Code PO208, fuel pump/ground/wiring?

Hi,

Could you double-check that code? A P0208 is an injector voltage issue on cylinder 8, which we don't have.

As far as the fuel pump issue is concerned, you shouldn't have power to the gray wire with the relay removed. If you do, we have a short to power.

I attached a pic below of the relay circuit. The arrows I included (sorry they are sloppy) show the power flow.

The PCM provided power to the primary side of the relay (either pin 85 or 86) which travels to a ground. When that happens, an electromagnet in the relay closes the secondary side allowing power to travel from fuse 39 in the under-hood fuse box to the gray wire you mentioned. The secondary side of the relay will include pins 30 and 87. The pins are identified on the relay itself. See pic below.

Also, let me know if what I just described is happening.

Take care,

joe

See pic below.

Thank you for the reply. The code is PO230. I have been fighting this thing for 3 weeks now with web searches. I am going to try and upload images. All images are key off. relay socket is with ground connected. Thank you for all your help. Please let me know if you need any other pictures or tests to perform.

Hi,

I need to know which connector post in the relay plugs into each connector pin in the box.
I noticed that three of the connector pins in the box show 0v. Did you test this with the key on?

Also, I attached diagnostics for the code you provided. Take a look through them and let me know if you are comfortable performing them.

Let me know.

Joe

See pics below.

Thank you, Joe.
I will try the diagnostics you supplied tomorrow.
I will post my results. I hope this will be the start of the solution.

Hi Joe.
Have not been able to complete diagnostics until now.
Battery charged and holding 13.7 volts

As per Circuit/system testing.
Ignition off-tested ground circuit and ground---5 ohms
tested with test lamp between control circuit and ground circuit-- nothing.
(relay just clicked)
fuel pump relay is new delco.
responds the same as the old relay

Component testing
85 to 86 terminals--106.7 ohms
30 to 86--0 ohms
30 to 87-- 0 ohms
30 to 85-- 0 ohms
85 to 87 -- 0 ohms

connected jumper wire from positive terminal to 85 and jumper from negative terminal to 86. tested 30 to 87--0 ohms.

relay terminals on relay corresponding to relay

front of engine===== 86 87
30 85

hope that helps with pictures provided

For testing I made 4 small jumpers to fit in fuse block and relay. connected jumpers from 86 which is power supply. connected jumper from terminal 87 to fuse block. jumper from 30 ground side to relay. 85 jumper to fuel pump. relay reacts the same, switched jumper from 30 to 85 and fuse block and ran ground back to fuel pump. same results.

also completed with ecm connected key on
front of engine.
86--12.39 volts 87-- .010 volts
30--.009 volts 85-- .040 volts

ecm disconnected key on

86-- 12.25 volts 87--.000 volts
30-- .008 volts 85-- .002 volts

if I jump 86 and 85 pump runs produces 60 PSI runs at 55 PSI.

have new flashed ECM to my VIN# and new fuel pump new relay.

ready to run toggle switch.

Thank you.

Hi,

Either pin 85 or 86 has to provide a ground path to complete the circuit. Have you checked if the PCM is providing the ground path? I ask because when you jump 85 and 86, it runs.

Let me know.

Joe

Hi Joe,

If I jump 30 and 86 the fuel pumps works.
I ran an ohms test today.
Front of vehicle
85 87
30 86

relay in, ignition off
pin 30----00.0
pin 86----.212

relay in, ignition on
pin 30----42.8
pin 86----.222

relay out, ignition off
pin 30---00.0
pin 86---1.4

relay out, ignition on,
pin 30----42.8
pin 86----25.9

pin 85 is constant power.
pin 87 is from ECM.

sorry about the pin sequence above.

As above I ran a separate wire from relay from pin 86 to fuel pump and a separate wire from
pin 30 to ground cable on battery. Relay makes contact as sone as I attach jumper to pin 86.

Thank you,
Mike

Sorry again, jumping pins 85 to 86 engages fuel pump.

