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  #1  
Old 02-04-2011, 11:45 AM
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Location: NE Ohio
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m117 Fuel Pump Relay Randomly Turning Off ???

Hey everyone,

My buddy's 560SEL's fuel pumps keep randomly turning off. The relay is new, we recently replaced the 12-pole connector as well. All the wires have are cleaned up and there isnt anything contacting out. The OVP is new as well also.

What would cause the relay to turn off?

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  #2  
Old 02-04-2011, 12:51 PM
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Overheating (excessive current draw from pumps) OR lack of RPM signal from EZL
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  #3  
Old 02-04-2011, 01:03 PM
JamesDean's Avatar
Electrical Engineer
 
Join Date: Apr 2005
Location: NE Ohio
Posts: 5,034
I checked the current draw to the pumps not to long ago, it was around 6.7-7amps.

What would cause the rpm signal from the EZL to cease functioning?

Is there not a connection to the starter lock out (NSS) as well? I did notice the other day the he could start the car in drive?!
__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

82 300SD 145k
82 300SD 265k
87 420SEL 230k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k

Last edited by JamesDean; 02-04-2011 at 01:28 PM.
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  #4  
Old 02-04-2011, 03:25 PM
JamesDean's Avatar
Electrical Engineer
 
Join Date: Apr 2005
Location: NE Ohio
Posts: 5,034
Tried to start it when I got to it today. No Go. Unplugged the relay got a meter on the thing. When I first checked there was only 4V @ the relay turn on pins (triggered by ignition switch) I thought this was odd. I double checked, said 4..plugged in the relay (ignition still on) and the relay click, pumps kicked on for a second...then off..and the car started fine.

I checked the voltage at the turn on pins again and this time it said battery voltage..odd. The TD signal was fine as well it was around 9v at idle. Spec is 6-12v. I found a TSB about dirty connections at the EZL and I sprayed some cleaning stuff.

Odd stuff.
__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

82 300SD 145k
82 300SD 265k
87 420SEL 230k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k
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  #5  
Old 02-04-2011, 04:51 PM
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Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
Power supply on pin 30 (large red wire) comes directly from un-fused connection near the battery.

Connector is X4/10 & supplies un-fused power to alternator & ignition switch as well.
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MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator
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  #6  
Old 02-04-2011, 05:42 PM
JamesDean's Avatar
Electrical Engineer
 
Join Date: Apr 2005
Location: NE Ohio
Posts: 5,034
Hm, I cleaned all the connections with some cleaner there was some crud on the EZL connections. Perhaps one of them was causing the TD signal to drop out.

For now, problem solved. We'll see over the coming weeks though.

__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

82 300SD 145k
82 300SD 265k
87 420SEL 230k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k
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