Low rail pressure 17500psi max
 

I did a rail pressure reading trying to figure out why my truck is pretty slow for what it is. I have good tunes, The truck has thrown one p1093 and it did it when was trying to figure out a baro sensor issue.

I was trying to log the actual vs commanded rail pressure but it kept saying invalid pid.

The point, I did four logs, all are at 4 - 5 psi at idle, max psi at 3200 rpm at 17500 psi. I watched the logs go through and it never appears to drop off it just gets to 17,500 ish and stays.

The truck other then being slow ish does not have any other symptoms, it idles smooth, no smoke, surged only when my map sensor was having crack for breakfast, starts easy.

Fuel Filter?

you may have a weak CP3

what PW are you running when it can't hold above 17,500?

a lift pump may help a weak CP3 or large PW

PSI looks ok at idle as long as you mean 4-5,000 PSI

Both fuel filters are new as of Saturday I logged on Sunday, I don't know what you mean by PW sorry. At idle is 4-5000 PSI yes.

sorry, PW = Pulse Width. the length of time the injectors stay open per each injection cycle. i saw that you had EFI Live in your signature. a tune that runs a large PW can drain the fuel rails under WOT and cause poor performance with a weak CP3 pump and even some strong ones.

did this truck run fine and then suddenly not? any changes made to shortly before it started running like this?

This is how the truck has ran since the twins went on (i was part of the install before I purchased the truck). I think this set of twins has been on the truck for about a year now.

I got the truck and started talking to other people and asking questions about what this set up should be like, then watching you tube of trucks with same basic set up or hp ratings (where mine should be) and noticing I was pretty slow.

Larry Jewell started helping me with my tunes to make sure I had a good one and told him what was going on as far as performance and he agreed i should be pulling harder then I am.

I think my PW are at 3200 ish. I cant confirm that without looking at them but i think that is about right.

i think 3200 is on the high side but probably where it needs to be to be able to make about 500+ HP on stock injectors. even a good CP3 will normally have a hard time maintaining 20K+ PSI unless it was opened up to improve flow. this is in the realm where a good lift pump should be invested in.

what could have happened is that the truck ran fine when the CP3 was relatively new but is now getting weak and cant maintain the pressure needed.

do some googling "CP3 mod" and "lift pumps" to learn how important it for the upper HP levels

thanks Jason

Thanks for your help I appreciate it. Is there a test I can do before I start throwing 600 for a lift pump or 1200 for a 40% cp3?

it depends, are you familiar at all with EFI Live tuning, i assume your still new to it. you can try dropping the PW down to 2800 or even lower until the CP3 can keep up. this can give you a rough estimate on the condition of the CP3. it may even run stronger with lower PW and higher rail pressure.

i found my new raptor 160 lift pump on ebay for about $150. results may vary

if you are mechanically inclined you could do the mods yourself for little to nothing, but this may not be worth it if the pump is worn.

try reducing the PW down some and test it first to see if it feels like it runs stronger

Add lift pump already to my sig.

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I will give the pw a shot, I am new to tuning yes but I have been getting some pretty good guidance and I am making progress. It is going to be a bit before I can use the butt dyno to see whats going on, weather has turned back to winter and the roads are in no condition for hammer down driving.

The closet real dyno is a 4 hour ferry trip and a 700 mile road trip after so all dyno runs are done with the highly accurate butt dyno.

I do all of my wrenching, If it turns out to be a cp3 I will be the one doing the install. Not by career I am a computer geek, I just hate paying people to do stuff I should be able to do my self.

wow that was fast! at that speed you should be able to install a couple hundred lift pumps a day:jump:

so if you already had one, then just do the PW test. let us know how it goes

i feel the same way

modded my own CP3, wow what a difference. there are great write ups floating around these and some other forums on how to do it. consider doing it to the one you may put in so you only have to do it once.

once again same here. dont know of any dynos near me so it is my butt for now. seem to have worked so far. have not lost to a stop light race so far. haven't challenged many other diesels though, mostly ricers and other gasser junk