I have a stock 01 duramax crew cab. The only mods I have is the PPE boost valve, stealth 2 programer and 33 inch tires.

My truck runs amazing. Starts right up, no smoke, burns no oil. I purchased the truck with 220K miles on her. She had the injectors replaced at 185K miles. Previous owner always used diesel Klean every tank full after the new injectors and I have continued this practice. I run the 50 hp tune for my truck as she is my daily driver, however I was amazed with the 135hp tune on my truck the one time I did use that setting..... but back to 50hp for me.

So, the first time I had a problem I got a code p0089 which is the FPR. I got the stealth 2 programer and the code went away. I purchased the FPR, but never installed it as my truck ran great after the install of the tuner and a new fuel filter. Last week, my family and I hooked up our 21 ft. travel tralier and the first hill I hit my truck went into limp mode. I thought it was becasue of hte tuner, so I pulled over and put her back to stock. Truck ran great and I was able to go over a similar sized hill, however, I then hit a very long hill and the truck went into limp mode again. I had to turn around and head for home. I got a code p0093 which I know is a fuel leak code.

I have done a lot of searches and it could be many problems.
First, I have found it could be as simple as a fuel filter, however, I recelty changed my fuel filter. Second, I have found that it could be a FPRV which I have the part and intend on installing this week. From what I have read, the FPRV is rarely the fix to the code 0093. I have found such thins as the CP3 or the fuel pump/lift pump.

My question is how can I test the CP3, the upper or lower fuel rail pressures, or the pressure of the fuel pump. Will my stealth 2 programer give me the values? Or do I need a special tool to find where I"m having fuel pressure problems? I have built pleanty of hot rods in my time, but this is my first diesel truck. I just need a little direction on how to test and troubble shoot my fuel problem.

Thank you for your help

 

Well, I replaced my FPR and I shimmed the FPRValve. What a job that was, I just hope that is my problem. I plan on hooking up my trailer and towing her on the freeway to see if the problem is fixed.

IF not, I need to figure out how to test my fuel pump vs my CP3. Can anyone point me in the diretion of finding out what tools I will need to diagnose the fuel pump and where to check the pressure of the fuel pump and also the CP3?

Thanks

 

Well, so far no one has been able to help me. I have done multiple searches with no clue on where to start to fix this problem. I just posted this in the distress forum hoping I can get some direction to find out how to test the fuel pump and CP3 to see if they are the problem or not??? I just copied and pasted my post incase I can get some help on this thread;

I posted a thread regarding some issues I have been having with my 2001 duramax silverado. If I drive it without towing, she drives amazing! Starts right up with no problems, does not smoke, maybe a little back with the stealth 2 chip @ 70hp setting, but nothing I would not expect with that chip and a heavy foot. The first time I towed with it, we had our 21 ft travel trailer and it went into limp mode while going up hill. I pulled over, read the code ...0093= fuel system leak. I contined on after I cleared the codes and it seemed like once I got between 65 and 70 mph, or a step hill, the truck was real sensitive & would throw the code 0093. I turned around and went home and parked her till we got back from our vacation. Intersting thing is that when I got off the freeway and drove on the back streets/highways It never threw a code. Once I got home, I hooked the trailer to our tahoe then contined on our vacation.

Now, when I first got the truck with 220K miles on her, I got a code 0089 = FPR. So, when I got home from vacation, I pulled the FPR and put in a new one with a new fuel fiter. I also did the shim to the FPRV. I took her out for a test drive with the travel trailer in tow. I hit the first hill where my truck got the code 0093 and went into limp mode. My truck pulled that hill like nothing. I thought, I hope she is fixed! I contined for another 15 minutes and once I hit 70, I was able to sustain that speed with no codes for about 5-10 minuts. Then, I got the CODE 0093 I was pissed! I turned around and went home.

I hooked up my Stealth 2 programer to watch what the fuel pressures were doing. The stealth 2 programers let me see the duty cycles of the injectors which all were the same values, 4.4-9.2 area. There are two fuel pressure readings One is Fuel ACT and Fuel DES. I have no idea of what the values represent? It seemed that when I was going up hills, at first, my fuel pressures read Fuel Des - 3055 and my Fuel Act - 2488. Granted, these values did jump around a lot. I had no problems on this first hill when I pulled these values from my stealth 2. Durring Criuse mode at say 68-70mph, these values read Fuel Des - 1800, Fuel Act - 9300, however they also seemed to read really consistant while at 60mph between Des and Act values of 4500-7500psi.
Now, when I hit some larger hills, my F-Des read 1800ish and F-Act - read 9300, yet would bounce around all over the place.

