I was going through an in depth engine maintenance on my 2006 6.0, coolant flush, new thermostat, oil and filters, fuel filters, new blue spring upgrade, all in all, I took a bit over two days to get all this done, one step at a time.

While I was doing the flush, I installed a new blue spring kit (since I'd already bought it and it was so easy with the radiator hose and cold air pipe out of the way), then I test drove it to verify success or failure. Everything looked good, deltas were much improved, fuel pressure was running right at 66 PSI on the gauge.I also changed out the upper fuel filter while I was in there.

Came back and changed oil and filter (Rotella T6 if that makes any difference), then fought my way through the primary fuel filter change and added the upgraded WIF plug while I was in there. I say I fought the primary filter because I had one heck of a time trying to get the cap up snug, or so I thought. It's kinda of tight and awkward on the 4 WD drives.

Took it for out for about 25 miles, fuel pressure held pretty much steady at 66PSI, dropping to around 59-62 on short WOT spurts. Thought I was good to go, so I came back and changed the oil and filter, then let the truck sit overnight.

Came out this morning to run into town and noticed that fuel pressure was running 42 PSI at idle. Having no more knowledge of what to do, I crawled back under the truck and managed to snug up the cap a bit more, but managed to draw blood on myself during that process. NO difference, 42 PSI.

Back under the truck, I shined a light on the filter cap and noticed that I could still see the O-ring, but it appeared to be tight against the housing. Could this be my problem, does the O-ring seat entirely into the housing?

Going into panic here, we're supposed to pull the 5th wheel out on Tuesday for her vacation and she hates to change plans when they've been laid.

Suggestions, questions, comments, help? Please

 

Did you Oil the o-ring before putting the filter on?

 

Dirty fuel?

 

Euroman - I don't think I did, I was so happy with myself that I got the old one out, I believe I omitted that step. I do happen to have an extra O-ring since there were two of the large ones in the Motorcraft box. I'll try that.

Bismic - Fuel is good, always have been around here. When I put the new water drain plug in, I couldn't see any water in the catch basin and the fuel that spilled out when I withdrew the filter looks pristine.

I'll try a new O-ring with lube and try that. I did look all over the place this morning and couldn't find any leaks.

 

OK - lubed up the new O-ring, cleaned out the ring seat and reinstalled the filter and cap. Managed to snug the cap up to the housing like it should be, but still only 43PSI, key or or when started.

The truck starts well, idles well and I gave the pedal a couple of blips, maybe up to 1200 RPM, sounded fine. I even went to the point of putting cardboard under the left side frame and under the engine - no traces of leaks at all.

Is it possible that my gauge or sending unit just took a dump on me? Right now I'm seriously considering trying to find a mechanical gauge to find out. Which may be a problem in this small town, might have to spend a two hour round trip to locate one.

Any other suggestions?

 

I would confirm with another gauge, before tearing things apart.

 

X2 - Diesel up the sleeve is one of my less favourite feelings 😀

 

After thinking it over last night, I plan to pull the sending unit and see if possibly something is blocking the hole in the base of it. If that's clean, then I'll try testing the gauge and unit with a low cfm air compressor, slowing adding air pressure to see if the gauge increases.

If that doesn't work, then I found one store that will be open today (55 miles away) that shows online to have a 0-100 PSI gauge in stock.

I'm leaning towards a bad unit since pressures were great the day before and the only thing I did after the test drive was change the oil..........

 

 

Below deck ---- Since you initially had problems with the lower filter (o-ring exposed), I'd go back and check the fit between the filter and the pump - poor seal here will introduce flow issues.

Topside ---- "opening up" the regulator may have introduced debris or the blue spring may be not completely seated, misaligned in cavity..........


Could also be related to quality of fuel filters used................fit, alignment, seal.........

 

I agree Jack, but if the check gauge reads considerably high than the gauge I've got in there now, I'll feel a lot warmer and fuzzier than I am right now. If they both read pretty much the same, then I guess I'll postpone the vacation and start digging deeper.

It's not a calibration in itself,, but I do have the ability to bounce the check gauge against a supposedly calibrated tire pressure gauge.

I just finished pulling the air cleaner box and cold air tube for access to the sending unit. Decided that was enough to justify a celebratory brew, then we'll see if I can solve this mystery, good, bad or indifferent. If it's not the gauge, guess I'll be back with more questions.

Thanks for all the inputs I've gotten.

 

F350 1990 - last night I pulled the filter off, installed a new, lubed, o-ring and the cap is now seated against the HFCM. I'm sure I didn't get any debris into the regulator since I had the upper radiator hose and cold air pipe off, plenty of room to work and I puffed everything with canned air before reinstall. PSI numbers looked good during the 25 mile test run, I just parked it for the night, then the problem arose.
Filters are all Motorcraft and I sucked all the fuel from the upper bowl, then inspected it before I pulled the regulator cover. Everything went back very easily on that part of the job.

 

Here's another situation you may be experiencing. Pete, 87crewdually posted about this several times about what he experienced. He is one of the most intuitive diagnosticians and competent in mechanics on this site so when he mentions something it's often good to take note.

The post



The thread
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https://www.ford-trucks.com/forums/1...l#post17556931

 

I'd recheck the spring install while I was that far in. Also, there is a chart floating around here somewhere that shows sending unit voltage output vs. actual fuel pressure that might tell you if your sender is acting up.

 

87Crewdually - you are the man, just as Jack credited you for being!!!!!!! Pulled the cover off and the seal on mine looked exactly like the one in your picture. After a lot of internet searching and phone calls, I finally located the only place around that had the kit in stock, and they were only 30 miles away. (I didn't even bother to look for just the seal, just wanted to get this thing hooked up and on the road, just so we can drive south straight into Alberto's rain, but hey, she said we were going to Florida.

Fuel is running 62 PSI again!!!! Oh happy day!

Sorry for all my delays in posting back, but we're dealing with heavy pop up showers, awesome heat and terrible humidity, plus we're so rural that anything we need is always an hour away.

Anybody know if you can buy just that seal? If so, I'll have a complete backup blue spring kit.

I want to thank everybody that chimed in and helped me out, saved me a lot of grief from the wife and probably a lot of money If I'd attempted to throw parts at this situation. Ya'll good people as we say down here