My '02 F150 with the 5.4 just recently started taking longer to start. It used to take about 1 second of cranking to start, it now takes about 4-5. It all started after I disconnected the battery when checking and adding water to it. I know it is not related to that, but just a weird coincidence.
If I turn the key on and wait 3-4 seconds, it starts immediately. It runs and idles fine, no black smoke on startup, no codes, drives just fine, no difference with engine hot or cold. Everything I read was leading to 4 things, fuel pressure regulator, leaking fuel injector, bad check valve or dying fuel pump. I figured I would start with the easiest and most likely culprit and replaced the pressure regulator. No change after replacement (I know, don't throw money at it till I have done the correct tests). So that leaves leaky injector (least likely I think), bad check valve (most likely) or bad pump (kind of likely). I did replace the fuel filter about 10,000 miles ago, so I don't think that is it.
I finally got a hold of a fuel pressure tester (AutoZone rents them, but forgot my wallet when I was by one, they let me use it in the parking lot).
It was at 10 PSI when I hooked it up (truck was off for about 15 minutes).
Turn the key on, still at 10 PSI, but after waiting 3-4 seconds (with it still at 10 PSI) it starts right up, pressure goes up to 34 or so for a second then levels off around 29. I know that is in spec (28-40 PSI is normal from what I have read), but at the low end. I disconnect the vacuum line to the pressure regulator with the engine running and it goes up to almost 40, so I know the regulator is good (duh, I just replaced it).
I turn the engine off, pressure drops from 29 to 20 in about 15 seconds, then seems to stay there for a few minutes and then very slowly drops down to 10. And it is back to where it started.
I forgot to check if pressure would build up with 2-3 key cycles.
So how can I differentiate between fuel injector, check valve or actual pump problem? I guess it really does not matter if it is the pump or check valve, both require dropping the tank to change, although there are pump replacement kits out there for around $60 vs the $170-250 for an entire quality pump assembly (but have not seen a check valve replacement). Seems I read about turning the key to on, clamping off the fuel lines and watching the pressure. If it drops, it is a leaking injector, if it stays, it is the check valve. I know I could pull the plugs and see if they are wet, but anyone that has the 2v modular motor knows what a pain that is.
If it is just a bad check valve, I can live with that and will let it be, just turn the key on for a few seconds before it starts. If it is a fuel pump issue or fuel injector, I really need to get it taken care of.
Any ideas or comments?
If I turn the key on and wait 3-4 seconds, it starts immediately. It runs and idles fine, no black smoke on startup, no codes, drives just fine, no difference with engine hot or cold. Everything I read was leading to 4 things, fuel pressure regulator, leaking fuel injector, bad check valve or dying fuel pump. I figured I would start with the easiest and most likely culprit and replaced the pressure regulator. No change after replacement (I know, don't throw money at it till I have done the correct tests). So that leaves leaky injector (least likely I think), bad check valve (most likely) or bad pump (kind of likely). I did replace the fuel filter about 10,000 miles ago, so I don't think that is it.
I finally got a hold of a fuel pressure tester (AutoZone rents them, but forgot my wallet when I was by one, they let me use it in the parking lot).
It was at 10 PSI when I hooked it up (truck was off for about 15 minutes).
Turn the key on, still at 10 PSI, but after waiting 3-4 seconds (with it still at 10 PSI) it starts right up, pressure goes up to 34 or so for a second then levels off around 29. I know that is in spec (28-40 PSI is normal from what I have read), but at the low end. I disconnect the vacuum line to the pressure regulator with the engine running and it goes up to almost 40, so I know the regulator is good (duh, I just replaced it).
I turn the engine off, pressure drops from 29 to 20 in about 15 seconds, then seems to stay there for a few minutes and then very slowly drops down to 10. And it is back to where it started.
I forgot to check if pressure would build up with 2-3 key cycles.
So how can I differentiate between fuel injector, check valve or actual pump problem? I guess it really does not matter if it is the pump or check valve, both require dropping the tank to change, although there are pump replacement kits out there for around $60 vs the $170-250 for an entire quality pump assembly (but have not seen a check valve replacement). Seems I read about turning the key to on, clamping off the fuel lines and watching the pressure. If it drops, it is a leaking injector, if it stays, it is the check valve. I know I could pull the plugs and see if they are wet, but anyone that has the 2v modular motor knows what a pain that is.
If it is just a bad check valve, I can live with that and will let it be, just turn the key on for a few seconds before it starts. If it is a fuel pump issue or fuel injector, I really need to get it taken care of.
Any ideas or comments?