I have no idea of where to start troubble shooting this problem. Of my many searches, I have found it could by my CP3 unit. I am wondering how to check the fuel pressure from the fuel pump? Is there a shrader valve where I can test this pressure and what is it normally supposed to be? Also, is there a way for me to check the CP3 unit? if so, HOW?

Anyother ideas of how to fix this code P0093 would be greatly appreciated!

Thank You!

 

sounds like you are on the right track. just remember any diagnosing should be done with the tune returned to stock so as to eliminate the tuner.

i would think that the next step would be to monitor the desired vs actual fuel pressure while under load to see if the CP3 can keep up.

it may also be that one or more injectors (i know, they cant be that old) are suffering for the high return rate issue and that, plus the demand for fuel is just too much for the pump to take. one method that you already touched on is the lift pump. this may get you by for awhile until you get around to the injectors. if it is the injectors then it will only get worse over time till the truck wont start.

hopefully it is the CP3 and not injectors as that is cheaper and easier to replace.

"I need to figure out how to test my fuel pump vs my CP3"

bay the way the fuel pump is the CP3 on the duramax

 

Thanks for the reply!

I forgot, I did return the turck to stock for towing.
This is my first diesel truck. I don't know how to monitor the desired vs actual fuel pressure. My stealth 2 programer allows me to see some things that are going on with the truck while drivng. The duty cycles on the injectors seem to be correct. I have a lot of experience in tuning gas vehicles via tuner pro RT. I've a 93 GMC typhoon that I have tuned...stock she runs 12.5's all day long. Anyway, the duty cycles seem to be all the same and change consistantly thoughout the rpm cycle and load. They change in concert as they should. I have no fuel in my oil so...so far they are ok. I HOPE. My truck starts up like a champ and the only time I get smoke...black (fuel) is when I have a heavy foot and am runnin the stealth 2 with a 70ph tune or more.

Now, the Stealth 2 allows me to see two values which I was guessing is the rail pressures. There is no definitions in the instructions of the quadzilla for the definitions One value is Fuel Des and the second is Fuel Act. Maybe this is fuel pressure desired and fuel actual? That would make sense due to the Des..ired and ACT ual. Now, while I"m cruzing at 60 mph on a flat run, both DES and ACT are reading about 3000psi. While I"m going up hill with a load, my DES is readin 1800psi, yet my ACT is reading 9300 and this is when I get the code 93. I replaced my FPR and shimmed the FPRV. My values jump all around from 400 psi to 9000psi. I suspected my fuel pump, however, I have no idea of what the pressure should be reading and/or where to test it. I have a gas Fuel pressure gauge that will measure up to 100psi max. I was thinking maybe the low pressure side was not delivering the fuel to the CP3. However, my truck runs great....it runs extremely well with the 50 or 70 hp tune WITH NO LOAD. Now, from all of my searches, there is a cosistancy of this problem being solved with a new CP3 which makes me think the problem is the CP3. I just want to be able to diagnose if the problem is the low pressure side or the high pressure side.

It's got to be either the low pressure pump..if is has one...I"m sure it does OR
The high pressure side CP3. After reading your reply, I assume the only pump on the duramax is the CP3? One would think that there would be a low pressure pump to get the fuel from the tank to the engine. Granted, I don't have much experience with diesel engines. If the CP3 is the only pump and we need a prime, maybe the CP3 pulls the fuel from the take by hydraluic action? Maybe this is what I'm confused about in regards to low pressure side vs high pressure side of the fuel system?

I'm just not sure where or how to test for the Low pressure side and how to test for the high pressure side. I' hope my programer can via the Fuel Des/Fuel Act.

How can I test the low pressure side and the high pressure side?

Thanks for the help.

 

"I have a lot of experience in tuning gas vehicles"

diesel tuning is almost a 360 degrees different then a gas engine, so you may have some learning to do.

"I have no fuel in my oil so...so far they are ok. I HOPE."

that is only one way they can fail. there is also ball/seat erosion which can cause high return rates and lower rail pressure. they can also stick or hang, but i don't think the latter is your problem. ball seat erosion is much more common.

"One value is Fuel Des and the second is Fuel Act. Maybe this is fuel pressure desired and fuel actual?"

