Crank, no start

[Rose820]

Hello all I am a new member and could use some help. Now to the vehicle, it’s a 2001 expedition 2wd 4.6 that I bought at a police auction. It was a police car, not a seize. 110k miles. When I first purchased it had the dreaded dashes on the odometer. After a month of sitting until I could work on it, the dashes eventually turned to numbers. I ended up replacing the fuel pump and it fired right up. I have been cleaning it up and it has ran fine the past month. Well, when I went to turn it on and take it for a final test drive, it began it’s initial symptoms again. Flashing theft light, dashes on odometer. Crank with no start. Weird thing is now, the fuel pump relay continuously clicks with the key on and there is no communication between the PCM and DLC.

The fuel pump relay has constant, steady power but from what I can see on the diagram, the PCM controls the ground switch. So I’m leaning toward a bad computer. But this still doesn’t explain the pats issue or no communication to the PCM. The DLC has power.

All fuses have been checked, relays swapped.

I am able to get a 5v reference at the TPS and 4.1v at the MAF.

Any ideas would be helpful. I’m pretty descent with automotive equipment but this has me at a loss.

 

[Rose820]

Forgot to mention, the dashes are gone but still flashing theft in the 1:6 sequence. I assume the PATS needs to be tackled first, then figure out why a scan tool doesn’t have communication, then figure out the fuel pump relay issue..

 

[stamp11127]

Welcome to the site.

How did you check the fuses? Going off memory, the pcm has 3 fuses.

Fuel pump relay: jump 30 to 87 in order to bypass the control circuit for that relay.

 

[Rose820]

I checked the fuses with a power probe. Here’s the weird issue, I checked the ground from the pcm to the relay which controls the pump on and off and it is sporadic.

 

[Rose820]

 

[stamp11127]

The pcm will provide a ground for 2-3 seconds to the fuel pump circuit. If the engine isn't running in that time it will open the circuit. Bypassing the relay will enable the fuel pump and provide fuel to the injectors. If it still doesn't start then it may be a lack of spark/ignition.

 

[Rose820]

Well I’m suspecting the PATS is a big issue with the theft light flashing and the no start. What you say makes sense. I’m not sure why the pcm would sporadically ground the relay. It’s a consistent open and close of the relay. It doesn’t stop unless the key is off.

 

[stamp11127]

The theft light will flash rapidly if there is an issue with the PATS, especially if it can't communicate with the pcm.

 

[Rose820]

Pulled the computer out and took a look on the inside. I believe this is the problem. Come to find out, someone trying to be helpful washed the engine compartment and I believe they didn’t unhook the battery.

 

[Rose820]