Rail pressure should be in the 4000s psi at idle. Up to 28-30k psi WOT. Use forscan to check for codes. I change my fuel filters every 10k, it's a pretty common consensus that 10k is best for maintenance minded folks. You need to monitor both low and high pressure fuel readings to identify which end the problem is coming from. If it's high pressure, look at dropping an oem rail in. Comes with sensor and regulator already installed. If you find metal shavings in the old rail, count on more money and park it where it's at.

 

I have checked for codes every time the warning light has come on and there are none at all which is part of what is bothering me.

I always use lubricity additive with every tank of fuel from my fear of the cp4 failure. So I was thinking that could have shortened the filter life span possibly. The new filters will be her tomorrow for me to put them in before the holiday.

 

I have checked for codes every time the warning light has come on and there are none at all which is part of what is bothering me.

It's a low pressure system warning...won't set a code unless the pressure falls very low or or has no pressure. If you can monitor the fuel lift pump pressure you can see what's going on when the warning displays.

 

I am using the Torque Pro engine management and diagnostic tool. I can never get Forscan to work on any of my systems at all.

I monitored the fuel rail pressure for my entire commute this morning. It was a balmy 27 degrees fahrenheit this morning. I got KOEO status first thing and the fuel rail pressure sensor was reading 190 to 250 psi with the engine off. So I wasn't sure if that was just like "waiting pressure". I hit the start button and it fired right up to 6k psi on a cold idle. I let the truck warm up for a minute and no issues. Stayed between 5 and 6k psi.

As I pull out of the drive way, the pressure comes up to 16k psi on a slow acceleration. It did this for a couple stop signs on my way to the highway.

I got stopped by a train and as I was coasting, the psi says it dropped to 250psi again for a second or two and then pops back to between 4 and 5k while at a warm idle.

I monitored it all the way to work. 35mph cruise was about 14k. 65mph cruise was about 20k. 75-80mph cruise was about 24k. All the way to work. As I'm decelerating i pull into the parking lot, it drops down to 250psi again for a second and then back to 4k. I pulled into the parking lot and put it into park. Steady at 4340psi as it sits. I let it sit for 2 minutes. Steady between 4 and 5k.

When I shut the truck off completely, the system is still showing 250psi on the scanner.

I checked again and no codes are stored on the ecu. I'll try to take it over to a dealership today at lunch and have them run it to see if they get any codes.

 

Hello Vile_Joker and welcome to the forum from N.E. Indiana!! I'm sure they'll get it figured out. Good luck.

 

And what is the low pressure doing during all of this? Does the drop to 250 coincide with a low pressure drop? If not, it's probably the regulator. If it does, you're looking at filters or pump.

 

I'm not sure if I'm doing something wrong, but my Torque app doesn't show a metric for fuel pressure besides the rail pressure. I have fuel flow rate, but I wasn't monitoring that.

Could it possibly be a bad sensor? because the truck shows no actual signs of having low pressure. There is no sputtering or lag or any change in the engine performance at all when when the low fuel pressure warning indicator comes on.

 

Typically low pressure failures are dependent on load (and occasionally temp, as the LPFP heat soaks), not RPM (Since the LPFP is electric). Your high pressure system on the other hand, is dependent on RPM since the CP4 is driven by the engine itself.

That all being said, testing and datalogs are gonna be your best friend in this case. There are some bidirectional tests you can do to cycle/check/test the health of the high pressure system (I do not believe Forscan has this function yet). Otherwise, datalogs are great for us to give insight as you continue to diagnose.

My from-the-hip guess is a lazy regulator. The dip in pressure while return to idle, but then sustaining leans towards a lazy regulator not being able to recover/retain pressure and pump RPM comes down.

If you need any help, feel free to reach out!

 

I can upload the data logs from torque tonight into google drive and send a link of that might help. But yes, it definitely seem like it's happening on the return to idle, at least from what I can see tell.

So would this be the part that I need?

https://parts.ford.com/shop/en/us/fuel-injection-and-pumps/fuel-injection-pressure-regulator-67l-p-cm5185

Should I use the Ford part or are there better options out there that I can use since I'm replacing it?

 

Oem is best. From the dealer. Jeff's advice is spot on. I always like to see both sides (low and high) as it gives me more evidence to base my assumptions on. Forscan can monitor both. It seems your sensor is reading accurately, but your systems ability to maintain the commanded pressure is lacking..

 

Any tips why I cannot get Forscan to work at all? I've hrard it's a better software, but every time I have tried to install it, it doesn't work.

I'll get the part ordered. I can still drive it while I'm waiting for the part, right? Or should I deadline it until I get that replaced?

 

Are you using a PC? That's the better way.

 

I would, but it's not like I can take my pc out to the truck to hook it up to the obd2 scanner. My pc is not a small machine. But I think I finally figured it out on my phone.

 

No laptop? Anyone you know have a laptop? I ditched the desktop 2 decades ago.. I don't think forscan lite is as good as the full version.

 

Only my work laptop, and I can't install any unauthorized software on that. I'll have to see what I can do.

 

FRP pressure at KOEO is normally around 200 PSI give or take a few. Reference value chart shows 210 PSI is expected. We are still not seeing any data on low pressure system - FLP is the PID.

 

 

was this ever resolved? I also have 200psi Koeo but I have a crank no start. chasing problem now. I also just installed the spa disaster kit

 

I hate to say, but not really. I put a tank of Rislone Diesel DPF Clean Exhaust cleaner through the system and it went away. I didn't end up changing anything out at all. It's been fine ever since. I have been running a tank of it once every month since then. So I am assuming it was a sensor? Shrugs

 

Let's hear it for liquid mechanic! Hey, if it works...

