down on power and rpms 454mpi...
 

ok heres what i have 96 454mpi (375hrs)that ran fine last year. first day out this year when i started it it was surging up and down alot and ran very rough. had a missfire that would come and go at all rpms...tank was drained at end of season so gas was brand new as well as tank being one yr old as well as fuel lines. new fuel filter as well. i looked at the plugs wires and cap/rotor.. there was some buildup in the cap but the plugs looked pretty good. i sanded down cap and it ran a little better but still going crazy surging. i ran it on the ddt and got code 23 iat sensor. i cleared the code ran again and it didnt show back up and ran better at idle. before i got to run it on the ddt i took it out a few times and i have been down on power and rpms. last year i would get 4800rpms no problem and this year only 3800-4000 rpms and down on speed obviously. i did a compression check and had 135-140 all around. i put it in service mode and pulled some plug wires to see if i had any dead cylinders due to bad injectors or something and maybe had one.. ddt said injectors firing at 2.3 something?
so im thinking i have low fuel pressure(didnt check yet) or bad injector or 2. the reason im thinking injector is because the miss fire comes and goes...and the screens were also removed mid season last year but ran fine till i put it away.. also i removed the vst tank and mechanical fuel pump. replaced with low pressure pump and cool fuel system. i ran the return line from the fuel rail back to tank so i know its no vapor lock but now i have 2 fuel pressure regulator one on fuel rail and one on cool fuel assembly. i have the vacuum lines going from the regulators meeting at a tee fitting and the to the throttle body nipple...let me know where im going wrong if anywhere, i couldnt get alot of info when i did this fuel system but it ran great for 125hrs.
which regulator actually controls the fuel pressure now? and how can i check individually?
what do you guys think is causing me to be down on power and 800 rpms? am i on the right track?
thanks in advance...jay
http://www.classicglastron.com/phpbb...5928&mode=view

open to ideas and suggestions....anybody....

engine rough
 

take one of the regulators out of the circuit. Use the one on the CF pump as your regulator leave the other open to atmosphere pressure, check your idle FP with the vacuum reference line removed, pressure should be about 40lbs. while idling replace the vac reference line, pressure should drop about 4-5 lbs. Under load you should see the pressure move up to 42-45 lbs. pressure should stay steady. and not vary more than 2 lbs. check your FP at key on engine off..... the prime pressure should go to 45 lbs and should hold pressure for about 15-20 minutes before bleed off. the resulting pressure will more than likely drop to about 30 lbs.

going thru this as we speak. thinking my electric fuel pump went bad. replacing it tommorow. its an aeromotive that acted up once in the past. uder 100 hours on unit. trying the marine one tommorow. will let you know.. mark

what does mpi stand for some type of fuel injection...

ok got the fuel pressure gauge hooked up, first test was key on pressure went up to 34 psi but started to drop as soon as pump shut off and kept falling to below 20psi in under a min..... at idle the pressure is 32psi and really didnt move alot, i put in gear tied to dock maybe 1100 rpms and pressure stayed the same.....
i dont have a shut off valve for the return line to do anymore testing but i was thinking maybe a leaking injector since the pressure dropped right away? can i remove all my spark plugs dry them off reinstall and then prime the fuel rail a few time and then see if any plugs are wet? if they are that means bad injector right?
the cool fuel pump and regulator were brand new last year and filter under regulator was spotless so im just looking for some advice on how to troubleshoot next to find this problem. also if it was a leaky injector would that cause surging as well?
thanks jay

want to know if i can test my injectors by removing the top of the intake, and then remove the fuel rail with the injectors still in it. by turning the key to on it will make fuel pump run and prime the rail and show any leaky injector? or will the pressure push the injectors out of the rail dumping fuel everywhere? what do you guys think..anybody ever do this?

put a longer hose on your fuel gauge and run the boat through the paces. fuel pressure should be a constant 40 lbs on a 502 mpi. mine actually jumped 2 lbs or so when we stabbed the throttle then it went back down to 40.

i want to make sure my injectors are good first and then do more tests with fuel pressure gauge. just not sure what the best way to test them is. also where do i get a shut off valve for the return fuel line and where do you put it inline?

Fixx
 

ohme out the injectors with a dvom,i think they should be arounf 12.9-13.2 ohmes. check the fuel filter and make sure its tight and check all the lines, because theirs fuel sucked through the filter and lines they wont leak fuel if any are loose..had one kick my A$$ last year and the tech working on the boat didnt tighten the fuel line after he replaced the impeller..

contact Marren fuel injection (injector.com). I had injector issues that blew a motor. I sent all 16 of them to him marking them as port/starboard and cylinders 1-8 so he could clean/test them. He called me back and told me which 2 pistons I burnt holes in after testing them. He sells new ones cheap too if you need replacements.

well i tried my idea of testing the fuel injectors while in the rail but lifted out of manifold and it didnt go so well, when i primed the rail with fuel it just pushed a few injectors out a little dumping the gas out. so now i cleaned them up and im gonna send them out to be balanced and flowed at cruzin performance.
i also cleaned the throttle body and iac. i see that the iac is spring loaded but when i push on it it only moves very little and wanted to know if that was normal?

ok heres an update, i cleaned out the injectors, iac valve, throttle body and the air cleaner, reinstalled everything and checked fuel pressure again.
key on engine off had 34lbs but started to drop right after pump stop and got to 0lbs after 3-4 mins.
engine running had a steady 34lbs also.
removing the vacuum lines from the pressure regulators showed no increase or decrease in fuel pressure, i removed one at a time for both tests.
the engine was running on the hose and when i revved it up the pressure stayed at 34lbs.
the good news is that the hiss from the iac pretty much went away and i wasnt having the surging problem like before.
so do i have a fuel pump problem or fuel regulator problem?
i have a low pressure pump feeding the high pressure pump but the inline gauge i install after pump before water separator shows only 1 to 3lbs of pressure when running....doesnt make sense to me...sometimes it shows 0lbs when running....

here is how my fuel set up goes from tank to low pressure pump which is mounted 1" below top off tank, into the water separator, out to the high pressure fuel pump on the fuel cooler, from fuel cooler it goes to the fuel rail in, and the fuel cooler regulator return line goes back to the water separator. from the fuel rail i also have a return line that goes back to the gas tank. when the engine is running there is alot of fuel being returned through this line and the more throttle i give the faster the return line flows back to the tank.
am i losing to much fuel pressure due to having 2 return lines ?
is one or both of the regulators bad?
whats my next step i should be trying?
really need some help with this one......

Fixx
 

sounds like the fpr is not holding its pressure, seems they are cheeper then a fuel pump and thats what i would replace first..

Multi Port injection

which regulator should i change? the fuel cooler one or the one on the fuel rail?
i have the green circle on my cool fuel regulator...is that the right one or do i need a different color/marking one?

did you ever ohm your injectors with key on?