Intermittent starting issue

[Dustan Tompkins]

Hey guys I have an 04' Ram 3500 SRW with the 5.9 305hp engine. I have an issue at start and only here and there nothing I do makes it repeat. So I bought the truck it's a 1 owner and had 137k last year. It was stock. Since then I added a FASS pump and a smarty tuner. So it's hard to explain but I'll do my best. When it does happen I start it like normal, it will crank 4 to 5 times and goes to fire then I see fuel pressure drop to 0 then after a few cranks it fires and runs normal. No smoke unless its cold out. Maybe a video or something would help if I can catch it doing it? Thanks.

 

[p-Bar]

I assume you are monitoring the low pressure side of the fuel system? A FASS shouldn't drop to 0 ? First I would call FASS and tell them what's happening . That is the cheapest thing to do. Video would be great!. I t could be a leaky injector and high pressure pump can't build enough pressure to fire.

 

[Dustan Tompkins]

I am watching the rail pressure. it goes to 6000 psi the truck stumbles then it shows 0 then back to 6000 psi and starts fine all within a few cranks. I was thinking maybe the fuel regulator on the pump but this is my first diesel.

 

[p-Bar]

Maybe bad FCA. Could try to put some 2 stroke oil in the tank as it will lubricate the FCA. It is located on the back of the CP high pressure pump.

 

[Dustan Tompkins]

Does taking it out and looking at it help determine if it might be bad? Can it be cleaned possibly i am running hot shots and it made it run a lot better. I'm also running a 12 valve tune 90hp

 

[p-Bar]

Some guys say they pull it out and shake it and see if it's loose. But not sure on that. Can you unload the tune and put it back to stock?

 

[Dustan Tompkins]

Yes I can, it was doing it before the tune as well. I will pull it out and see what is to be seen I guess. Thank you sir!

 

[HPSimpson]

How old are your batteries, condition of cross cable between the right and left batteries, as you probable aware the batteries cause all sorts of mystery electrical problems, specially starting.

 

[Ozymandias]

Sounds like air in the line, dropping so suddenly to Zero.

My idea is that you have a small leak between FASS and CP3 that let air enter the system over night (building a bubble inside the sustem), fuel draining back to the tank.

 

[p-Bar]

Ozy if it's on the pressure side you would have a fluid leak. Sucking air can only happen on the vacuum side (tank to FASS). Your thoughts?

 

[dieselshadow]

Not so. The 12v’s were famous for leaking air from the short rubber hoses under the intake manifold, both supply and return. They would leak air in, but not fuel out. So don’t rule that out yet. I’ve seen this on some tractors and other trucks as well. Even though the line looks good, they were cracked internally.

 

[Ozymandias]

Ozy if it's on the pressure side you would have a fluid leak. Sucking air can only happen on the vacuum side (tank to FASS). Your thoughts?

Yeah, i had that happen on the pressure side to, tiny little leak, maybe from a brittle hose. Let air in but no fuel out under the light pressure that the lift pump apply. Not even a wet spot on the outside.

 

[Dustan Tompkins]

So the hose from the tank to the CP3 is brand new. I am also running a sump. I got it to do it today.

 

[Ozymandias]

You didn't mention, is it only in the morning, first start of the day - or totally random.

If it is random then forget my theory with the air bubble.

 

[Dustan Tompkins]

Completely random but seems to do it more after it was running then shut off to go into a store.

 

[p-Bar]

That is usually signs of bad injector(s) and you can't build enough rail pressure to start. Tolerances change when hot .