 

Well, the main problem is that I have no idea what the previous owner did for proper maintenance on this truck, so I'm shooting in the dark on these things. I figured I would try the lease expensive option first and then work my way down the line. Based on the fact that there was never a loss of power or any stuttering or any idling issues or anything like that, the engine never seemed to be starved for fuel at all when the pressure dropped. It had, literally, no other signs f an actual fuel problem. So I figured I'd start off light and if that didn't work, then progress to the next step.

And from what I saw inside the throttle manifold when I had to replace the cold side charge tube, it's not entirely great in there. I am going to have to take it to a mechanic and have them clean out all the soot build up from inside the entire intake and EGR cooler if my eyes did not deceive me. It was thick black crap inside there.

 

The carbon build up is normal. Unless it becomes extreme it's typically not an issue but then you have to determine why it's so excessive. Scaping and cleaning the lower intake is fine and I have done this many times... typically when installing a new service engine so I often wonder if, in the worst examples, the valve covers also need to be removed and cleaned. Usually the heaviest build up is in the throttle plate and EGR inlet area so cleaning that is probably enough. Even if it's not causing any performance concerns cleaning it certainly won't hurt. Mitigate it using a good fuel conditioner (for cetane) and limit idle time if you idle a lot. I do not see many EGR cooler face plugging or restriction concerns any more. That seems to have been a problem on the earlier model year production engines.

 

Ok. I f I get a chance, I'll try to toss up a picture of it. The cold air charge pipe pops off easy enough and I can snap a shot of the throttle. It doesn't seem to effect engine performance, but I worry that something may dislodge and head pistonward. I run fuel conditioner/lubricity additive with cetane each fuel tank for the truck. I'm overly paranoid about CP4 failure and I have not had a chance to install a "disaster prevention kit" yet.

 

Last few months I’ve been chasing a low rail pressure code following an engine light. If I drove like a grandpa on flat ground I never saw the light or had an issue. If I was pulling a trailer and cruise control downshifted demanded more fuel, light popped. If I went past half throttle as an example, light popped.

First thing I did was swap filters and look for glitter. None.

I then replaced the fuel rail pressure sensor above drivers wheel and nothing changed.

Being in denial about it being the cp4 I just drove like a grandpa. I had my buddies shop hook it up to their scan tools and drive it. He said it wasn’t meeting the threshold for rail pressure when it was demanded. He said my cp4 was failing. I ordered a dcr and he installed it. Found some wear in the cp4, but not where I hear people talk about it.

Truck runs so much better now. It’s deleted and I can feel power diff and response diff in each tune.
I think the cp4 was failing somehow over time and the power was just sneaking away as to not notice it.

 

Last few months I’ve been chasing a low rail pressure code following an engine light. If I drove like a grandpa on flat ground I never saw the light or had an issue. If I was pulling a trailer and cruise control downshifted demanded more fuel, light popped. If I went past half throttle as an example, light popped.

First thing I did was swap filters and look for glitter. None.

I then replaced the fuel rail pressure sensor above drivers wheel and nothing changed.

Being in denial about it being the cp4 I just drove like a grandpa. I had my buddies shop hook it up to their scan tools and drive it. He said it wasn’t meeting the threshold for rail pressure when it was demanded. He said my cp4 was failing. I ordered a dcr and he installed it. Found some wear in the cp4, but not where I hear people talk about it.

Truck runs so much better now. It’s deleted and I can feel power diff and response diff in each tune.
I think the cp4 was failing somehow over time and the power was just sneaking away as to not notice it.

A failing CP4..............who woulda thunk!

 

Oh I thought. I didn’t wanna believe it.

 

Believe it. They're happening more and more. Hopefully Ford does something about it besides blame customers like they've been really good at.

 

Do you usually see the good in people too, like when they eff you over you come up with an excuse then on why they did it? Cause that’s what ford is doing but only relative to rams recall and fix. Ford said they would reprogram a couple years for cooler fuel temps? Really. Hahaha. I’ll own another one, but def with a warranty

 

From my last 30+ years of truck ownership I've watched how Ford takes care of diesel warranty and I'm not impressed. Ram has done a much better job.......considering my Ecodiesel and the fact it has the CP4.2 pump also, Chrysler recalled the pumps. They still installed another CP4.2 but the new ones are pinned to prevent plungers from spinning. Why in the hell isn't Ford doing this???? I know they are the masters of the bean counters but this one is ridiculous considering the failure potential. Instead of updating current production they double down and blame the customer. Silly.

 

Yes when I saw ram using a new cp8 n ford doubling down on cp4 I believe there is more to it. Maybe they bought so many units or a promise to buy xxx amount in order to maintain a certain price or they simply don’t feel they can admit there is a problem bc then they’d be in a world of financial hurt.
I think ram did it bc a few bucks now keeps them from going under later.

Unfortunately I think ford can survive a span of people not buying one product line for a time period, where I think if stellantis lost sales of the 2500-2500-350-5500 they’d have a very good chance of going under. They don’t have much to offer other then wranglers and rams

 

Anymore updates vile? I’m dealing with the same issue. Only difference is I have S&b sending unit and air dog lift pump. Both were replaced and problem has been gone for a few months and now it’s back giving me the same low fuel pressure warning. I read in another forum that the fuel relay wiring could be going bad which would cause a no start which was the original problem. But now the truck runs and gives the warning