350 MPI hard to start, runs terrible

[vroom ZOOM]

2001 350 MAG MPI (MEFI 3). This one has me really stumped. Last year, it wouldn't run at all. I replaced all the spark plugs and the distributor cap and rotor, and it fired right up. Come springtime, the engine started right up, but upon acceleration would sputter and blow black smoke. I figured it was too rich so I put a fuel pressure gauge on the rail, and when I turn the key, the fuel pressure would jump to 70 psi and settle at 20 psi. When tried to start it the fuel pressure was all over the place and sometimes would peg my gauge, so I figured the regulator was shot. I put in a new OEM regulator, and the fuel pressure jumps to about 60 and then stays at 30 when the pump turns off. I tried to start it but it just fires once and then absolutely nothing. I tried a new sensor in the distributor but that did not help. When trying to start it the fuel pressure is jumping around 60 psi.

Thinking that maybe something was reading wrong, I hooked up my diacom laptop and looked through all the parameters. All the sensors were reading the correct values. No fault codes. I took the spark plugs out and they were all sooty. I cleaned them with a brush and the engine eventually started but it runs like a pile of poo. I decided to do a cylinder drop test so I started pulling the plugs off the injectors and broke one off.

two questions:

1. Any ideas on how to fix this engine?
2. I badly need a new injector QUICK. how many pounds per hour are these injectors at 30 psi?

 

[alldodge]

What is your serial number????????

 

[vroom ZOOM]

What is your serial number????????

M072758

 

[alldodge]

Your FP regulator should be 807952A1 and should read 30 psi. The Reg should have a pink ring where the vacuum line connects.

Getting higher readings above 50 can damage the Reg.
Did you remove the screen (item 16) to see if it was clean?

Have you tried to see if there are any codes by using a LED or digital meter with a tone option?
https://www.mercruiserparts.com/bam/subassembly/31746/4848/100

 

[vroom ZOOM]

Your FP regulator should be 807952A1 and should read 30 psi. The Reg should have a pink ring where the vacuum line connects.

Getting higher readings above 50 can damage the Reg.
Did you remove the screen (item 16) to see if it was clean?

Have you tried to see if there are any codes by using a LED or digital meter with a tone option?
https://www.mercruiserparts.com/bam/subassembly/31746/4848/100

not sure on what you meant by the codes with a tone meter. As I mentioned, I hooked up my diacom laptop and there are no codes shown there (that is the first thing I did). Also when cranking I am getting a good engine speed signal, so the cps should be ok. I also checked for spark with an inductive timing light, also looks good.

As for the regulator, the pressure stays at 30 psi when the pump kicks off, but when the pump comes on the rail pressure reaches 60 psi. I don't know if this is normal, should I return the regulator to the dealership and tell them its defective? I will check the screen under it, but I don't think that would cause very high fuel pressure?

 

[alldodge]

not sure on what you meant by the codes with a tone meter. As I mentioned, I hooked up my diacom laptop and there are no codes shown there (that is the first thing I did). Also when cranking I am getting a good engine speed signal, so the cps should be ok. I also checked for spark with an inductive timing light, also looks good.

Sorry missed the diacom

As for the regulator, the pressure stays at 30 psi when the pump kicks off, but when the pump comes on the rail pressure reaches 60 psi. I don't know if this is normal, should I return the regulator to the dealership and tell them its defective? I will check the screen under it, but I don't think that would cause very high fuel pressure?

The pump should never be able to reach 60 psi. The reason this can happen is either the return line has a restriction (item 16, the line or fitting going back to filter) or the Reg is defective/wrong part.

The Reg appears it's working because when pump stops it holds at 30, it's just unable to return excess fuel fast enough

 

[vroom ZOOM]

Ok, I managed to get the fuel pressure in check at 32 psi with the pump on. I did take the little screen out, and although it looked clear, I blew it out with some brake cleaner and it helped with the fuel pressure. So I guess it was the screen plus the regulator that got the fuel pressure where needed. The engine started and ran just fine on the trailer, but when launched in the water it would crank but not start, just fire once and that is it. Once I gave it some throttle and started it it ran fine up on plane etc. I have a feeling I don't have enough battery juice to start it up, how much voltage does the MEFI 3 ECM need while cranking to fire? Also a possibility is that it does not open the IAC enough when cranking, how does the ECM decide how much to open it, and is there a bypass adjustment?