Originally Posted by subford

You may have to get a test light (meters do not work well in this circuit) and trace to where you are losing power.
Make sure the small black wire with a green stripe leaving the NEG post of the battery is well grounded to the NEG post.
Make sure the body (not the frame) also has a good ground from the NEG post of the battery to body with a 10 GA wire.
Make sure the fuel pumps ground at the radiator support is OK.

If all of this is OK and you still have problems start at the battery side of the starter relay on the fender and try to pull the fuse links apart by hand. If one of them stretches it is bad.
Then check the wiring under the fuel pump and ECC Power relays. It is a common problem on an 88 to have bad wiring here and you may have to replace the relay sockets.

Then check the big yellow wire at the fuel pump relay for power, it should be hot at all times.
Unplug the high pressure pump on the frame as we do not want it running without cooling fuel going through it.
If all OK above at this point jumper pin #2 to pin #6 of the EEC self-test plug and turn on the key.
Both relays should click to their make (picked) state.
Check for power leaving the fuel pump relay (brown wire).
Next check the power entering and leaving the Inertia switch (brown wire in and pink wire with a black stripe leaving).
If OK go on to the Selector switch and check for power going in the switch and the selected wire leaving the switch (see diagram below for wire colors).
If the power is still OK and the selected pump is not running unplug the plug on top of the tank and see if you have power on the pump power wire.
If not start back tracking towards the firewall (safety wall) plug.
If you have power at the plug then ground your test light with the plug and check for power again at the pump power wire. If the test light lights change the in tank pump.




/

Originally Posted by larrylass

its ok Bill youve been a huge help so far!! There is a relay in the corner of the firewall and fenderwall with the wires colered
Brown
black/white stripe
black
red/white stripe

on the two relays next to each other by the EEC test port:
relay #1
Brown
yellow
red
tan/green stripe

relay #2
Black/yellow stripe
black
white/blue stripe
blue

Would you be able to name these relays for me bill and what they do??

Thanks

larry

Originally Posted by subford

Relay #1 is the Fuel Pump Relay.
Relay #2 is the EEC Power relay.

I have no idea on the other one right now.

Come to think of it you do not have a firewall/safetywall plug on a 1988.
1989 and all newer trucks have a plug for the main harness where it passes from the cab to the engine compartment.

Originally Posted by subford

You may have to get a test light (meters do not work well in this circuit) and trace to where you are losing power.
Make sure the small black wire with a green stripe leaving the NEG post of the battery is well grounded to the NEG post.
Make sure the body (not the frame) also has a good ground from the NEG post of the battery to body with a 10 GA wire.
Make sure the fuel pumps ground at the radiator support is OK.

If all of this is OK and you still have problems start at the battery side of the starter relay on the fender and try to pull the fuse links apart by hand. If one of them stretches it is bad.
Then check the wiring under the fuel pump and ECC Power relays. It is a common problem on an 88 to have bad wiring here and you may have to replace the relay sockets.

Then check the big yellow wire at the fuel pump relay for power, it should be hot at all times.
Unplug the high pressure pump on the frame as we do not want it running without cooling fuel going through it.
If all OK above at this point jumper pin #2 to pin #6 of the EEC self-test plug and turn on the key.
Both relays should click to their make (picked) state.
Check for power leaving the fuel pump relay (brown wire).
Next check the power entering and leaving the Inertia switch (brown wire in and pink wire with a black stripe leaving).
If OK go on to the Selector switch and check for power going in the switch and the selected wire leaving the switch (see diagram below for wire colors).
If the power is still OK and the selected pump is not running unplug the plug on top of the tank and see if you have power on the pump power wire.
If not start back tracking towards the firewall (safety wall) plug.
If you have power at the plug then ground your test light with the plug and check for power again at the pump power wire. If the test light lights change the in tank pump.




/

Originally Posted by subford

I guess the 89 also started grounding the fuel system at the radiator support and all I can find on a 88 is the fuel pumps ground to the engine block.
There is a small black wire with a green stripe leaving the NEG post of the battery as this is the computer ground.
If you do not have this one it will not run.
It would not hurt to run a 10GA wire from the NEG post to the body as the more grounds you have the better.

By the way I see in the manual that there was a plug at the firewall from the engine compartment to the cab on a 88.

Originally Posted by subford

Jump pin #2 to pin #6 of the EEC Self-Test plug and turn on the key.
Does the fuel pump relay click and the brown wire have power when you do this?
Does the fuel pump(s) run when you do this?



/

Originally Posted by larrylass

If you have power leaving check for power at the plugs on top of the selected fuel tank.
If you have power at the plugs on top of the selected fuel tank then you have a bad pump (s) or a bad ground. <!-- / message --><!-- sig -->
__________________


What??? this makes no sense Bill!!!

larry

Originally Posted by subford

If you have power leaving the selector switch going to the wire for the selected fuel tank then check for power at the plug on top of the selected fuel tank. If you have no power at the plug on top of the fuel tank then you have a bad pump or a bad ground.

I do not know how else to say this.