On a '97 F150 w/ 5.4 the fuel pump relay is getting the proper power, as in none.

The 30 terminal is getting battery voltage when the key is on, which is the fused side in the power distrib box.

Is there a way to check on the other wires... according to the diagram they look like they go to the PCM and what not.

The main power wire coming off the Starter realy is fine also.

I'm going to check the PCM power distro box and see if anything is screwed there. Anything obvious to look for?

 

wanted to add i checked the fuse for PCM also on the smaller fuse panel (engine something one IIRC its was called) and it was good.

My friend told me it puked as they went over a bridge and i'm wondering since the wires that aren't getting power for fuel pump relay are going to the pcm is if a wire there broke. But i also don't know where the pcm is

 

The pcm is under the dash on the passenger side. Its on the sidewall above the kickpanel. The wires going into the pcm are behind the battery.

 

I'm not sure I understand what you got but here is some info.
Power comes thru fuse 19 to the pump relay then to the inertia switch then to the pump.
Try resetting the inertia switch before you tear anything apart.
It's above the PCM at the top of the kick panel.
May have tripped it trying to fly over the bridge.

 

the proper power is getting to the fuel pump relay. Power is coming from fuse 19 when keyed on. The 85 & 86 terms on the fuel pump relay aren't getting anything from the PCM.

The inertia switch is further down the line and not even effecting the prob, btw it was the first thing i checked when i went to give them a ride.

 

You probably need to back up and see if the PCM power relay is working. Quick check: Does the CEL come on when the ignition switch is first switched to RUN from OFF? If not, go to the last paragraph......

If not, you're troubleshooting the tail of the problem instead of the head. Since you don't have any power on the FP relay coil terms, I suspect this is the case.

How it works:

Key to RUN or start. PCM power relay energized via BJB F16. BJB F24 supplies C (30) term on PCM Power relay. When relay energizes, power is supplied to the PCM other places, and importantly, the 86 term (high side of coil) on the fuel pump relay.

The PCM, as part of it's boot-up cycle, grounds the 85 term (low side of coil) for two seconds. This switches the ALWAYS HOT power (via BJB F 19) on the 30 term to the 87 term and supplies the interia switch which supplies the fuel pump.

The fuel pump is only turned on for these two seconds until the PCM detects an accelerating crank signal during startup attempt.

If you need an electrical diagram, PM your email address and I'll send you a pdf file of the circuit.

Personally, I suspect you'll find that BJB F24 is blown. If so, you probably have an O2 sensor harness melted onto an exhaust component.

Steve

 

Dup. after edit.

 

Explanation for info:
When the ignition is turned on, this causes the PCM to put out a ground for about 2 seconds then opens up until the engine is cranked. At this point the crank position sensor signals the PCM as well as the cam position sensor and causes the PCM to re-ground the lead to the fuel pump relay for starting.
Are you sure you still have a problem with these actions as given?

 

I have a good diagram but thanks for the offer. What are you meaning by BJB before your fuse numbers? Are you reffering to the Power Distro Box?

Good guess on the CEL light, its not coming on with the Key. F24 in the Power Distro Box isn't blown though


Just was looking at things, not look like the o2's are melted but it is hard to tell. FOund one fuse that was blown and the was the F30 under the dash and in the owners manual says that is for PCM power also, so far no luck with replacing it as i still don't have a CEL key on

 

Yeah, BJB is the underhood box. Wrong terminology on my part, confused with my Contour's terminology. I should have referred to it as the PDB (Power Distribution Box).


I noticed another mistake in my analysis above. I referred to BJB F16 as suppyling the PCM power relay. Should have read PDB F30, the exact one you said you found blown. I mistakenly substituted a connector pin number for the fuse reference designator.

A blown F30 would account for all your syptoms. If it blows again upon replacement, disconnect the RFI caps (there's one on each bank). There have been several reports of them shorting and killing the entire engine management system, exactly as you have described.

Steve

 

i thought underhood is 16 and under dash, the one i found, is 30?

Yea it is blowing upon key on power

 

Disconnect the RFI caps and see if the short circuit goes away.

Steve

 

k, i'm going to look, hopefully they are easy to find

So I'm guessing they are the little black things with a single wire going to them, mounted on the front of the heads?

If so i unpluggled one on each side and it still blew the fuse upon the key being on for a few seconds......hopefully i jsut unplugged the wrong thing

 

Per the factory EVTM, PDB Fuse F30 feeds the following: PCM Power Diode which then feeds the coil of the PCM Power Relay) , COPS 1-8, RFI caps (one on each bank).

Disconnect them all and see if you have shorted component or a wiring harness that has chafed and has shorted out to ground.

Yeah, that describes the RFI caps....

Time for a meter or test lamp, fuses have to be getting expensive....

Steve

 

I removed the diode from the Power Distro Box, still blew. I measured the resistences on each side where the diode connects and its around 8ohms which seems to high to be a short.

The RFI wires going back to the harness also had some resistance, higher than what i would expect for a short.

So I'm assuming the COPS are the coils, thats the last thing i need to disconnect to check on it. Thanks for the help