88' 300 dual tank

[99BlueOval]

Last week I found out my rear pump wasnt working, replaced it. Also found vacumn leak in the pressure regulator line. The truck hasnt ever ran better. Today, I go to move it out of the driveway & it wont start .. Seems to be a fuel related issue. It turns over & i can get it to start briefly with starting fluid. Problem is pumps dont prime when first turning the key on. Although jumpering, on the diag plug gets good 40+ psi to to rails.

[subford]

Try pushing down on the reset button on top of the fuel cut-off switch.

If that does not help check to make sure the small black wire with a green stripe has a good connection on the NEG (-) post of the battery.

If if still no go check the wires under the Fuel Pump & EEC Power relays sockets. They give a lot of problems.

If they look OK see if the Fuel Pump Relay clicks when the key is turn on by holding your hand on it. Note it will click on for one second and then back off.

Let us know at this point what you find so we know how to guide on to your repair.

[99BlueOval]

inertia switch isnt tripped
Other than a ground from the negative side, I have a single black wire going to a connector running into a loom in front of the radiator & core support.
The foward relay clicks, but not the rear of the 2

[subford]

Ground pin #6 of the EEC Self-Test-Connector and turn on the key and see if it clicks (Makes) and if it clicks do the fuel pumps run now?



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[99BlueOval]

yes.
Apparently i have to type more than just yes to get the message to post

[subford]

I take it you are saying the fuel pumps run with pin #6 grounded.
If so you need to check the plug (pins bad or wiring bad from the pin #22 Computer plug to pin #6 on the test connector) at the computer and if that is OK you may have a bad Computer.

[99BlueOval]

so pin 22 of ecu supplies the ground under running conditions?

[99BlueOval]

BTW, I was expecting computer behind the glove box or passenger kickpanel. Not there, Where?

[99BlueOval]

NM, Drivers side.
If 22 supplies the GND, why cant i short#6 to GND when trying to start it?

[subford]

Originally Posted by 99BlueOval

so pin 22 of ecu supplies the ground under running conditions?

Yes it does.

Originally Posted by 99BlueOval

If 22 supplies the GND, why cant i short#6 to GND when trying to start it?

You can but if the computer is bad more than likely it will not be grounding the Fuel Injectors either.

Make sure you are getting power and a good ground to the computer also.

I think you found the computer in the drivers kick panel.

[99BlueOval]

Do you mean #22 of the firewall bulkhead connector or the computer. HTH do you get the computer out anyway? I removed the single bolt holding it, but does the backside have a latch or keeper, holding the harness?

[99BlueOval]

whats the pins on the bulkhead or computer to check for PWR & GND? Is the PWR - KOEO or all the time?

[subford]

It is pin # 22 of the computer and NOT the bulkhead connector if you have one. I though the bulkhead connector started in 1989.

[subford]

Originally Posted by 99BlueOval

whats the pins on the bulkhead or computer to check for PWR & GND? Is the PWR - KOEO or all the time?

Pin #1 has power on all the time but pin # 37 & # 57 have power just when the key is on or in the start position.

The ground pins are #40 and #60.



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[99BlueOval]

is the ECU harness in the back or side? I cant get the damn thing to come out. since I have the bulkhead connector, are they same pinouts 1for1?