Fuel Pressure Loss
Thread Starter
|
Registered User
Joined: May 2018
Posts: 4
Likes: 0
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; May 15, 2018 at 11:50 PM.
Thread Starter
|
Registered User
Joined: May 2018
Posts: 4
Likes: 0
Thanks,
the starting system system is fine, 6mo old battery and starter cranks good.
to make things more complicated, this morning I went to test it after sitting all night and rail pressure went from 0-52psi and fired up on first crank.
problems that disappear during diagnosis suck.
the starting system system is fine, 6mo old battery and starter cranks good.
to make things more complicated, this morning I went to test it after sitting all night and rail pressure went from 0-52psi and fired up on first crank.
problems that disappear during diagnosis suck.
Thread Starter
|
Registered User
Joined: May 2018
Posts: 4
Likes: 0
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.
All Star
Joined: Mar 2015
Posts: 752
Likes: 24