86gxl_fc

fuel pump works when i crank it up..
problem is that once i stop cranking (when its about to catch on)
the pump shuts off..
is there anything i should do to fix this problem?
any wire that should be plugged it. i replaced the passenger side harness.
my old harness wasnt allowing the injectors to spray properly.
now my injectors work, but now my problem is that it doesnt allow the fuel pump to stay constant.

dreadseb

I had this same problem in the past I'm not exactly sure what i did to fix it to be completely honest. To begin with i just unplugged the circuit opening relay and hot wired the pump through its own fuse and a switch just so I could drive it again. Then when I had time here and there I cleaned up the contacts at the AFM and at the circuit opening relay and then when I tried it again it magically worked. not much help I know but a start.

NZConvertible

Most likely you have a bad AFM. There's a switch in the AFM that opens when the flap is closed (i.e. no airflow), and that turns off the circuit opening relay that powers the pump. If there's a problem with the switch and it doesn't close the pump won't run after cranking. You can confirm this by jumpering the yellow fuel pump check connector, which bypasses the airflow switch.

86gxl_fc

i jumped the yellow plug to bypass it to make sure the pump worked, and it still doesn get any power.
anything else i can check, maybe something i missed to plug in?
i went over all my plugs and i replugged to sensors i was missing on the actuators.
aside from those, i dont think i missed any plugs.
this sucks because i've passed by Rotary Performance, hopin they'd have a chance to look at it (it shouldnt take longer than an hour to figure it out with their experience i'm assuming)
bad news is that they're going to be busy up until august.
and Marvelspeed seems to have closed down..
the only other place i have left to take it to is Gotham Racing about an hour or so away...
seems like its out of my hands right now, cuz i cant figure it out.

NZConvertible

The fuel pump circuit is very simple, and should be easy to troubleshoot. Grab the wiring diagram (FSM page 50-36) and study it so you understand where the pump's power comes from. Then check for 12V at each component in the circuit in turn until you find where the power stops.

The circuit is:

Battery > 60A BTN fuse (engine bay) > ignition switch > 15A ENGINE fuse (cabin) > circuit opening relay > pump > ground

If the ENGINE fuse is okay, with the ignition on there should be power at the circuit opening relay (the thick black/white wire, not the thin one). With the check connector jumpered there should now be power at the light blue wire. If not, remove and test the circuit opening relay as per FSM page 4A-74.

86gxl_fc

great, thanks i appreciate you breakin it down for an electrical noob, lol.
i was also curious how to know if i have high impedence, low impedence injectors.
i had kept my old injectors from my 86 gxl and injectors (at the wreckingyard) are dime a dozen so i pick them up if i find some.
incase i need an extra one to make sure they are spraying right...
or better yet, how do i know if i have a high impedence/low impedence wiring diagram.. i'm assuming the FSM would have that info?
i have an 87 SE.

NZConvertible

Measure the resistance across the pins on the injectors. 2-3ohm = low impedance, 12-13ohm = high impedance.

Cars with low impedance injectors have a resistor bolted to the right inner fender below the MAP sensor under the airbox. It's shown in the Haynes manual on page 116 (Fig. 1.1b) and on page 143 (Fig. 19.1). To see the difference schematically, page 283 shows the low-imp wiring (look for the "solenoid resistor") and page 289 shows the high-imp wiring.

86gxl_fc

what determines high/low impedence. the ecu?
reason being is i kno what plug your talking about. my old harness didnt appear to have it at the spot your referrin to. but the harness i put it was from another SE. like my model, and it did have that plug.

NZConvertible

It's nothing to do with the ECU, it's the resistance of the the coil inside the injector. The lower the resistance, the higher the current, and the current must be limited to prevent frying the ECU injector drivers. So low impedance (resistance) injectors need an inline resistor to do this.

RotaMan99

Could you replace the low resistance injectors with high resistance one and eliminate the inline resister all together on the 86-87 models?

SureShot

N/m

classicauto

iTrader: (3)

Check the voltage going to the pump while you're cranking it over. I'll put $50 on it being the resistor. The unit that lessens the voltage for cruise/idle, then increases it for load.

I've had the same trouble before.

86gxl_fc

which resistor might that be?
got any pics handy? =D

HAILERS

Series four non turbo cars do/did not have the Fuel Pump Resistor/Relay assy, so don't think about it.

NZConvertible

Yes, but you'd also need to replace the injector connectors. Why would you though?

You just lost $50 then. S4 NA's don't have this system. Notice it was missing from my circuit description above.

RotaMan99

The connectors? I thought they were the same? If I remember, compairing a set of 86 to an 88 the connectors seem the same.

I don't really see a reason for swapping them out but I figured I'd ask.

classicauto

iTrader: (3)

ba, for some reason I thought this was a TII..........gimmie yer paypal

86gxl_fc

nah, the only difference i saw on the injectors from year to another.
theres the little nub on the plug for the injectors, on some its centered.
on others its off to the side a little, which would need to have the correct plugs to plug in.

NZConvertible

86 injectors are low-impedance, 88 injectors are high-impedance. Obviously swapping them is not a good idea, so the connectors are different internally to prevent accidentally installing the wrong type. Externally they look the same.