Is it possible the ECU is at fault? I am puzzled with this problem due to the fact the car will sometimes start normally with all components in place and it appears the relays are getting the appropriate signals.

Been reading this thread but couldn't find what prompted you to change your fp relay.

One more thought.

Electrical portion of ignition switch.

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1U40N9POF1UJ153VY1&year=1986&make=MB&model=300-E-002&category=M&part=Ignition+Switch

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

Yes, I am guilty of not troubleshooting thoroughly in the beginning. When I jumpered the fp relay pins and the pumps ran I made an assumption it was the fp relay at fault. In addition, the fp relay was original (1986) and have a reputation for failure.

Thanks Mike, that a good idea. I will check it next and let you know what I discover.

Did you check if there's power going into the relay between socket 9 and 11 of your diagram?

If there's no power try removing fuse 7 and check its continuity with your meter.

I am getting 10v between pins 9 and 11 with the ignition on which is good. I am getting power since I get a good reading between pins 7 and 8.

Also checked pins 10 and 11, I get 10v with the ignition on but it drops to about 7 volts while cranking the engine but I am not sure if thats a sign of a problem or not.

call me at 2149567007 and i will walk you thru it. david poole e.p. dallas tx.

call me at 2149567007 and i will walk you thru i9t. david poole e.p. dallas tx.

Thanks Dave, I will call you when I get home from work which will be 6-7 pm EDT. I live in eastern Pennsylvania.

Isn't 10V a little low? Just saw a pic of the fp relay for a 201 and it says 12V on it.

Some relays don't activate unless it gets its rated voltage though I'm not sure if it applies to this relay.

Thats what I am wondering, pins 10 and 11 should have greater than or equal to 10V while cranking according to the manual. I have 10v with the switch on but it drops to 7v only while cranking the engine. When I relaese the key it jumps back to 10v.

Based on the manual 6-12V is acceptable between pins 10 and 11. This is for the rpm signal.

It's the power input to the coil of the relay that's low at pins 9 and 11. Reading should be 11-14 V. Probably you have a poor ground connection or the incoming power is grounded somewhere. Also what's your battery voltage?

Just wondering, are your electrical centers (battery and fuse box areas) dry?

Oops, my bad. I'm talking about my car. 87 190E 2.3

Confirm the values for your car.