I didn't check the PSI, for $150 of the regulator, I'll just get new. I have a new electric high pressure fuel pump, never used, so if the pressure regulator won't fix the issue, I'll change the fuel pump. Just looks like a bit(h to swap the regulator. Not sure if I can get to it.

Let me be a voice of reason.

Alot easier and cheaper (free) to see if fuel psi issue. If psi is fine, you saved labor frustration and money.

Autozone and other part stores rent tools free. Ask to rent free a fuel pressure tester.

Also, What where the codes ?

I don't have the codes here at work. I have to read them later this PM.
Merc suggest it may be the coil pack too.

check the fuel pressure. It’s a 5 min job. The shraeder valve is under the cover. Get a cheap fuel pressure guage.

changing out the regulator without checking fuel pressure is a waste of time.

I might even have a pressure gauge. I have one for cyl compression, but I don't even know where to put the fuel pressure connections. On the rail ok. but where and do I need to check the mechanical pump too? I guess it should be 43 PSI I read, but where to put the leads to check?? I need an arrow or a finger to say. " put gauge line here" lol. I'm a good part changer, diagnostics are not my cup of tea. (that why I got you guys for) :)

TTT,
How about a fuel pressure check connection spot?
THX
P

it’s underneath the intake on the fuel rail next to the injectors...

It resembles a tire valve.

Padraig

Thanks, I found it, and of course the gauge I rented doesn't have the right fitting. GGGRRr

OK. Rinda scanner sux. I bought it, installed it, NOTHING. No codes. POS for Merc racing. I called, Now they tell me that their stuff will ONLY read codes, no descriptions nothing. Per Rinda Merc did not "gave" them the info. $600 down the drain. Fuel pressure is around 42-43 at idle. Rinda has a few tests injectors firing. Wires, plugs, etc unknown. Rinda has no clue. While I admit I have no idea with a lot of Rinda stuff, where I click on the button to see codes and there is nothing, Rinda is worthless. Don't waste your $. There is a test to see the coils, so I did it. 1-4 is testable, 5-8 Rinda says "not existing". Supper pissed and frustrated. Then I broke the plastic housing on the ECM connecting wires ( 12 -16 pins, left side, ) and I can put them back. It was stuck, used screw driver to get it off and I broke it. OK that's on me, but no clue how to get the pins back to the right spot.
So, when I install the Rinda thing, there is not even an option for merc. Crusader volve etc. nothing for Merc. I called before I paid, they told me it's ALL good. I will have one hellava conversation in the AM.