Checked the FP in my truck last Friday. Had the gauge hooked to the post filter port, filter has around 1000 miles on it, hutch mod completed last summer. At idle it was right at 60psi. Took it for a drive and WOT it dropped down to 40psi.

Shimmed the FPR with a bb. fired truck up it was now at 100 psi, also real confident I did not have the spring in there cocked or anything. Didn't go for a drive, shut it off and removed the BB. Fired truck back up without the bb and it was back to the 60psi.

I did notice while I had the fpr apart the what I assume is the poppet looked like it was made out of plastic. It also had a pretty good wear mark on it. Looking at the FPR rebuild kit the replacement poppet is brass. Is this something that has changed over the years?

So my question is, is my pump getting weak or is my regulator not able to maintain the fuel pressure required.

 

So many people misunderstand the fuel system, you are not alone in wondering how this all works. I'll translate the fuel system into as few words as I can:

The pump has one job - supply fuel up to a specific flow and pressure.

The regulator has one job - NOT let the pressure go over a set value.

A pressure regulator can only reduce pressure to a maximum value, it can't do squat about low pressure - that's the pump's job.

Air in fuel can lower your fuel pressure... as can a flow restriction from the fuel supply. The Superduty is notorious for fuel supply problems, this is why so many people do the Hutch mod (myself included). I'd check the quick-disconnects on the fuel line from the tank and listen for bubbles in the fuel filter housing... before I loaded a round into the Buck$Zooka.

 

The in tank mods have been done, along with removing all supply side quick disconnects and line between the tank and pump with 5/16" hose.

If I get time this week I'll tap into the prefilter port and see if the readings are the same

 

40 psi at WOT doesn't sound that off to me. The pump could be getting weak. If pressure continues to drop, it could be the pump. These pumps have about 50-75,000 miles in them, in my experience.

 

i'll have a new pump installed as soon as usps delivers! I'll retake readings after the new pump is installed on both sides of the filter.

It makes me wonder tho, you read a lot of post about shimming the FPR and using a bb is pretty common. Wonder how many people out there read, stuff a bb in there and go about their business without actually checking their fuel pressure.

 

Many. That's one of the problems with forums - anybody can say anything, but this stuff needs to be validated.

I've said stuff in the past that I have recanted, but those are opinions... not data-related. I have faith in numbers - like "What does the fuel pressure do when I do this?" or "What does the boost do in relation to the EBP?".

Claims like "You'll get more fuel pressure if you shim the FPR" doesn't tell me how much pressure to expect at max, nor does it tell me how to resolve low pressure when the pump is maxed out. What it really tells me is somebody was hot-******* and believed he had low fuel pressure. He felt the regulator just had to be the cause... so he took it apart. Looking at it, he said "Shooot... I c'n fix that raught thar." and went rootin' around the garage for something to compress the spring (to some mystery pressure).

For all I know, maybe he had a broken or tired spring, and the BB was the magic number for that singular situation. Maybe he had a temporary FP gauge on there and saw a pressure he liked, then pulled the gauge and moved on... not knowing what happened afterwards.

I do know what happened next: He got on the forum and typed "Compress the spring with a BB in there, y'all will get more pressure." It sounds reasonable - if one does not fully understand the pump/FPR/demand relationship.

 

Is this a platonic relationship? Or incestuous?

 

Codependent... but almost nobody ever understands them, so they try to interfere. This invariably causes more strife in the relationship.

 

Tugly (or anyone),

I have a 2001 F250 SuperDuty, 7.3L. I put the Hutch Mod in it a couple months ago to correct the 1/4 tank shutdowns from the breaking pickup foot. All seems well except when starting the truck if I turn the key after the glow plug light goes out it turns over but doesn't want to start. I've noticed the fuel pump running an additional 20 or so secs after the light GP light goes out and if I wait until the fuel pump stops running it will generally start. I seem to recall in researching this prior to doing the Hutch Mod that I read something about when adding a pre-pump filter that the fuel pump had to be stronger. Could that be the issue with mine running, what seems to be, a long time? I honestly haven't checked for any air leaks. If I need a stronger pump (Bosch on it now) which one should I look for?

Thanks ahead of time for any input.
Bob

 

When the key is turned on, the pump will run. If the engine is started, the pump will continue to run. If the engine is not started, the pump will shut off after 20 seconds. I don't think the fuel pump is related to your starting problems. It's more likely a glow plug issue.

 

I appreciate the reply but am aware that when turning the key to the ignition position that the fuel pump will run to fill the fuel lines and achieve pressure. My point in my post (I guess I could have been clearer) is that it seems that prior to the Hutch Mod the pump didn't run as long and the starting wasn't an issue. I was thinking the new rail pre-pump filter (came in the Strictly Diesel kit I bought) is straining the pump too much to allow it to maintain adequate pressure or the pump is wearing out or both. Another reason I say this and don't suspect the glow plugs is because it will also do this after it is warmed up shut down and restarted thus taking the glow plugs out of the equation (if I understand the role of the glow plugs). I admit I am new to diesels, but not to auto mechanics.

Bob

 

The length of time the pump runs is totally unrelated to pressure; the PCM has no way of monitoring fuel pressure. It runs at 100% duty cycle while RPMs are detected. If RPMs are not detected, the PCM runs the pump for 20 seconds and shuts it off. The Hutch mod, dirty fuel filter, or the addition of a pre pump filter won't change the amount of time the fuel pump runs.

 

 

One thing that really surprised me was how a slight drop in fuel delivery can make smoke. My truck started smoking at WOT a couple weeks ago but the FP gauge was only dropping into the mid 50's (it normally never drops below about 59 PSI). Changed both filters (pre-pump and post-pump) and no more smoke, FP back to normal. My filters had less than 10K on them but I am suspicious of a tankful I got at a deserted station when I missed the turnoff for Pilot. I knew better but I filled up anyway.
Pulled a sample with a siphon hose and it was a bit darker than normal, kind of dark yellow, but no black crud in it.

 

Sorry wrong channel, I asked question 6.0 powerstroke
https://www.ford-trucks.com/forums/9...-spring-2.html