fried pcm, now fuel delivery prob

[scubajoe17]

I have a 2000 Escort zx2, the pcm fried due to a coolant leak. I replaced the pcm, and now have power to the fan, fuel injectors, ac, and the fuel pump. the fuel pump is not kicking on, so i checked the voltage to it. With the harness unplugged it reads at 12.4V, but then with the harness attached it only reads 2.3V. Can anyone tell me why this is?

[tripletdaddy]

Where are you probing? At the pcm connector or at the fuel pump connector? Try probing your wires to body ground than to each other if you haven't. So, when you have everything connected you don't get the pump to come on? You need to test for this voltage when you turn on the key, as it will only come on for a second if you haven't. You will need help to do that.

[scubajoe17]

Im probing at the fuel pump conection. i've done some more testing and found that the fuel pump has no pwer going to it and the fuel pump sending unit has the 12v down to the 2v reading. I have not checked the connetion at the pcm yet though, but the fuel pump fuse has power. I cannot find the fuel pump relay in the car, it's not on a ussual relay block. I have a haynes manual for it and it shows that the pcm and fuel pump relays are in the same assy. any ideas?

[scubajoe17]

THe pump hasn't come on at all unless I jumper wire it, and still I have a no start.

[tripletdaddy]

Did you replace the pcm or the ccrm. The latter has the fuel pump relay in it. If you have power at the pcm and the ccrm, then you need to check/reset your inertia switch. Supposedly that is the last thing in line to the fuel pump.

[scubajoe17]

What is the ccrm?

[tripletdaddy]

I now realize you may not have one. It is a constant control relay module found in earlier models. It consists of relays that control the fuel pump, the high speed fan control, the ac clutch control, and possibly others things as a single unit. Based on what I could research on your vehicle, you probably have individual relay modules for all of those circuits. Possibly your fuel pump relay is attached to the inside fuse block, but since you have a manual and hopefully your Owner's Manual, they should tell you. I have manuals for Taurus and Windstar of similar years, so I assume your Haynes has the same information on the PCM, fuel pump electrical system, etc that detail exactly how the electrical signals and supply voltage are operated and supplied and to troubleshoot it that I believe you would find very useful and more clear than I can type and paraphrase. Some was in fuel systems, electrical and emissions. In the electrical section , you can try and find your fuel system parts on the wiring diagrams and trace them in the order described in the fuel section and hopefully help.

Now you said you replaced the pcm. I saw it for over $150, does that sound like the same thing, so I know we are talking about the same thing?

Like I said, I found the fuel pump module is separate and only $10 (likewise for others). The ac controler is variably more expensive.

[scubajoe17]

I paid $200 for the pcm from ford. The haynes shows that the pcm power supply relay and fuel pump relay are located together on the wiring diagram but it does not show/tell where it accually is. The wiring system in these cars are a nightmare for me, I usually only work on old school stuff. I'm about to take it up the the dealer or drop a 350 in the dang thing. I'm pretty much stumped, well, sick of lookin at it is more like it! thanks for the advise. If you think of anything else please let me know. thanks again.

[tripletdaddy]

Did you follow what I previously suggested? I highly recommend reading the sections of the fuel chapter in your Haynes that covers the fuel pressure relief procedure to find the inertia switch and the section on fuel pump/fuel pressure check to locate the fuel relay and give you more information on how the fuel electrical sytem works. Yup, you sure did buy a pcm for that price and not a ccrm which I expect to be half as much. The good news is if you need a new fuel relay, they run about $10 at the parts stores and also is a common relay that you probably could swap around to see if it works and use one you know works in place of the fuel relay to test if it gets the fuel pump going. I worked on a fuel system on a friends blazer that a so so mechanic worked on but couldn't figure out the electrical on the fuel system, etc, etc. The relay was reliable maybe 90% of the time, so it was difficult to diagnose. Hang in there. If you were close, I'd give you a hand, or pay me what you'd pay the dealer. Good Luck