87 E-150 w 4.9l C6

Mystery black/brown relay...?

Went into the store about three weeks ago, came out and van wouldn't start... Had fuel, spark, and it cranked, but wouldn't fire.

Today i actually started tearing into it. Determined that the fuel pump was faulty cause i pulled the line off the front of the frame mounted one and cranked, no gas. Pulled the line off the back and it dribbled constantly as if being siphoned from the full tank it has. Bought new fuel pump.

Just before installation, check the wires at the pump- was getting no voltage. Traced the red and black wires from the pump plug to two black wires- one connects directly to the negative terminal on teh battery, the other disappears into the wireing harness.

Using the continuity tester i think i found the other black wire (which turned into a black and white wire...) ending in a black and brown relay, located under the dash by other relays and the computer. Don't think it is the fuel pump relay as i think i've already replaced that one and remember it being green, plus the one they showed me at the parts store had an extra pin.

Any ideas on what this black/brown stock relay is called so i can get a new one?

 

EEC Power Relay.
And no the fuel pump wire does not go to it.
The fuel pump wire goes to the Inertia switch and then to the fuel pump relay and then to a fuse link at the starter solenoid.

/

 

Thank you for the reply.

I just got home after finding out what you just mentioned, i was chasing the wrong wire...

So now i'm back to square one- no voltage at the frame mounted fuel pump. The wires into the inertia switch have voltage, so am assuming that switch is good. The relay clicks on and off, so assume that is good (been replaced before)?

And why the color change? There is a redish wire, and a solid black wire on the fuel pump, that plugs into a connector that turns both into solid black wires. At the inertia switch, there is neither black nor redish, think one is orange and blue, and not sure the other...

 

Try pushing the button on top of the inertia switch.
I have not heard of anybody reporting the colors that you have and they do go along with the shop manuals but it should be wired like the diagram above irregardless of the wire colors.

 

That looks about right, although my inertia switch is on the passenger side. I clicked the button a dozen times, what exactly is it supposed to do? The grey button on top of mine pushed down, clicks kinda, but pops right back up, did the same even when it ran. Plus i had voltage between the wires while priming, and cranking...

 

You should not have voltage between the wires, if you do the switch is open (bad).
You should have voltage from each of the wires to ground with a test light, a meter will not work good here.

 

Ahh, well that makes a lot more sense now. So is there a way to bypass the switch to see if it is that?

I was under the impression that when it was tripped, it killed the link between the two wires, but it's backwards from that? Shouldn't i be able to simply unplug it and it should start, if that is in fact the problem? Cause i think i tried that with no luck...

Thanks again for all the input subford.

 

You could short the two wires together.
No you were right, it will open the circuit when tripped an kill the pumps. No that will kill the pumps.

 

Alright, well i will give all this a shot tomorrow between classes. Thanks again, will update.

 

Well, i put my mulitmeter upto the inertia switch. Got continuity, and had about 3 ohms. Tripped it, no continuity, no Ohms. Reset it, continuity and about 5 ohms.

I am assuming that means it's good? If so, back to square one...

Would there be anything wrong with running a hot wire and toggle for the external pump? I'm about to that point... However if the external one isn't getting any power, don't know if the internal one is, haven't had a chance to drop the tank to see.

 

Do you have power at the inertia switch?
If not then it could be the Fuel pump relay or the fuse link.
You need to check for power at the fuel pump relay also.

If you go to the toggle switch wire it through the inertia switch.
Also the pumps will run all the time the switch is on and could be a fire hazard.

 

Power at the inertia switch, but not at the pump. Which wire should i test for power at the relay, a red one? Wish i could cart the computer to where the van sits...

 

At the fuel pump relay it would be the Yellow wire feeding the relay. The Red one is coming from the EEC Power relay to the coil of the fuel pump relay. The EEC computer grounds the coil of the fuel pump relay to send the power from the yellow wire to the Pink wire with a black tracer.

But if you have power at the inertia switch you do not have to check the relays anyway.

Sounds like you have a bad wire from the inertia switch to the Hi-Pressure fuel pump on the frame.

 

The intertial switch opens up on a hard impact, a collision, to shut off fuel flow.

On mine the wiring harness plug going to the inertial switch got loose, heated up, and melted.

Honestly? I just wired past the useless thing. Cut off the damaged plug and wire-nutted the two wires together.

 

I had tried jumping the two wires on the inertia switch plug, and i was still not getting power to the pump. Concluded that there is a break in a wire somewhere in the loom from the inertia switch to the pump...

For now i have (not the smartest) a hot wire to the fuel pump with a toggle just to get it going. Plan on running it through the fuse panel so i don't have to keep turning it off. Both of which are a quick fix till i can have time to tear into the loom...