2002 Explorer 4.6L dies when warm

[ab_slack]

Wish I had a wiring diagram for your rig--Does your 2002 have a relay, powering up the pcm/computer??--if so, replace it!! Almost sounds like your getting weird voltage, to the computer. I replaced a lot of these, and they caused really strange issues, some of which happened while the vehicle was running.--resistance in the relay,(or else where, if no relay) would trick the computer/make it think a restart had happened, when it didn't, and ect. Just a thought

Was away for awhile but back. After some thought I was thinking fuel pump cause of how it ran till turned off. Got myself a fuel pressure gauge, got some baseline info when running well.

Key on no crank it went ton 10 PSI
Key off then on, no crank went to 40 PSI
Key off then on, no crank went to 60 PSI
Key off then on, no crank no change, stayed at 60 PSI
Crank engine runs fine, holds 60 PSI
Stomp throttle drops to 55 PSI then back to 60 PSI within a second.

Went on my test loop, got problem to replicate.

Put pressure gauge on, showed 10 PSI when attached.
Key off then on, no crank no change, stayed at 10vPSI
Key off then on again, no crank no change, stayed at 10 PSI
Crank engine, runs very rough, pressure slowly drops stalls around 8 PSI
Came back up to 10 PSI after stalled

Hitting pressure release on gauge, goes to zero and the back to 10 PSI.

Not sure what holds the pressure. I let a small amount of fuel drain but came back although ignition off. Not sure how normal that is.

So thinking filter maybe but more likely pump cause filter shouldn't suddenly be a problem with a key off then restart. I can however see a pump off not restarting.

I am also wondering how it regulates pressure, if there could be a regulator problem or if there is a separate high pressure pump in addiiton to the main pump.

 

[acsnowrider]

you definitely have low fuel pressure--Original Pump in Tank??? They stop running while driving often!! If you can get the pressure to drop off again while the Pressure Gauge is on it, use a deadblow type hammer, thump, the bottom of the tank in the center area, see if the pump starts running again, and pressure comes back to 60LBS--This pressure usually indicates you have a "returnless" fuel system--Just check the number of fuel lines connected to the Fuel Rail-if one only, its returnless, and the pressure is controlled at the Fuel pump module/in the tank. The 5 LBS drop in pressure on throttle stomp, is normal. Hope this helps!

 

[ab_slack]

If you can get the pressure to drop off again while the Pressure Gauge is on it, use a deadblow type hammer, thump, the bottom of the tank in the center area, see if the pump starts running again, and pressure comes back to 60LBS

\This pressure usually indicates you have a "returnless" fuel system--Just check the number of fuel lines connected to the Fuel Rail-if one only, its returnless, and the pressure is controlled at the Fuel pump module/in the tank.

Thanks for diag tip. As I have researched fuel pressure regulator, I discovered what you said, that it is a single line system and that it has a fuel pressure stabilizer instead of a regulator.

After letting it cool down it started with pressure floating between 40 and 50 psi just sort of moving around then suddenly jumped up to 60 and was stable again.

Another reason for believing fuel pump is that I ran out of fuel the week before issues started to show up and they started to show when very low fuel.

I also believe I know why it came back up to 10 PSI. I am thinking that was caused by pressure build up in the tank from the warmer day. Does that make sense? Or maybe that indicates an issue with my vapor recovery system? I see to recall gas cap is supposed to hold pressure to some amount but allow air in.

It occurred to me that perhaps vacuum in the tank could cause problems, and have meant to do a check by popping off the fuel cap. I guess I can check that with the 10 PSI suspicion the same way. Just not so easy to replicate to try all the different things.

 

[acsnowrider]

Thanks for diag tip. As I have researched fuel pressure regulator, I discovered what you said, that it is a single line system and that it has a fuel pressure stabilizer instead of a regulator.

After letting it cool down it started with pressure floating between 40 and 50 psi just sort of moving around then suddenly jumped up to 60 and was stable again.

Another reason for believing fuel pump is that I ran out of fuel the week before issues started to show up and they started to show when very low fuel.

I also believe I know why it came back up to 10 PSI. I am thinking that was caused by pressure build up in the tank from the warmer day. Does that make sense? Or maybe that indicates an issue with my vapor recovery system? I see to recall gas cap is supposed to hold pressure to some amount but allow air in.

{Yes, you get residual pressure readings at the engine, from tank pressures!!!}

It occurred to me that perhaps vacuum in the tank could cause problems, and have meant to do a check by popping off the fuel cap. I guess I can check that with the 10 PSI suspicion the same way. Just not so easy to replicate to try all the different things.

If you conclude the fuel pump is fault, need to verify voltage is stable/not dropping to the pump. And if replacing the pump, install a "module/assy"--Do not go cheap here!! seen lots of people try to replace just the pump, splicing it in to the fuel lines--splice is "in the tank", and the clamps on the fuel hose, cut into the lines over time, causing a high pressure fuel leak, in the tank! USE A MODULE!



I had good luck, with this one aftermarket brand--AIRTEX

https://www.ebay.com/p/76360298

 

[ab_slack]

An update on this. Turns out to be a fuel problem. Pretty obvious when I was able to get a pressure gauge on it. I opted to replace both the filter and pump as I only had time to deal with it once. Either could have been causing it.