SubDriver02

When the temp is up over 95 degrees and you're running relatively high speeds (55-75) the car will start losing power like it's running out of gas, then it will die. After sitting for a few minutes (sometimes just a few seconds), it will start up again and run fine... until it does the same thing again a few miles down the road. It first did this about 6 years ago on a road trip from Missouri to Texas--died four times. I replaced the fuel pump relay and the fuel filter, to no avail. On the way back to Missouri it didn't happen again. It was hot--over 100 degrees in Texas. Then, just this year, it started again. In mid July I drove it to St Louis and back (300+ mile round trip) with the outside temp in the mid-to-high 80s with no problems. Then again to St Louis and back two days later with the temp in the mid 90s. It died on the way back, about 10 miles outside of my town. Started after less then 5 minutes of rest, and drove the remaining 10 miles with no problems. Then just last weekend it did it again. Temp about 90 degrees in the evening, my son drove the car about 30 miles no problem, but on the way home, in the afternoon with the temp at about 98, it died three times--so it's getting worse. My first inclination is to blame the fuel pump. However, my experience with fuel pumps is that they just go out, none of this on-again-off-again stuff, especially not over the course of 6 years. Any thoughts? Anybody else experience something like this?
KJHansen,
2002 Suburban 1500 4wd, flexfuel vehicle (I did try E-85 for a month or so quite a few years ago), 188,XXX miles

SubDriver02

So, no replies yet. Hmmm. Another related question. I've decided to go ahead and replace the fuel pump, but all the parts places say it's either an oval connector or a square connector. How can I tell without pulling the tank and the checking? Is there a manufacturer's date when they started using the oval one or the square one?

in2pro

Welcome to the forum...
I'd be suspicious of the fuel pump but checking the fuel pressure will be the best way... You might run your VIN up to the parts department of your local dealership and they maybe able to tell you which one you have...
As for working or not working ( fuel pumps) if the pump itself dies, your right its dead, but it could be a check valve or a blocked intake screen causing the problems and the heat just exacerbates the problem when the fuel gets hot and causes things to start expanding...

SubDriver02

Thanks for the reply. I did as you suggested and called the dealership. They gave me a part number, but didn't know if it was the oval or square connector--in the picture it looked like it had a square connector. So I called the local O'Reilly's and gave them the GM part # which they cross-referenced, and they had one on hand--one oval connection and one square one. But kind of expensive still. I ended up ordering one from Rock Auto. It was listed as being for the "Z" engine code in the VIN while the others were for the "T" code. My Sub's VIN has a Z and no T at all, so I ordered the Z code pump.

deweronick

Hi There. Just wondering if you ever figured out for sure what the problem was?? I'm having same issue with my 02 Burb 1500 with the flex 5.3 as well. Like yours, It Seems to act up only when its extremely hot outside and on long trips. I'm in VA visiting my sister and it "acted up" 15 miles from her house...(350 miles from NY and it was 97 outside)....Did it once before in NY on my wife, when it was hot outside and after an hour or so of driving..She coasted to side of road, and it seemed to start right back up and has run fine since. So While here, I replaced fuel filter ...Still got it to acted up after a bit of driving hard yesterday..(again its about 95 hot and humid here in VA)...When its acting up, the fuel pressure just drops from the normal 45 lbs way down to 10 or so..(I hooked up a pressure meter and have it peaking out the hood near windshield and can watch it as I drive) ... I also replaced the fuel pressure regulator, as some have said they had an "intermittent" problem with there FPR and I will try and drive it hard today locally to induce the symptom....I did buy the fuel pump (delphi brand of course) and have it just in case.....I'm getting ready to return to NY in 2 days, Just worried that it is the "intermittent" fuel pump problem that some report vs. the belief that "the fuel pump either works or does not work" .....Any help or insight would be appreciated. Doug 703-221-6465 in VA

