2000 Freightliner Classic 500hp Detroit won't start without ether

I could pull in to fuel and it wouldn't restart sometimes for 20 min but once restarted would run and run. SRS sensor will do this and this is why; the ECM does not know which cylinder to fire on start up until the SRS tells it when number one cylinder is timed. The synchronizing sensor {SRS} is the upper one behind the air compressor on the drivers side. If you have ever had the bull gear off to replace it like I have, you will see a button on the back of it, that button is the trigger for the sychronizer. The only time that sensor is used is on start up, once the ecm knows where the engine is at in the firing order the lower sensor pointing at the crank takes over to run the engine. These older 60s are really very basic electronics and easy to diagnose, a prolink box is your best friend if you can find a used one on ebay or somewhere, it will sit in a box under the bunk for months and then one day save the day. I bought both the sensors for about $170 , Installed the upper one and saved the run sensor in the jockey box. Easy to change, the one behind the compressor looks tough but it isn't. It is one bolt, take that out and use a long screwdriver and gently worry it out. It has an O-ring on it so it should come right out, the new one will have a new o-ring. Now to install the new one here is the trick; plug it into the wire harness and lower it down till it lines up with the hole and use the socket and extensions that you used to remove the bolt to GENTLY push it back in the hole. Reinstall the retainer bolt no adjustment in or out is necessary it is all preset. Just point of reference, I had already installed the fuel check valve the previous winter so I knew that was good. Oh just one more thing, the two sensors ARE different so you have to get the correct one. Hope that helps
later J-J

 

Srs sensor still say

 

Sounds like loosing prime check out the check valve on the back of the head and all the fuel line also look for cracked filter base

 

Detroit needing ether to start is nothing new. Hahaha.