2nd Gen Fuel Filter Head Question

MicroBruin · **Posted:** Thu Apr 02, 2015 4:09 pm

So, I started thinking maybe my recent tougher starts were related to fuel supply. The FSM states that poor fuel supply when starting can result in a fog-like white smoke from the tailpipe, which I've had a little bit of (in warm temps). I've replaced two glow-plugs and I'm code free, but the truck has still been starting a little poorly. It used to start immediately.

So, anyway, I'm trying to figure out what's normal for this 2nd gen fuel head I have. I thought it was normal for there to be pressure on the plunger before starting, indicating that the fuel line is full and ready to go. Two starts ago, I decided to purge, and there was some air that came out before the diesel showed up. Also, just for kicks, on my first start of the day yesterday, I put the key in and turned to the on position. I waited 10-15 seconds, then checked the plunger on the fuel head, and was surprised to find that I could push it almost a full 10 times before it reached pressure. I didn't follow up by bleeding, but instead, went and turned the key, and she started immediately, and purred like a kitten. So, my questions are:

Is it possible that there is a fuel delivery issue that only affects the starting phase, and does not affect drivability at all? The truck runs beautiful once it starts, even when pushed hard.

Is my understanding of the fuel head/plunger correct? Should it maintain pressure at all times? Am I not giving the pump enough time to do its job?

I can't figure out how air getting into the system would only affect my starts, and not how it runs....confused....

Thanks.

mass-hole · **Posted:** Thu Apr 02, 2015 4:27 pm

I think this is why people are installing lift pumps. Also, I dont think the plunger would be under pressure after you you run the engine since fuel is being sucked from the tank by the high pressure pump. That means everything before the pump is under vacuum during operation and there would be no reason for there to be resistance on the plunger after you drive other than the force of the spring.

papaindigo · **Posted:** Thu Apr 02, 2015 4:50 pm

A bit of white smoke on cold engine startup is not abnormal and some CRDs do it more than others. My son's 06 trails a bit of white smoke for the first 200 yds or so but my 05 has none.

As to the filter head. Turning the ignition to the "on" position and waiting does nothing to fuel pressure at least I don't think the CP3 does anything until the engine is cranked. In any case I just checked my 2nd gen filter head - vehicle off plunger is stiff but not hard until like 5 pumps - engine running same situation. I have not had air in fuel issues since I put the 2nd gen filter head on. That said the 2nd gen filter head will NOT prevent air in fuel it will just prevent air in the fuel from a burned filter head fuel heater element or other issues directly related to the filter head (bad bleeder screw seat or bad plunger seal for example). If you continue to get air in the fuel it's coming into the lines from the supply line quick disconnect fittings back by the tank.

An in tank pump will likely cure that problem by pressurizing the fuel line and those fittings from the tank outlet forward or you can drop the tank and replace those fittings with a bit of diesel rated marine grade fuel line and clamps which is cheaper and stops the air leak at those points.

flash7210 · **Posted:** Thu Apr 02, 2015 5:24 pm

If there is any kind of leak in the fuel line from the tank to fuel filter, air will get in and fuel will drain back to the tank. It will happen slowly when parked for several hours.
After installing the new fuel filter assembly I was still having air in fuel problems. I went and cut out the quick connect on the supply line back at the tank and replaced with regular fuel line with regular hose clamps. The air in fuel problem went away after that.

BTW, weather here in Sarasota has been beautiful this week.

Heading back to JAX tomorrow.

MicroBruin · **Posted:** Mon Apr 06, 2015 11:53 am

Thanks for chiming in guys. I was noticing in the FSM that there almost appeared to be a two piece fuel line connection on the exterior of the tank...at the top of the tank, then another less than a couple of feet up the line. Can anyone confirm? I really dread the idea of dropping the tank if I don't have to. I dread the idea of installing a lift pump even more. I don't have a lot of time right now, unfortunately... It just seems odd that this all happened after glow plug replacement. I'd hate to install a lift pump, then find the problem lies elsewhere. I might try the "cardboard test" described in the manual, as it seems to be an easy way of checking for a high pressure line leak.

BTW, forgive my ignorance, but is there a scenario where fuel delivery issues would only be occurring on start-up, and not when driving. I guess I can't wrap my head around air being in the fuel when I try to start, but no problems while driving....????.....

Thanks, again.

thermorex · **Posted:** Mon Apr 06, 2015 12:08 pm

If you have a place on the supply line that is not perfectly sealed, then you'll loose pressure (or more exactly vacuum in this case) while the car sits more than you loose when it is already started. It's like sucking a drink through a straw, if you have a small hole in the straw you can still suck liquid through but you get a bit of air. If you stop sucking liquid (like engine stopped), then air will get in the straw and all the liquid will drop in the straw till the spot where the hole is (this is just how physics works). The stock Crd setup is this: fuel gets sucked from the tank by the cp3 through the supply line, through the fuel filter, in the cp3, it gets pressurized and delivered to fuel rail. If you have a small air leak, then cp3 will suck fuel and air, hence it would run normal once it started. If the leak is small enough, your cp3 will get enough fuel for pressurized delivery to the rail. But when you stop the engine, cp3 won't pull fuel through and the existing vacuum from the fuel line will be lost to the air that gets in through the leak. This is why it starts harder if it sits for a while, since cp3 and the fuel rail will need to purge the existing air first, and only then will be able to deliver pressurized fuel to the rail (air being less dense compresses easier and also expands easier in volume). Also, consider that fuel density is higher than air density, so you may have an air leak but not a fuel leak, even if you add a pump to the tank, which is the best solution. If you want to sort of fix the air leak issue, then install a free flow inline fuel pump (like Kennedy diesel) as closer to the tank as possible. You may still have a small air leak but the inline pump will force pulling the fuel through, which will help your fuel line filling up sooner with fuel.

2nd Gen Fuel Filter Head Question

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