help diagnosing engine running rough/ low fuel pressure

[green99saleen]

Hey everyone,
Im new to the forum and havent joined any others before either, but I've been chasing issues with my mustang for about 3 months and have spent too much time/money on it and run out of ideas, so I'm on here to pick yalls brains and possibly get new ideas.
first off heres the details of the car.. 1999 mustang gt, 2003 cobra bottom end, saleen series i supercharger(i know its a sh*t blower but it was cheap) 42lb injectors, 90mm mass air, ford gt supercar fuel pump, CMS stage 2 blower cams and comp high lift valve springs.
the issue I've been having started out as I noticed the fuel pressure had dropped from around 45psi to about 20-25 psi at regular cruising.. I have the saleen gauge on the pod on the dash to monitor fuel pressure. When I would accelerate heavy the pressure would go up slightly but dropped to 0-5 immediately after letting off the gas. When this started the car ran good and pulled hard but progressively got worse. The car then began misfiring but it was barely noticeable, however as time went on(under 150 miles) it has become so bad I no longer drive the car and it doesnt run smooth at all. I have replaced the fuel filter within 1200 miles so im thinking thats fine, the pump is run with gates fuel line from pump directly to hat/fuel feed line, bypassing pprv as well as the part that feeds fuel back into the tank as I've drilled holes in the hat to not suck it dry. The only known issue right now with the car is the rear o2 sensor harness has burned through, which im under the impression they only monitor the condition of the catalytic converters anyway not air/fuel so I dont think its related but ill be fixing that soon anyway. Ive replaced all 8 coils and the plugs and injectors only have 1000 miles on them. It ran slightly better after the coil change but still is definately not right. I've exhausted all my ideas on this car and im still thinking its fuel/ fuel pressure related, though I could be wrong. also this evening i ran my sct tuner on it to check for codes and it threw p0602 which is something wrong with the pcm.. possibly the harness burning through for the o2 sensors shorted and fried the pcm? Im stumped.. Any and all help greatly appreciated..
Thank you,
Thomas

 

[2013 Laguna Seca]

Suggest to fix burnt wires first.If a power and ground are touching,you can have all
sorts of problems.Also lift off fuel rail and turn key on and see if any injector is
leaking.

 

[green99saleen]

I will fix the o2 sensor harness soon, just need to locate one and splice it in as its not an over the shelf item. also when you say lift the fuel rails up, where would they leak? wouldnt the injector just pop out of the rail? (meaning a certain leak?) Its dry around all 8 injectors. I can check that on the driver side but the passenger side the rail is directly under the intake elbow/throttle body of the supercharger, and theres zero room to lift the rail. In fact just to get the injectors out i had to "rock" them in as there wasnt enough height to just pop them in as usual, without removing the blower. In case that sounds confusing, what I had to do is set all 4 injectors in their hole angled towards the front of the car and slide the rail rearward as it seats over the injectors. It was quite a pain, thank you for the reply though!

 

[green99saleen]

Do you mean leaving the injectors in the rail and out of the intake, and just turning the ignition on priming the pump? Looking to see if fuel comes out of the bottom of the injector?

 

[2013 Laguna Seca]

Yep,like i said though,fix that harness that could be your problem.Could be "confusing the pcm".

 

[green99saleen]

Repaired the harness today with the exception of the downstream passenger o2 sensor, I need a new female end to splice into the harness but i have removed the burned portion and made sure none of the wires are contacting eachother. Noticed the MAF plug was rubbing the fender where my intake runs through and the wires were bare and touching the fender, most likely shorting out. I repaired this and moved the MAF so there nowhere near the fender now and the car runs much better, however, theres still a fuel pressure issue. It no longer drops to 0-5 as it had in the past after letting off the gas which is good, and it rises when I accelerate, however I noticed the pressure doesnt rise any when unplugging the FRPS and plugging the vacuum line? Its still also only mainting 25 psi at idle, though it goes up to 35-40 with throttle even before boost. Im under the impression it shouldve risen 5-10 psi with this disconnected and plugged? The car is much smoother now but Im curious why the pressure doesnt rise in that case.. Anyone have any ideas?

 

[2013 Laguna Seca]

Does the regulator vacuum hose have any fuel on it?

 

[green99saleen]

no it doesnt, Ive replaced the FRPS within 200 miles (original was fine) and it also has the kenne bell disc under it to prevent rupturing.

 

[green99saleen]

UPDATE: found the issue. Ran a compression test and found cylinder 3 to be dead. Pulled valve cover and found 1 broken valve spring, 1 broken rocker arm and 1 rocker arm just bouncing around in there fallen off. This is only 900 miles after the entire top end was assembled and the cam is torqued properly. My question is what could cause this to happen? Thanks to raptor10 for letting me borrow the compression tester!

 

[2013 Laguna Seca]

Keepers improperly installed posibly.I would call the shop that did all the work and explain the
problem.Any respectable company would honor their work after only 900 miles.Need to make sure neither one of those valves smacked the piston.Your welcome for the compression tester,anytime.

 

[green99saleen]

Yeah Im praying the valves are okay.. Thing is 250 miles after I got it done the first time, a timing chain broke broke and bent 6 valves on the drivers side.. 1600 dollars later they fixed it all and now 900 miles later the passenger side has issues. Im not pleased to say the least and feel they should take responsibility of it this time, seeing I've had to bring it back twice within 1200 miles for valvetrain issues.

 

[2013 Laguna Seca]

Wait,so 250 miles you break 6 valves on passenger head? Only thing that can cause that is the timing was off. Now this problem, I dont know man sounds like someone
is not doing a very good job. You should call Performance Autosports and talk to Mark
and see what he thinks,maybe he can help you out.

 

[green99saleen]

no 250 miles in the timing chain broke, thats what caused the valves to get bent. Nobody had heard of this happening before including him. And it was the drivers side. This time its the passenger side with issues.

 

[2013 Laguna Seca]

Ahh ok,yeah i have never heard a chain breaking either.