fuel pump drops to 6 volts?

[Lex]

Here's the circuit opening relay and pump section

As you can see the relay can be opened (pump can be turned on) in 1 of 2 ways. The first is when the starter is engaged and the second is when the VAF is opened. The starter wire that opens it is the violet wire. That should only be opening the relay while cranking on a stock car.

The light green wire is grounded when the airflow meter starts opening. When the VAF is completely closed, the pump is switched off for safety reasons. So grounding this light green wire will keep the pump on permanently as long as your ignition is ON. You can ground the light green by jumping it and GND and F/P in the diagnostics box in the engine bay.

The white/red is the 12 V wire that should be 12 V when ignition is on. The B/P wire going to the pump is what powers it, and it should be 12V when the car is running (VAF opened or cranking). The black wire from the pump down should be a solid ground.

So in other words, all you need to power the pump is to have the W/R wire have 12V, ground the light green wire, Ensure the B/P wire is 12V after you've grounded the LG wire, and ensure the black wire from the pump is a solid ground.

If you want to bypass the relay altogether, jump the B/P with W/R on the relay plug with the relay removed while the ignition is on.

Hope this helps!

[stylingtwagon]

ok i shorted the green wire to ground and the pump came on !!!!! for the first time but as soon as i let go the pump turns off so if the light green wire is not being grounded what does that mean ?

[stylingtwagon]

ok so this is a new problem so what could make this happen in the first place y do i have to jump the green wire ? do u want me to join the black/pink with white and red that does nothing only the green wire to ground i think hold on

[Lex]

You've found your problem; your light green wire is not being grounded by the VAF. So is the VAF plugged in? Is it opening at all when cranking.

With the ignition ON, open the VAF door by hand and see if the pump comes on. It should. If it doesn't you have an issue with the VAF not grounding this light green wire.

If you open the cover of the VAF and look inside you will see a switch that the vaf opens when it is fully closed. That switch should be closing as the VAF opens and it's that switch that turns on your fuel pump.

In the meantime, you can permanently ground the green wire to keep the pump on while the ignition key is on. However, remember that the pump will now always be on as long as ignition is on. So getting the issue with the vaf sorted out would be good.

[stylingtwagon]

ok but i still dont get fuel when cranking either so is that the starter ? oh ya it runs i started the engine bad news is boost controller is all the way down and i still hit 12 psi while the charge pipe did not have 1 hose clamp on it

[Lex]

ok but i still dont get fuel when cranking either so is that the starter ? oh ya it runs i started the engine bad news is boost controller is all the way down and i still hit 12 psi while the charge pipe did not have 1 hose clamp on it

Glad you got it working.

[stylingtwagon]

how should i go about finding the problem

[yunvmyegt]

found this on identifix...

Customer Concern: The engine will not start, there is no fuel pressure and no power to the fuel pump. All fuses check out OK and the pump runs and the engine starts if ground is applied to the Light Green (LG) wire at the fuel pump relay.



Tests/Procedures: 1. The LG wire gets its ground from the Vane Airflow Meter.

2. Check for a good ground at terminal B of C158 at the meter.

3. If OK, jump the Black (BK) wire at terminal B to the LG wire at terminal A to bypass the meter. If the fuel pump now runs, replace the Vane Meter.

4. If the pump does not run, repair the open circuit between the Vane Meter and the fuel pump relay



do you have another vaf to try?

ill see what else i find....

[stylingtwagon]

um ya some where but this is a 89 rx-7 vaf it was kinda hard to find in my town .will a bp vaf work

[yunvmyegt]

was it on the car running the n/a b4 the swap? but yea just to make sure its not shorted throw on the bp one, what else did you put on in the swap beside just the obvious turbo parts, did you change any sensors,wiring?

[Lex]

Just plug in your BP VAF ans see if it starts. Easiest way to see whether it's the VAF or the wiring. I got my money on the VAF.

[yunvmyegt]

yea i had a bad one, i put the stock bp vaf parts in it for something to do....

[stylingtwagon]

i did the bp swap over a year ago all i sawped was a lower milage 95 bp motor and all the turbo parts but i have a few funky wires like for two years my starter is now way related to ign switch i have a 10 gauge wire going from batt to switch in car then the starter i have a flexalite cooling fan ajustable control (160 to 240 deg ) lots of extra grounds um i did not swap the full gt harness the dash harness is still lx thats why i used the flexalite system . no but hen i try to start it now its gos putt putt puut then nothin
somthing not right i dont thing the timing is right is a bpt souposed to be at 8 how do i set it at 8 with out it running ?i need a professinal for three hrs to fix my fu*k ups damn .