you need to hook up a scanner and find out what cranking rail pressure is

 

Thanks,
Can the scanner display pressure during cranking?
Do you what pressures I should see during cranking and at idle etc?

 

a scanner will show that. i dont know about a cheap one though. iirc you need around 5kpsi for it start and idle is around 7kpsi

 

Followed a trick I found on youtube:
Removed the FCA, (it looked very clean), hosed it down in WD40, reinstalled.
Subjectively, i would say there is a slight to moderate improvement to starting in all conditions, hot, cold, restart, etc.
Also seems to drive slightly better. The idle seems more stable when pulling down idle speed with the clutch from a dead stop.
(The you tube vid suggests that if this makes any change in performance, it is time to get a fresh one).

So my cheap model Edge tuner has just enough scanning capabilities.
(Displays in Mega Pascals, but I converted it to PSI).
(This was checked after lubing up the FCA).
During cranking it is hovering around 1000psi, building, and peaks at 2000psi right before it actually fires up.

Right after it fires it overshoots to 8700psi, then settles down to 6800psi at idle.

It builds great pressure well beyond 20,000psi when I rev it.

When I shut it down, rail pressure will drop to 0 within about 1 second of the engine stopping.

Seems to suck at building pressure while craking, but is all good once it is running.

based on the above i am leaning toward ordering a new FCA.
Any thoughts?

Talked to the shop owner today.
He was rather reasonable and sympathetic to the situation.
We agreed it is a waste of both our time's to put the original injectors back in. (even though that is what I would want in a perfect world). I am going to meet him half way, he will refund labor and parts margin, but I will pay his cost on parts.

 

thats a good out come with the shop, sounds like a good guy.
2kpsi is low, it may not take 5kpsi to start, i just cant remember the exact number. an fca aint too spendy, so i would replace that and see if fixes the problem. if it doesnt you at least have a new fca and a spare.

 

Agreed.
Thanks for all the info.

Only things that make me worry is that this problem seems to be rather uncommon. (most of the time, I have the exact same problem as everyone else). And, if its NOT the FCA, I think I am running out of possible problems. A leaky pressure limiting valve would make some sense too, but if its not that, or the FCA, The only thing left is a new injection pump.

Kinda bummed how the whole thing is working out.... I cant remember the last time I took a truck to a mechanic, and then this happens. I took it to someone cause i am SOOOOOO busy with house, kid, bikes etc etc etc. All I wanted was to pay to save some time. Instead, i have to invest all the time anyways, and I am out thousands of dollars anyways.
"Sometimes you eat the bar, and sometimes, the bar eats you"

At least I learned how this fuel system actually works, and that I need 2 micron filtration. I bought a sweet filter kit, but I am not putting it on until the problem is solved to eliminate variables. Also got a case of stanadyne.

 

take that case of stanadyne back and use non synthetic dexton ATF. it works way better then any other fuel system clean and has fixed guys issues that all the other cleaners could not fix. just put 1 qt on when you fill your tank and do this for a few tanks. i did that when i was having issues and it cleaned my fuel system fixing my issue. now i just put half a quart of ATF in the tank every few tanks. i also add ashless 2 stroke oil (tcw3) to help lubricate things. i just use the cheap walmart oil and ATF.
your PRV may not be leaking, but you dont know if that is the problem or not. you gotta start somewhere to get it fixed and i would start with the FCA. its not gonna make things worse. so "if its NOT the FCA" then you move onto the next thing.

 

Still have the starting problem.
The FCA did not fix it. (But I think made a slight improvement).

Still only have 2000 psi while cranking.

I finally got a new pressure sender, so i can see lift pump pressure. (my dipricol had failed a long time ago).

Measuring at the bottom of the filter bowl, measured pressure leg is between the filter and the CP3.

I am getting a solid 10 psi, dropping to 7.5 under slight load, and 6psi under heavy load.

Because the gauge is electronic, i cannot see the lift pump pressure while cranking, voltage is too low.
Before starting, when cold, it will usually build to 10psi,

When hot, it might only build 5psi but it is bleeding down about .5psi per second after the pump shuts off(Before cranking).
It will eventually bleed to 0.
So it has to be leaking back to the tank somewhere.

Question, is this bleed back normal? does anyone know what the pressurs/leak rates should be at key on but before cranking?

I assume there are only a few check valves that should hold back pressure. One would be the pressure limiting valve in the fuel rail. another I assume would be the pump itself, It should likely hold back pressure better.
Are there other places that should hold back pressure but might not be doing it?

Not sure if i should buy a lift pump or a pressure limiting valve.... any thoughts?

 

you lift pump pressure is good and it is supposed to drop pressure. if it didnt, fuel would shoot out from the filter bowl every time you changed the filter. the PRV is the next item i would into. your lift pump is fine. start up your truck and unplug the FCA, what does the RP go to when you unplug it?

 

I have already run it with the scanner and it goes well past 20kpsi just reving it. (should I do another rail pressure check again with FCA disconnected?) It has also already been checked with a controller that can step the pressure up and down.. it responds well.

I tried another test,
disconnected the line above the pressure relief valve.
Ran the motor both with and without the FCA disconnected.
Result was lots of fuel out of the tube(I think it is common with the entire return system.), but no noticeable flow out of the pressure relief valve in either case. (but the general area was getting drenched by the tube flow).

Not sure if I should try to block the return tube so I can take a close look at the relief valve flow. But it is definitely not a major leak.

I am at a loss. Not sure what to do next, other than more research.

One thought though.... the behavior is very similar to what you would get when the system is not bled well of air. example, when you change out a fuel filter, and have to get air of out the system, it is pretty much the same kind of thing, but just various cranking times. Only thing i cant figure out is where the air would come from..... the whole system is above atmospheric pressure when it is running, and has no leaks. The only logical source of air I think would be if the lift pump pickup tube was broken in the tank and pulled some air. But the problem there is that the problem can be bad even with a full tank of fuel.

 

its a self purging system, so you dont need to bleed the system. clean up all the fuel around the PRV and start the truck with the FCA disconnected. see if its leaking from the PRV

 

I would but I dont have anything to block off the return tube. There is a lot of fuel dumping out of it.
If I am not mistaken, that tube is in common with the entire return system, so all return flows combined would be coming out of it.

 

keep all of the lines connected. the only thing that will be disconnected is the FCA plug

 

Thanks,
I will run that test, and report peak pressure while running with the FCA unplugged.

Another thing bothering me.....
While the truck is running, the lift pump pressure looks good.
But,
If i just key ignition on, and do not engage the starter, (When the lift pump runs for 2 sec and then stops), Sometimes it hits 10 psi, sometimes 5, sometimes 1 psi, or anywhere in between..... wondering if there is some kind of problem with the lift pump, or if the pickup is clogged. Is that behavior normal?

One of the key indicators though, is while cranking and failing to start, the rail pressure is less than 2,000 psi.

 

the pump will stop after a few seconds with the key. it will start pumping again once you crank the engine over. as far as the different fuel pressure numbers it hits, i am not sure. but you are getting good pressure from the pump when driving it.