What should fuel pressure be on a 2001 sohc 4.0l?

[cowboycowboy91]

I had to fix the rear timing chain cassette on my 4.0l and now have issues. I got it all reassembled and started it and it idled perfect, but stumbles bad when I apply throttle. I took the valve covers back off and put it back on tdc and confirmed my cam timing hadn't moved, and it still looked spot on. So, I reassembled it and let it idle for an hour or so and no change. I tested compression and had 155 to 160psi on all 6 cylinders. I tested the fuel pressure next and I am only at 25 - 27 psi. The only code that popped up is bank 1 too lean. I got a fuel filter and will install it tommorow. It should be noted that I don't trust my fuel pressure tester. I had a good old one, but lost the rubber o ring and it leaked like old faithful. So, like an idiot, I went to harbor freight and bought a Maddox brand. It wouldn't even read if I screwed it onto the Schrader valve all the way. I had to leave it slightly loose. Harbor Freight.... So, take that into consideration here.
Also, I may have a vacuum leak. I keep thinking I hear it sucking air around the upper plenum. I did have all the hoses off, so I triple checked every connection and don't see anything off or out of place. What reading should I have on a vacuum gauge? Or should I smoke test it?

 

[alwaysFlOoReD]

Fuel pressure should be ~65psi.

 

[cowboycowboy91]

Fuel pressure should be ~65psi.

Ok, that may be my issue then. I am not even close to that. It just puzzles me how it happened right after I did all the other work. I didn't touch anything to affect fuel pressure...maybe it is just a coincidence.

 

[cowboycowboy91]

Well, I changed the fuel filter and it didn't change the pressure readings, but it did make it run a fuzz better. Is there anything else on the fuel system that will cause this? Does it regulate and return through the filter? It has 2 hoses in and one out. I can't get over the fact that it started doing it right after I did the timing cassette. I had the engine pulled and the single fuel line connector loose. I also had the ecm main harness loose...maybe it is an electrical issue? Does the pump regulator work through the ecm? Anyways, I am really not wanting to do a fuel pump on it. It holds steady at 27. Under heavy load it may drop to 25 psi....am I pulling a pump on this one?

 

[cowboycowboy91]

It looks like pins 12 and 40 on the pcm control fuel pump actions. I don't know if that has anything to do with it.

 

[cowboycowboy91]

Forget anything electrical. The return line in the tank has an old school regulator that maintains the steady pressure. It's in the sending unit return side. I also read that the fuel damper diaphram will collapse and restrict fuel flow causing low pressure. So, I need to measure the pressure before the damper to see if it reads 65. If not, then I will have to get a pump assembly. I can't find the return regulator sold individually. I am just keeping this post updated as much as I can in case someone else needs info later. Thanks guys.
Edit- seeing where the fuel damper is located (on the back of left fuel rail), I don't see how it would ever cause a low pressure issue. Maybe just wild fluctuations in pressure though.

 

[cowboycowboy91]

Changed the fuel pump and it fixed it. I guess it was just a coincidence that my pump went out at the same time as the other work. Anyways, it was just a weak pump.