Baja 272 454 EFI RPM issues
 

I'm chasing down an RPM issue with a fresh rebuild 454 mag EFI in a Baja 272. I've just eliminated the manual fuel pump and the VST and replaced with an external Aeromotive electric fuel pump, adjustable regulator and all new plumbing. My first question is, what do you do with the factory fuel regulator at the end of the fuel rail? Do you leave it in place? I am regulating the fuel on the return side of the fuel rail and returning the fuel back to the tank.

Second question and a little more history; I purchased the boat with a spun bearing so I did not hear the boat running before hand. A complete rebuild was done with some modifications. Cam, H-beam rods, Scat crank, .60 over (due to water laying in one cylinder) .100 dome pistons and everything ballanced. Comp Cams Xtreme Marine (Duration @ .050 is 230 for the intake and 236 for exhaust) Valve Lift: .547 for both intake and exhaust. Part# CCA-11-451-8 Comp Cams roller rockers, ajustable rocker kit. The cam was installed at 110 degrees. After rebuild it labors around 3k rpm's and tops out at around 3500. I had the ecm reprogrammed to match the modifications but still little to no improvements. Timing set at 8 degrees using a timing tool. I have a constant fuel pressure now of 43 psi. I just sent the injectors out to be reconditioned by Bill Johnson at Mr Injector. (Very nice guy and reasonable) He stated that the injectors were not off enough to create that much of a loss so I can rule out the injectors. The engine idles great and runs good up to 3k rpm's. I'm at my wits end and almost at the point to scrap the EFI and bolt on a carb. Any help would be greatly appreciated at this point.

I did a similar change over with my fuel system, but I am regulating the fuel pressure on the inlet side of the fuel rail, and bought a plug for the outlet side of the fule rail and just left the stock because it isn't doing anything. You really need to check the advance when under load to see what your timing is at. I assume you put the ECU in base timing mode before setting it at 8 deg. If not then that is a problem that needs addressed. Start by checking the plugs to make sure they are all firing, it could be just a bad plug or wire. I know they are all new, but they can be bad or get cracked when installed. I had a problem with a buddy's boat (454mpi) after we reassembled it, that sound similar, loss of power and only hit about 3000rpm. We found an injector plug poped off because it didn't lock on good. We reattached the injector plug and it ran great. Keep plugging away and you will get it figured out!

Ok, just installed the reconditioned injectors, replaced the knock sensor and still no change. With the new fuel pump, plumbing, regulator and injectors, I think I can rule out fuel delivery problem. The engine sounds like it is laboring around 3200 rpms and will not rev above 4000. Any other thoughts?

Will it rev over 4000 in neutral, or is the description while driving the boat? If in boat, what prop is on it? Need a little more info on what's happening to help out better. Who did your reprogramming and have you talked to them about the problem?

4000 max rpm's, doesn't mater if in water or on the hose. I tried neutral and in gear while on the hose and no difference. 23P prop. It's almost like it's on rev limiter but no backfire or rough running from idle to 3000. I have been in communications with the Total Marine Performance in Ohio who sent the computer off for reprogramming and we continuing to diagnose but running out of suggestions. I have either checked or changed everything mechanical that I can think of except the distributor. Any help would be greatly appreciated. If I don't get it resolved soon, I'll have plenty of EFI crap to sell because a carb will be my next option.

Did you check to see where the timing is at 4000 rpm ?

+1, It sounds like you have all the basics covered. If it won't rev past that in neutral then there is something way off. Putting a carb on it may not fix your problem either, but i suppose it could be computer related and that is where the programmer needs to verify programming or send another ECU to test with. What does it do between 3000-4000rpm? Just thinking out loud, I would also check TDC with a TDC stop to make sure the harmonic balancer isn't off. I wonder about the timing chain being off a tooth, which could be checked by pulling a valve cover. I'm sure you don't want to start taking things apart, but you might have to. A vacumm leak on the intake would cause major lose of power, but usually they will spinup not under load. I wouldn't rulle out the distributor either, so maybe find one to test with or change the module as they aren't that expensive.

Ok, while in the process of eliminations I decided to see if the problem might be in the fuel tank so I disconnected the tank and ran the fuel line from a gallon fuel can to the fuel pump. It sucked down the one gallon in less than a minute at idle! What would cause this?? ECM, even though I had it reprogrammed? I found the rich condition by mistake when I changed the fuel filter and put it on empty which caused a lean condition. It ran great or at least until the filter filled up.

did you route fuel return to jug also.

No, dummy me. That would explain the the large amount fuel consumption. Still I have very rich condition that I cannot seem to pin down other than a ECM issue.