Truck idles but bogs while driving or rev it up
01-22-2018, 07:22 PM
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Truck idles but bogs while driving or rev it up
Hi I have an ‘04 Cummins. It’s had some fuel issues lately. My truck has been hard starting, bogging and also stalling a lot the last few months which has kept me from driving. I changed the #6 injector a couple of months ago thinking that was the issue after my mechanic ran a kill test on it and he told me that it was a weak injector. I changed it out since I had all these symptoms and still the same thing. I got some advice from others then installed the FCA on the back of the cp3 and still nothing
Today I decided to mess with the truck again. I tried to start it a few times and it wasn’t turning over. I removed the fuel filter from the housing. (It’s a new Baldwin filter) It started up after I removed it. The lift pump is a new Mopar pump with less than 1,000 miles and it’s getting power to it. It kept stalling out with the filter removed after about 3-5 seconds which it usually does when I do finally get it started. I decided to hot wire the lift pump and hook it up to the battery to see if it would run any different. After I hooked it up and started it, boom it idled perfectly with no sputter at all. I had it idling for around 30 minutes. But when I tried to give it a little gas it bogs. I tried taking it down the street after it was warmed up and it still bogs pretty bad and it stalled twice after it bogged down
Does this sound like a failing/weak cp3 since I removed the filter and hotwired the pump then it idled fine? I’ve heard that when the cp3 goes the truck usually doesn’t start up at all. The truck has ran on WVO from one of the previous owners and it’s also the original cp3 with 96k on it, so I guess it’s a good possibility. The PO changed 4 out of 6 injectors(not sure why he didn’t do the whole set) but I ended up doing the #6 since it wasn’t changed and my mechanic said “it was weak on his scanner”. So now every injector has been changed besides #1. I haven’t tested the rail pressure while cranking or at idle yet. I’ve been trying to get my mechanic over to do so. I have a rail block off cap, I tried capping off the injector I just changed and it didn’t make a difference at all. I may try the other injectors as well. I might just buy my own rail pressure gauge if it helps pointing me in the right direction
Do you think I should try and test the return flow of the injectors, or does this sound more like a fuel pressure limit valve, internal leak, or a cp3 related issue? Thanks a lot guys, any comments or ideas will be greatly appreciated!
Today I decided to mess with the truck again. I tried to start it a few times and it wasn’t turning over. I removed the fuel filter from the housing. (It’s a new Baldwin filter) It started up after I removed it. The lift pump is a new Mopar pump with less than 1,000 miles and it’s getting power to it. It kept stalling out with the filter removed after about 3-5 seconds which it usually does when I do finally get it started. I decided to hot wire the lift pump and hook it up to the battery to see if it would run any different. After I hooked it up and started it, boom it idled perfectly with no sputter at all. I had it idling for around 30 minutes. But when I tried to give it a little gas it bogs. I tried taking it down the street after it was warmed up and it still bogs pretty bad and it stalled twice after it bogged down
Does this sound like a failing/weak cp3 since I removed the filter and hotwired the pump then it idled fine? I’ve heard that when the cp3 goes the truck usually doesn’t start up at all. The truck has ran on WVO from one of the previous owners and it’s also the original cp3 with 96k on it, so I guess it’s a good possibility. The PO changed 4 out of 6 injectors(not sure why he didn’t do the whole set) but I ended up doing the #6 since it wasn’t changed and my mechanic said “it was weak on his scanner”. So now every injector has been changed besides #1. I haven’t tested the rail pressure while cranking or at idle yet. I’ve been trying to get my mechanic over to do so. I have a rail block off cap, I tried capping off the injector I just changed and it didn’t make a difference at all. I may try the other injectors as well. I might just buy my own rail pressure gauge if it helps pointing me in the right direction
Do you think I should try and test the return flow of the injectors, or does this sound more like a fuel pressure limit valve, internal leak, or a cp3 related issue? Thanks a lot guys, any comments or ideas will be greatly appreciated!
01-23-2018, 02:48 PM
#2
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I’m no expert, but since no one else replied- high injector return flow seems to mainly show up as long crank times in cold start cold weather, or in warm climates long crank time or no start when trying to start a hot engine.
Bogging when attempting to accelerate, and stalling I would think would point to either a restriction of fuel flow (gunk left by waste v oil?) or a problem with the CP3.
