Black Scorpion fuel issues

[jcarrick]

Hey guys,
My 2000 Ski Sanger has the 5.7 Black Scorpion MPI motor in it and I'm having a fueling issue. I checked fuel pressure yesturday at the fuel rail and I'm only getting 22psi at idle.. It slowly starts to climb to 30 at WOT. I believe it's supposed to have at least 35-40psi at all times..

Here's what I have done already: replaced the water seperator and cleaned the anti-syphon valve. I also replaced the fuel pump about 2 months ago.

Is there more than on filter on this engine? Any ideas on what my problem is. Please help!

 

[w317chester]

Re: Black Scorpion fuel issues

hey sounds like we are having the exact same issue, so ill help you with what i know and you help me with what you know. i think you have already posted on my thread but here it is, it might help you out:

http://forums.iboats.com/showthread.php?t=415900&highlight=fuel+pressure+issue

but to answer your question, yes there are two fuel filters (at least on my 1996 anyways). there is the water separating filter and then there is an inline filter(mine is located on the fuel line going to the first fuel rail).

 

[w317chester]

Re: Black Scorpion fuel issues

something else you can check is your fuel pressure regulator:

1)get a vacuum pump/gauge(can rent from autozone or buy one for like $25)
2)hook gauge up to plenum vacuum port and gauge should read between 10-15 in.mg. at idle.
3)unhook gauge/pump from plenum. hook vacuum pump/gauge up to fuel pressure regulator and apply 10 in.mg. and fuel pressure should drop around 5in.mg.

 

[jcarrick]

Re: Black Scorpion fuel issues

w317chester,
Yes, i just realized i did post on your thread! That was before i did the pressure test last night. Its sooo weird that we are getting the EXACT same symptoms and problems...

I have had the hose from the pump to the fuel rail off of mine before and theres no filter in it... i just have a screw on filter on the drivers side of the engine.

I will definitely be checking the FPR this weekend. That was one of my prime suspects. Another thing i think we should check is available voltage at the pump and resistance in the positive wire for the pump and ground wire for the pump.

Another idea that i have is that maybe this has something to do the PCM on the boat... If we are both getting the same low fuel pressure reading maybe theres a stored code of something in the computer??

 

[w317chester]

Re: Black Scorpion fuel issues

well I plugged my code reader into the ecm and it doesnt give any error codes. it gives the default ignition on code which lets you know that the system is working. and from my understanding the fuel pump pressure cant be changed through the ecm so im not sure if it has anything to do with that (but im no mechanic, i could be wrong). but yeah i would like to check the voltage and resistance to my pump wires. any idea of what the correct values should

i just installed a new FPR and tomorrow i will be installing a new fuel pump and idle air control (IAC) valve and I will let you know if anything changes. im installing a new IAC because a faulty one could change the vacuum in the plenum which could offset the FPR.

so i will let you know

 

[jcarrick]

Re: Black Scorpion fuel issues

Thats good to know.

Well, as far as i know on most engines you want to see almost battery voltage at the fuel pump. Which could but up to 13-14 volts. And any resistance above like .1v should be checked out.

Just an idea as far as putting new parts on goes. Why not put one on at a time to see which one made a difference. That way if one of them fixes it you can return the rest and save a little. Also this way it would help us figure out what is causing the problem so we can prevent it later on

 

[w317chester]

Re: Black Scorpion fuel issues

right, I will put them on one at a time and test it after each part. I just went ahead and ordered everything i thought it might be and im gonna return what i dont need. thanks. when u say resistance should be below 0.1v, u mean
0.1ohms right? when i check the resistance i am check resistance thru the fuel pump while it not plugged up right?

 

[jcarrick]

Re: Black Scorpion fuel issues

Well theres a couple ways to check resistance. The first is to isolate the component you are testing, put your meter on ohms, and find the resistance. The second, which is the way i prefer, is to do a voltage drop across what you are testing. To do this you will have to have the engine running so that the fuel pump is also running. Then go from the power side of the fuel pump to the pumps power source and find the voltage drop. And from the ground side of the pump to the ground terminal of the battery. This will tell you if theres any resistance in the power supply to the pump and anywhere the pump ground.

Be sure to also check the available voltage at the pump by placing your red lead on the power side of the pump and your black lead to a known good ground. You can also check the voltage drop of the pump by placing your too leads on the two wires of the pump. This will tell you if your pumping is dropping all the voltage

 

[jcarrick]

Re: Black Scorpion fuel issues

Hey,
Just curious, when did your problem first start? Was it gradual or did it happen right after something?

 

[w317chester]

Re: Black Scorpion fuel issues

well i just bought the boat and it was having problems when i got it so i dont know if it happened all of a sudden or what. but i actually think i may have figured out the problem today. think it the fpr. im not 100% sure but some test ive run led me to this belief. would you want to exhange phone numbers so we could help each other out easier? my email address is ccarte45@gmail.com if you want to give me ur number, so u dont have to post it on here so other people wont be calling you.

 

[Bt Doctur]

Re: Black Scorpion fuel issues

http://www.boatfix.com/merc/Servmanl/16/16C5R2.PDF
For TBI and MPI ,might have something you could use

 

[jcarrick]

Re: Black Scorpion fuel issues

Thanks, that link has been very helpful. Im doing the FPR test from it today

 

[jcarrick]

Re: Black Scorpion fuel issues

Hey guys,
I figured out the problem and the new part is on the way!! Bad Fuel Pressure Regulator

Heres how i came to this conclusion:

I was getting 22psi in the rails. So theres only a few things that could cause this lower pressure: restrictions in the lines (None), bad pump (possibility), or fuel pressure regulator (possibility.
I was able to test both of these at one time. I blocked of the return line from the FPR. According to a diagnostic tree if the fuel pressure went above 38psi, the FPR is bad and you have a good pump. If the fuel pressure is below 34psi, you have a week pump.
My pressure was 85psi! So... New Fuel pressure regulator it is. There was a hole in the diaphram allowing most of our pressure to bleed off back to the tank.

Hope this helps anyone with similar problems. Feel free to PM me if you need any help!

w317chester,
Sorry i gave you the wrong number, that was a total accident. I hope you got the other email i sent. Feel free to call me anytime and we can discuss this in more detail!

 

[w317chester]

Re: Black Scorpion fuel issues

jcarrick I actually just found out what my problem was yesterday also. Mine was also the FPR. I put a new one on yesterday and it ran great. thanks for all the help though. im glad we both got it figured out.

 

[jcarrick]

Re: Black Scorpion fuel issues

Hey guys,
So bad news... I put the new FPR on and we're still only getting 22psi... I can't figure this out! Back to square one.. Any suggestions??

 

[sallingear12]

Did anyone ever find a solution for this issue? I am having the same problem. Replaced pressure regulator and fuel pump. Still getting 20PSI. Pressure goes up when I clamp the return line or pull the vacuum line