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Try a relief valve cap, that may be your issue. Cheap and easy. Rules out that if doesn't change the numbers.
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Mark Chappel, of (TST)
Originally Posted by 5.9Excursion
(Post 1950900)
So my max pressures are low... This kind of explains why in stock form (no smarty I thought it was a dog), with the smarty on 8 it is acceptable (little better than stock).
Until last night I didn't have a vehicle speed signal fed into the engine ECM, which I read somewhere may cause the engine to defuel. Scott at Destroked said I could use either the tranny sensor or the Ford rear end sensor to fix this. The ford wiring was easier to get to so I spliced it in last night along with the rail pressure gauge install. However, it still drives the same and the rail pressure readings sort of prove that it is defueling. I guess I'll have to try the dodge speed signal next and see if it changes any. I'll check for codes again, but previously I never had a low rail pressure DTC. How low of a pressure do you guys see with automatics (with a rail gauge obviously) when you slow to a stop. Does it never drop below 4000? Just on my way home from church this morning with the family, it dropped to around 1000 as we pulled into the driveway... |
AHA! - There's yer prob - without VSS iput, ECM thinks yer sitting' in the driveway, revvin' it up in Park\Neutral - which may also explain why no DTC's for rail pressure performance - should be getting a P0500\equiv for VSS input, tho.
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I have no vss wired into mine and have no defueling issues. I think your problem lies elsewhere. Could also be an injector issue.
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What physically determines the rail pressure? Isn't it mainly the FCA?
I don't see how the low rail pressure could be injector related, they are just check valves that let the pressure out into the cylinder. I wouldn't think they would limit the overall rail pressure (unless ofcourse the injectors are huge or you have alot of duration which would drain the rail, if that was the case it would be making more power too). I've been wrong though... Destroked said the VSS input was year specific, can't remember which ones needed it or didn't... Where can I find more info on the rail cap that someone mentioned? |
Just for kicks......unhook the fca and see what you can get for rail pressure. Maybe there is a problem with the lines/filters/cp3/fca/ ect, not letting it achieve the needed rail pressure. It may not be an electrical problem, but more a fuel delivery problem .
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I can try that tonight, do I just rev it in park/neutral and check the pressure or do you mean go for a drive with it unhooked? Is it supposed to go to full pressure or low pressure with it unhooked?
EDIT: I just read on the forums that with the FCA unplugged, it calls for max pressure. It should start and rattle alot... not sure what pressure I'll see though... |
I believe it should go to full pressure. You can also unhook the rail pressure sensor, and you should be able to hear the difference. Problem is.....with the rail pressure unhooked, you can't actually see what the pressure is. It's kinda hard to determine if it is a sensor problem or a fuel delivery problem, but between these two ways you should be able to tell .
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Man it's cold, finally went outside to try the stuff mentioned earlier. It's a whoppin' 8 degrees outside, hard to type, fingrs still nubm.[dummy]
Anyway, check codes, had P0646 and P0533 I think. (Again very cold out and Smarty screen was hard to read, probably shouldn't leave it out there...) Unplugged FCA and started it up, rail pressure went to 26000 are just over and ran rough. Plugged it back in, back to before. I unplugged the ford speed signal from the cummins ECM, as it didn't work and I lost my antilock brakes too. So now the antilock brakes are back. Next, I have to hook the 48RE VSS signal up, I have to lay on the ground to get to that wire, so it will wait until it's warmer or I can get it in a shop. So far, it seems to point to an electrical/ECM issue, hopefully the VSS input will solve it. |
Those DTC's are both a\c related - prolly no need to worry about 'em till summertime
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So we now know your CP3 is capable of producing higher pressures, so why isn't it? Rail valve bad or FCA???
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That's exactly what I'm thinking.....or ECM defueling because of torque management because it doesn't see the correct VSS.
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Originally Posted by vzdude
(Post 1954120)
That's exactly what I'm thinking.....or ECM defueling because of torque management because it doesn't see the correct VSS.
I had 5 codes total. Two are related to the fuel level circuit (not hooked up to the ECM), one is related to the PCI bus (trying to talk to a Dodge PCM that isn't there), and then the two I listed above. I hadn't seen those before, but I looked them up and they are related to the AC system. Don't have the compressor lines on yet so it isn't hooked up. But no codes related to no VSS signal, defueling, or low rail pressure (seems weird). I wonder how much power I'm down right now (rail pressure 15000 vs. 26000)?? Can't wait to get this fixed, it should run awesome... |
Oh yeah......I think you'll be impressed! I know before my upgraded lift pump, I was limited on HP even with my mods. They came alive with the added lift pump psi! So you add in 10K in rail pressure..........you'll be smokin'!
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Really interested to see what the fix is with this. By the way did your ever figure out the loud injector problem or whas it even a problem?
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