Diesel Bombers - Guide to The 24V Fuel System

Fueling System Trouble Shooting Guide

This guide will start with the fuel tank and make its way step by step through the system. I am sure there will be other things to add to this but these are the problems I have come across.

1. Fuel Tank:

A. Rollover Protection Valve sticking shut. This will prevent your system from being able to pull air in to replace the fuel you are using, thus creating a vacuum. This vacuum will slowly pull your fuel pressure down as you drive. When removing the fuel cap you will hear the air pressure release. To test this try driving with the cap loose and see if that corrects your problem.

B. Fuel Pickup Tube corrodes on the outside or cracks inside the tank. The fuel pickup tube on the early models of 2nd generation trucks have a tendency to corrode and leak air into the system right on top of the module where the fuel line connects to it. If it cracks on the inside your truck will run fine until your fuel level gets below the crack. Then it will pull air mixed with the fuel. This is the same thing as putting a hole in your drink and trying to suck through it, you will get some drink but it is mixed with air. This will create low fuel pressure and a loss of power.

C. Fuel Pickup Screen clogs with debris inside the tank. On the bottom of the pick up tube is a fine mesh screen that sometimes will clog itself up if you have gotten bad fuel. This will sometimes fall lose when you shut the truck off and then re-occur as your driving. No real way to diagnose this except to get inside your tank and check it.

2. Lift Pump:

A. There’s only one thing to say about the stock OEM lift Pumps, regardless of which type you have. They are not sufficient to provide enough dependable fuel flow to the VP44 to keep it cooled off. If you are running any type of performance mods this just increases the weakness of the stock system. A fuel pressure gauge that is visible to you as you drive is the only assurance you can have to know if your lift pump is functioning properly. You can have 20psi at idle, but when you get on the go pedal that could drop to 0psi and then the very expensive VP44 is on its way to the graveyard. If you only do one Mod to your truck, make it a fuel pressure gauge.

3. Fuel Filter:

A. The Water Drain Valve sometimes leaks fuel. If your lucky you can jiggle it around and break lose whatever is blocking it from closing completely, if not it will need to be replaced.

B. Seals go bad. Many of us have a tendency to change the filter but not use the new seals that come with the filter. It is important to change these to maintain to maintain an air tight seal.

4. Injector Pump:

A. Also known as the VP44, the injector pump is fuel cooled. The lift pump is expected to not only pump enough fuel to feed your injectors but enough excess to provide cooling action to this pump. The main failures to this pump are to the electronics that overheat and lose there ability to control the fuel flow. There are many different symptoms associated with this. Among them are a noticeable loss of power, loss of fuel mileage, hard starting when warm and/or a code of 0216 on the code reader.

B. Fuel Pressure Regulator is nothing more than a banjo bolt on the outgoing side of the fuel flow that maintains 14psi of fuel inside the VP44. If this goes bad it could either stick in the open or closed position or just get weak and not hold enough fuel pressure to the pump. If it sticks open or gets to weak to maintain pressure it will let the fuel just bypass the pump and return thru to the tank, not feeding the injectors. This will result in low to no power situation. Many $1000 pumps have been replaced because this $12 banjo bolt went bad. Test it before you replace the pump!!!

5. Banjo Bolts:

A. You have several Banjo Bolts throughout the fueling system. These are the most restricting part of the fuel system. They are just a brass bolt with a hole drilled through the length of it and another that meets it drilled high on the threads to meet together. They allow fuel to pass through this hole when transitioning between fuel lines and the components on your truck. There are two on the fuel filter, two on the VP44 and two on the lift pump. Some people have drilled the hole out bigger on these bolts to allow more fuel and some have replaced them with High Pressure fittings and gotten rid of them all together. The only one you can’t do anything with is the Fuel Pressure Regulator bolt, which is the outgoing line on the VP44. resulting in codes being thrown and eventually putting your VP44 into self protection/limp mode.