Fuel Pressure (and other) problems

[lloydfarmer]

First time poster, so I hope it's in the right place. I bought a 2000 v8 Mountaineer, and I’ve been going through some maintenance but have a problem I can’t quite find the answer to. I’ve been searching and using these forums to perform the work I’ve already done because I’m pretty new to this and trying to learn. I want to thank any of you who have posted “how to’s” because they have already helped me do things I never thought I could do.

My main issue right now is that I have to crank the engine for several seconds (4 or more) before the Mounty will start. The shop (one I normally trust) told me it was the check valve on the fuel pump. I put in a new Delphi fuel pump, assembly and filter, and it didn't fix the problem. If I do a key on/engine off about 4 times to build up pressure it will generally start right up.

Other issues:

The idle begins loping after about a minute when cold, continues up and down for a couple minutes, then settles and runs and idles fine after it warms and I start driving. There is a tapping noise that starts about a minute after start up that seems to come from the top of the engine but I haven’t put a stethoscope on it yet. The tapping quiets to where I don’t notice it at idle after the car warms up. Once running, the car seems to run great, no noticeable issues. The check engine light is on and Autozone pulled two lean codes, one for each bank.

Work done:

I have put in the new fuel pump, pump assembly and filter (Delphi). I have replaced the fuel filter. I have changed the oil (Mobile 1 full synthetic 5w-30) and oil filter (Motorcraft). I have replaced the spark plugs (Autolight dbl plat.) and the wires (Motorcraft). I’ve cleaned the MAF and IRC (both with MAF cleaner). I put on a new ERG tube because there was a crack in the old one. I seafoamed the engine through the PCV and replaced the PCV (Motorcraft). I have run two cycles of Seafoam through the gas tank. I've done a compression check and it came out ok (over 100 and all within 13 of each other.

I did a fuel pressure test today three times to be sure and got the same results: 0psi on the first key on/engine off. This rose slowly and progressively to around 20psi by the fourth key on/ engine off. Start it up and pressure jumps to 58psi and stays there—doesn’t budge. When I cut the engine off, the pressure plummets and is below 10psi in about 40 seconds. It’s at 0psi soon after. I can’t see any noticeable leaks around the injectors (the six I can see) or the fuel lines. I don’t smell gas anywhere.

Amongst the other issues, does anybody know what other than a fuel pump might cause the fuel pressure to be low at key on/ engine off, good while running, and instantly lose pressure after shutting down the engine?

Any help, ideas or experience with this would be much appreciated.

 

[koda2000]

general information: the 2000 model has a return-less fuel system. the fuel pressure regulator is part of the in-tank fuel pump assembly (which you stated you replaced). the fuel pressure at the fuel rail should be around 65 psi, you indicated you're getting 58 psi which is pretty close. when you turn the engine off, the fuel pressure should not drop as quickly as you say yours is doing. the 2000 model uses a fuel pressure damper, the purpose of which is to prevent pressure spikes and dips.

you state that you can get the engine to start if you cycle the ignition key around 4 times. doing this causes the fuel pump to prime the system, which shouldn't be necessary except when you do something that causes the fuel to drain from the fuel line.

if you hadn't already replaced the fuel pressure regulator (FPR), I'd think that was causing the problem. I don't believe the damper would cause the symptoms you're experiencing.

maybe someone else will post their opinion, but other than perhaps a defective FPR I'm stumped.

as for the ticking noise that lessens once the engine gets hot, the 5.0's tend to suffer from exhaust manifold cracks. it sounds like you may have a small crack that closes once the cast iron heats up and expands.

as far as the loping when cold, it might be a bad coolant temp sensor... ?

 

[lloydfarmer]

Thanks for the fast reply, Koda2000. I've read quite a bit from you before, and you've helped me get a better understanding of my new vehicle and to go through some test and maintenance. This is my first Mountaineer/Explorer, and I can't wait to get it running right so I can put some 31" on it and post a pic. I'm really liking driving it, but this starting issue has me stumped.

 

[drdoom]

Maybe a leaking injector?

 

[koda2000]

Thanks for the fast reply, Koda2000. I've read quite a bit from you before, and you've helped me get a better understanding of my new vehicle and to go through some test and maintenance. This is my first Mountaineer/Explorer, and I can't wait to get it running right so I can put some 31" on it and post a pic. I'm really liking driving it, but this starting issue has me stumped.

my 2001 Eddie Bauer, kind of has a similar problem, which I haven't figured out yet. it will always start immediately when cold, but after sitting hot for 30-45 mins it cranks for about 4 seconds before it will start. it runs perfectly otherwise. I find if I turn the key ON and just wait until the seatbelt reminder chime stops (about 5 secs) it then seems to start ok. it's been this way since I got it 2 years ago.... ??? I'm sure it's fuel related.

 

[imp]

Maybe a leaking injector?

Would that not cause rich mixture, which would generate a trouble code and CEL? imp

 

[lloydfarmer]

That's part of what has me stumped. From what I've read, a leaking injector would cause a rich mixture and put gas in the oil. I'm getting lean codes and no signs (or smells) of gas in the oil. Logic tells me that it can't be just a clog because that wouldn't explain the loss of pressure as soon as the engine is turned off, at least I think so. So, the system has to be loosing pressure somewhere, right? Unless I got a new fuel pump with a bad check valve, which seems unlikely to me, I would have to have a leak somewhere, I believe. But, it's not showing the signs of one anywhere.

Does anyone know of any way to test the system for pressure leaks?

Thanks for the replies, so far.