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6.0 poor low fuel psi.

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You're checking it at the test port and not the filter lid, right? Remove the return line from the regulator, install your FP gauge, and start the engine. There should be a small amount of return flow at all times from the de-aeration port in the secondary housing, but there should not be a large amount of return flow. Remove the regulator again and see if there is debris present or if the "rubber flap" is flipped over on the regulator valve. Did you check/replace the primary filter (or both filters)? I've seen a lot of bad pumps cause low pressure. Are you sure it's not bad? 45psi is low unless the new "bypass" tool is installed. Was your deadhead test done by stuffing a gauge in the feed line with no flow?

 

 

Good Luck!

 

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Here's a bad shot where you can just see the edge of the rubber flap near the base of the regulator pin. I've got better pics but not real handy right now. I have seen the "rubber flap" flip over once, lowering the fuel pressure by allowing too much return flow. You might want to pull yours back out and recheck it.

 

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Once again, how are you checking the deadhead, and where are you checking the pressure at?

 

 

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My guess would be the cap o-ring. I can't tell you how many trucks I have had towed in after a customer has changed his filters or BECAUSE they changed the filters. For 6.0L trucks the most common problem is that the cap is not fully seated and we all know that the filters in these trucks need to seat to open the inlet valves. I too have never seen an o-ring torn but I have seen one or two rolled and sticking out the side of the cap. Two problems here are one, that many people don't lubricate the seals before installing the caps and two, they don't use a socket to remove and install the cap. Using channel lock pliers takes forever, damages the cap and does not promote a fully tightened cap!

 

I have had several 6.4L trucks towed in because they try to start the engine without bleeding the fuel system first. If they only knew to cycle the Key 6 times... had my first customer with a repeat fuck up on this today as a matter of fact. To make it more interesting, he didn't know that there is a filter in the frame rail and it was clogged. Are these people getting just the secondary filters or what?

 

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I had to replace a set of injectors once because of a lid that was not tight and the customer drove around a few days and wiped them out.I always pull the filters anytime pressure is not up to spec first thing and have found ten or so not fully seated by the customer.

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