I'm Stumped

[Matthew T]

I have a 1998 Expy XLT 4.6l 4x4. I had a no start condition that was preceded by a rough idle and the truck dying while driving. I replaced the fuel pump, filter and relay. The truck started and ran fine for 10 min. yesterday. Today I started the truck and it ran for about a minute and died and now will not start. Any suggestions would be greatly appreciated...

 

[1955moose]

Lets assume the motors ok for now. The fact it ran for the 10 minutes is why. First thing, let's get a fuel pressure test. Key on engine off should show 28-35 psi, if it will fire up, running pressure is 35-45, and hold that pressure. Next pull one of the front sparkplug coils up, stick a sparkplug or spark plug tester, ground against engine. Have an assistant crank engine. Be sure nice blue spark. You can rent the fuel pressure tester from any major auto parts store. One last thing, switch the fuel pump relay with one next to it. My 2000 shorted it's out. Ran fine after switched.

Sent from my N9131 using Tapatalk

 

[Matthew T]

The fuel pump relay is new, and I have good spark. I checked this before I replaced the fuel pump.

 

[Machete]

Too vague. Does it turn over? Or is it dead?

 

[Matthew T]

I turns over, but will not start. I replaced the fuel pump, fuel filter and fuel pump relay. It started and ran yesterday for 10 min + on 2 occasions. today it started and died in about a minute and has gone back to the crank no start condition it had previous to the fuel pump, filter and relay replacement. I can't figure out why the repair seemed to work and then didn't.

 

[ExplorerTom]

Vacuum leak.
Idle Air Control valve
Battery/alternator
Check engine codes?

Just what comes to mind based on what you’ve given us.

 

[Matthew T]

No check engine codes. battery tested fine when I diagnosed this before the repair. IAC and vacuum leak do sound like possibilities. But why would this thing run fine right after I did the fuel pump replacement? It went from a crank no start to running and is now back to the crank no start condition.

 

[stamp11127]

What you "had" before the fuel pump replacement compared to what you currently "have" can be two different things. Either the fuel or spark have dropped out. Get the facts.
What is the fuel pressure before cranking?
Is there spark while cranking?
Can you connect to the pcm with a reader?

 

[gbosin]

On a different Ford of that era I had a similar condition. PCM relay was shorting and blowing the PCM fuse. Check your fuses?

 

[grantpa]

Based on the symptoms you gave us-it ran, but now it cranks with no start, let's assume that you have spark, HAD fuel, and it has air, I'd start with addressing the fuel angle.