Fuel pressure loss

[Mark Price 2]

Hey All, having an issue on first start of the day. Even after an hour sometimes. Getting worse as the months go by. It takes 2-3 attempts to start. When I prime the fuel pump 2-3 times first(KOEO), it starts no problem. No drive-ability issues.



I finally got around to hooking the fuel pressure gauge up. Here's what I found. KOEO jumps right up to 60+psi then quickly drops to approx30psi then slowly to 8psi and holds there. Runs steady at64psi. Turn key off after running-drops just the same.



IIRC, is this because there is a check valve in the fuel pump assembly that went bad? If so, I guess it's time to order a new assembly. Or, leaky injectors?Seems to much of a drop though and no initial high idle at start up. I couldn't locate a fuel pressure regulator. Is there one? Any other checks I should do before ordering a new assembly?

Anyway, just looking for direction for my next step. I believe I will be fine and not breakdown until I can fix this. Correct?? ...I'm not too concerned with doing a fuel volume test at this point. I don't know the spec for it anyway. I would do a current ramp test on the pump but I don't own a scope. Not too concerned with that either. It runs fine. No sputtering or loss of power. I cant read the fuel trims either. Decent scanner is on the X-Mas list.



Here's a video I did doing the check. (Pardon when I say PVC. I meant PCV.) It's unbearably hot outside today and it's my first video EVER. I was a little nervous. I'm not much of a talker in general. Especially to myself

Thanks.



Youtube videosorry it's about 8min): see below



Fuel assembly thinking of getting from rockauto: AIRTEX Part # E2444M $169 5-pin connector according to my wiring diagram. I Hope that's correct.



I cant afford the Motorcraft and it's not so clear in the description which one is correct. Guess I can call. There is also Spectra. I've used there rads many times before without issue. But, not so sure of their pumps. If someone can convince me to hold off and save for the Motorcraft unit.(double the $) I will do so.

 

[Mickey Luis]

I have an '03 Sport with the same 4.0 engine. I just went thru some fuel injector rail problems recently. On the drivers side hidden on the very end underneath the ignition coil pack bracket is a fuel rail damper. It's silver and about the size of a toy "C" battery. It's not a fuel pressure regulator on your '03 but a "damper" to smooth out the fuel rail pulses. It also is vacuum controlled like a regular fuel pressure sensor and has a rubber hose attached. Just like the FPS it can leak internally and allow fuel to escape into the intake and a lost of fuel pressure. I would check this fuel damper first by removing the rubber hose attached. If fuel leaks out, that is a sure sign it is bad and leaking internally. If no apparent leaks then try a vacuum tester to see if the fuel damper holds pressure.



Before I would condemn the fuel pump, I would disconnect the single gas line in front of the fuel filter. Using some rubber fuel line (plus clamps) on the end and making some type of fitting to connect your fuel pressure gauge, I then would check to make sure that the fuel pressure was still dropping. This would be more insurance the fuel pump check valve is working or not.

By the way that little fuel rail damper is over $300 from Ford and aftermarket about $150. I brought a used fuel rail that came with the fuel damper for $40 at my local yard.



Nice video

 

[Yardsale]

My vote is the check valve. I like Mickey's idea of testing closer to the pump to get a better indication of where is the leak.

 

[Mark Price 2]

Thanks Mickey!

I will definitely try to access the damper and inspect/test it. I guess the vacuum line points down? I didn't see it earlier. There's not much access back there. I suppose I could get better access to it if I put on these valve cover gaskets that have been sitting in the garage for a few months (i did do them on my 02 Sport though)



Also, I like that idea of putting the gauge in-line. Might take some finagling to hook up but I like the way your thinking.



This might take me awhile guys. This was my last day off for the next few weeks. But, I'm more than willing to test everything before dropping this tank I would be pretty upset if I changed the assembly to find out it was the damper. I have studied a lot (my hobby) over the last few years to try not to be a parts changer. Also, I don't like wasting my hard earned money. Its not much but it goes straight to my kids and wife.



Thanks again Mickey and thanks for watching and liking the video. I feel better about it now. If I show that video to my wife she wouldn't believe it was me speaking for 8 minutes in a row.

 

[Mark Price 2]

Yeah, me too Yardsale. Maybe there's a rubber line closer to the tank I could hook into?

 

[Yardsale]

I don't believe there is anything exciting between the fuel filter and the tank (going upstream), so that may be close enough. There is the fuel return line; guess that could be tested (it's a sealed, recirculatory system, though, so I'm not sure there's useful information there).



While it's possible, I don't recall reading about leaky injectors as a ST problem.

 

[Mickey Luis]

The fuel rail damper on the assembly line was traditionally with the vacuum hose end pointed up making for easier testing. On mine's someone pointed it down so I had to squeeze between the firewall and the fuel rail (tork screws) to take it off before I could check it for a vacuum leak. Mine's was bad and did cause loss of fuel pressure but not as quickly as yours did in the video.



In some fuel pressure kits there is a metal "T" type fitting in which the pressure gauge can be screw into the middle. Close off the open end and the other end goes to the added fuel line attached by rubber hose to the fuel filter. Take your time and if I can help with more info latter on, let me know.