my usual diagnostic steps on gm trucks... pull the fuel pump relay... open it.. inspect the contacts.. or replace the fuel pump relay.. on gm trucks up thru 2003.. the fuel pump relay and the outer 2 wires of the oil pressure switch are in parallel to supply power to the fuel pump... at that temp.. the oil might be too thick to pump up fast enough to push closed the contacts under the cap of the oil pressure switch.. you will want to inspect the terminals on the bottom of the fuel pump relay.. you may want to check the insertion force also. i have found the relay socket terminals really sloppy. a fine tipped right angle scribe can be used to get under the tongue of the terminal to snug it up. .

i usually also plug the bare frame fuel pump relay.. and test the fuel pump turn on.. a bunch of times.. with a hand held digital volt meter that has at least a 10 amp DC setting. . i will pull the fuel pump fuse and lightly stick the probes into the socket without forcing them between the terminals.. so i don't distort them and then squeeze the fuel pump relay.. you can then monitor the amp draw of the fuel pump by itself.. amp draw should never increase. most of the pumps i have tested are less than 7.1 amps. do this test for at least a minute.. i know its cold.. this is probably the most optional part of the diagnosis. .

i normally test the oil pressure switch by pulling the fuel pump relay with the engine running.. if the engine dies.. then the oil pressure switch is probably bad also.. this has nothing to do with the oil pressure gauge reading . that is a different circuit on the middle terminal of the oil pressure switch. .

if you have a hand held digital volt meter.. you could perform this test.. http://i.imgur.com/WMDprhm.jpg it takes 4 or 5 minutes.

i have found so many issues on GM trucks with this test.. you should perform it anyway... if you don't have a digital volt meter.. print several copies of the test.. and get your mechanic to perform it step by step. the extra copies are for.. once somebody performs it.. they will usually want several copies. as they may realize how much a time saver it is..

with a test light.. up under the dash above the brake pedal.. this usually requires some help with the ignition switch..

http://i.imgur.com/zDbdXyJ.jpg

at 260K.. your ignition switch contacts could be going bad.. the white wire in C1 should have power in RUN Cranking and Run. the pink wire in C5 should also have power in RUN cranking and run.. the orange wire in C6 will have power in RUN.. the brown wire in D6 will have power in run also..

the idea is to have somebody slowly turning the ignition key while you are probing the wire terminals i described.. not others..

these are just diagnostic steps i do every time i work on any GM truck.. the ignition switches vary from decade to decade..

you might find out you may need to use a plug in battery warming blanket. to keep the battery warm enough to work..

again.. these are JUST DIAGNOSTIC steps to identify known issues ..