Hello I'm new here. I have a 75 450sl that has an intermittent problem with energizing the fuel pump. Sometimes when I turn the ign. switch to the on position the pump will not run and the engine won't start do to lack of fuel. My understanding is that there is a low pressure switch that engages while the ign. is initially energized and once the engine starts it disconnects. For the life of me I can't find this thing. This has been an extreme pain in the ass causing me to have to replace the transmission after it wouldn't start and it was improperly towed. I've had this vehicle 4 years and I love it but I think I would love it more if I had a little more confidence in it's ability to get me home. Thanks, frank220-450.
Iv'e already replaced the fuel pump and swapped out the relay. This is an obscure problem, hopefully one that someone else has encountered and addressed. I am @ my wits end. Thanks and good lookin' out, frank220-450.
Iv'e already replaced the fuel pump and swapped out the relay. This is an obscure problem, hopefully one that someone else has encountered and addressed. I am @ my wits end. Thanks and good lookin' out, frank220-450.
My problem lay in an aftermarket engine management system. I have a tec-ll electomotive control module. The internal fuel pump relay has failed and tech support has informed me that this is common and that most guys just bypass it externally. They say it would not be worth it for me to send this unit back and have it repaired. That's nice. I believe I have this figured out and when I complete the repair I will post instructions because other members with similar fuel pump issues could benefit from the information. Thanks, frank220-450
75450SL fuel pump relay, Help! 
Problem solved 
Linear Mode
