1972 280SEL, couple questions plz - Page 2 - PeachParts Mercedes-Benz Forum

bill4247 · #16 02-13-2008, 11:54 PM

Be aware that the fuel pump will run for about 3 secs if the engine does not start so it's a two man job. Someone cranks engine while the other listens to the pump or you could put a test light on it. It should light for a few secs while you're cranking. But it's definitely a fuel delivery problem cause it runs with starter fuild.

bill4247 · #17 02-13-2008, 11:55 PM

But be careful of sparks around the pump/tank.

tecrekka · #18 02-14-2008, 12:04 AM

Quote:

Originally Posted by bill4247

Be aware that the fuel pump will run for about 3 secs if the engine does not start so it's a two man job. Someone cranks engine while the other listens to the pump or you could put a test light on it. It should light for a few secs while you're cranking. But it's definitely a fuel delivery problem cause it runs with starter fuild.

Thats exactly what I was thinking. Besides, anything mechanical rarely fails that immediatly you know? I can't get over the fact that this '72 is FI! I think I might have listened for the fuel pump earlier if I could get my mind around the idea of FI in this car!!

I have a friend to listen for the pump, rather, turn the key while I listen!

Thanks!

bill4247 · #19 02-14-2008, 01:31 AM

If you get power to the terminal at the pump but the pump doesn't run you got a bad pump. If you don't get power then check fuses, relay, pressure sensor etc.

douging · #20 02-15-2008, 10:33 AM

Quote:

Originally Posted by tecrekka

I have a friend to listen for the pump, rather, turn the key while I listen!

Thanks!

A brand-new pump that I bought last year has a very audible hum when I turn the key from the driver's seat and door open. The two used pumps that I had prior to the new one didn't make any hum. In other words, a functioning pump will be hard to miss when it turns on.

douging · #21 02-15-2008, 10:37 AM

Quote:

Originally Posted by tecrekka

Is that under the hood? I didnt see a fuse on the drivers side that was designated for anything engine related and I haven't yet located the other fuses.

For the fuel pump, I think it is fuse #4 in the interior panel, along your left shin. I'm almost positive because I've pulled it numerous times to keep the fuel pump off while draining the tank...

goodguy2 · #22 02-17-2008, 11:16 PM

The fuse box or panel is slightly above and to the right of the hood release as you enter the drivers side. There are two knobs that retains the fuse panel cover. There should be a fuse guide in the fuse panel cover to tell you what the fuse is for. I had the same problem. The car would not start. I called my mechanic and he told me to check the fuses. Look at each fuse and then move the fuses in place to allow good contact with surface at both ends of the fuse.

tecrekka · #23 02-19-2008, 08:26 AM

Well, the pump definitely isn't getting power, but I haven't checked the terminals with a voltmeter yet. I finally located the fuses under the hood. I missed them at first as they really look like relays until you pop the cover off. I didn't have any problem locating the ones in the passenger compartment, but I will go through them again to be sure. The diagram in the cover of the fuse box is entirely in German so that wasn't a huge help! I will go for #4 first, I hope that is it! (thanks douging)
I was telling a friend about my purchase the other day and it just happens he has a very large factory service manual that he is sending me today. It will be nice to have a wiring diagram and a detailed description of the car.
goodguy2- Yeah, I've gone through and spun them all; but I guess today, to be sure, I will take each individual one out (especially #4!) and make sure the ends are good on each of them.
Thanks everyone for taking the time to input!

Fisherman · #24 02-19-2008, 09:45 AM

The pump only runs for a second or two when you turn the key so be sure it is NOT running before diving for the balance of the stuff. I have a 72 also that I am in process of reworking and I chased this pump issue around for a long time before I finally figured out that my pump was frozen due to old gas gumming it up.
The other potential issue is a solder end into a relay breaking due to vibration. I have had to fix 3 of them so far and one of them was on the pump relay which took me three days to find and fix.

Get the manual from the dealer if you want it on the PC. It was inexpensive and is just like the old ones that used to cost 100's. Not as accurate as a 115 or 126 manuals but close.
If you need to replace the pump you may as well buy one cuz I could not find the right size o-rings for my life. Even fastlane couldn't source them...

It is definately fuse #4 on the kick panel.

Let me know if I can help with anything.

tecrekka · #25 02-19-2008, 02:05 PM

Quote:

Originally Posted by Fisherman

I have had to fix 3 of them so far and one of them was on the pump relay which took me three days to find and fix.

Where is that relay anyway?? lol Thanks for the input, I sure hope this doesn't end up being a "3 hour tour"...!

Fisherman · #26 02-20-2008, 09:39 AM

The pump relay is under the ECC on the front wall of the engine compartment behind the passenger headlight. There are actually two relays and switch down there in a really hard to reach spot. I thought I had the relay in hand only to find out that there was another there. If I remember correctly the pump relay is the one to the outside of hte vehicle.
I would definately NOT suspect this relay but would think that the power wire may have been a good suspect as it was a sudden stop as you mentioned without hard vibrations like running through potholes or something of that sort.
Is there anything else you did under the hood the day it died?

tecrekka · #27 02-20-2008, 12:12 PM

Quote:

Originally Posted by Fisherman

Is there anything else you did under the hood the day it died?

No, sure didn't. I hadn't really messed with anything under the hood at all with the exception of replacing the air filter and removing and painting the air cleaner assembly. That particular day I hadn't even had the hood open, but was just moving the MB to another part of the driveway.
Yesterday I had a chance to see if the pump was running and it definately is not. I did not have the time, however, to see if there was power at the pump, which I will check today when I get home.