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Discussion Starter #1
Ok need some advice. Every so often the truck goes into some kind of limp mode. Usually happens after I get on it a little bit. Seems like the truck goes into some kind of limp mode where it will not go over 2000 rpm's. If you try to go over 2000 rpm's it shuts the fuel off. Until you get back under 2000 rpm's.
Seems to happen about once a week or so. Truck only gets driven on the weekends for the most part.
Here are some things I can say for sure.
Fuel filter changed less than 200 miles ago. Happened right before I changed fuel filter. Happened again yesterday afternoon 150 miles after fuel filter change.
Edge J/A settings don't seem to matter. Has happened on level 2, 3, and 4.
I know some people are going to say it is the Edge. I have had the Edge since 2005 with probably 12k on the truck. I have never had an issue with it.
No CEL.
Truck runs fine, no smoke, shifts fine just will not go over 2000 rpm's no matter what gear.
MAF sensor cleaned 1k miles ago.
Run Diesel Kleen every couple tanks. Just added some last tank. Have 1/2 tank diesel now.

My first thought is that it is a fuel limp of some kind. Maybe the fuel lines collapsing. Have not had a chance to get it on the lift to check the fuel lines but hope to tonight. Anything else you think I should check.

I can stop and cycle key 15 - 20 times and it will go back to normal.
 

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I'm gonna guess its a low rail pressure code. Do you have anything to read codes?

Sent from a combine cab using AutoGuide
 

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Mine would do it every so often right at 95mph....didn't matter what throttle position was.

Changed my AFE out for an S&B....hasn't happened since. Mine was one of the older AFEs that the MAF was pretty close to the filter. Never popped any codes or anything, weird part was it didn't start happening til over after a year of owning it.
 

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Discussion Starter #4
I have Torque downloaded on my Android. It has limited functionality reads codes. I will check to see if any are present.
 

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Discussion Starter #5
Mine would do it every so often right at 95mph....didn't matter what throttle position was.

Changed my AFE out for an S&B....hasn't happened since. Mine was one of the older AFEs that the MAF was pretty close to the filter. Never popped any codes or anything, weird part was it didn't start happening til over after a year of owning it.
I have an older AFE as well. The MAF is right up against the filter housing. It has been on there for 6 plus years. Would be pretty odd if it was causing it now. I have the stock intake still so guess I could swap it out easy enough to rule it out.
 

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I'm new to the site and have the same truck with an older afe intake as well. I had this happen to me a few months ago and changed the fuel filter and the truck ran fine until today. I'm also curious as to what causes this because it would be nice to fix the problem permanently!
 

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Discussion Starter #7
Update:
Ok so I hooked the truck up last night and there are no fault codes. Not even anything pending. Checked air filter and cleaned it. Pulled MAF sensor and cleaned it. Put truck on lift and checked fuel lines. They all seem fine. Nothing seemed to be collapsed or soft.
Not sure what else to check.
Any suggestions?
 

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It sounds like low rail pressure limp to me, my lbz did the EXACT same thing on big tune until i got lift pump...

BUT...I got a code when it did it..
 

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Discussion Starter #9
I thought low fuel rail pressure also but it happens on any tune and I don't get any codes.
I guess I need to find a way to look at the rail pressure and see if I can narrow it down.
 

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The problem could be a weak FPRV-- which is common on LLY engines. Do the bottle test--

At the back of the fuel rail -- on the driver's side- there is a small "U" shaped hose-- remove the hose from the rail nipple, plug the hose. Now add several feet of hose to the rail nipple and put end in a bottle. Now drive the vehicle hard-- if you have fuel in the bottle, the FPRV is not holding pressure-- so either shim the valve or replace it. Some use a Race Valve, but that does not release any pressure and can cause a high pressure spike.
 

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Ok need some advice. Every so often the truck goes into some kind of limp mode. Usually happens after I get on it a little bit. Seems like the truck goes into some kind of limp mode where it will not go over 2000 rpm's. If you try to go over 2000 rpm's it shuts the fuel off. Until you get back under 2000 rpm's.
Seems to happen about once a week or so. Truck only gets driven on the weekends for the most part.
Here are some things I can say for sure.
Fuel filter changed less than 200 miles ago. Happened right before I changed fuel filter. Happened again yesterday afternoon 150 miles after fuel filter change.
Edge J/A settings don't seem to matter. Has happened on level 2, 3, and 4.
I know some people are going to say it is the Edge. I have had the Edge since 2005 with probably 12k on the truck. I have never had an issue with it.
No CEL.
Truck runs fine, no smoke, shifts fine just will not go over 2000 rpm's no matter what gear.
MAF sensor cleaned 1k miles ago.
Run Diesel Kleen every couple tanks. Just added some last tank. Have 1/2 tank diesel now.

My first thought is that it is a fuel limp of some kind. Maybe the fuel lines collapsing. Have not had a chance to get it on the lift to check the fuel lines but hope to tonight. Anything else you think I should check.

I can stop and cycle key 15 - 20 times and it will go back to normal.
Friend just got his '05 LLY back with exact same issues you are having, no codes. Has same setup as you do. Ended up being the FPR on the CP3. Limited to 2000rpm's. Just a suggestion. Chris
 

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I have the same problem, and I'm 100% sure the cp3 its on its way out! Haven't fixed for money reasons :-(.
 

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Discussion Starter #13
Well I have found out it is indeed the FPRV. I did the bottle test this evening and drove about 4 miles getting on it hard from time to time. Filled a 20 oz Gatorade bottle about 2/3 the way up. So the FPRV is weak and not holding the pressure needed for fuel demand. Ordered a the new parts to fix it up today so should be good to go first part of the week. Thanks for everyone's input.
Also thanks to Husker Diesel for answering my questions giving me the advice I needed and getting me the parts in the mail.

Thanks
 

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i took mine in to get looked at and the mechanic told me i used a bad fuel filter when i changed it last. I dont really think that was the problem so if it is the fprv what whould i get to fix that problem?
 

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i took mine in to get looked at and the mechanic told me i used a bad fuel filter when i changed it last. I dont really think that was the problem so if it is the fprv what whould i get to fix that problem?
Do the bottle test, it will tell you if you have a bad fprv. If your fprv is weak you can shim it (shim kit available from venders here) or replace it with a PPE race fuel valve (fancy name fr an fprv). Do a search for the bottle test, it is very easy to do.
 

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Discussion Starter #16
First thing to do is the bottle test.

To do the test all you have to do is;
At the back of the fuel rail on the drivers side there is a "U" shape hose connected at the back. It is not hard to find. I was not sure where to look myself and found it easily. Just pop the hood. Look towards the back on the drivers side and you will find it. Unhook the hose towards the drivers side. Plug the hose with a bolt and a hose clamp. Then hook a 2 foot section of hose to the nipple that is free. Put the hose in a bottle. I used a gatorade bottle with the cap on. Drilled a 1/2" hole in cap and stuck hose in it. Clamp the hose on the nipple with hose clamp. Zip tie the bottle somewehre out of the way. I zip tied it to the hydro-booster.
Now drive the truck around a couple miles getting on it hard some.
Check the bottle. If you have more than a small amount of fuel in bottle. Your FPRV is week.
Your choices to fix are;
Replace
Shim
Go with a race valve.
Hope this helps.
 
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