Timmie

so I have a whole lot of issues lately.

first my car shut down while driving and I couldnt get it to start on gasoline anymore.
brought it to the garage, but since they are very bussy, i'm doing some troubleshooting myself since i know the car inside out.

its a 91 camaro 3.1 V6.
the first weird thing happening is that the car wouldnt start running with the TPS sesnor connected.
so I thought maybe a faulty TPS sensor ( its 22 years old so chances are its bad )
today I went back to the car, trying to run some more tests.
and the car wouldn't start ( yet again )
so I put my laptop with tunerpro on the car and starte reading out data.
fist, it looks like my TPS sensor IS working right, 0,75V closed and +4V wide open.

but, my fuel pump primes, but it doesn't run when I crank the engine.


so I checked the relay, and put a brand new one in there, and it looks like it doesn't click on. I checked the wires of the relay ( got 12V on the orange wire.
and the black wire is going to mass)

so I hotwired the relays by putting 12V on the red wire of the relays. making the pump constantly prime.....



NOW the wierdest part.
the moment the engine is running the car starts running weird because the fuel pump is not getting power. ( but I put 12V straight from the battery on the red wire )
if I shut down the engine and set my contact back on, I see again 12V at fuel pump.
I start the car and 0.00V at fuel pump....


I am LOST here, really lost.

whoaru99

The fuel pump is powered both through the relay and through the oil pressure switch in parallel with each other.

The overview description also says that for the ECM to turn on the fuel pump/fuel pump relay that it has to be getting reference pulses. To check that I think you can disconnect an injector plug and put a test light across the terminals in the harness connector then crank it over. If the light blinks then you should be getting the reference pulses.

Timmie

But my injectors work, because it runs when i hotwire the pump.

NINÅ

Timmie

I HAVE FOUND THE PROBLEM.

and you where actually really close.

when I put my contact on , I was getting 12V. put when I started the car, or when it was running. little shaking of the engine made sure the negative injector cables where hitting the engine block ( near the aircopump). this way the injectors opened, but because the ecm didnt get any pulses anymore because the signal was already at the mas without going through the ecm.
it shutted of the fuel pump.
I re isolated the injector wires and the car fired right up

Timmie

scrap this last post.
car still wont go.


not 1 error with tunerpro.
the computer isn't giving power to the fuel pump whatever I do.
the oil pressure swich itself is broken,
if I start the car with it connected it will blow the 20 amp fuse, and its even capable of melting a 2mm wire to cross the gap....

but even without the oil pressure switch the ecm should still be pulling the relay ( and no the relay is not broken , just to be sure I have put 4 new relays into the system and I know they work )

anyway, the ecm does not activate the fuel pump relay so my car wont go anywhere.
if I put power on the grey wire, or the red wire, the car will fire right up and keep running.
but the moment I disconnect that wire the car will just die....

I also looked at tips like the TPS, I did readings, its .,74V closed, and its none adjustable.
I changed it with a brand new unit, and the new one is also 0,74V closed.

it seems whatever I do, the ecm just dont want to fire up the fuel pump relay.
and I'm REALLY , Really, Really lost here.


the garage my car is at hans't taken a look at it, and because they dont have enough space. they parked it back on the road....
so I went over there every day when I came back from work to work on that car, and now even the neighbours started complaining for to many noise. ( and I cant even get the car to run ).....

uemf

The FP relay only primes the system. brining the fuel system up to pressure, only running for 5 - 10 sec. it's not used after that . the oil pressure switch takes over when the oil pressure rises. The oil pressure switch is a pressure activated relay
Replace the oil pressure switch.
you can verify this by juming the 2 wires from the oil pressure switch connecter togeather. FP should run full time and not blow any fuses.

Timmie

Oil pressure switch is only a failover. Normaly your relay takes care of the fuelpump. - have driven the car for atleast 5 years with th ops switch disconnected....