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How brutal to change the FRP sensor?

37K views 19 replies 7 participants last post by  Joseph.Piechota 
#1 ·
I get an occasional FRP fluctuation only at idle and I suspect the FRP sensor. Is there a way to test it? If it is bad, how tough is it to replace?

Thanks.
 
#2 ·
There are other things to suspect before that... Just sayin.. :) filters, primarily..

The frp is easy... Remove air box, disconnect harnesses, remove oil tower, remove valve covers, remove and replace frp, reverse order... Bleed bleed bleed... Purge the air for all that's holy... You're in business.. it's an odd size... Something like 1 1/8" or 1 1/16" or something like that. I had to buy one as it was the only one I didn't have, and then saw it in half for the space... A matter of fact, I can mail you one side of that wrench!! :) lol...
 
#5 ·
Ok, good. What symptoms prompted you to replace your FRP sensor? Mine starts and runs like a champ but occasionally when stopped at a light, the idle will get quite rough and my H&S mini maxx shows a significant FRP fluctuation.

Thanks again for your feedback.
 
#7 ·
And do it sooner rather than later or that sensor will be the least of your worries. If you can't maintain consistent pressure to the hpfp you will be very unhappy in short order.
 
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#8 ·
I am having the same problem. Minor idle fluctuations. Has new filters (2,000 miles) Started having minor fluctuations at idle almost like a miss. You can see fuel pressure fluctuations only at a miss, other than that dead steady at 4.8 just like my other 6.4 with a minimaxx. Has also idled steady for 20 minutes at 4.8 recently, blipped the throttle and the problem returned. No codes, scanned with a newer Snap On scanner with a Ford tech and no bad data we could see. runs fine other than that??????
 
#9 ·
How much is it fluctuating? Mine will idle and it stays at 5.2 until over 100*eot then holds at 5.1... Never changes unless I hit the throttle.
 
#10 · (Edited)
I have 2 6.4's and both have 4.8 for fuel pressure as shown on the mini maxx normally at idle and it never changes. The one with the problem idles at 4.8 then in half a second reads 4.8-4.4-5.5-4.8 and then stays at 4.8 again for several seconds on the mini maxx.
 
#11 ·
I would agree with drew, test the fuel pressure from the hfcm. It is also possible you have a bad hpfp, or just got some bad filters.
 
#13 ·
Again, it is most likely a failing hfcm. That is the FIRST place I would start. It is little to no cost to test, and takes minimal effort.

There are a limited number of options when you are having fuel pressure problems. They generally stem from pump issues to blockages and injector problems. None of them are cheap to fix, the cheapest and probably easiest is the HFCM. If it having a problem holding pressure to the hpfp then you will be spending big money to replace more of your fuel system than you needed to originally.

We said check your filters because it isn't unheard of for a fuel filter to be bad out of the box and can show problems just like you are having... And generally a frp sensor would be showing issues while driving too...
 
#15 ·
One other thing mine will only do it when it has been driven and it is up to operating temperature then shut off and sits for a few minutes. Happens only after it is up to temp.
 
#17 ·
Since I have a minor fuel system issue... I've heard many people say test the HFCM pressure, but not one person indicated how to do so....

anyone?
 
#18 ·
The textbook answer is "at the supply port", which is to say "rig a line that clips on the fitting and which has a pressure gauge on the other end, and supply power to your hfcm.

I had one rigged up once, and it may still be laying around. If so, I'll take a pic. The gauge was analog and only went to 25psi, iirc...

That's the right way.. another way is to slap a gauge on the return test port w/o starting the engine.. the idea is that once supply to the bowl is achieved, it starts rerouting back to the tank via the fuel cooler, before being dumped. That port should have some pressure on it from the hfcm alone, though it's not a real good place to look. Furthermore, te issue may not be with pressure, per say, but keeping up with demand (volume) and not blinking on and off at times.
 
#19 ·
Bringing back a dead thread but my brothers 2010 6.4 threw the P0193 code and the minimaxx shows 28.9k rail pressure koeo. The truck runs perfect other than an occasionally rev in idle or blip in the throttle when driving. No misfiring , smoke, lope etc. Pretty sure its the sensor and was wondering if anyone has a write up on how to replace it. Thanks in advance
 
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