[Horsecamper]

I've been having intermittent starting issues with my 2003 GMC Sierra, apparently relating to the fuel filter. I replaced it not long ago because it was acting like it was clogged, even though it only had 10K miles on it. It worked fine for awhile, then starting having starting issues again, especially when it was hot, sometimes stalling out at idle. It would improve if I pumped the manual primer on the fuel filter, it would start again, and run as long as I kept the rpm up. Then yesterday, in an attempt to tighten the bleeder screw because pumping alone wasn't working, it broke (cheap nylon kind). It took awhile and some imagination to get the broken bits outs, but in the process, I'm wondering if I damaged something. I replaced the bleeder screw, and managed to drive it about two miles, though it was quite dodgy, which I thought was just air working it's way out of the system, even though I bled it before I started out. Then it stalled out entirely and I couldn't get it started again, no matter what I did. Had it towed home. This morning, I took out the bleeder screw and looked inside, thinking maybe some plastic bits and gone into it and clogged something, and I noticed that at the bottom of where the screw goes, there's sort of an opening, like a crescent moon shape on one side of the bottom of the housing. I'm wondering if maybe I punched a hole in there when I was trying to fish out the old screw, or if that opening at the bottom is normal? Any other clues to my problem would be helpful. I'm pretty sure the fuel pump is fine, because I do hear something running in the engine compartment when I turn the key on, but not back at the fuel tank. It just cranks and cranks and doesn't catch. This is my first diesel and I'm still trying to find my way around. Thanks for any and all help you can give!

 

[Ron Nielson]

The BEST thing you can do, my opinion, is to replace the fuel filter head with a new OEM part. Yours is almost 20 years old, no telling how it is worn or damaged. Alternatively, you could buy a rebuild kit and replace/install alll the parts in the kit into your existing mount. Sometimes that works fine, sometimes not or not for long.

 

[Horsecamper]

Thanks, Ron. I've been trying to determine if it might be the fuel pump, but the fuel pressure gauge I have is so old, it doesn't even have the shrader valve end, just a rubber cone. Is there another way to test whether my fuel pump is working? If I find the fuel test port (wherever that is) and just remove the cap, will that be a good enough indicator if I crank the engine or just turn the key on? If fuel comes out, then the fuel pump is working, right? I know I"m jury-rigging this diagnosis, but my options are limited right now. And back to my original question, if there's not supposed to be an opening on the bottom of the bleeder screw housing, could that be where air is coming in and messing things up? I'd sure like to know if that opening in the bottom is normal or not...

 

[ShopSpecialties]

Thanks, Ron. I've been trying to determine if it might be the fuel pump, but the fuel pressure gauge I have is so old, it doesn't even have the shrader valve end, just a rubber cone. Is there another way to test whether my fuel pump is working? If I find the fuel test port (wherever that is) and just remove the cap, will that be a good enough indicator if I crank the engine or just turn the key on? If fuel comes out, then the fuel pump is working, right? I know I"m jury-rigging this diagnosis, but my options are limited right now. And back to my original question, if there's not supposed to be an opening on the bottom of the bleeder screw housing, could that be where air is coming in and messing things up? I'd sure like to know if that opening in the bottom is normal or not...

The test port is to check for vacuum and or lift pump pressure if you have an aftermarket lift pump. You check injection pump pressure with a scan tool. Sounds like you are sucking air at the filter head. What brand of filter did you install ? Here is a gauge that will tell you when filter is plugged or you have a restriction.

Fuel Filter Restriction/Lift Pump Psi Gauge Kit for Duramax – Kennedy Diesel

www.kennedydiesel.com

 

[Horsecamper]

The test port is to check for vacuum and or lift pump pressure if you have an aftermarket lift pump. You check injection pump pressure with a scan tool. Sounds like you are sucking air at the filter head. What brand of filter did you install ? Here is a gauge that will tell you when filter is plugged or you have a restriction.

Fuel Filter Restriction/Lift Pump Psi Gauge Kit for Duramax – Kennedy Diesel

www.kennedydiesel.com

I bought a Wix filter, it had the O-ring on it. I made sure the old o-ring came out when I changed it. I thought maybe that was the problem, but I took it off and reinstalled it this morning, everything seemed fine, and it's doesn't seem to be leaking any fuel, even after I hand prime it. My brother is coming over tomorrow with a fuel and vacuum pressure gauge, hopefully will help confirm part of the problem. So are you saying a pressure test won't indicate a fault in the injection pump?

 

[ShopSpecialties]

I bought a Wix filter, it had the O-ring on it. I made sure the old o-ring came out when I changed it. I thought maybe that was the problem, but I took it off and reinstalled it this morning, everything seemed fine, and it's doesn't seem to be leaking any fuel, even after I hand prime it. My brother is coming over tomorrow with a fuel and vacuum pressure gauge, hopefully will help confirm part of the problem. So are you saying a pressure test won't indicate a fault in the injection pump?

