99 GMC Sierra Stalling Problem

Discussion in 'GM Powertrain' started by Mr. Sierra, May 23, 2011.

  1. Mr. Sierra

    Mr. Sierra Member

    Started about 2 years ago, truck will stall randomly about 4 times a year. Until recently would always restart after 10 to 15 minutes. Since then, I have replaced the Fuel Pump, Fuel Pressure Sensor, and the Crankshaft Sensor (most recently).

    A few days ago, it happened again, I was out of town so had to call tow truck. The tow truck dude came and squirted ether into intake and viola! it started and ran. So I took it to the gas station and filled tank while leaving it run as battery was dead. While in the store paying for Gas, it died. I bought ether and tried same trick, car would not start except for when ether was being shot. Almost as if no fuel. So I let it sit overnight stayed in local hotel and called a tow truck to get it into shop next day.

    The tow truck guy rapped on the tank, and asked me to try to start it again... It fired right up. Then I followed him to the shop to have a scanner put on it. No Codes, but they did have a tool to check the pulse to the injectors and weren't getting any readings. That's when I agreed to have the Crank Sensor installed. BTW the fuel pressure was 60+ psi so it is not the new fuel pump.

    Paid up and drove home, 20 miles later it died again, but this time unlike the night before it started after 10 minutes. I've checked all the relays and am stumped what to do next. Could it be EGR? PCM? Fuel Rails and Spider? Are there any other "shut engine down" controllers out there? Vacuum leaks?

    Last edited: May 23, 2011
  2. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    I would actually carry a spare fuel Pump relay and find it so you can easly change it out before you leave. And if it stalls try changing the Fuel pump relay. I have a feeling you are having a problem with it overheating, (wiring issue between pump and relay) that is causing it to overheat and shut down.
  3. Mr. Sierra

    Mr. Sierra Member


    On more than one occasion I did swap the relays. There are three of them with same part number, I rotated each one to the left one slot, plugging the last one into first slot. Didn't help. Could all the relays be heat sensitive? But if so, why would all three be running at same hot temps as fuel relay?

    ---------- Post added at 12:14 PM ---------- Previous post was at 12:11 PM ----------

    So based on latest information, the fuel pump is at proper pressure, the pressure regulator is new, the CrankShaft Sensor is new, and the relays could be bad but probably are not due to having swapped them with same results.

    I have to agree with you though that it appears to be heat related. Because after cooling either 15 minutes or (overnight last time) it always starts right up...
  4. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Another thought it to take a look at the Fuel Pressure Regulator.. see if raw fuel comes out. Because you do have a NBS Sierra Right? (99-06 body style) with the 5.3L or the 4.8L??? Because something is overheating for sure
  5. Mr. Sierra

    Mr. Sierra Member

    I do have the 5.3L. The fuel pressure regulator is only one year old, but I don't want to take that for granted. How do I check for raw fuel? Doesn't the top of the regulator have a vacuum line? When I installed it, it was a bear, I had to put a lot of pressure with tools to get it to fit. Maybe the OEM part was not quite right?
  6. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    When you remove the vac line if it is bad fuel will come out of it. As to removing it with the tools did you relieve the pressure at the fuel rail first?
    But this sounds alot like you actually have an ignition problem and not a fuel problem since you have 60PSI when you should. So something isnt causing it to spark. Or pulse the injectors... Take a look at the ignition module/what causes the ignition and fuel injector pulse. I cant remeber at the moment what does that on the 5.3L since it is coil on plug.
  7. attaboy

    attaboy Member

    Try replacing the fuel pressure regulator (not expensive). Mine did the same thing as yours and the FPR was the problem. Mine tended to stall while waiting for a light or making a turn (no fun loosing the power steering while in a turn). Anyway, it's a thought....
  8. Mr. Sierra

    Mr. Sierra Member

    The problem appears to be both fuel starvation and pulse. Here's why, last time it died I had to call tow truck, the guy squirted ether into manifold it started right up and ran for 15 minutes. After it died second time at gas station, the ether trick kind of worked but motor wouldn't run on it's own. I let it sit all night came out next morning it started right up. Took it to a garage and the only DX was there was no pulse. They put in new Crankshaft Sensor, I drove 20 miles it died again. Waited 10 minutes it started and I drove 60 miles no problem. So the garage guy found no pulse. But the night before ether started it and it ran (almost like fuel starvation). The pulse should be fixed now, but I don't know if he reprogrammed the unit to accept new Crankshaft Sensor.

    ---------- Post added at 03:44 PM ---------- Previous post was at 03:41 PM ----------

    I can try to replace FPR...Thanks for tip...even though I just did this last summer.

    ---------- Post added at 03:51 PM ---------- Previous post was at 03:44 PM ----------

    It's almost like something in the PCM or ignition key lock system is shutting it down. Or it's a heat issue...
  9. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Sounds to me like you need to find what part it is on the NBS trucks to send the signal because the spark and the injector pulse are both usually controlled via the same component. Im just not 100% on what that is. but that part is most likely overheating. I would also try and clean up the grounds etc.. And what is the Oil pressure when this happens? because i know the oil pressure switch can stop the motor from running if it doesnt detect oil pressure. Which may be happening as the motor warms up.

    ---------- Post added at 04:10 PM ---------- Previous post was at 04:00 PM ----------

    Also when you get a chance buy a new Fuel Pump Relay.. and when/if it does that swap in the new/cool one as mentioned above..
  10. Mr. Sierra

    Mr. Sierra Member

    I'll have to check oil pressure and get back to you. I just thought of one possible other detail. When I put new fuel pump in I debated putting in new fuel lines but didn't. Could the fuel lines be loosing pressure and causing this?

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