When I started my truck the first time with the new ECM the fuel pressure was at its normal range of 14-15psi. After I shut the truck off I replaced a wire on my switch box and accidentally knocked a wire from the fuel pump relay. When I started it again I noticed I had zero pressure. Thinking I could figure it out quickly, the truck ran out of fuel. Once it was sorted the truck obviously wouldn’t start. I loosened the fass filter and ran the pump until it gushed and then retightened. I then cracked 2 injectors and cranked until they bubbled out fuel. The truck runs but now it takes a a few extra seconds of cranking when cold to start and the fuel pressure gauge doesn’t read until a few seconds after it has started. My pressure is now at 18-19psi. The truck runs and drives fine, not sure what to do.

4 hours ago, Sycostang67 said:

The truck runs but now it takes a a few extra seconds of cranking when cold to start and the fuel pressure gauge doesn’t read until a few seconds after it has started.

It is likely that you still have air in the fuel system. Do you have an electric fuel pressure gauge? If so, is the sensor remotely mounted? If it is, then there will be trapped air in the line going to the remote mount. Eventually, this air will work itself out of the system.

• John

My sensor is mounted on the pump, but I imagine the line would still have to fill before any pressure was created. I do have a sensor closer to the VP but that had the Quad plugged into it which is no longer with us.

8 hours ago, Sycostang67 said:

When I started my truck the first time with the new ECM the fuel pressure was at its normal range of 14-15psi. After I shut the truck off I replaced a wire on my switch box and accidentally knocked a wire from the fuel pump relay. When I started it again I noticed I had zero pressure. Thinking I could figure it out quickly, the truck ran out of fuel.

If I am understanding correctly, the engine died because the lift pump was not operating. If this is true, then one of two things could be happening:

1. The engine died because the VP44 internal vane pump could not pull fuel through a non operational lift pump. Some lift pumps are built this way, others have a directional free flow when non operational.

2. The engine died because the VP44 internal vane pump was drawing air mixed with fuel from possible leaking fuel line / fuel line connections between the lift pump and the VP44 injection pump.

I would be more suspect of #2 since you are seeing it take awhile to build lift pump pressure after the engine starts.

I have actually installed a fuel line with a check valve that bypasses the lift pump just in case I have a lift pump failure. If a lift pump failure occurred on a road trip, the fuel supply would not be interrupted - the fuel would be drawn around the lift pump by the VP44's internal vane pump - no performance loss and no damage to the VP44. I could repair the truck when I get home.

• John

Edited September 16Sep 16 by Tractorman

I need to change the oil this weekend so I’ll crawl around underneath and see if I notice anything.

Double-check any of the suction side lines. Remember, these lines don't typically leak outwards. Being a vacuum allows it to lose its prime. Do you have metal JIC fittings or plastic quick-lock fittings? On those types of fittings, if you suspect a fitting to be leaking air, you can wipe a bit of grease on the smooth bore and leave it a bit thick. This typically fixes an air leak temporarily. Metal fittings you might want to double check the mating faces and make sure there is no damage. These must be smooth both sides! Any bad faces you'll end up replacing both fittings.

I have the metal push lock fittings. I didn’t see anything wet, but it has gotten better. It’s still not as good as it used to be but is starting and building pressure better.

On 9/28/2025 at 12:01 AM, Sycostang67 said:

I have the metal push lock fittings.

So you have the JIC type push loc fittings?

Still, you should check the mating faces to make sure there is no grit or damage to the mating faces. I just had a hard start on Beast just yesterday, and my head is already processing. Suction side never leaks out but will continue to allow air in. Yeah, I've got the same fittings as well. The mating face if damaged or rusted, will typically start to leak (loose prime or leak outwards)

Thor on the other hand has the plastic quick connects. On these you can grease the smooth bore tip and the grease will aid in sealing.

Edited September 29Sep 29 by Mopar1973Man

Yeah, those are the ones. I’d really like to replace all my fuel lines as the blue stuff that came with the FASS looks like crap. I’m broke as hell right now though so it will have to wait. I will take a better look at the fittings though, I was supposed to the other day but had so much other stuff going on at the same time I totally forgot.

Last time I bought a roll of 1/2 inch line from DAP. Can't remember the price but it was about 20 feet on the shipment. Mine just found out in the landslide the other day.