1999 Chevrolet Suburban 2500 Fuel Delivery problem

This has the 5.7L, single tank. 226,000 miles on the truck, I am pretty sure fuel pump is original.

The last week or so I noticed the truck hesitating a bit at various speeds, especially starting out from stop lights. It stalled out a few times, but I was able to restart it; that is until yesterday when I could not. It cranks fine but does not fire/start.

I sprayed some starter fluid down the throttle body, and engine started and ran fine on the starter fluid. I do not hear the hum of the fuel pump priming when I turn the key to the ON position; and the hum is normally pretty easy to hear.

I tried banging on the bottom of the gas tank with a heavy rubber mallet. No go.

I opened the relay box and there is power and computer supplied ground to the control side, and on the load side when I applied power to the pin supplying power to the fuel pump. still no hum. Anything else I should check before I drop the tank?

Any ideas appreciated! Thanks! ~Pop

Check for power and ground at pump connector and ground wire location on frame rail. Other than that if those look and test good then a pump it is.

Will do! Thank you!

UPDATE: I finally had some more time to work on this today. I could not get access to any wires near the tank/frame rail so I went ahead and dropped the tank. I back-probed the gray (power wire) at the connector to the fuel pump and applied 12V to it using my power probe. Weird thing is that the the fuel pump ran when I applied power to it for two seconds at a time. Though to my very inexperienced ear it sounds weak. Then I wondered it it would prime if I turned the ignition key. I did hear a faint hum, and I had my son turn the key while I listened at the gas tank. There is a hum, the prime is nowhere near two seconds it is more like 3/4 of one second. Could this be because the tank is completely empty of gas? ( I siphoned all the gas out). One time it sounded intermittent, it did the short prime, stopped, and then started again for a tenth of a second or two. I am not sure what direction to go now. Any suggestions?

Put a few gallons of gas in it and hook a pressure gauge up to it. See what pressure it reads with key cycled and then with power probe. Let me know what you get for pressure. You may have a power feed issue if it gets better pressure with probe. Also take a 3157 bulb and hook one end to battery positive and the other to the fuel pump ground at the connector. Does it light brightly compared to negative hooked to battery negative?

If ya can light a headlight bulb during the prime your good. But also crank it with a headlight bulb as a substitute load see if it still lights. Or do a voltage drop test multimeter leads black on battery negative positive lead on pump ground with plugged in pierce wire or back probe crank it should stay below 200 mv on ground. Then positive side hook lead up to battery positive then negative lead on gray wire at pump crank should below half a volt

Here is what I have done so far today. I hooked up a headlight bulb (3157) and connected it to wires back-probed to the gray power wire and black ground wire at the connector. I left my iphone video camera trained on the test bulb. When I turn the key, I *am* getting a two second prime, and the light bulb stays brightly lit for the whole 2 second prime (light is just about as bright as when I connect it directly to the battery). I don't really know why I am getting a full 2 second prime now, maybe I just could not hear as well from the front of the truck. I did a 4-second cranking test with key in START position, and the bulb stayed brightly lit and fuel pump hummed for the whole 4 seconds. Tank still does not have any gas in it, so I know I don't want to do a lot of these tests as I know the gas is needed to cool the pump. Are there any more electrical tests I should do, or should I at this point put some gas in the tank and check the fuel pressure? And here is kind of a dumb question -- where is the fuel pressure test port (if any) on this 1999 Chevrolet Suburban 2500 5.7L? I cannot for the life of me find it. I do have a fuel pressure test kit...

I'm with Cheryl - put a few gallons of gas in and test further. A 3157 bulb will only draw a few amps, not the 8-10 like the fuel pump, but it should still be a heavy enough load to expose a problem.

The fuel pressure test port should be on the pressure line (the bigger pipe) leading up to the upper intake plenum. Probably on the back of the engine, drivers side. It's been awhile since I tested fuel pressure on one of these! :blush:

OK, I got out there after work today and put 5 gallons of gas in the tank. I turned the key to ON several times, and the prime would only produce about 8 psi on the fuel pressure gauge. When I turned the key to START, the engine would actually run weakly for a few seconds before cutting out, but the fuel pressure still never went above 8psi. I got out the power probe again and applied 12V directly to the back-probed gray power wire on the fuel pump connector. The pump sounded weak and couldn't crack 8psi. Same deal with applying both power and ground directly to fuel pump from power probe. My inexperienced DIY brain is leaning heavily toward calling a fuel pump. But there is the nagging question, is there anything else it could be? What do you guys think?

Only other thing is if you wanted to eliminate everything but the pump would be find a way to hook your fuel pressure gauge up directly to the pump outlet line or feed line at the pump. And power it up with the power probe. Usually on those ya have an adapter you put in place of the fuel filter. And on a 20 year old truck who knows how hard the filter is to get off. But if just put a pump in it call it done

8 psi is way too low for it to run. I believe it should be 55-62 psi. I would say it needs a fuel pump if all of your power and grounds to the pump are good.

Thank you, folks, for all your awesome expertise and advice. My hard-to-find fuel filler neck hose finally came in from the west coast (I had to cut the old one out) and I have the new fuel pump in and tank reinstalled. The truck runs like a champ again! It's really good to have it back in service, and it was really good to be testing and not just parts-cannoning. YOU GUYS ROCK! ~ Pop