Need Help Diagnosing 2003 Sierra Denali - No start

Got the new tires on it today. Got the inspection done and it passed with no issues. Came home parked it and went inside for 30 min. Got back in it and got about 1/4 mile down the street and it started to hesitate and then it dies. It will crank over fine and tries to start but acts like it is running on only a couple cylinders then dies. Really feels like a no fuel problem.

The tank is 3/4 full) I filled it yesterday and I have only gone about 60 miles.

No check engine lights either.

So fuel pump?

Filter?

Both?

Fuze?

The truck has 310K but was running great.

AAA is dragging it back in about an hour and I can start digging into it but I am not as well versed in these trucks as I am with other brands. My last two trucks have been fords.

Any help or guidance as to where to start and what to look at would be helpful.

I may just toss a Fule pump and filter at it only because I don't know the service history on this truck and for piece of mind I would know it was done.

Beat on the bottom of the tank while somebody cranks the engine. No start- beat- starts equals new pump.

Think I am going to purchase a fuel pressure gage. I just went looking for mine and I seems to have gone missing.

I can assume that I will need to drop the tank on this beast?

the easy button is have someone turnthe key on while you're back at the tank and listen to see if it hums. IF it does, check the pressure at the rail and go from there.

Usually raising the bed up is easier, 4 bolts and 4 buddies does it. As streetwise says, banging on the tank may jar the fuel pump back to life, may not?

I am going to try a filter first since it is a new to me truck with no records.. I can call the po (friend of mine) but he probably will not remember.

Take the bed off for the fuel pump change. Fuel pressure tester be my first check. Gm trucks seem too crap a fuel pump every 150k

Then this is due as it just passed 310k

So the tow truck driver said that he sees lots of these. He tells me that he can diagnose it for me. He gets a rubber mallet out and with it up on the truck hits the bottom of the tank 3-4x. Then he sais if it starts when we get back it is the pump. It started just fine after we got it off the truck. Looks like a pump yes?

I am still going to check the pressure at the rail and I am going to do the filter and the pump no matter what. Just for piece of mind.

While I was waiting for the truck I looked up how to do it and it really looks like ti not that bad a job. Unbolt the bed. Put a jack up against a 2x4 that runs down the side of the bed and lift it up. Stick a couple pieces of dunnage in there to hold it in place for safety and then you have access to the top of the bed.

My thanksgiving car to do list just got bigger.

Oh and a huge complement to ProTEch Towing (sent by AAA) They are a big outfit in the area and I have been towed by them in the past and every time the guys are great. It is great to watch a person that is good at his job do it. He had the truck snatched up and on the truck in no time. Unloading was equally as fast and precise. He put it exactly where I asked him to.

Sure sounds like a pump, pressure test will confirm. Reset the computer (battery disconnect) before starting it with the new pump, they tend to run worse than before if you don't.

My neighbor just chased a similar issue on his '99 Express. After a pump and then a relay 2 weeks later, today they ran a new ground wire for the pump.

Actually, the pressure test won't tell you a damn thing after the hammer test in most cases. As a matter of fact, even scoping the power supply won't generally tell you much, after you've hammered the brushes back into good contact.

Just put a pump and filter on it. And use a Delco or OE pump. The rest are junk. Even the Delco ones are only fair sometimes.

Is Bosch a good option for these pumps? Pricy compared to the Delco pump. But I don't mind spending a little more in this case.

So I am in the middle of the repair. I got the bed up and the pump out and I have learned a couple things.

1. Don't try and lift the bed by hand. Instead use a 8' 2x4 or 6 and pry up on it using the tire and pry against the middle bed rail. Leverage is your friend. Then slide a piece of 2x6 (or similar height piece) in between the bed and the frame. Then take you floor jack and slide it in where the 2x6 you used to pry it up initially and jack the thing up. Just be careful to not have the jack slide off the bed rail. I did not have a problem but I could see this happen if you don't get the jack in fat enough. Then I put a pair of jack stands under the bed on the frame to provide a safty. This is MUCH easier than trying to lift the bed up while trying to shove something into hold it in place.

2. Make sure you get a new locking ring for the tank. I did not and they are always rusted. They use to come with the pumps but not anymore. They are also unobtanium from all the local parts stores. Even NAPA did not have it. I salvaged mine cleaned it up and painted it so I should be good to go.

3. The bed bolts came out very easy

4. You don't really need to undo the wiring to the rear light. Just don't lift the bed too far. I had plenty of slack in mine

Oh and I found the issue I think. The in tank sock was completely clogged. Nothing in the tank. IT must have been a bad tank of gas or something.

Another thing the Bosch pump I got is made in America. So is it a re branded Delco?

In reply to dean1484:

I don't think Delco makes anything anymore, could be a reboxed Delphi, which is probably the OEM.

Streetwiseguy wrote: Beat on the bottom of the tank while somebody cranks the engine. No start- beat- starts equals new pump.

Unless the ground strap from the engine to the frame has died, in which case the fuel pump will also not work since it grounds to the frame. The battery grounds to the engine and the body, and the frame is remarkably well isolated electrically.

That one kicked my ass hard. Lesson learned. Worst part is the ground strap looked fine, just a little green. Then I grabbed it and it crumbled.

Do what a few have said. Lift the bed, and make sure your grounds are 100%. Not 95%.

I will do that!!! I have the bed up at the moment.

But I really think I found the issue the sock on the pickup was completely clogged.

But I will go after the grounds as well

Thanks!!!

All done. Inspected all the grounds and even replaced the connectors at the pump (because I could) When I started It I looked at the codes and there were a couple stored codes telling me that it was lean on both banks. To me this means low fuel pressure. I also noticed something else. Before I changed the pump it was laying over 3/4 throttle a bit and it was getting worse leading up to this. Now no more laying over this thing goes like crazy!!! Nothing like 6 liters of LS power to get 5000+ lbs you down the road. I am really amazed by this thing. It has 310K and the motor sounds and feels like it has 1/2 that.

THANKS to everyone that chimed in on this!!!! The tilt bed method and checking the grounds and what not were all very helpful.

It is what makes GRM Great!!!!

I think I may be needing to do this on my 04 suburban soon. It's starting hard, but seems to be better if I cycle the key a few times. I haven't checked pressure, but I'm thinking pump or filter.