Gitch

Bascially the code p0148. I put in new injectors, ran better but still had the code and had no power.

It would run good and have no codes when the fuel tank was BELOW 1/4 tank. So i figured it was the lift pump. So i just installed an airdog100 yesterday. But Still have the same problem.

The only other thing i think that could make it act like that with the correlation of the fuel level would be the return line back into the tank.

So im thinking that when the fuel is below the end of the return line in the tank there is no pressure holding the fuel from dumping into the tank and no code. But when there is fuel in there and its submerged under the fuel its too much back pressure for the fuel to return into the tank.

WHich is causing lots of black smoke and sometimes stalling out. Unless there is something else i dont know about thats the only thing i could come up with. Still would like to test out someone elses fca to see if thats the problem or not.

Otherwise i might have to consider running a brand new higher flow line from the front to the back of the truck and dump it into the tank filler instead of the top of the tank.

Any ideas?

AH64ID

Fill out your sig so we know what year truck you have.

But I would guess a clogged fuel filter or a FCA would cause this. Failed lift pumps generally wont throw codes as lift pump pressure or flow isn't monitored.

Gitch

Ill fill that out now. Its a 2006 mega cab. All stock except the airdog100. And new ss bodies with stock nozzles...

Well the fuel filter problem shouldnt be an issues since the airdog is about 12 hours old now.

I just dont understand the correlation between the fuel level and the code being thrown...

AH64ID

I am not sure on that one, but would assume its FCA related.

Did you bypass the OEM canister?

Gitch

Yeah the kit just goes directly to the cp3. But the return is still stock. Its very tempermental as it has been running pretty well all day.
But still has the engine light. I just scratch my head and this truck because i dont get why it does what it does sometimes.

AH64ID

You may have to have the code erased, not all codes are self-resting.

What filters came on your AD? What kind of drain does the f/w sep have, metal or plastic?

SpeedyWS6

P0148 is set when there is a difference between the fuel pressure set point commanded by the pcm and actual fuel pressure. I'm not sure on how much it takes, but I have seen the code tripped when you can't even really tell the truck isn't running 100%.

Since you say it gets worse as fuel level drops I would think that you may be sucking air. The return is only going to return what needs to be returned and shouldn't be effected by fuel level.

How does the AD100 pull fuel from the tank? It could be a problem with your canister is why I ask.

Try running it with the fuel cap off also. I doubt it's the problem, but it's an easy test.

Gitch

Actually is backwards. Runs like a dream when its LESS than 1/4 tank. When its full it runs like complete crap. THe airdog runs with a metal draw straw that goes to the bottom of the tank. You cut it yourself and put notches in the bottom so it can suck fuel from all directions. It made a big difference in how smooth it ran overall. When i get to down around 1/4 tank it really rips like it should.

But when i just fill it its hard to even accelerate on the highway. Every single time.

Although the airdog seemed to help run smoother etc. It still acts exactly the same as the stock lift pump as far as acting up. So i know its not that.

I Had the codes cleared with an actual 20k Chrysler scanner. (well i dont know the price of them but they are not something you can just buy) The thing would even tell me when i didnt wear a set belt!

So after resetting it with that. I had a 1/4 tank of fuel. Drove around for about half hour. Doing anything and everything i could to get it to trip again with the scanner connected. NOTHING. THen i took off thinking it was just the simple clearing of the code.

Well drove an hour or so.. stopped to get some fuel. Only filled to about 3/4.. got a mile down the road and DING. engine light and ran like crap again.

SO whatever it is it has to do with the tank being full. or atleast more than 1/4 tank.

WHich is why i orginally thought it was lift pump. Only thing in the tank and they seem to go back more frequently than other things.

So thats why i got the airdog but still the same problem.

WHich leads me to think it has something to do with the return line.

OR the fca is acting up and pushing to much fuel through and when the return line is submerged its causing to much back pressure to cause it to throw the code. Just enough to put it over the top.

Does any of my logic make sense or am i just crazy.

IM gonna start this week with an fca swap with someone with a full tank. Have the codes cleared and see what happens.

IF the Code doesnt come up again i know it was the fca and the return line is adequate.

IF that doesnt work my next Cheap step is gonna be Running a direct line from the engine bay to the Fuel filler tube so there is nothing restricting the flow.

IF that doesnt fix it then its something else. Maybe rail pressure relief valve. I will test that as well.

If not that maybe the check valve on the back of the head. Not sure how to test that yet. There is a youtube video ill check out again for exact procedure just requires special tools.

If its not that maybe CP3?

ok time to spell check for inappropriate language!

SpeedyWS6

My bad I read that part wrong... You need to get it back on the scanner when it is acting up. Verify for sure what the rail pressure is doing. Higher or lower than set point.

Now for sure run it without the fuel cap. I have seen bad fuel caps cause problems on other diesels. And usually the more fuel the worse.

mq105

Tank not venting properly? Ever hear air sucking into the tank when you remove the fuel cap?
I've heard of similar situations where the tank can deform/collapse enough when empty to allow fuel to get out, but when full, the tank can't collapse. If the ventilation can keep up with fuel demand at low power/cruising, you have no problems. But, as demand increases, the poor ventilation doesn't allow enough air to enter quickly enough and creates a vacuum. As you let off the throttle and demand decreases, ventilation catches up and the engine runs ok again.
Maybe a possibility. We need to know what your FP is when you have the problem, and when the truck is running well.

Gitch

Ill run without the cap a couple times and see what is happening. Would upset me if thats all it was. ha.

I dont have a fp guage yet. The airdog is set stock at 15psi give or take over the 8-10 from factory. I can add the high pressure spring to see if that makes a difference or not.

mq105

If improper venting turns out to be the problem, check the two vents on top of the tank as well as the cap.
I don't think more pressure from the LP is necessarily the answer. It would be helpful to know what FP is.

Gitch

Well the venting made no difference. But today i noticed a NEW code.. yay.

p0251. So its looking like fca or cp3 may be the problem. Im going to swap the fca with a buddy here in a couple hours and see what happens. But any other quick checks pertaining to that code would be helpful.

SpeedyWS6

The only test is for electrical problems on the FCA circuit, and I seriously doubt yours is electrical other than maybe a bad FCA.

If the FCA swap does not fix it I would suspect the pump, but get us some pressure readings before you spend that money.

oldblu

gitch, im suscribing to this thread mine has been having same code for awhile now, mine would do it when pulling trailer up hill or getting on throttle hard, so just like you i assumed bad lift pump, well i put on airdog 165 and same thing so far. Thinking it might be injectors on mine cause have another code that has to do with them the p2146. Only my truck doesnt run horrible but i dont think it runs like it used to for sure, airdog mighta helped a little but it doesn't run like it should i don't think. So wondering bout the fca also and called shane at wicked to order an arson kit, figured it came with upgraded fca and id need more fuel in future anyways, but he is out of them till first of jan so will wait and see if yours fixes it. Sorry not trying to hijack your thread but hope we both get this thing figured out.