runnermedic

hi friends
need some help here with my 1998 4runner limited,the problem is that the fuel pump doesnt shut off with the key in the on position,if im not wrong its supossed to prime then turn off and when the engine is running turn on again.
i can hear constant little zoom noise in the engine bay,engine runs great and starts ok every time.

kball

The fuel pump is in the tank not under the hood. You must be hearing something with the evap system or abs.

runnermedic

i know the pump is in the tank but the noise can be heard in the engine bay,if i disconet the fuel pump the sound is gone i can hear fuel dripping back to the tank so im thinking maybe is an open injector,make sense the little hiccup when taking of,another thing i was thinking is that if the fuel filter is clogged the priming would be hard and the hiccup when taking off is the proof that the filter is clogged.

runnermedic

little update here
new spark plugs and fuel filter
maf cleaned
evap vsv tested ok
fuel tank evap vsv tested ok
tps tested ok
coils tested ok
so im thinking that if the fuel is dripping back to the tank with the engine off it may be a faulty fuel pressure regulator and this is causing the pump to keep on building pressure
the hesitation is when i press the pedal from idle and then in heavy load if i push the pedal to the floor it will hesitate then slowly build up speed.
im going to pinch the fuel return line and see what happens,maybe this is why rpms are low while idling

runnermedic

hesitation cured after cleaning the maf with CRC cleaner

still searching for the fuel pump issue,pinching the return line does nothing,fuel pump continues to pump

no fuel in the vac line so FPR is not broken
while engine is not running the fuel rushes to the return line,i can feel the fuel passing the return line
while engine is running at idle i can feel fuel pulsating trough the return line
removed the rs300 security system that PO disabled(dont have the remotes) no change
COR tested ok
no fuel odors
starts quickly everytime,runs good,but uphills i notice a little bit of hesitation, barely can notice but it happens.maybe is running lean?
fuses are all ok

something that is incorrect is that the fuel pump assembly harness was cut by PO maybe to replace the whole fuel pump assembly.so the wires colors dont match at all. it works but dont match,that is an issue maybe the PO was quessing about the wires,maybe the whole assembly is from a different year or a 4cylinder one ,maybe also that is the cause of the fuel level gauge not working properly,outside the tank fsu works fine, assembled only marks 1/2 tank fsu readings are different 1.23 empty 1.58 ohms full (if someone can send me a picture of the fuel pump harness would be great)mine is 98 i know 99 up use 2 connectors at the fuel pump assembly.

weak pump????
can it be possible that 3rd gens are equipped with inertia switches like lexus or landcruisers?

Texas_Ace

Wiring issue is my guess if there was a security system installed. Those can screw up all sorts of things.

runnermedic

i removed the sec system and it was pretty easy it was plug and play no wires to cut or add,every plug is connected and no visible cables are loose or damaged.im going to chase the b- and b+ from fuel pump to ecu,i was thinking that if the sec system was malfunctioning the engine will not start because of sec system disabling fuel pump and other things,maybe po decided to rewire the fuel pump making it constant.

Texas_Ace

Anything is possible I would backtrace the fuel pump wires to start with and make sure they are connected to the right place. If that checks out then check the relay (or check it first since it is easier) and make sure the relay is still good and not stuck on.

runnermedic

Traced all fuel pump related wires and everything is ok ,relays are ok
Too much fuel pressure will cause en open FPR? maybe the FPR es stuck open.

Texas_Ace

The fuel pressure has no effect on the pump running or not.

If the pump is running and working correctly you should not hear the fuel dripping back into the tank but pouring back in. It should have some force behind it and be moving pretty good.

runnermedic

I was reading some info in the mitchell software that shows different PSI values in 4cyl and v6 engines,maybe the po replaced the entire fuel pump assembly with the wrong one
And this is why the fuel pump es not priming correctly
(I need a picture of the fuel pump harness to determine that)

DeathCougar

iTrader: (23)

No. No 3rd Gen 4Runner has ever been equipped with an inertia switch.

And as far as I know no Toyota or Lexus has ever been equipped with one either.

runnermedic

Ok
Discarted
Mitchell on demand shows some lexus and landcruisers using inertia switches for the fuel pump

Texas_Ace

Doubtful. The fuel pump itself doesn't effect when it turns on, just weather it works or not when it does get power. Your problem is something before the pump, for some reason it is getting power when it should not.

Do you have a 4runnner or a hilux?

runnermedic

mine is a 98 4runner limited

runnermedic

found this comment in a web page

First the only time the pump runs is in the start position. Once the computer sees Cam and crank sensor input it then keeps the pump running by way of the circuit opening relay. There is a check valve in the pump then the pressure regulator on the rail. These 2 things isolate the fuel pressure. Have you put a gage on it to monitor how fast the pressure pops up once the key is hit to the start position? It should only take .5 seconds and you have 40 psi. This is normally not going to cause an extended start if the pressure bleeds down over night.

Read more: 1996 camry: fuel pressure held..new fuel pump..crank..car starts - JustAnswer http://www.justanswer.com/toyota/6en...#ixzz27FKmMKXk

???????????

Texas_Ace

Yeah, that is how it should work but for some reason yours is not. If the wiring and relay are working as they should then the issue lies further back in the system.

Time to trace the relay wires back, pretty sure they go to the ECU in which case the ECU is to blame for the pump staying on.

Either a short of some kind or for some reason the ECU thinks the car is running or trying to start when it is not.

runnermedic

some update here
traced the fuel pump circuit cables up to the ecu and everything is ok i also removed the ecu to visually check internals and seems to be ok,no acid marks,water damage or previus jobs marks.
tested the camshaft sensor again cold and hot and its ok
the only thing i cant test for now is the crankshaft sensor because of the location
i know that some fuel pumps works by the signal of the camshaft signal but i dont know if the 5vz uses the signal from both sensors or just one to turn on the fuel pump.

dbryant

Not sure if it helps, but on mine, camshaft sensor runs the spark, the crankshaft runs the injector pulse, But mine won't start now. Had no pulse to the injectors via a noid light, but had spark, changed the cranks position sensor now have pulse at the injectors, have spark, but still won't fire....but thats my problem...lol. You can Ohm them both to check pretty easy.

runnermedic

im trying to locate another ecu to test it,i read something in the web that some cars ecu controls the fuel pump priming timing ,then when cranking it sends a signal to the fuel pump to turn on again,maybe the problems is the ecu becuase i cant get the obd codes at all,the obd is wired correctly and seems to be working pins 4 and 5 are grounds 16 is b+ and 7 is signal from ecu i trace it and it goes where it should be so a short is discarded .so if the obd is not working maybe the problem is caused by the ecu.