SubDriver02

Classic fuel pump failure symptoms. Fuel pump replacement fixed mine and just last month my '95 Ford F150 had the same symptoms and fuel pump replacement fixed it too. Just gotta bite the bullet and get 'er done. Labor will be at LEAST half your cost, so if you can do it yourself or get a friend to do it for you, you'll save a bundle
Keith

deweronick

Hi Keith.....Thanks so much for replying back.....I did end up replacing the fuel pump yesterday for piece of mind as I dont want to have a breakdown again on my return to NY tomorrow. (Had already replaced the fuel filter, as well as the fuel pressure regulator).... I ended up cutting a hatch panel to access the pump from the top like a lot of member are doing , especially since I had 3/4 of fuel in the tank. Not a bad job as long as your careful with the grinding wheel and take your time. But glad to know that the fuel pump solved the problem, as I had my doubts. My fuel pump was quiet, never really let it run below 1/4 tank, and most still feel that the fuel pump either works or doesn't.....I'm glad to know that a "tired" fuel pump can actually start to cut out when "pushed" (long drives , coupled with hot temps in both our cases).....I know its been over 2 years since this thread, So just to clarify, After replacing your pump, the long trips in hot weather no longer induced the symptom we had? Thanks

cleveland63b

if you were dropping pressure then you needed the pump, I hope you sealed your access panel very well. The possible dangers created from that are not worth it in my opinion.

SubDriver02

It's been 2 years since the fuel pump replacement and no fuel-related problems at all. We did get a broken mirror at a car wash. Just be aware that in some of these car washes they have big machines that run back and forth and spray your car as the "rags" whack at it. Very effective, compared to the spray-only car washes, BUT the big machines (big yellow boxes in this case) move in towards the car in the last few rinse-only cycles. One caught the passenger-side rear view mirror and flipped it back and forth. This cracked the plastic and splintered the glass. I was able to find a mirror for only $28.95 delivered online and the car wash people paid for it, so all's well that ends well, to coin a phrase. But be careful with these large vehicles in car washes! I think I'll stick to hand washing, whether in a car wash that has the hand-held brushes, or in my driveway.
Keith

Tom Mitchell

VERY IMPORTANT WHEN YOU READ THIS NOTE THAT REPLACING THE CAMSHAFT POSITION SENSOR AS WELL AS THE CRANKSHAFT POSITION SENSOR THAT THE SENSORS WILL NEED TO BE RELEARNED UNLESS YOU HAVE THESE SPECIFIC METER TO DO THIS YOU WILL NEED TO TAKE IT INTO YOUR LOCAL MECHANIC OR FIND SOMEONE WITH A METER THAT WILL RELEARN YOUR POSITION SENSORS IF YOU INSTALL THESE WITHOUT RELEARNING THEM YOU WILL ASSUME THE PROBLEM DID NOT GO AWAY AND START TROUBLESHOOTING OTHER THINGS LEADING YOU AWAY FROM THE INITIAL PROBLEM IF YOU DO NOT HAVE THESE SENSORS RELEARNED,IT IS TRUE THAT SOME VEHICLES DO NOT HAVE TO HAVE THEM REAL EARNED BUT WITH GMC, CHEVY, AND ANY OF THE 5.3 L TYPE MOTORS THEY HAVE TO BE RELEARNED OR IT WILL NOT CORRECT ITSELF IN THE PROBLEM WILL NOT GO AWAY.

