03 Crank no start

[jhoney]

After replacing the ECU, the truck fired up almost immediately. However, shortly after died and now has a crank no start. I have spark compression and fuel and the mass air flow meter changes when I floor it so I know it's working. Any thoughts?

 

[whtbronco]

If you have spark, compression and fuel along with it turning over it kinda has to be a timing issue.

 

[jhoney]

But it fired on first start and Timing chain is new.

 

[whtbronco]

Could still be an issue with the crank or cam position sensor. Do you have FORScan or something else that can really look at data?

 

[jhoney]

I do have a scan tool and crank and cam position sense are new.

 

[whtbronco]

Are you certain you have fuel pressure? If the fuel pump or the relay failed it may have enough pressure to start and run at idle for a bit, but would die and then not restart.

I'm not referring to just a code reader, you are likely to need something to look at the data streams.

Since it's cranking it shouldn't be the PATS.

My only other thought is to check fuses and relays.

 

[jhoney]

I have 57 lbs and I can read pods with my scan tool. I'm leaning towards the fuse junction box but not sure how to diagnose that.

 

[whtbronco]

That's certainly enough fuel pressure.

The central junction box(fuse box) is pretty much a simple PC board. You can check for continuity, look for burned fuses and relays and not much else. Well you could run a voltage drop test on each circuit as well.

 

[Hamfisted]

Check the PCM relay there in the fusebox. The top right relay. See if there's melted plastic on the relay, or the socket it plugs into. You can swap those top three relays around to test with another one. Do you have a noid light you can test the coil plugs with ? Just to confirm you're getting a spark signal . Or pull the coil off the plug and stick an old sparkplug in the coil boot and test it like an old lawn mower plug. Your security LED isn't rapid flashing right ? Do you have any starter fluid you can spray into the throttle body while you try to start it ?