Testing fuel pressure and pressure check valve. - Ford Powerstroke Diesel Forum
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Old 08-15-2013, 04:35 PM
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Testing fuel pressure and pressure check valve.

So last time I posted on here I ended up having a $3700 rag stuck in my intake passage for cylinder no.1 oops. Got the head studs and peskie oil leak fixed. And looking through my paper work I see that the injectors were replaced about 60k ago with alliant power factory Injectors. Problem is the other day driving home I dropped #2. completely dead with #2 contribution code. No smoke just shook like a b on lock up. Was getting ready to pull injector and decided to check fuel pressure for the hell of it. KOEO pump runs right to 60 psi. Immediately after pump stops it drops to 0 within 5 seconds. That to me being a fleet mechanic with gas engines and fuel injection seems to be an issue. I know that there should be a check valve but where is it? And how long should they hold pressure? Is that normal? I have noticed when it starts in the morning that it kinda... "Barks" when it starts to fire up. Now my first baby is on the way and mamma don't want me spending all my time and money on it so any help is appreciated.


P.s. I checked the whole injector harness ficm voltages and did cylinder contribution test which confirmed #2 and with valve cover off I can hear and feel the injector working electronically.
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Old 08-16-2013, 08:39 AM
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I called another diesel shop In town and they said that it is normal for pressure to drop to 0 after pump stops running. Can any one confirm that? It just doesn't seem right to me. Also in the process of checking pressure ad getting my adapters all leak free I noticed when the pressure was dropping there was a bunch of bubbles leaking from where my fittings were loose... Why would there be air in there? Hope tonight I can try out my "special" tool to check static and dynamic pressure (after changing filters again) with out leaving the shop
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Old 08-16-2013, 05:00 PM
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Mine drops to 0 as well
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Old 08-18-2013, 04:31 AM
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Can any one else chime in? Is it normal for the secondary filter do drain to empty in 1 day? I pulled the filter while seeing if I had any injector seals leaking and the next day it was empty.
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Old 08-18-2013, 05:22 AM
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It should not be empty while sitting. My pressure falls very slowly after pump shuts off but not to zero.
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Old 08-18-2013, 08:31 AM
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I'm no mechanic but I to have been having injector problems. And I was told when my #5 injector went to check for air bubbles coming back in the secondary filter. Mechanic told me if there was then its a cracked injector tip or bad seal on copper washer. And behold the copper washer was broke in half. Hope that helps.


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Old 08-18-2013, 09:44 AM
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There were no bubbles and the pressure slowly drops to about 5 psi and will stay there for a few seconds then drop to zero. Only reason I'm wondering is to find a root cause of my issues. Starts rather rough and poor throttle response. I also have a hard time believing the injectors went bad after 60k. And I just had them all out when doing the studs and gaskets less the 5k ago. Can't really afford to "shotgun" injectors at it just to get another 60k out of them.
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Old 08-18-2013, 01:05 PM
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Pressure dropping to zero after the pump shuts off is normal, due to the air eliminating orifice at the top of the regulator. In my truck, KOEO, fuel pump running you can hear some air hitting the pump, and running you can see this in my pressure gauge, some slight fluctuation. I have been through the entire system to eliminate this, even in the tank, and have pretty much deduced it is because Diesel cavitates very easily and the OEM draw straw system is to blame. But thats not to say there isn't a problem with your pick-up. As for the secondary bowl being empty after sitting, thats very strange. It sounds like you trying to perform the bubble test. Are you doing it properly? By that I mean removing the secondary filter cap, and filter and energizing the starter and watching for bubbles coming from either of the lines going to the heads

Last edited by michaelaiman; 08-18-2013 at 01:11 PM. Reason: Clarification
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Old 08-18-2013, 03:18 PM
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Yes cap is off both fuel pump and ficm relays are removed. Is it possible to see bubbles in the bowl instead of removing the lines and doing the baloon test. Is there a check valve in the pump to stop it from draining? I checked pressure again 60 psi engine off and through fords factory orifice simulating wot and max load was just below 50 psi.
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Old 08-19-2013, 04:41 AM
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If the fuel is draining back could that could have caused my no start after a weekend at the cabin? A month or so ago we went to the lake and after being there for 3 nights the truck wouldn't start. Cycled the key plenty but probably got a little pissed of and eventually cranked it until batteries were low. Got it towed home and it started right away.
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