please help, truck wont start
January 21st, 2017, 6:39 PM
#1
CF Beginner
Thread Starter
Join Date: Sep 2013
Location: england
Posts: 3
Likes: 0
Received 0 Likes
on
0 Posts
please help, truck wont start
I have a 1998 k1500 suburban 5.7 vortec that refuses to start. Just a bit of background, i am a mechanic by trade and have owned the truck 4 years but im in england so getting parts just to try is a bit of a pain with a long wait.
The truck has been running fine until i sat it up about a month ago, fired it a few times since then, and it struggled to run, and now it refuses.
I noticed that my fuel pressure was a bit low so i have replaced the pump and also fitted a new ac delco mfi spider unit. i know have 58 psi with ignition on, and holds at 62 psi when cranking even though the truck doesnt even try to fire. i have checked compression which is all good and checked that the timing hasnt jumped.
I have spark although the pattern to the spark is a little weird.
The craziest think is if i just flick the key in half a second bursts the car tries to fire, and i have managed to get it to eventually start if i keep doing this for around 5 mins, when it does fire it runs perfect, but turn it of and it does the above again.
It is the strangest fault ive seen, and leads me to believe that cranking is somehow upsetting something, if i hold the key in the start position it will not hint at firing.
Also plugged on with obd, and on crank im getting 120rpm, is this normal or two low, my battery is also at 10.8v on crank which i assume is acceptable.
Sorry for the long write up just hoping someone can shed some light for me..
Thankyou
The truck has been running fine until i sat it up about a month ago, fired it a few times since then, and it struggled to run, and now it refuses.
I noticed that my fuel pressure was a bit low so i have replaced the pump and also fitted a new ac delco mfi spider unit. i know have 58 psi with ignition on, and holds at 62 psi when cranking even though the truck doesnt even try to fire. i have checked compression which is all good and checked that the timing hasnt jumped.
I have spark although the pattern to the spark is a little weird.
The craziest think is if i just flick the key in half a second bursts the car tries to fire, and i have managed to get it to eventually start if i keep doing this for around 5 mins, when it does fire it runs perfect, but turn it of and it does the above again.
It is the strangest fault ive seen, and leads me to believe that cranking is somehow upsetting something, if i hold the key in the start position it will not hint at firing.
Also plugged on with obd, and on crank im getting 120rpm, is this normal or two low, my battery is also at 10.8v on crank which i assume is acceptable.
Sorry for the long write up just hoping someone can shed some light for me..
Thankyou
January 22nd, 2017, 5:28 PM
#2
CF Junior Member
Join Date: Aug 2007
Posts: 36
Likes: 0
Received 0 Likes
on
0 Posts
Crank position sensor
Hi. Also in the UK. Not sure what the setup is on yours but a faulty crank position sensor can stop the firing sequence. I'm down south in Surrey and gave a full otc genisys if you want to try it. Julian
January 22nd, 2017, 6:17 PM
#3
CF Monarch
January 23rd, 2017, 11:06 AM
#4
CF Junior Member
Join Date: Aug 2007
Posts: 36
Likes: 0
Received 0 Likes
on
0 Posts
From the workshop manual.
From the workshop manual. Are the plugs getting wet when if doesnt start. It first asks you to check if the security system is causing the VTD Fuel Disabled parametric to remain active. After that it suggests you check the throttle body position sensor (should be 2.5v at idle). Then it's final suggestion would be the engine coolant temperature sensor aa the car won't try to start if it thinks it's below -30c though a fault here should cause a fault code.