Those Wix filters are not very good. The filter is on the vacuum side of the IP so it will suck air and not leak fuel. Now if you have an aftermarket lift pump then there will be pressure and the leaks will show themselves. What gauge are you going to use that will measure 20,000 PSI of injection pump pressure ? There is a fuel pressure sensor in the rail that will measure PSI and you read that with a scan tool.

 

[Horsecamper]

I don't believe I have an aftermarket lift pump (I bought the truck used). I have no idea what kind of gauge he has, kind of doubt it will read 20k psi, I thought it would just attach to the shrader valve and read the pressure, and it if was too low it meant the CP3 injector pump was bad. Thinking this may have to go to a shop, might be more than I can handle. Seems to have so many variables! How do I find if and where it's sucking air if there's no fuel leak? That seems to be my first dilemma.

 

[ShopSpecialties]

I don't believe I have an aftermarket lift pump (I bought the truck used). I have no idea what kind of gauge he has, kind of doubt it will read 20k psi, I thought it would just attach to the shrader valve and read the pressure, and it if was too low it meant the CP3 injector pump was bad. Thinking this may have to go to a shop, might be more than I can handle. Seems to have so many variables! How do I find if and where it's sucking air if there's no fuel leak? That seems to be my first dilemma.

That Schrader valve is not for checking injection pump pressure.

It is very common for filter heads with age to start sucking air. If after sitting you have to pump the primer to get it to start then the filter head is more than likely sucking air and needs replaced.

 

[Horsecamper]

That Schrader valve is not for checking injection pump pressure.

It is very common for filter heads with age to start sucking air. If after sitting you have to pump the primer to get it to start then the filter head is more than likely sucking air and needs replaced.

Is there any way to know for sure it's the filter housing? Shouldn't I see leaking? I hate spending money on parts I end up not needing, just because I can't seem to find the exact problem. I'm sure I'm not the only one!

 

[ShopSpecialties]

Is there any way to know for sure it's the filter housing? Shouldn't I see leaking? I hate spending money on parts I end up not needing, just because I can't seem to find the exact problem. I'm sure I'm not the only one!

You will not see it leaking because it is on the vacuum side.

It might be best if you take it in to a good local reputable shop to help you out.

 

[bellassaiw10]

Is there any way to know for sure it's the filter housing? Shouldn't I see leaking? I hate spending money on parts I end up not needing, just because I can't seem to find the exact problem. I'm sure I'm not the only one!

Considering you stated that when you pump the primer it works properly the easiest way to tell is your primer should always be pretty stiff if at any point it is not then the filter head is leaking air. This can be done with the truck off, prime it until its tight then check back a day later and see if its soft.

Honestly if its that old and you already stripped the bleeder I would order a new one regardless and a rebuild kit to slap into the old one as a spare. I rebuilt my stock one and about 2 months later it started leaking again so I just ordered a new one and kept a spare.

 

[Horsecamper]

So I ordered a new fuel filter housing, and asked my brother, who is a pretty good mechanic, to give me a hand. We've got the old one off and then he got stymied putting the new one on, because he's not sure which fuel hose goes where, kept cutting back the long hose because it seemed too long. Should have taken a pic, I know, but I give him maybe a little more credit that I should. So does the short hose go to the port that's closest to the engine or closest to the wheel? I'd like to nip that argument in the bud when he comes back tomorrow to finish the job. Any help is appreciated!

 

[DMAXfirefighter]

Oh boy... Fuel line comes out of the FICM (control module on the passenger side front corner of engine) to the front or right side of the filter housing. I think the ports will have arrows for direction of flow maybe, the ones I remember do anyway. Then comes out of the filter housing on the engine side port and goes to the junction block behind the alternator that splits off to the cp3 and the test port

 

[Horsecamper]

Okay, so we got it all figured out and installed the new fuel filter housing, and, disappointingly, had the exact same problem. It cranks and cranks, but won't catch. The brother tried spraying some starter fluid, and it would just about catch, then die immediately. So now I'm where I was hoping I wouldn't be, changing parts for the sake of figuring things out. Wish there was a more specific way to diagnose this stuff! Couldn't find a local shop that would work on it, so I'm still vamping in place here. Thinking the only other thing it could be is the fuel injector pump? Or is there something else I need to look at as well? Parts changing I can mostly do, it's the dang diagnosing that kills me every time. My only other options are to try to find a mobile mechanic nearby or to tow it 30 miles. Suggestions? Anyway to confirm what component needs replacing? Any and all help is appreciated!

 

[ShopSpecialties]

Do not use starting fluid. Are you sure you got the lines on right ? Did you pump it up until you have no air ?

 

[Horsecamper]

Starter fluid wasn't my idea, it was my brother's. He did it without telling me. Yes, lines are right, yes, we primed it repeatedly, and repeatedly, and repeatedly. It sounds just like it did before we replaced the filter housing.

 

[bellassaiw10]

Did you install a new filter with the housing? and if you prime it is there any air coming out of the bleeder screw?