Taking my 05 PS in Friday for my last warrenty visit. Just installed the fuel pressure gauge last weekend. It has been suffering from extended weak starts.

New batteries in Feb
Fuel filters 4,ooo ago
Fuel pressure cold in morning about 34 38 degrees 50 PSI
Fuel pressure Lunch break approx 4 - 5 hours 47 -48 psi
Fuel pressure if starting after operating temp is up within an hour 45-46 psi

I am getting the AG fuel regulator kit installed after that they will check the HFCM

What would cause fuel pressure deviations as described above could it just be outside temp or underhood temp or are there other causes you can think of. Thanks as always

 

I am unsure of a cause due to temps but you are flirting with the lowest recommended fuel pressure.

 

What's your PSI cruising and when you call for a heavy demand of fuel? Not exactly WOT, but just a sudden high demand for fuel. rickatic is right, you are skirting with very low PSI.

 

After operating temp is reached cruising is at around 50 and WOT drops to about 42. Know I have a problem that has to get corected immediatly so it going into the shop for the AG fuel reg kit and then go from there. I was just thinking it would be smart to ask everyone here who knows the 6.0's what questions I should ask the techs like did you check this. This is my last visit to a dealership under warranty and I want to make sure I get as much looked at and taken care of on Ford's dime. After this it will be up to me and my stuborn streak and the help of the members of this great forum. The thing that makes me nervous is I had this truck in Dec and told them to go over it with a fine tooth comb and told them I felt I had a hard start issue you think they would have checked the fuel pressure which they can't recall now. It really pissed me off when I just installed the fuel pressure gauge and found out I was flirting with disaster and they got the message thats why I am getting this last visit 3 months after warranty was up on them.

30 years ago I was a ASE master in auto/Diesel and cut my teeth on the Olds 350 converstion and the Chev 6.2 diesels gave it up to Millwright in a Saw mill for and extra 20 grand a year, marriage and kids will do that for you. So any way not afraid to dive in but just got to get up to speed again. Just trying to learn as much up front from all you guys before I dive in and learn for myself. Again thanks for all your help and I hope to return the favor with my experiences soon as this truck is getting a total going over as I plan on keeping around for a long while.

 

Assume you addressed filter issue and there is not new crud clogging filters.

Could it be a weak fuel pump?

What is mileage?

Someone come in and talk about the new Ford upgrade kit (new spring) that gets higher fuel pressure that cheezit posted about.

 

Particularly with what I've heard about the new primary fuel filters that now have 2 o-rings. I don't know from first hand knowledge because I no longer have the stock primary system, but I've heard that the addition of that new o-ring prevents fuel from going underneath the filter to supply fuel and it forces the fuel to go through the filters.

Now of course, it could have started off as a problem with fuel filters, but if it was like this for awhile, it could have cascaded to a weak pump or maybe injector(s) as well.

 

Filters got 4 thousand and the secondary looked good when I had it out for the fuel pressure gauge install. Was planning to change filters anyway this weekend and install the new AG kit but the dealership talked my in to comming in on them. So I guess we will see.
Can't see where a the temp comes into play, you would think the secondary filter might explain if it where bad and fuel viscosity were at play this might increase the pressure in the secondary housing if it the filter was retricted. And you would think that if the primary filter was restrictive it would drop the pressure in the secondary housing when the fuel was cooler is viscosity was in play. I do wonder about the hotsoak condition under the hood being in play but you would think that if air was be introduced the effects would still be there in the morning. Got me baffeled but I am probally over thinking it as I do on most things

 

When you open up the fuel system, there is a "purge" procedure that has to be followed to rid the system of air.

Did you do it?

 

Accually I have a bleeder valve on the new line for the fuel pressure gauge the bleeder is at the highest point I could get by the master cylinder and had a buddy pressurize by turning the key on while I bleed the system. Got to perfect that procedure was a little exciting as I only had a small container for a catch (Surprise). After words I used the purge proceedure 3 cycles.