Automotive Forums  Where Car Enthusiasts Go to Discuss Cars Online

98 Chevy Surburban 1500 gas efi vortec 5.7L v8

Engine shuts down/off without warning after 1-2 hours of runtime in 95 degree weather. Starts right away, but shuts down within 5 minutes. Allow engine to cool for an hour or two, and resume normal operation. Night time driving, no problems. Water temperature gauge, and all other gauges normal. No check engine warning/code. Fuel pump noisy, but otherwise OK. Would have no idea of existing problem on short runs around town.

Any suggestions would be appreciated.  

there are a bunch of things that can cause this...

first.. i would get under the hood.... open the relay box next to the master cylinder...  figure out which relay is for the fuel pump..

buy a new one...  

use a sharp probe and care with a lot of skill..  work in the female  terminals in the socket where the relay plugs into... you need to figure out how to close the openings slightly to create a tighter grip on the relay terminals when you insert it...

i have found several that just did not hold tight on the relay pins......

i have a relay i pulled from a 98 C2500 that had this problem.. when i pried the relay from its cover.. then removed the spring from the movable fingers.. when i slipped the movable finger back so i could see the contacts.. they were in terrible condition...

in that i was not paying attention to what i was doing.. i used the end of my dental hook i used to remove the spring without damage.. i burnished the contacts before i realized i should have photographed them..  the contact faces are silver.. and rubbing with a proper round sided tool will push silver around  and if you do it right.. restore the convex curve to the face ...

the oil pump pressure switch is probably also bad...   thats on the back of the motor under the distributer...

these work as a pair to power the fuel pump ...   both closed to ensure that the engine does NOT die..

if you decide to change the oil pressure switch also...  try to order a delco version if you can.. i have found that some of the aftermarket versions are threaded to 1/2-20 UNC...  not 3/8 NPTM..  i have called the manufacturers.. but have gotten no response..

you can monitor the fuel system with one of these 20 amp tools.. there are 2 sizes.. one for the smaller fuses and one for the slightly larger ATO fuses..



its still easier to change the fuel pump relay.. takes about a minute... including the time to open the hood...  

next.... i would take a digital volt meter...

set it to 20 volts DC scale...

start the engine and turn on the headlights..

1. test between the positive and the negative battery posts.  14.1 to 14.8 volts is expected.

2. test between the negative battery post and the engine block. 0.04 volts is expected..

3. test between the negative battery post and the body... 0.02 volts is expected..

4. test between the Engine block and the body..  0.02 volts is expected.

if you get 0.00 on the last 3 tests.. change the meter setting to 2 volts DC scale.. and retest.. the last 3...

this test takes about 2 minutes...

post your results by test number..

if you get more than the 0.04 or 0.02 volts on the display...

you have a bad ground between those parts..

you can get to the ground wires on the front of the engine from under the front right of your truck.. the ground wires are attached to the lower front of the block passenger side..


you might also want to pull the cover off the relay box.. and test from the positive battery post to some of the tops of the fuses inside...  use the 20 volt DC setting .. then the 2 volt setting..  again.. the headlights on and the engine running.. 0.04 volts max..

i have found the wire across the engine that powers that box needs the end unbolted and the wire brush both sides of the ring terminal... and the mounting pad for the terminal..  

next...  onward to the ignition system...

if you have a timing light laying around.. hook it to the coil wire..

tape the trigger ON... lay the timing light on the windshield under the wipers so you can see the flashing easily while driving..

does the flashing stop as soon as the engine dies but before it stops turning..   or  does it continue flashing slower and slower until the engine completely stops....

if it just instantly cuts out...

i would get back under the front of the truck and carefully change the crank sensor in the bottom of the timing cover...

they have been known to be heat failure items..

the crank sensor pigtail has also been know to fail..  so you might want to wiggle it from under the motor with the engine running... if it dies.. change the pig tail also..

there have been reported problems with the reluctor wheel on the end of the crank shaft hitting. brushing the end of the crank sensor just slightly.. causing all kinds of damage.. there are shims available from GM.. you will have to find the TSB to get the part number for them..  this allows you to space it back slightly..


so far you have changed 2 or 3 items.. non very expensive...  compared to shop time...