In the GMC and the Chevy Tahoe suburban etc what a fuel pump goes out it will not only a cup on hot days and it will not be intermittent restarting in just a few minutes or sometimes immediately after the vehicle has stalled, that's not to say that if your car stalls on a hot daythat you should dismiss a fuel pump either but simply understand that in 99.9% of the cases were a fuel pump goes out the vehicle only restarts once maybe twice the heat never has anything to do with it and then it will shut out completely,. SOLUTION.... MORE OFTEN THAN NOT IT IS GOING TO BE YOUR CAMSHAFT POSITION SENSOR WHICH IS under the intake manifold towards the back of the engine, and or your crankshaft position sensor yes these are two separate sensors your crankshaft position sensor is typically located under the motor you'll need to remove the starter to find it it's held on typically by a 10 mm bolt and they average about $25 to buy in town or $10 to buy online.MORE OFTEN THAN NOT THIS IS MISDIAGNOSED FOR A VERY LONG TIME BECAUSE IT THROWS NO CODES BUT ONE WAY TO TELL if it is your crankshaft position sensor is that when the car guys when you go to turn it over again you'll watch the tachometer very closely, if the motor is turning over but the tachometer is not moving whatsoever and the car won't start more often than not that is your crankshaft position sensor located below the motor because it is the sensor that tells you the RPM so if it's not working it's not reading.
Also this seems to effective vehicle only when it's hot outside temperatures over 80 degrees for myself it was anything on a hot day 84 or above, 88 degrees for sure I would come to a stop light it would be idling just fine and sometimes within 10 seconds other times within 30 seconds it would stumble and die, sometimes I would have to sit there for a couple minutes and then it would fire back up and do it again at the next light other times it would fire up within just a few seconds but again the problem would not stop. Then I would go out in the evening temperatures below 80° drive it all over town and back without one single issue day in and day out of this happening draws you to only one conclusion. The chances of it being a fuel pump are slim to almost done with these type of symptoms. The symptoms for the crankshaft position sensor as well as the camshaft position sensor are almost identical. My recommendation would be that if you were doing this yourself and you had the mechanical skills to watch the video on YouTube made by A-1 Auto and it will walk you through changing the camshaft position sensor the tools are relatively simple a 10 mm wrench with extension a fuel line separator 3/8, flat blade screwdriver, a vacuum for cleaning up around the top of the motor so no debris falls in not your wife's vacuum from the house by the way oh, you will need a Shop-Vac, of course you will need a new camshaft position sensor, and if I missed anything if you watch the video it will go into great detail step by step on how to change a camshaft position sensor in the Chevy and GMC Tahoe and suburban again this is by A-1 Auto on YouTube.
I was unable to find A-1 Auto crankshaft position sensor but I did find another very helpful video on YouTube by " 2carpros" and that was for changing the crankshaft position sensor.

YES THESE PARTS ARE TWO DIFFERENT SENSORS SOME PEOPLE AND SOME OF THE THINGS YOU WILL SEE ON THE INTERNET WILL TELL YOU THAT THE CAM AND CRANKSHAFT SENSORS ARE ONLY TALKING ABOUT ONE SPECIFIC SENSOR THIS IS NOT TRUE ALL CARS HAVE A CAMSHAFT AND A CRANKSHAFT EACH ONE HAS ITS OWN SENSOR IF YOU CHANGE ONE CHANGE THEM BOTH IF YOU MECHANICALLY INCLINED TO IF YOU GO TO A DEALER THE LOWER ONE WILL PROBABLY COST YOU ABOUT $200 INSTALLED WITH PARTS IF YOU'RE LUCKY MAYBE UP TO 300 BUT THE TOP ONE THEY WILL CHARGE YOU FOR PROBABLY SIX HOURS OR MORE BOOK TIME IN REALITY IT'LL TAKE THEM LESS THAN AN HOUR AND A HALF IF THEY KNOW WHAT THEY'RE DOING BUT YOU WILL PAY BETWEEN 3 TO $500 BECAUSE THEY HAVE TO TAKE THE INTAKE MANIFOLD OFF AND TO MECHANICS THEY THINK THAT WERE ALL STUPID, they make it sound like a process that it doesn't actually have to be the reality of it is a qualified mechanic that knows the fundamentals of a shop in his first 30 days would be able to have this part removed and the motor put back together in less than 2 hours, unfortunately mechanics get to rip us off so if you have to have this done don't be cheap and only put in 1 sensor, make sure you get the old sensor back and even go as far as tell them once they have the motor apart just before they pull out the old sensor you like to kind of take a look at things any reputable mechanic will let you view as long as it is safe to do so and does not interfere with the daily operations of the shop or the repair that is going on will have no problem providing to you to prove that the item was removed and a new one installed and it is up to the customer to make sure this happens as in many many cases mechanics do not replace this part but simply take it out clean it up and reinstall it to save $5 and charge you up words of a hundred for that part, depart cost less than $25 to us and cost less than $10 to them, but they will charge you $100 for the part alone so unfortunately of these are the symptoms religiously stalling and restarting on hot days above a certain temperature running great in the evening when it's cooled down acting like it's running out of fuel when you go to restart it acting as if it's out of fuel the firing up after just a few minutes sometimes shorter sometimes longer more often than not it will be your crank or camshaft position sensor you'll need to have them relearned and you'll need to replace both of them if you are having any symptoms as there's no way to test them accurately and they both give off the same issue and many times are both bad at the same time.