Project Iona Part 3: 1997 Mercedes S500 Fuel Pressure Regulator Replacement 

Thanks for the kind words and watching the channel. Happy to help the community and my fellow W140 owners.

Welcome to the channel and congratulations on the 1999. A rare model year for these W140s. Hopefully one day the channel grows enough for meet ups and even more projects. I’m hunting for 1998 and 1999 S500 and S600 models every day for more wrenching and learning.

Hi sir. I'm from Charlotte to we can meet some times I have 1999 S500

Right! It goes everywhere. Good times changing the fuel filter as well. Gravity is unrelenting. Thanks for watching and thanks for the comment.

Thanks for watching the channel and what a great comment and question. Yes, Iona started exhibiting the same long crank that you described. Some mornings she started right up with no problems and seemingly random times she would crank for an eternity before firing off. I started with fuel lines and hoses along with the regulator. Pressure was not constant in the fuel rail so that was an early part needing replacement. The long crank continued so the pump and filter were next. Ultimately the pump nixed the long crank. While waiting for parts to arrive I would turn the key to key on engine off position twice to prime the pump. It worked intermittently as the problem was fixed with replacing all the system from tank house to rail.

@@w140restorations I changed the fuel pressure regulator 👍🏼 24 hours now and it seems that it fixed the probleme. starts right up! I think the pump and filter are not that old im getting well above 50 psi engine on. well above 40 psi engine off. good thing I started with the regulator. thanks alot for the video 👍🏼 great help

Thank you for the kind words about the channel and thanks for watching. One thing you may check, after all else fails with the fuel system, is the immobilizer, and parity between master keys and the ignition system. You may not be getting signal to the fuel injectors. I’ve seen this before. Good Luck with your W140 and thanks again for watching.

Thanks so much for the comment and liking the channel. I’ve been thinking on this over and over since it was posted. What I come back to is the question of what changed to create this new issue. Is there any chance the new pump is bad? Yes. Is this the most likely culprit? Maybe. I’m not familiar with your two scanners but no leans and no pressure means potentially a bad pump. For any misfire without check engine light I check for vacuum leaks and aged plugs. I hope the comment helps and all my best getting your W140 running strong again.

Thanks for watching and supporting the channel. What a great question. It sounds like there is a lot of love for your W140. As to your question about the vacuum line that connects the fuel pressure regulator to the intake, I’ve looked through three reference materials and cannot find the part listen anywhere. Two more searches and no go for three national Benz parts catalogs. I know what part you are describing but cannot find a number for you anywhere. There’s a tremendous community of W140 fans on here. Someone chime in if you know the part number. Thanks again for watching and I hope you like the channel.

I’m a basics first and complex second when chasing down intermittent issues. If it were Iona I would start with looking for loose vacuum hoses and any cracked fittings and junctions. Vacuum does funny things with these M119 V8 machines. Can you twist the MAF on top of the throttle body and are the connectors tight fitting? I would probably start looking at the MAF itself for age, dirt, and debris. Did this happen after any recent changes to the car is also a first question I ask myself when diagnosing a problem. Depending on the age of your MB, facelift or pre-facelift could be plagued by common items that require replacement like plugs and caps and rotors if you have a pre-facelift V8. MAF issues are a catalyst for rough idling, terrible fuel economy, and other issues you described. Recently I’ve encountered and have been running down a coil that went bad on Project Iona and rough running until that got sorted. Good luck with you W140 and thanks so much for viewing. I hope your MAF issues get resolved and you get back to many more miles.