Not sure if the lift pump is flow through, but I'll give it a try, if not, I can make up some fittings to bypass it
LLY: New Cp3 leaking
- Thread starter frankenstien
- Start date
Not sure if the lift pump is flow through, but I'll give it a try, if not, I can make up some fittings to bypass it
I unplugged the lift pump and took it for a short drive, it was short because the truck did not like that.
under light load its ok, you put your foot into it and the truck was bucking, fuel rail pressure was all over the place, tanked as low as 1.7k, made the turbo cough. drove it till i could get to a safe place to pull over, hooked up the lift pump and it ran fine.
it was only a 2 or 3 mile adventure, i usually got 10 miles or so, i checked, but did not see and new fuel in the valley of the motor, however it smelled like hot fuel, so I'm guessing i didn't run long enough to have the fuel run back where i could see it, I will check it again in the morning
I am going to call Fass in the morning and ask them about if it can pull through or if it causes a major restriction, if they say no go, then i have a fitting made up to put in place of the pump. or maybe i can turn it way down to like 1psi?
Also, i may have forgot to say, when you truck sometimes it fires off, then the rpms dip way low, then comes back to normal idle, it did the same thing with the lift pump disconnected, but i cant remember for the life of me before i changed the pump
Running poorly at high throttle is expected with the lift pump disconnected. I'd just drive gently for the test. It isn't worth making a bypass IMO.
If you have access to a cheap borescope or GoPro camera, you could try stuffing that down near the CP3, then go for a drive.
Sent from my Cat S60 using Tapatalk
If you have access to a cheap borescope or GoPro camera, you could try stuffing that down near the CP3, then go for a drive.
Sent from my Cat S60 using Tapatalk
Still trying to learn here myself. But wasn't there a post recently that his fass pump failed and it still ran great. No issues. Only way he new it was from fuel pressure gauge reading zero or changing filters I believe. Or does the second filter cause that more strain on the suction?
I'm not sure in that case mine is just a pump, it is not the whole filter setup. I just called Fass, they said to bypass it.
Quick update.
Put my bypass fittings online, unplugged pump, ran it maybe 15-20 miles today, ran it hard, truck runs just fine.
NO fuel in the valley.
Dave when you say supply side when hot, do you mean the high pressure side to the injectiors? Or from the lift pump to the engine?
The little rubber line for the inlet is brand new when I installed the pump, and I have put screw type hose clamps on it, and have not been wet yet, leak in the valley or not.
Put my bypass fittings online, unplugged pump, ran it maybe 15-20 miles today, ran it hard, truck runs just fine.
NO fuel in the valley.
Dave when you say supply side when hot, do you mean the high pressure side to the injectiors? Or from the lift pump to the engine?
The little rubber line for the inlet is brand new when I installed the pump, and I have put screw type hose clamps on it, and have not been wet yet, leak in the valley or not.
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If it doesn't leak when the lift pump is bypassed, then it must be the section of line between the lift pump and the gear pump in the CP3 that is leaking. I'd double check those rubber lines and clamps, especially when hot. They may be ok when cold, but if the line gets soft when hot, an extra turn on the clamp might solve it.
Sent from my Cat S60 using Tapatalk
Sent from my Cat S60 using Tapatalk
When the lift pump is running i have always at 11psi, I had to re adjust when I put everything back together, it ended up at 12, I am measuring it by the ficm, was measuring it on an aftermarket fuel filter housing in stock location.
I'll give em another turn when they're hot.
I have a few theories at this point,
1. The pump is fine, intermittent leak from rubber line on supply side from lift pump.
2. Lift pump pressure too high.
3. Too much supply not enough return giving the weep hole leak like S&S said
4. Some unlikley super rare defect i drew the short straw on
I have been checking for leaks with a UV light and fuel dye and everything top side has been dry and no glow under UV.
Thanks for everyone who has been helping me figure this thing out, really appreciate it, still hoping I don't have to pull the pump again
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that would be very unlucky, did it do it at idle? cause mine only seems to leak under load.
