I have a 2017 L5P, it’s deleted and tuned. Had a head gasket failure. Ran fan coming in my shop started great, sounded great etc. get the cab back on, plug everything up whole nine, crank no start. Stock lift pump, kicks on I get fuel all the way up top into the rails, no high pressure fuel whatsoever. FPR on HP4 pump is good, pump should be good, no metal in any filter, only thing I’m concerned about is I’m getting a bunch of rerun fuel with the pump on. I’m not well versed in these trucks whatsoever. Also a back story on this truck, both heads cracked, 3 injectors holes on one head and 1 on the other, brand new Chevy heads, and ARPs. Cranks strong, I’m getting low pressure fuel but 0 high pressure, I am lost in the sauce, TYIA
L5P fuel issue.
- Thread starter Kheyevee
- Start date
I’m not 100%. Truck has 108,000 on it. I pulled the FPR out of the pump and there was no metal shavings. Rail pressure regulators are both getting 5v reference, which in turn I suppose they could still be bad. But the FPR out of the pump had no metal shavings, and testing the connector there is no voltage while cranking or while key is on if that helps at all.
The HP4 regulator is PWM controlled. Higher duty cycle = lower fuel pressure. So, reading zero volts would mean maximum pressure or flow.
If the connector on the rail pressure regulator is unplugged. What do you get for rail pressure and fuel return flow?
I’m not 100% on the acronyms. But I do no there is zero voltage too the sensor on the pump, I believe when we unplug the rails it’s still 0. Now, this is a 2017 just for reference but the relay number 66 pin 30 has constant 12v, 85 shows ground, 86 shows 2.4v and 87 shows nothing. Thats with the relay unplugged, now when it’s plugged in, it every pin shows ground. The relay doesn’t click, I’ve verified that the relay is good.
I’m starting to chalk it up to something we did in correctly whilst putting the cab back on. Haven’t found any pinched wires, all the grounds are seemingly good.
Did you check for codes?
Check regulator 2 on the back of the driver's side rail. Is it dumping fuel while cranking? You should be able to disconnect the hose from the rail and see if fuel is coming out of the rail. Make sure you crimp the hose so you don't spray return fuel everywhere.
It’s got a steady stream cranking
There you go...
Injectors, or rail? Also relay 66 is not clicking on
Rail pressure regulator. But as Josh said. You need to pinch off the other side so fuel coming out of the injectors and pump don't spill out. Pull the hose off the rail pressure regulator and see if you have fuel dumping out. Sounds like you do. So, new regulator it seems