Fuel Pressure Loss
#1
Fuel Pressure Loss
I’ve had my 2006 4.7 4x4 CC Dakota about 6-months since my 04 got written off.
It’s always had a slight whiny, sucking noise when cruising and just touching the throttle. I haven’t been able to figure out. More or less throttle and it stops. I’ve thrown a new TPS at it after a buddy suggested and that did nothing. It doesn’t cause any drivability issues, just annoying. This may be unrelated to my main problem.
my main problem is starting. Last month I started having hard-starting after I hadn’t driven it a day or two, then every morning, now anytime the engine is cold. It cranks and cranks and will eventually start but also throws a code. I haven’t had the code read but I assume it’s just a symptom and not the real problem. I’ve found that if I cycle the key a few times to let the fuel pump prime it starts fine. So I suspected a failing pump. I threw a new pump assembly in and for two days thought I had cured it, then it came back. I also threw a new gas cap at it because I needed a locking one anyway.
today I got a fuel pressure tester to check bleed-down. It runs at 55psi and sits at 52psi after shutoff, then after a few minutes start losing pressure until 0psi after about 70-minutes. I pinched off the return line at the tank and got same results. So now I’m thinking leaking injector(s)
the wierd thing is, if I bleed off all the fuel pressure to zero, but the engine is still warm, it will fire up right away still.
I don’t understand why 0psi when warm starts fine but 0psi in the morning won’t start without priming cycles.
Help please.
It’s always had a slight whiny, sucking noise when cruising and just touching the throttle. I haven’t been able to figure out. More or less throttle and it stops. I’ve thrown a new TPS at it after a buddy suggested and that did nothing. It doesn’t cause any drivability issues, just annoying. This may be unrelated to my main problem.
my main problem is starting. Last month I started having hard-starting after I hadn’t driven it a day or two, then every morning, now anytime the engine is cold. It cranks and cranks and will eventually start but also throws a code. I haven’t had the code read but I assume it’s just a symptom and not the real problem. I’ve found that if I cycle the key a few times to let the fuel pump prime it starts fine. So I suspected a failing pump. I threw a new pump assembly in and for two days thought I had cured it, then it came back. I also threw a new gas cap at it because I needed a locking one anyway.
today I got a fuel pressure tester to check bleed-down. It runs at 55psi and sits at 52psi after shutoff, then after a few minutes start losing pressure until 0psi after about 70-minutes. I pinched off the return line at the tank and got same results. So now I’m thinking leaking injector(s)
the wierd thing is, if I bleed off all the fuel pressure to zero, but the engine is still warm, it will fire up right away still.
I don’t understand why 0psi when warm starts fine but 0psi in the morning won’t start without priming cycles.
Help please.
Last edited by Jeremy Clarke; 05-15-2018 at 11:50 PM.
#3
#6
I replaced the whole assembly.
Strangely, the problem has entirely gone away now. I still lose all rail pressure after an hour, but it fires right up. I had dumped a bunch of Royal Purple fuel system cleaner in the tank the week before, maybe that finally cleared things out? Maybe the back-pressure from the sudden releasing of rail pressure a few times? IDK, but I’ll take the win. Thanks for the help.
Strangely, the problem has entirely gone away now. I still lose all rail pressure after an hour, but it fires right up. I had dumped a bunch of Royal Purple fuel system cleaner in the tank the week before, maybe that finally cleared things out? Maybe the back-pressure from the sudden releasing of rail pressure a few times? IDK, but I’ll take the win. Thanks for the help.
#7