this is a follow up to the out of gas at 1/2 tank issue...

looking for the fuel relay and fuse setup (dont see a fuse marked fuel pump in the box) on my 91 300e.

The car ran well today for about 1 hour straight. did run a bit rough for the first few seconds at startup - but has done that all for months.

want to check the fuse relay and related , then try the fuel filter and save the fuel pump for last...

Thanks in advance.

Don

Your '91 has a MAS Control Unit that acts as the fuel pump relay. http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1RS0URX0T1RS0US5JN&year=1991&make=MB&model=300-E-002&category=P&part=MAS+Control+Unit


You can jumper pins 7 and 8 to fire up the fuel pumps if/when you get to that step.

Good Luck

__________________
-Paul-
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi

Actually, pins 1 & 2 power up the fuel pumps.

http://www.peachparts.com/shopforum/showthread.php?t=9535&highlight=fuel+pump+relay

http://www.peachparts.com/shopforum/showthread.php?t=96488&highlight=MAS

One or both pins is hot, so be careful when you place your jumper in place. You'll get a spark if you don't hit it just right.

If the car starts with 1 & 2 jumpered, you may get a Check Engine light while it's idling. This will clear up once you're running off the MAS again, at least that's been my experience.

Hope it ain't your MAS. Been there. Better part of $500.

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

Thanks Mike for the correction.

I was thinking of the fuel pump relays on the pre-MAS 300E's. You can often find used MAS control units on Ebay for ~$30. In fact I have a spare one from my junker if you find that yours is bad.

Good Luck

__________________
-Paul-
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi