hey all,

i'm finishing up cleaning the mess the previous owner gave me. i pulled the dead alarm siren and wiring and now i'm working on cleaning up the interior.

my question is, what makes the stock boost gauge not work anymore? there's an aftermarket boost gauge taped on the dash right now. i'm trying to figure out if the aftermarket one was placed there because the old one broke for legit reasons or because of something else. i'm leading toward something else because i found a straightpipe in one of the storage bins.

i'm going to go out on a limb here and pretend that this guy knew what he was doing. perhaps he knew about raising boost and fuel cut-off and all that good stuff. if so, where would i most likely find his fcd? if he was smart enough to put one on?

the car is a 88AE. pictures would be helpful if possible.

thanks all.

 

Most likely by the pressure sensor. Facing into the engine bay, by the left side is where the sensor is, and there might be some wires that may be coming off of it that arent for the stock wiring.

 

An FCD might look something like this.

 

do you have any more pics of your engine bay? Thanks thing looks clean!!!! Very nice.

 

Boost gauge not working? - Could be
Pressure sensor
engine harness
ECU input
ECU output
main harness
dash gauge

Most common problem - the dash gauge connector.

 

Hopefully he didn't just remove the pressure sensor's line and use it for the new gauge instead...

When you say the gauge is dead, does is not move at all when the ignition's on (electrical problem) or does it shoot up to zero when the ignition's on but not move from there (vac line problem)?

A FCD can be wired in at the pressure sensor or at the ECU. How much boost are you running? If you're not reaching 8.6psi then you don't need one. If you're reaching 8.6psi and hitting fuel cut then you don't have one. If you're exceeding 8.6psi and not hitting fuel cut then you probably have one.

 

the aftermarket gauge is T'ed into one of the rubber lines. there's no electrical wiring coming from or going to the aftermarket gauge. one of the problems i have is driving around at night, i can't see the reading.

i looked at the picture posted. i have the N37x item. I don't have the stock box and all that other plastic in the picture is all gone and replaced with a cone filter.

the boost pressure is stock as far as i know.

the original boost gauge doesn't move at all under any situation.

anyone have a picture of these places so i can confirm them?

the highest reading i've seen on the aftermarket gauge is about 6. i've never seen it go up any higher than that and i've never "felt" the fuel cutting out. i didn't really stomp the pedal since i've just recently put a remanufactured engine in and i'm about 500 miles into it.

thanks for all the suggestions so far.

 

ok yesterday I replaced all the vacuum hoses going to the stock blow off valve ,pressure sensor N370 , and to the actuator above the turbo..The stock boost gauge was working fine ...I replaced the old stock hoses with bmw vacuum lines..and now I start my car and it reads 0 all the time..??whats wrong with my boost gauge??
I did unplug the stock pressure sensor to get space to install the new vacuum hose ..cleaned the contacts and reinstalled the plug into the stock pressure harness..Now WTH it dosen't work anymore..
when i step on the gas while driving the boost gauge says 0 all the time?!?@!#!!The stock blow off valve still
releases pressure when i let off the gas but the boost gauge stays at 0??I am waiting for my FCD still so i never step on the gas since i have a full RB exhaust and don't wanna hit boost cut..I'm sure i didnt damage anything but some weird reason it just stopped working..Since i didnt have a FCD it would cut out when I hit over 10psi but after the boost gauge stopped working now i can full throttle my car and it won't cut fuel anymore..Gauge still reads at 0 psi?? whats wrong?? please help me too!!

 

Does the stock boost gauge really read zero.....or is it always below zero?

Your NEED to put a meter on pin 2H of the ECU and check the input voltage from the pressure sensor. At idle, and with the vac hose off the sensor and plugged, the voltage should read 3.4 to 3.6v on a series five car. IF you go for a ride and boost, the voltage should rise. Does it?

You NEED to download the free fsm online. The Fuel section in particular. It tells you how to check the pressure sensor.

My guess is that the pressure sensors vacuum hose if not connected to the right nipple on the intake manifold or is disconnected. That's why it does not cut fuel anymore. It ain't a seein the boost pressure so it ain't a cuttin the fuel. Because there is no reason for it to do so.

 

Well the reading on my car stays at 0 unless i turn the car off it wont move from 0 reading once the car is turned on..Whats the problem still??Ima go and redo the lines right now and see what happens..