Pins 85 and 86 are both for the primary side of the relay. If jumping them (with the relay in) turns the pump on, there must be a problem with the relay. You indicate pin 85 has constant power. It should only have power with the key on. Then, when the PCM provides a ground path to pin 86, that completes the primary side, and an electromagnet closes the secondary side allowing power to run from the fuel pump fuse to the pump.

If you have to jump 85 and 86, that tells me the ground is present and power is present but the electromagnet in the relay isn't closing the secondary side. For that to happen, I would say the relay is no good.

Let me know.

Joe

Hi Joe,

Now have 3 relays, original one for fuel pump, 2753 relay I purchased new, took headlamp relay which is a 2753. pump will run when I jump 85 to 86 whether the relay is in or not. (All three relays respond the same) Made jumper wires to connect fuse block to relay pins. I can connect all pins but pin 86. All relays respond the same, contacts are open until I connect pin 86 the contacts close. All 3 relays respond the same. Even if I run a wire from pin 86 back to fuel pump positive feed and cut OEM wire and attach jumper wire.

It acts like there is a back feed through the harness on the positive side, but I cannot locate it. Does the power wire to the pump happen to return somehow? I also noticed that the vapor canister underneath in front of the fuel tank has 12 volts constantly on 1 side and 5-volt output on other side of connector.

Thank you.
Confused and frustrated

Hi,

Something isn't right. Pins 85 and 86 should not turn the pump on with the relay out. Have you followed the wiring to the tank?

What color wires have power at the canister? Do they have power with the key off?

Let me know.

Joe

Hi Joe,
Added some pictures.
First is relay compressor clutch. has power to terminal 85 with key off. relay contacts close when installed and gets hot.
2nd picture shows voltage to compressor clutch relay pin 85, key off.
3rd is picture of jumpers for fuel pump relay. As stated above, if I connect and disconnect pin 86 relay contacts disengage and engage again when connected. No response from fuel pump.
4th picture is the terminal that plugs into vapor canister under car. showing constant voltage on the red or pinkish wire with key off. If I connect it, 5 volts measured on white wire.
Thanks, Mike

Hi,

Okay, that makes sense. It sounds like the relay is working as it should. If it is getting hot, then we have too much resistance at some point, a short, or the fuel pump itself is faulty.

When you checked the circuit in the diagnostics, did everything test good?

Let me know.

joe

I completed the diagnostics you sent me, and everything checks out.
I have removed all the trim from the right side of the vehicle interior and checked the wiring harness inside and outside and under the hood. I can't locate any bare wires. I removed the 1/4 trim and cleaned and checked the ground wires.
As explained prior I have a new flashed ECM that responds the same as my old ECM in all respects to the problem. All systems are the same with ECM connected or disconnected. I have a new fuel pump assembly that responds the same. I have ran a wire directly from the relay pin to the fuel pumps and a ground wire from the battery to the fuel pumps and with the same results.( fuel pump hot wire and ground wire cut in harness near fuel pump and new wires spliced in) I have removed the protective sleeve from the wires under the hood and rear harness where it exits the body. no visual damage to wires.

Thanks
Mike

Hi Mike, something is causing it to get hot. It could even be under the wire insulation where there is a break or damage. Other than that, it could be the connection at the relay box.

Have you tried running a new test wire from the box to the pump? Please bear with me. Not being there makes this more difficult.

Let me know.

Joe

Thank you for all your replies and suggestions.
I went out this morning to a local salvage yard and purchased a under-hood fuse box.
installed and all is working as it should. Ran scanner and no codes present.

Mike

Hi,

Excellent!!! Thank you for the update and good news. I needed it. LOL It was the box itself causing the resistance. I was questioning that, but wanted to have you run a new wire and see if it changed anything before making the suggestion to replace it.

Regardless, I'm glad you resolved the issue and appreciate you letting me know.

Take care and feel free to come back anytime in the future.

Joe