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hey guys, I have a 70 c10 I just put an lq4 in. it has a cam, long tubes, and typical supporting mods. I'm running an aeromotive fuel pump and bypass regulator into FAST fuel rails. the PCM has been tuned by Nelson. the problem is, it starts, but dies after 2 or 3 seconds. I was hoping someone could help diagnose this or point me in a direction. thanks in advance
Dratically losing fuel pressure, or VATS
check fuel pressure, unless it's a corrupt pcm, it def won't be vats, we turn that off for sure.
pm your name and info, we'll compare notes.
btw, fuel pressure should be 55psi or so. what did you set it for?
Nelson tuned it and they knew it was a swap, but maybe they didn't eliminate vats? and as far as I can tell, the regulator stays strong at 58 psi. but, as soon as the pump shuts off, pressure drops immediately. should this happen?
Fuel pressure regulator?
regulator is an aeromotive bypass regulator, set at 58 psi. this is a new swap, and hasn't run yet, so could there be other possibilities also?
blew a hole or have a leak in the fuel line between the pump and the tank metal fitting.
The pump shouldn't be shutting off... but yes, the pump shutting off should definitely result in a loss of fuel pressure...Quote:
Originally Posted by Silverado889
put a one-way check valve between the pump and the fuel rail to hold the pressure if it's bleeding back through the pump. How do you have your fuel lines plumbed? Pump to rails, rails to regulator and then bottom port of the regulator back to the fuel tank?
Actually, shutting the pump off should result in a loss of fuel pressure over an extended period of time... not instantly by any means. My truck will still be holding 50+ psi after 5 minutes of the truck being off.Quote:
Originally Posted by Wagonbacker9
This is with the truck not running. His pump shuts off while the truck is running so the injectors will keep pulsing causing pressure to drop in the rail until there is not enough pressure to supply fuel. It sounds like an issue with either the PCM or VATS to me.Quote:
Originally Posted by pl4yboy
well I found it. as far as fuel pressure, I'm just going to check valve it after the regulator to the rails to maintain pressure after the trucks initial prime. I'm also just going to run the pump key hot since I'm running a bypass regulator and there's no reason for the pump to ever shut down. as dumb as it sounds, the engine is a junk yard motor. the cam position sensor was damaged at some point in time and wasn't working. I swapped it out, and after it learned it's idle runs great. thanks to everyone for the help!
Dumb as it sounds, the pump shuts down to keep from burning you alive in an accident. If the fuel line is ruptured in an accident, the engine dies and the fuel pump shuts off. If the fuel pump kept running while you're unconscious inside the truck and something ignites the fuel that is all around you have an instant car-b-q and you are the main course.
Just an FYI. The reason fuel pressure goes away is because ur running an aftermarket fuel pressure regulator. That is normal.
Has nothing to do with the injectors bleeding off fuel pressure. Keep the pump on the PCM and don't hot wire it directly to the ignition. If the engine stops due to a crash the pump should stop. Some oem setups even run the oil pressure switch thru the fuel pump relay wiring. Oil pressure goes away so does fuel pump.
Glad to hear u got it running.
ok, you guys are rite. I guess if its firing up and running no problem then theres no reason to change it anyway. I am going to check valve after the regulator to maintain pressure in the rails after the prime... On another note, does anyone have thots on all the different heads out there? im running a 228/230 .588 .591 cam natural this season, but will be going turbo over the winter. Should i wait and get optimum chamber sizing for boost vs. the natural setup im running now?
If you're boosting, thats the time to head swap. the 5.3 I'm looking at has cracked head(s), so I'm going to have to put my boost heads on it NA, so I'm probably going to set it up with a CR in the middle which isn't ideal.Quote:
Originally Posted by Silverado889