LLY: Filter housing primer??

[RZRSharp]

Is the prime button on top of the filter housing supposed to maintain constant pressure??

Had a hard time starting my truck yesterday, and the prime button had no pressure at all. After I primed it it started relatively easy??

I guess this could be contributing to my p1093 code!


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[ripmf666]

Is the prime button on top of the filter housing supposed to maintain constant pressure??

Had a hard time starting my truck yesterday, and the prime button had no pressure at all. After I primed it it started relatively easy??

I guess this could be contributing to my p1093 code!


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Yes it should stay hard. Sounds like you need to rebuild it. I have the kits here but first look around it for fuel leaks.

 

[RZRSharp]

I didn't see any leaks at all. Everything looks pretty dry. I just replaced the filter a few weeks ago. Might have pinched an o-ring maybe?


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[Hound]

The primer does not stay pressurized all of the time. Under normal starting conditions, when the primer is not used to assist with statrtng your truck, it will not be pressurized. If you pressurize it to get your truck to start, it should maintain pressure until you try to start the truck using the starter. It does not remain pressurized while the engine is running.

 

[Bryce418]

The primer will lose some pressure over time, Gm has a spec for how much degradation over a set timeframe but I can't recall what it is at the moment.

 

[RZRSharp]

Okay with that said, shouldn't it stay pressurized enough to keep fuel in the lines, or enough to start the truck?

I would think that if you had to pressurize the filter to start the truck, it's not staying pressurized like it should.

But, when not pulling a trailer, it does t seem to lose pressure as quickly. Any ideas on how that happens?


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[Hound]

Okay with that said, shouldn't it stay pressurized enough to keep fuel in the lines, or enough to start the truck?

I would think that if you had to pressurize the filter to start the truck, it's not staying pressurized like it should.

But, when not pulling a trailer, it does t seem to lose pressure as quickly. Any ideas on how that happens?


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You're only pressurizing the fuel system from the fuel filter forward as there's a check ball in the fuel filter head. Everything behind the fuel filter head is under vacuum when you're talking about using the priming pump. Once the truck is running, everything behind the CP3 is under vacuum, including the fuel filter, unless you're running a lift pump.

You won't likely be able to feel a difference in the amount of pressure applied to the priming pump between a truck that has just been shut off from running and restarts normally, and a truck that needs to be primed using the priming pump in order to start.

If you have to use the priming pump in order to start the truck, you most likely have air entering your fuel system somewhere. The most common places are fuel filter, WIF sensor, WIF drain, and the bleed screw.

 

[RZRSharp]

Thanks for your help. I'm gonna pull the fuel filter and do some inspecting Thursday.

It's just weird that it doesn't happen without hauling anything. It takes a second to start, but I don't have to prime it.

On the other hand, when I pulled my trailer the last time. The p1093 code came in...I pulled over, killed the truck and then it wouldn't crank until I primed it.

So I guess with the air leak in the fuel system, under that much load, it's getting too much air and losing prime....

Would that be a true statement??


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[RZRSharp]

And also under load, with it losing prime, that would cause the low fuel rail pressure code too right?


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[JSTTRUKN]

just curious if you ever figured out the issue...mine did the same thing this weekend when towing.