Bingo! you my friend are a winner.

if you can watch or have someone watch it while towing. see if it sticking close to each other. if not there is fueling issues

"both DES and ACT are reading about 3000psi"
"DES is readin 1800psi, yet my ACT is reading 9300"
"My values jump all around from 400 psi to 9000psi"

now there's your problem! no really something is wrong with these numbers. idle should be in the 5000+ psi range, cruising should be around 8500 to 16000ish psi. full or heavy throttle should be upwards of 20K to 23K psi. double check your numbers here. your truck would run like crap if you could even get it started if these where the readings

"I'm just not sure where or how to test for the Low pressure side and how to test for the high pressure side."

stay away from the high pressure side testing, it can be quite dangerous. use the digital gauges only. for the low side pressure use the port just to the left of the alternator pulley. black cap covering a brass port looking somewhat like a 134A refrigerant fitting.

"It's got to be either the low pressure pump..if is has one...I"m sure it does OR
The high pressure side CP3. After reading your reply, I assume the only pump on the duramax is the CP3? One would think that there would be a low pressure pump to get the fuel from the tank to the engine. Granted, I don't have much experience with diesel engines. If the CP3 is the only pump and we need a prime, maybe the CP3 pulls the fuel from the take by hydraluic action? Maybe this is what I'm confused about in regards to low pressure side vs high pressure side of the fuel system?"

the CP3 is the only fuel pump in the truck. the CP3 is located in the valley of the engine near the front. it is driven by gears off of the cam shaft. the pump comprises of two major parts: a gear pump and a piston pump. the gear pump is what sucks the fuel all of the way from the tank through the filter and FCIM (injector controller computer) and pushing it into the piston part at about 75 psi. between the gear pump and the piston pump is a fuel pressure regulator. this part is the primary part responsible for regulating the high pressure side generated buy the pump pistons.

the CP3 fills the two rails over each head/valve cover. the injectors obtain there fuel from the rails.

the differences between the high and low fuel line besides the obvious pressure differences is that the low side is before the pump and the high is after the pump.

test the high side with a programmer or other device that plugs into the OBD port. for the low side use the port mentioned above or install a "tee" in the rubber line after the filter housing and use a gauge that can show vacuum of at least -10 psi. i think anything more then about -8 psi is too much and can cause fueling issues. i think -4 psi is more normal.

 

Thanks for the info!

When I purchaed my truck, I had no intentions on getting into the tuning of the diesels. I just purchased a stealth 2 programer for 200 and called it good. I have spent so much time tuning my GMC typhoon and I did not want to invest more time tuning my truck. Hell, I use my truck for my DD and pulling our trailer/boat. My typhoon, still tuning I got her bone stock running 12.4/12.5. I have heard of others getting into the hi 11's. I'm happy where she is for now, that is untill I build a monster V6 engine and tranny..and larger turbo .....and the list goes on and ON!

Regarding my truck. I have been spending hours on the net looking for info regarding my current towing issue. Seems like at idle my Fuel desired/actual is around 5K at idle. However, while I'm driving, thoes values are all over the place depending upon what i'm doing. The concerning issue is that I see my acutal fuel go from 3000 and as it's all over the place, I see values as low as 110psi, maybe for a mili second, but it's still low. It has to be one of two things.

Fuel lines
CP3

I found a thred of how the rubber braided fuel lines get soft and collapse after a few hours of driving. I took her out yesterday with the trailer for about an hour. I got under the truck and the lines felt a little softer, but were still firm. THEN, I looked at the one fuel line that was the 1/2 inch line. It has a nice kink in it. My plan for today is to go get a fuel line disconnect tool, remove all lines and replace them, then test my truck.

Do I think this will work, no. I suspect the CP3 is bad. With the fuel values jumping all over the place, it really sounds like a bad CP3.

Keep ya posted,

Thank you for the help!!!

 

the collapsing or kinking rubber lines are defiantly something that needs to be addressed first. no need to replace the CP3 if it is a cheap rubber line that is causing it. lift pumps are a great way to keep this from happening again in the future as they provide positive pressure rather then the negative it normally is at.

 

I replaced the fuel lines today and what a PITA! I had to cut the line where the rubber hose meets the steel line in two places becasue it was a compression fitting and the fuel disconnect tool would not work on that type of fitting. I can remember how much fuel dumped on me, but it was a lot! NEVER want to do that again! To boot, I live in the rual area and it takes me an hour to get to the store. It took me over 3 hrs to find the right compression fittings to repair two pieces of 1/2 inch line and to find the proper fuel lines. I've yet to test her out, but I know it's the CP3 just how the irratic fuel pressures are reading. I'm gonna test her out on Friday when I get home, but I highly doubt the fuel pressure readings will change much.

We will see.

Thank you for your help and guidance!

 

you might be surprised.

even a tiny air leak or kink can cause a huge headache.

it seems to be covered well, but it sounds like your not getting enough supply to the CP3 under load. a kink in the line would do it. fingers crossed for ya