Fuel pressure help

[Logan1994]

My 535 won't hold a steady afr under boost. Tuner said it goes from a steady 10 to 20 when he changes the table slightly. I had it tuned on wastegate at 7psi and it did fine. Then I did my head gasket, head studs, new turbo, boost controller, and Walbro 255lph and now it is messing up. Do I need a different fuel pressure regulator? Or is my inline pump messing? Any help is appreciated

[Mark 88/M5 Houston]

My 535 won't hold a steady afr under boost. Tuner said it goes from a steady 10 to 20 when he changes the table slightly. I had it tuned on wastegate at 7psi and it did fine. Then I did my head gasket, head studs, new turbo, boost controller, and Walbro 255lph and now it is messing up. Do I need a different fuel pressure regulator? Or is my inline pump messing? Any help is appreciated

Sounds like you need to monitor the fuel pressure as the first step in troubleshooting the problem.

[Logan1994]

Ok. He said it drives around fine but it is running really rich and then it leans way out. The car is at his shop so it's hard for me to know what is going on. Could I have messed up a sensor when when I changed my head gasket?? I'm not great at diagnosing problems and he said he doesn't know enough about older bmws to know where to start. He is mainly a evo/sti tuner. I am going to have him datalog Thursday and send that to TCD so he can have a look at it. He was leaning toward my megasquirt as the issue. And he said to get ahold of Peter Florence. But It ran fine before I did the head gasket and studs. Then it started doing this.

[marc79euro645]

It could be a lot of things, clogged filter, pick up screen, dented fuel line,fuel pump voltage,fuel pump failing.etc.. I would start with voltage at pump. I had a similar experience, where tune was good, then started getting lean. I rewired with relay off battery in the trunk. Now I can hear my twin pumps spooling. My electric oil pressure gauge servers double duty as fuel pressure gauge when needed. I just move sensor to fuel rail. This has helped diagnose problems for me.
good luck

[Logan1994]

It's a brand new Walbro and I changed the filters too. I will hopefully be picking the car up today so I can check all the stuff myself. I will start by checking the voltage and go from there. Maybe one of my connections on the pigtail to the new pump got messed up

[Logan1994]

Ok so I got the car home last. I babied it all the way home and it seemed to do fine so I figured what the heck I will try get into boost. Did that car did fine seemed the same as how it ran before I did all the work on it. Wideband flashed 7.4 pretty much the whole time every once in awhile it would read some random numbers while cruising. No hiccups, stutters, it weird sounds and I didn't notice and black smoke coming from the exhaust. I'm almost leading toward the wideband being screwed up. I will do some more testing and update.

[Logan1994]

Update.. Fuel pickup line for the intank Walbro split so found part of the problem. Now for the fuel pressure readings. At rev and slight throttle fuel pressure goes down to about 35 psi. Idle and slight boost is 42 psi and under wot around 50 psi. Wastegate is set at 10psi. I know I need to get the car retuned but I want to turn the boost up also to about 17psi. Also had the megasquirt checked out and Peter Florence said nothing wrong with it. Should my fuel pressure drop down to 35psi??

[T_C_D]

Now for the fuel pressure readings. At rev and slight throttle fuel pressure goes down to about 35 psi. Idle and slight boost is 42 psi and under wot around 50 psi.

This seems correct.

[Logan1994]

Anyone have any idea why my car would lean out to 14-15:1 afr when I barely get on the throttle. It happens until the turbo starts to spool then goes to 12:1.

[tschultz]

There's a lot of possible causes, and you haven't really described your setup for us to be able to help you...

[Logan1994]

M30b34 with mls headgasket and head studs. 42lb injectors, intank Walbro 255lph, a/a intercooler, flipped intake manifold, 60 trim comp turbo, megasquirt ms2, aem wideband. Thats about it

[Logan1994]

Now I feel really dumb... The new line I put on the fuel pump pickup split at the clamp.

[tschultz]

So is it all fixed now?

[Logan1994]

Seems to be holding now that I soldered a hardline reducer on it.