As the title states. Parked the camaro (1988 5.0 TPI IROC-z) awhile back to do the clutch and flywheel. Took awhile due to work load, but finally got to the point to where it is time to start it. At first I had just removed the fuse for the fuel pump so I could bump the motor over a few times-to get oil running. Put the fuse back in and I have no power to fuel pump.

In fact, the gray wire is now a ground.. I've no idea why. I've tested the relay and the wires to the relay and even there the gray wire shows as ground. All fuses have continuity and power as they should.

Pretty much now I am just tracing the gray wire with a test light trying to find where it may be grounding out. Any suggestions or ideas would be helpful. I know that I didn't tamper with the large jumble of wires that pass above the bellhousing. I am wondering if I may have disconnected something else in the process.. something else that might stop the fuel pump circuit.

 

I just looked at the 88 shop manual and it doesn't show a grey wire anywhere related to the fuel pump. My 91 has a grey wire to the pump for power ( shown as TAN on the 88 diagram. )

"Jump" the fuel pump with power to be sure it works. Then start at the other end starting with the in-line fuse. Be sure it Gets and Sends power ( hot at all times ). Once you verify that the pump works and that the IN-Line fuse is sending power, there can only be 2 other possible culprits.... The ECM or the oil pressure switch. The oil pressure switch will cost about $25. Be sure it didn't get unplugged ! The ECM will cost ? depending on who's selling it !

http://berlinetta.info/help/88FuelPump.jpg



That diagram was taken directly from the 88 manual..... ALL engines used the same fuel pump wiring.

Hope that the diagram helps troubleshoot! !

 

Hey John - I have a related question.

I am changing my '88 305 from stock to carb'ed (and therefore changing the fuel pump from tank-internal to external). I'm trying to get power to the pump by re-routing the power that was going to the internal tank pump.

Looking at all the wiring diagrams, they all seem to make sense, but i have one problem:

Once I find the right wire, how do I get power to the pump if I am no longer using the ECM/computer? Will I still have to use a fuel pump relay?

Thanks in advance - much appreaciated!

 

I'm probably not the best person to ask to be honest - but I'll try ! (I always remove the in-tank pump and go to a block mounted pump when swapping to Carb ! )

MANY people simply run their external electric pump by a toggle switch. Even on regular TBI set-ups were something went wrong - most guys just stick a toggle switch on the dash to get around the defective part.

I "THINK" the stock ECM only sends power to the pump when the key is first turned to 'prime' the system. I THINK that once the car is running the Oil Pressure switch throws power to the fuel pump. I BELIEVE this was done so that the fuel pump only gets power if there is oil pressure ( the car is running )

If you use a toggle switch than at least be sure to splice into a "switched' power wire and not a "hot" wire. You would only want power to the fuel pump after turning the key ! Also be sure to check the TBI boards,.... I'm sure there must be many members using an electric pump to run their carb set-ups.

 

where is the (fuel pump switch )shown in the diagram I need a picture of what it looks like E-wire orange goes to fuel relay fuse another orange wire goes to (fuel pump switch )on the other side of fuel pump switch it tan/white which goes to pcm fuel control on my lt swap the pump is no turn on and I dont if there is a fuel pump switch thanks

 

Red:

I used my stock fuel pump relay, and the wires from the oil pressure sending unit. I ran a 12v+ hot-in-run wire to relay, a ground, and the orage and red wires from the OPSU. Turn key ojn, 12v+ energizes relay, connecting the orange and red OPSU wires to run the pump. No toggle to remember, as long as key is on pump runs. Make sense?

 

Ok the Relay are A=Tan/white goes to fuel pump B-black ground C- green/white goes to ? D- small orange wire E- larger Orange wire this is hot at all times I have this connect to fuel pump fuse from to lt1 hood fuse box in here third gen lt lx swap they say to splice a wire from relay to A7 fuel Pump control Red Pcm connector, is this the way you connected yours a hot to relay was this was this connected to E-Orange right ?your ground was B -black the OPSU go to D-Orange on relay and C-green/white this what I got for 86 fuel relay connector A tan/white B - black C- green/white D- small orange wire E larger Orange wire thank you for your help

 

Why didn't you leave stock setup in place and just run the new control wire to the relay.
That way you would still have the OP switch circuit as backup should the relay fail

 

Much easier to understand it you put some spaces in

Op switch wire does not go TO relay.
It is a common 12V power supply from battery to both relay and OP switch then to fuel pump
If you put 12V on the green / white wire the relay will operate

See the diagram above.
Green / white is the wire to the computer to operate the pump relay which is the one you are asking about (PCM fuel pump RELAY control )

Once again look at diagram.
Tan/white is power to pump and also connects to PCM .The PCM needs to see the pump is running before it will pulse the injectors.
( Actually it needs to see oil pressure above 4psi which is when the OP switch closes to run the pump so you could say OP switch is doing two jobs )
Have you got tan/ white connected to the right terminal on PCM
Fuel pump control ; not fuel pump relay control

 

A --tan/white goes to fuel pump and a tan/white also goes to fuel pump control on ECM
B2 would this go to Lt1 PCM A7 fuel pump control red connector

B -- blacl/white ground I ground mine on engine block

C-- green/white Ignition A1 on ecm would this go to PCM Connector B (BLACK) b-5 Igniton control ? on LT1 PCM

D to ALCL =dont what this is

E--Orange hot at all times
and thanks for your help