03 tahoe: troubleshoot possible fuel pump problem

Messages
1,317
Location
South Texas
I have a 2003 Tahoe 5.3 Flex Fuel LT 2WD with 90k miles. I only use 87 octane, no ethanol or other flex fuel b.s. Last night I filled up the tank, and drove it home. A few minutes later, I tried to start it. It cranks over strong, but did not fire. The cranking was strong, the headlights were bright, the power windows worked. So I figured the battery was good. I jumped it any way but still didnt start. I'm thinking it's a fuel issue. How can I trouble shoot the fuel system? I dont have the manual. In the fuse box, which fuse is for the fuel pump and relay? How should I determine it is for sure the pump before I pull the tank? Any tips on removing the tank? Any specific brands of fuel pumps? Thanks!!!
 
Messages
1,589
Location
NC
Im having the same issue with my blazer and i can tell that the pump is not comming on. When you first turn the key to on, you should be able to hear the fuel pump come on for a few seconds. Im not sure if the tahoes are different but on my blazer there is a relay in the front fuse box labled fuel pump. it is about in the middle and there is four of the kinda in a row and the top one is the fuel pump and the fuse that runs it is the ECM B which is beside the relay on the left. From what i understand this is a common problem with the chevys and most recommend against using a cheap airtex, carter, bosch and recommend the AC Delco but i dont know if that is just for my truck or for most of the chevys. My truck was running great then when the wife was on her way home from getting gas, it just shut off completly. Like you said above, it will crank untill the starter burns up but 0 chance it is going to run. I checked my relay and fuse they were both good. im going to check the voltage at the fuel pump connector and if it is good there, then it is a fuel pump issue. sorry i couldnt be more help. As far as removing the gas tank, again this is for the blazer, most say there is a little vent valve that tends to break if you put to much pressure on it by lowering it before it is disconnected. Most seem to have issues with getting the fill hose and vent hoses off. Look around on blazer forums to get what im saying from the horses mouth but im not sure it will be exactly the same for your tahoe. good luck and keep us posted on your progress.
 
Messages
19,479
Location
Chicago Area
OK. for a quick check, give it a shot of starting fluid in the intake. If she pops over, you know it's fuel. Bad fuse or relay, maybe the inertial switch, a connection or wiring, the pump itself, or the filter, are things to check then. Also test for power at the injectors. A 'NOID' light is handy. A bad ground to the computer can cause this. There often is a special dedicated ground wire from the battery.
 
Messages
998
Location
Lexington, SC
I didn't think the late model Chev Tahoes had an external fuel filter. If this one does, it would be a good thing to check. Listen to hear the fuel pump run a few seconds as someone switches on the key.
 

Islandvic

Thread starter
Messages
1,317
Location
South Texas
it Has external fuel filter. I put the rear on jacks, and had my wife turn the key to the accessory postion while I was under the truck. No noise or hum from the pump. I even checked the fuse relay. It's good.
 
Messages
25,161
Location
Upstate NY
So time to replace the pump. Does the vehicle have an access panel or do you have to drop the tank? The pump is not that expensive, also get a new prefilter which looks like a small paper sock. I assume you have one. I have done my older Suburban twice. I had to drop the tank a few inches so I could undo the wiring and hoses. In my Suburban it had metal lines coming from the tank with a rotating threaded connector on the end. The connector screws into a flex hose from the vehicle. I did not spray any PB Blaster on the rotating connector and it was rusted to the fuel line tubing so when one unscrews the rotating connecting you twist the metal tubing and snap it. Thus I needed a new fuel sender assembly which costs more than the pump. I am not sure it would have come apart anyway but one never knows. The second time I did it the rotating connector unscrewed as it should. The cover for the fuel sender assembly is covered in waxy goo. I scraped it away and used new wax from a toilet bowl seal, seems about the same stuff.
 
Messages
2,340
Location
La.
If there's no fault codes, it's the pump. If you replace the pump, be sure the wiring to the pump has no burn marks on it.
 
Messages
379
Location
Mi
Avoid aftermarket pumps,Airtex and Carter.They have lots of failure rates.Stick with a Delphi pump instead from the dealer or your nearest Carquest parts store.The Delphi pumps come with the updated plug with the new fuel pump sometimes.
 
Messages
25,161
Location
Upstate NY
I would figure out what you need by dropping the tank (if thats needed). If you can get the fuel sender assembly out in one piece then you just need the pump and the filter sock. But I ruined the fuel sender assembly getting it out. I talked to a trusted mechanic and he said he prices in a fuel sender assembly in most cases since half the time it gets ruined.
 

Islandvic

Thread starter
Messages
1,317
Location
South Texas
I checked the fuses, replays and there are no codes. I can get a FD discount at a local parts supply wholesaler on AC DELCO parts, so I will get the pump from them. Thanks for the help so far, I keep you posted.
 

Islandvic

Thread starter
Messages
1,317
Location
South Texas
The fuel pump was replaced two weekends ago. Runs great now. Replaced fuel filter with WIX. It was a PITA to get off. The whole Flex Fuel system adds more parts and lines and makes the connectors different on some fittings than the normal fuel system. Makes it more difficult to drop the tank. I hope the US Govt does away with Ethanol subsidaztion!
 

rat

Messages
361
Location
Michigan
GM had a bulletin awhile back to use Chevron Techron fuel additive frequently, as it is the only additive proven to remove sulfur deposits from fuel pump module assembly and incease the efficiency of the pump.
 
Messages
502
Location
Canada
 Originally Posted By: Islandvic
Rabbler.... I don't know where it is? I figured it calculates mileage based on injector duty cycle...
Just curious. I'm learning a new course on the GM flex fuel and hybrid full size trucks. Only the early trucks have a fuel composition sensor. It measures the actual amount of ethanol in the fuel so the PCM can compensate. The later trucks just use an algorithm in the PCM that figures out approx ethanol content based on O2 sensor readings. I've never actually seen one with the sensor. They're kinda rare, especially in Canada.
 
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