98 K1500 Wont Start

stick6 · September 12, 2008

Hello! I'm new to the site but not to working on cars. just like it says the truck will not start and seems to be getting fuel and spark but just spins over. Wasted 250.00 dollars today and 2 weeks ago threw another 400.00 at it for a GM fuel pump (old one died). it is a 5.7 vortec 4wd. Today it was sort of damp out, when i went to start it. It acted like it was going to fire and run when i let off the key, it dieseled and finally died only to just spin away while i tried to restart it. With 140,000 on it, i thought it could possibly be a crank or cam sensor so i went to the dealer and bought both. No fix. When i checked fuel psi, it seemed to go to 60 then right down to 0. I thought it probably was a blown regulator. Ran to NAPA and bought a 92.00 regulator. Put everything back together only to hear the starter just spin motor over and over....... I really need some help here i need my truck for my lawn service. ANY HELP would be greatly appreciated. I also have a scan tool and i found no DTC's. It almost acts as if it jumped time. Is this possible or better yet how likely? Sorry for being so drawn out. Cash is getting tight so i dont really have room for the wheel barrel method if you know what i mean. Thank you.

minibike132 · September 12, 2008

You can follow along with THIS. I know it's a different engine but your fuel system is pretty much the same as his.

When i checked fuel psi, it seemed to go to 60 then right down to 0.

You replaced the regulator. Are you still falling off to zero with the pressure test? If you have a new regulator and pump unless they are bad all that is left is one or more of the injectors being stuck open If it still drops to zero. Pull the plugs, are any of them completely fuel fouled? If it is not dropping off anymore perhaps you fouled out the plugs with the old regulator, try clear flood mode first. That is accelerator to the floor before key on, then key on and crank, that commands minimum fuel delivery. Sometimes that will clean up flooded plugs. If not pull them out and clean or replace them.

minibike132 · September 12, 2008

Oh by the way welcome to the site.

stick6 · September 13, 2008

Well i got home earlier than expected and tried the " clear flood mode ". It took awhile but it finally was able to fire and actually stay running on its own . My next question is do i have to do a crankshaft relearn after replacing the sensor. Reason i ask is because on my OTC scan tool i tried to do it, which required raising RPM to 4000 but it kept saying waiting for enable which i thought once i reached 4000 it would do something but nothing happened and i even went to maybe 4200-4300 and still nothing. What do you think? THANK YOU SO MUCH FOR YOUR HELP.

minibike132 · September 13, 2008

Sorry I missed the fact that you replaced the crank sensor. Yes you do need to relearn it. I'm not sure how your scanner will work but I can tell you the perameters that need to happen before crank relearn can take place. It has to reach operating temperature and closed loop. I think it's looking for 210f degrees but I can't remember off hand. What I usually do is start it up outside and let it run while I work on something else. Then shut it off and key on go to the crank relearn. There should be specific instructions on your tool, the Tech-2 I use tells you about the operating temp thing that should be achieved then tells you to turn the key on and place your foot on the brake with the vehicle in park and make sure all loads including the a/c are off. Then it will tell you when it is ready to do the learn. The actual learn is when you snap the throttle till fuel cutoff occours. It should tell you after that weather it learned or not. Good luck and I'm glad you got her running without spending any more cash.

minibike132 · September 13, 2008

I forgot to mention, you were flooded, CHANGE YOUR OIL. If too much fuel got past those rings you will spin a bearing in short order. If your running and not missfiring now change the oil before heating it up and stomping it up to 4000 rpm.

pennzoil29 · September 13, 2008

I figure I better ask. Are you sure you have to do the crank relearn on these models? I replaced both the cam and crank sensors on my '99 5.7, and didn't do a relearn, and the dang thing runs fine. I did this last December, froze my ass off doing it, but like I mentioned, I don't seem to be having any issues. I just thought I would ask.

minibike132 · September 13, 2008

The crank variation has no effect on driveability as far as I know. I'm sure you know that missfires are picked up by variations in the crank signal, get a miss and the crank will slow down. The problem is that you can't get 2 different sensors to line up exactly the same and you can get false missfire codes. I am positive more than one person here has chased a missfire that didn't exist because they didn't do the relearn. It's not critical to do, it'll run fine, but I would do it.