks again.

Dylan

jhodg5ck · #4 03-25-2007, 05:00 PM

NP. The later cars (you 560) have both relays behind the bulk head/in the middle of the car. The 500's have the one Klima relay external to the fuse box w/ the FPR hiding inside.

Jumper pins (in the receptacle for the FPR) 7&8 w/ a suitable piece of wire and that will fire up your fuel pumps if everything else is kosher.

Any pics of your AMG/SEC?? I'm a big fan myself;-)

Jonathan

#5 03-25-2007, 09:51 PM

Thanks again for the extra info Jonathan. You're proving to be very helpful, and again I appreciate it tremendously.

I popped the relay, opened it and checked for bad solders, it looks brand new. I also tried to jump pins 7 and 8 with a nice solid piece of copper that fit real snug, but apparently the relay is good.

Although it showed a brief sign of wanting to start, it did that as well when I popped the relay back in. And popping off the main fuel intake to the engine proved I'm still not getting gas. When I pour a little gas into the air cleaner, the car pops off and runs like a gem, until the gas is used up and then it quits. I guess my next course of action is to pop the fuel line in front of the fuel filter to see if it's actually pumping fuel out of the tank. Then I would know I just have a blocked or pinched fuel line.

If you have any ideas on what I might want to check next, please keep the advice coming. Again I appreciate it very much.

Thanks again,
Dylan

p.s. I'll get some good pictures taken of the car this week and post them in my gallery. But please note the car is in need of a little body work and restoration, which I guess could be expected from a 25 year old machine. (Though it still looks super nice from 30 feet =). It's sort of my project car, but it runs so good I wouldn't hesitate to drive it to Georgia......if it would start.

jhodg5ck · #6 03-25-2007, 10:44 PM

can you hear the pump running?? W/ the wire in there you should have a Definite audible hum from the pump.

If you do not hear the pump running check your positive battery terminal, make sure it and the two 10 gauge wires feeding off of it are snug.

If the pump is humming and you are not getting any fuel I'd worry that you either have a clogged line somewhere in the system but we'll tackle that next.

Also, if you are working on the car and want to chat in real time feel free to give a ring, 404 805 1357.

On a side note, how far is GB from Madison? I spent some time up there and Really enjoyed it.

Jonathan

#7 03-26-2007, 11:42 PM

Hello again Jonathan,

Alright, so I got some free time today and went back at it (it was an unbelievable 80 degrees here today =) and a great day for getting some work done in the garage). First thing I did was jump pins 7 and 8 again, and turn the key to the "On" position, to get a good listen at the fuel pump. At first I didn't hear anything, except for a humming sound up in the firewall, which has been happening every time I turn on the ignition, though I'm not sure if it's related to the issue at hand as the car has a few quirks aside from it's new found reluctance to start. But when I climbed underneath the back end, I did hear some faint noise coming from the fuel pump, although not what I would call "definitely audible", and after about a half minute the fuel pump started to get warm, then very warm.

So I checked for the wires you spoke of, and there are 2 wires feeding off the positive cable to a wiring block just a few inches away from where they come off the main positive cable. I followed the wires connected to these two in the wiring block back into a hole in the firewall on the passenger side of the car, and they looked alright, with no easily visible flaws. The positive cable itself is secured very snugly to the terminal and I'm sure the battery is good, because it's almost brand new and has endured quite a few starting attempts without recharge from the alternator. So I decided to sit back and think of what problems I've had in the past, thinking maybe one is uncovering itself.

But although I'm handy with a ratchet, I'm not really a great mechanic and thought maybe some of the things that seem trivial or unrelated to me, might be great clues to a very knowledgeable guy like you. So here's what I know:

1) The car has always had a "hard time" starting, sometimes spinning for up to 15 seconds before the engine fires. But once it starts, there has never been a problem.

2) The starter, at random times, does not engage the flywheel and just grinds, so I know it's going bad and will need a replacement soon. This got me to thinking that the positive battery cable leads directly to the starter. If the starter, although it spins fine as of recent, had a bad solenoid or was shorting out, could this cause the fuel pump to not work properly? Or would a problem like that show itself much more evidently?

3) The passenger side seat belt arm has worked like 3 times randomly since I've owned the vehicle. I wouldn't bother mentioning this, but upon reading another thread about an SEL with starting/idling issues, the guy mentioned after he fixed his issue, his passenger side seat belt arm just so happened to work again.

My next thought is to take an electrical tester and see exactly where and how much power/voltage I'm getting, starting with the terminals on the fuel pump and going from there.

If anything I've told you has helped, great, if not, well now you know a little bit more about my car.

I'll be back in the garage as often as I have time and will continue to update you on my progress, or lack thereof. If I can get in there at a reasonable hour, maybe I will give you a call. (thanks for the offer by the way)

Thanks again for your help,

Dylan

p.s. Green Bay is about a hundred miles from Madison, and I love it there too, used to live just north of it and am quite familiar with the area. I also have a friend who lives just outside of Atlanta, and next time I visit him, I will definitely take a stop by your shop. I would love to see your car collection, and if I ever have the cash, might have you do some, or a lot of, work to my car. I've heard good things about BlueRidgeMB, before you started helping me, I don't recall from exactly where, but the name of your shop rung a bell the instant I saw it, remembering reading an online post praising your work. Which made me very pleased to see that you were the guy willing to offer some advice. Thanks again.

jhodg5ck · #8 03-27-2007, 08:26 AM

Hello Dylan,

Well, unless you have some serious hearing issues I'd say your pump is bad....they make a noise loud enough that if one is running and you are w/in 10 feet of it you'll hear the pumps hum quite clearly.

With that in mind, I would see about a replacement pump & fuel filter while you are there. Also, if this car has sat all winter w/o any fuel stabilizer it would be wise to let the tank drain and add 5 gallons of fresh gas.

Reason I mentioned the battery leads is sometimes when people take the terminals off they loosen these nuts by accident, making the voltage to the pumps spotty @ best.

As for your starter, prob. the bendix is dry..happens with age. You could try dropping the starter/cleaning/lubing said gear, but then again taking the starter off is a PITA so out and out replacement is usually the safe way to go.

Your presenter either has a bad micro switch or the relay is on it's way.

I would also recommend swapping out all your fuses for aluminum ones. It would also be wise to go through all the other relays and @ least spray contact cleaner on all contacts/receptacles etc...

One thing we never talked about but how many miles are on your coupe? Do you know if the fuel pump/filter has ever been changed?

Come on down to Atlanta any time..I don't think I'm going to be in Wis. anytime soon but should that change I'll let you know;-)

Glad you heard good things..I don't often hear much, ya know;-)

Jonathan

#9 03-28-2007, 10:19 AM

Sure as heck, it's the fuel pump. I'll be purchasing one soon to get her back on the road.

Bye the way, my SEC has 106,000 miles on it. And I am unsure if the fuel pump/filter have ever been replaced.

Next time I'm in Atlanta, I'll definitely stop in.

Thanks again for your help Jonathan.

Take it easy,

Dylan