Mercruiser 502 MPI 1995 Running issues
 

I have a 1995 Mercruiser 502 in my shop that I rebuilt for a customer that is driving my crazy. I rebuilt the engine and put a roller camshaft and lifter kit in it. The MEFI one computer had been done by CP Performance and I went by their recommendations as to what camshaft I should put in. So the computer and the camshaft are supposed to be matched. It starts hard and runs rough at idle and has no power. When I hook my computer up to it and put it in base timing mode, it just dies. I have tried another distributor I had laying around that came off a known good running engine and it doesn't change anything. I have checked to make sure the firing order is right and that all the plug wires are on correctly about 6 times. I have checked all the ground wires on everything and even went back and put dielectric grease on all the connections to make sure all my connections are good. For some reason the injector wires weren't on the way the book shows. so I put them on as the manual shows. It didn't help, so I went back to the way it was when it came in. It was running good before, it just had a flat tappet cam and some valve issues. I also just noticed when I changed out the distributor that I am starting to get a little water in the oil and I just had the block decked and pressure tested for leaks. I also had the heads decked and rebuilt. I have spared no expense on this thing and have changed all the plugs, wires, rotor and cap. I pulled the spark plugs out last night and discovered cylinder number 2 and 7 are burning nice and clean, but the rest are all burning really rich and black. I am in the process of pulling the engine out of the boat again and am going to check the valve adjustment again and inspect the intake manifold for cracks, it's the only place I can think of where water could be coming in. Any help would be greatly appreciated, the customer is getting very impatient with me and I'm going to have to figure something out really quick or I will have to work something out to give him his money back. I am at my wit's end. Thanks!

post what cam you used,also what doe,s it have for exhaust system?

A 1995 MPI with a flat tappet cam - that's new
The injector wires only go on one way, there keyed. Can mix the connectors but not how they go on

Injectors are batched fired so 2,3,5,8 with Dark Blue and 1,4,6,7 with Light Green


What fuel pressure are you seeing and is this cool fuel, VST or other?

Fuel Pressure is 45 psi and doesn't drop under full throttle. Cool Fuel
Injector wires were on 1,4,5,8 Green and 2,3,6,7 Blue I know it's not the way the book shows, but I took pictures and I guarantee that's how it was when it came in the door. LoL

Have the injectors been cleaned and flow tested?

I tried posting pictures with my phone, but I guess it's taking longer or something. The exhaust is just a standard Mercruiser exhaust with silent choice and the cam is a Comp part number 11-000-8
Grind number Camshaft, 3110B/3112B HR 114.0 + 4.0
SPC INSTR 1:
SPC INSTR 2:
SPC INSTR 3:
Intake Exhaust
Valve Adjustment Hyd Hyd
Gross Valve Lift .566 .578
Duration@
.006 Tappet Lift 284 290
Valve Timing Open Close
@ .050 Int: 2

Injectors have not been flow tested, just cleaned on the bench.

I don't think they came out with roller cam until 1996 according to parts break down.

if the injector harness is uncut or modified, Id put the injector connectors on as the book shows, it may be firing the injectors on the wrong rotation, or have you tried that.

Yes I tried that and it seemed like it was worse, so I put it back the way it was.