I have a 2003, Mercedes E 500. I am having a starting problem sometimes the car will start and sometimes it will not whenever I put the key inside of the ignition to crank the vehicle. The fuel pump does not prime, and the starter does not kick on sometimes if it’s left out and I haven’t touched it for a while. The fuel pump will prime in the car will start and run, a little backstory this car was bought off of a kid who put holes in the Cadillac converter which burnt and Chrisp the fuel line after replacing the fuel line, the car started I let it sit and every so often I’ll go outside and start the car and let it run so that the air suspension can lift the car up after this problem has started I begin looking at the wiring harness, thinking that one of the wires is burnt and is having a false connection so I re-bandaged up the wiring harness and hit protect it all around it via wiring harness cloth tape. The vehicle had a misfire on cylinder eight in the cylinder. Seven injector was left wide-open so I replaced those and don’t have a misfire , I however, have two codes for the Cadillac converters due to the holes being in the exhaust which causes it to misfire and I plan on fixing that problem with long tube headers but now I’m trying to figure out does sometimes start sometimes not start situation and begin to check fuses and relays starting from the back where the fuel pump relay in fuel pump fuses sound I was getting power to the fuel pump fuse, but didn’t have anything to test the fuel pump relay, knowing that the car start Sometimes I know that the fuel pump relay is good same as a starter relay. I don’t want to start ripping apart the dash and testing every single component just to get to a loose end so I’m asking for help if anyone is came across this problem and what they did to fix it I thought about wiring a switch from the battery to the fuel pump and a push starter button switch to the starter to see if it bypasses everything .

 

Are you sure the battery is okay?
You should check both batteries - it has a main one and a smaller, auxiliary one.


Just for your information:

• your post is a little difficult to read without paragraphs
• a more descriptive thread title will get more replies
• it's catalytic converter, not Cadillac converter

 

It sounds like you might be dealing with issues related to the ignition switch or the immobilizer system, especially given the intermittent starting problems and previous wiring repairs. Additionally, the modifications to the catalytic converters and fuel lines could have introduced electrical shorts or disrupted the grounding, affecting both the fuel pump and starter circuits. Faulty connections within the main power distribution or issues with the Powertrain Control Module (PCM) might also be causing these sporadic starting failures. You should probably run a full system scan. There should be fault codes on at least one or more control modules related to this. You will either need to take it to the mechanic, but if you want to figure this out yourself, then you will need to get a full system scanner. the "youcanic full system scanner" is very good at diagnosing all systems and can run an in-depth all system scan as well as diagnostics.