If I recall there is a procedure to test the volume of output of the lift pump/filter, involving a fitting to measure the vacuum on the suction side. I think I’d start there, before $$$ CP3. Could be goober of grease in the tank, pickup screen?
Bogging when attempting to accelerate, and stalling I would think would point to either a restriction of fuel flow (gunk left by waste v oil?) or a problem with the CP3.
If I recall there is a procedure to test the volume of output of the lift pump/filter, involving a fitting to measure the vacuum on the suction side. I think I’d start there, before $$$ CP3. Could be goober of grease in the tank, pickup screen?
01-25-2018, 07:13 PM
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I’m no expert, but since no one else replied- high injector return flow seems to mainly show up as long crank times in cold start cold weather, or in warm climates long crank time or no start when trying to start a hot engine.
Bogging when attempting to accelerate, and stalling I would think would point to either a restriction of fuel flow (gunk left by waste v oil?) or a problem with the CP3.
If I recall there is a procedure to test the volume of output of the lift pump/filter, involving a fitting to measure the vacuum on the suction side. I think I’d start there, before $$$ CP3. Could be goober of grease in the tank, pickup screen?
Bogging when attempting to accelerate, and stalling I would think would point to either a restriction of fuel flow (gunk left by waste v oil?) or a problem with the CP3.
If I recall there is a procedure to test the volume of output of the lift pump/filter, involving a fitting to measure the vacuum on the suction side. I think I’d start there, before $$$ CP3. Could be goober of grease in the tank, pickup screen?
I also cleaned out the entire tank bone dry, installed a new lift pump, new ground wire, new power wire, and blew out the feed line from the tank to the fuel filter housing with compressed air while it was disconnected to make sure there wasn’t any dirt stuck inside. The new pump turns on and works perfect as it should, I don’t think there’s any crud in the tank either
I guess there may be a possibility I have a high return flow in at least one of the injectors, I wonder if that alone could cause bogging and/or fuel restriction as well?
Yeah I was also thinking maybe a piece of gunk/sludge from the previous wvo system could of freed up inside the cp3 making it clogged up and restrict the flow. (The wvo was hooked up directly to the cp3 so it did take a direct impact) I just don’t know why it would happen now, I put a bunch of miles on since I got it and so did the po after it was disconnected. I do believe it is the original cp3 pump and it’s quite rusty, so maybe it’s just getting weak or there’s an internal problem.
Is there an effective way to somehow test the fuel output of the cp3, or would that be just checking the rail pressure to determine whether it’s working properly? I just don’t want to buy a new cp3 and have it be a different issue
~Danny
01-31-2018, 10:37 AM
#6
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Since no one replied I would assume if when the engine acts up if the lift pump pressure is good and rail pressure is not, the control actuator or injector return flow might be suspect, or the CP3 internally.
The fittings required to measure injector, and cp3 return flow aren’t super high dollar, so it might be worth doing. I don’t know if the cp3 could be leaking along the shaft either, or how you’d determine that. Maybe send oil sample to blackstone?
The fittings required to measure injector, and cp3 return flow aren’t super high dollar, so it might be worth doing. I don’t know if the cp3 could be leaking along the shaft either, or how you’d determine that. Maybe send oil sample to blackstone?
02-12-2018, 03:20 PM
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Since no one replied I would assume if when the engine acts up if the lift pump pressure is good and rail pressure is not, the control actuator or injector return flow might be suspect, or the CP3 internally.
The fittings required to measure injector, and cp3 return flow aren’t super high dollar, so it might be worth doing. I don’t know if the cp3 could be leaking along the shaft either, or how you’d determine that. Maybe send oil sample to blackstone?
The fittings required to measure injector, and cp3 return flow aren’t super high dollar, so it might be worth doing. I don’t know if the cp3 could be leaking along the shaft either, or how you’d determine that. Maybe send oil sample to blackstone?
I don't mind buying a cp3 if it’s the issue. I just don’t want to get a new cp3 and have it be high injector return flow or something else
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02-12-2018, 08:33 PM
#8
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I think Miller 9011 and 9012 are the tools to block off an individual injector line from the rail, and to seperate the CP3 return flow from the injector return flow so both can be measured.
This might be helpful.
This might be helpful.
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