Starting Problems after sitting

[GuyM]

My 97 GMC 5.7L starts very hard if it sits for 72 hours. It turns just fine, just will not fire. It makes no difference whether it’s in the heated shop or unheated shed.

 

If it’s sat for 24 hours it will start with less than two seconds of cranking, 48 hours, 2-3 seconds of cranking. 72 hours, lots of cranking, maybe 3-4 ten second tries, before it will fire. Once it starts it runs just fine. I took it to the dealer and he tested the fuel pressure and said the pump appeared to be fine and had no idea what was causing the problem.

 

Yesterday it finally failed to start after repeated long cranks, 6 or more 10 second tries, it didn‘t even attempt to fire. The battery was getting low so I put a charger on it and walked away for a half-hour or so. When I came back it started and ran fine within 1 second of hitting the starter.

 

When the key is turned to “on” I can hear a relay click under the hood and the pump will run for about 3 seconds, as it should.

 

I let the truck sit outside last night, the low was –5 degrees, after sitting for 27 hours it started and idled fine in less than 2 seconds.

 

The dealer says he thinks it the fuel pump, but can’t prove it.

 

Anybody had anything like this before?

 

Guy