LS Swap won't start. Cranks but no fire or fuel pressure
11-17-2015, 08:41 PM
#1
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LS Swap won't start. Cranks but no fire or fuel pressure Swapped an LQ9 into my K5 and have put about 500 miles on it with just the normal break in issues. In the last week it started acting funny during startup and would crank but not fire. Did it once and started the next try. Two days later wouldn't start and I check the wiring at the pump and grounds etc and it started
Then it wouldn't start at all and with relays firing for pump, I couldn't hear the pump priming on startup.
Thought I had a bad pump. I had ran out of gas and thought that I might have fried it. It was a Walbro high pressure pump for the LS motors.
Swapped out the pump for a AC Delco 62 PSI pump and still no go. The pump is priming but I have no pressure at the rail. The inline filter / regulator is clear but nothing.
Every tenth try it tries to fire, but doesn't. The PCM is seeing RPM so I don't think it is cam or crank sensor.
I am completely out of ideas and ready to burn the f$*#(# down.
Then it wouldn't start at all and with relays firing for pump, I couldn't hear the pump priming on startup.
Thought I had a bad pump. I had ran out of gas and thought that I might have fried it. It was a Walbro high pressure pump for the LS motors.
Swapped out the pump for a AC Delco 62 PSI pump and still no go. The pump is priming but I have no pressure at the rail. The inline filter / regulator is clear but nothing.
Every tenth try it tries to fire, but doesn't. The PCM is seeing RPM so I don't think it is cam or crank sensor.
I am completely out of ideas and ready to burn the f$*#(# down.
11-17-2015, 10:01 PM
#2
What year K5 do you have? There are two different gas tanks in then. One is deeper than the other. Did you swap senders and did you use the correct depth of sender? If you used one for the deep tank but have the shallow tank, you may have the pump choked off at the suction. Of course that wouldn't stop you from having fire.
11-18-2015, 11:31 AM
#4
It not going to start if you don't have fuel at the rail. Mine primes right to 58 psi as soon as I turn the key. You might have a clogged or pinched fuel line. If you can make a quick fuel line jumper from your filter to the rail with a new piece of line and make sure there's fuel pressure it should fire right up then you'll know your lines clogged.