Been super busy, I had bypassed the lift pump and have been running no lift pump and put screen clamps on all the soft lines. No leaks.
Monday, I hooked the lift pump back up, turned pressure down to about 7, it rangers from about 7-8.5, will dip to about 5 when hammering on it.
Was good for a few days, no fuel in the valley when I got home from work wednesday night qt 11pm, sat til friday morning, drove it to drop the kids off at school and get a load of water, fuel in the valley, not as much as it was before, but still due
All the soft rubber lines are dry.
Could a restricted fuel cooler cause a cp3 sea to wrap like I have going on?
Monday, I hooked the lift pump back up, turned pressure down to about 7, it rangers from about 7-8.5, will dip to about 5 when hammering on it.
Was good for a few days, no fuel in the valley when I got home from work wednesday night qt 11pm, sat til friday morning, drove it to drop the kids off at school and get a load of water, fuel in the valley, not as much as it was before, but still due
All the soft rubber lines are dry.
Could a restricted fuel cooler cause a cp3 sea to wrap like I have going on?
been stupid busy, finally took some time to swap back in the old cp3.
the old cp3 is also leaking same as the new one, so that rules out the cp3 being the issue.
only idea I have is to bypass the cooler and see if it quits. I have the fittings and hose to hook up to the return fitting on the back of the engine, and the sending unit and run 3/8'' rubber line. Its winter time, so I dont think fuel temps should be an issue for a temp trial. I have a Derale cooler to replace the factory one, but I have to make up a bracket for it
if my injectors are returning too much fuel could it be causing too much resistance on the cp3, causing it to leak? I have a kit to test return rates
Ive seen alot of posts where guys just run a 1/2'' line directly to the cp3 and have no issues, my 1/2'' line goes to the 1/2 quick connect on the drivers side back of the motor
the old cp3 is also leaking same as the new one, so that rules out the cp3 being the issue.
only idea I have is to bypass the cooler and see if it quits. I have the fittings and hose to hook up to the return fitting on the back of the engine, and the sending unit and run 3/8'' rubber line. Its winter time, so I dont think fuel temps should be an issue for a temp trial. I have a Derale cooler to replace the factory one, but I have to make up a bracket for it
if my injectors are returning too much fuel could it be causing too much resistance on the cp3, causing it to leak? I have a kit to test return rates
Ive seen alot of posts where guys just run a 1/2'' line directly to the cp3 and have no issues, my 1/2'' line goes to the 1/2 quick connect on the drivers side back of the motor
I think i figured it out today, went and ran a line directly from the return fitting on the motor to the sending unit on the tank.
I was able to blow through the fuel cooler easy enough. Rigged up a line to blow through the return fitting, took off fuel cap, it was VERY hard to blow through, guessing the return side has a bunch of crap in the hole at the bottom of the sending unit for the return
I was able to blow through the fuel cooler easy enough. Rigged up a line to blow through the return fitting, took off fuel cap, it was VERY hard to blow through, guessing the return side has a bunch of crap in the hole at the bottom of the sending unit for the return
Yeah, not sure what I picked up, or whats inside there, but that return should be very free flowing correct? You have to chipmunk cheek it to blow through it.
I found this video, after a painful amount of googling
https://youtu.be/jk-pROpwt2s
Skip to 18:10, he pulls off the little log manifold thing at the bottom of the sending unit, looks like the supply pulls from the return and tank, and his is also clogged up as well
One the earlier models, maybe even the later too, there is a little jet that the return fuel squirts through to create a venturi to draw more fuel into the bowl. I could see how this could get clogged up if you had junk get pushed down the line
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yeah, that's what I'm hoping/guessing, to me, there's a restriction in the return in that sending unit, i would think it should be easy to blow through
I would think that if the pressure was high enough it would just blow that jet out the bottom. Then you would be experiencing the "empty at 1/4 tank" issue. That fitting is just pressed in and is a snug fit but not super tight. The bottom of the fuel tank I guess helps hold it in too
Had mine fall out once before. Have no clue why
Had mine fall out once before. Have no clue why