This article originally published in Issue 56 of the Turbo Diesel Register.

The Way We Were

I HATE TO DO THIS - FUEL TRANSFER PUMPS REVISITED

Let’s continue and discuss fuel pressure, fuel pressure gauges and opinions. To start let’s look to Webster’s dictionary for a definition.

Webster’s: opinion n. 1. A brief, conclusion or judgment not substantiated by proof. 2. An evaluation based on special knowledge.

The TDR offices are only 20 steps away from the accessory business of Geno’s Garage. The Geno’s phone rings and the voice on the intercom asks for assistance, “Can someone help the customer on line one with a fuel pressure gauge question?” Should the Geno’s staff offer an opinion based on Webster’s first definition or Webster’s second definition?

Future success in business dictates that definition 2 be used. As I’ve overheard the dialogue so many times, the exchange goes something like this:

GG: What year model truck do you own?

Customer: It’s a truck (pick your year ’98.5 to ’02) with a 24-valve engine. I’ve heard opinions that I need a fuel pressure gauge. What do you think?

GG: Yours is a 24-valve engine—yes, you need to monitor the fuel pressure. We’ve got gauges and accessories in stock that will make installing the gauge an easy project.

Customer: Okay, what do you suggest and how do I install a gauge?

GG: Do you want the long story or the short story?

Customer: I’ve got time.

GG: Here goes... The 24-valve engine’s VP-44 fuel injection pump relies on fuel from the transfer pump to keep the VP-44’s internal parts lubricated and cool. A bad fuel transfer pump (and the transfer pump is known to be problematic) means a loss of fuel pressure to the VP-44 and often leads to the demise of the very expensive VP-44 injection pump. A fuel pressure gauge for a 24-valve engine is mandatory.

As for the installation, you will be dealing with fuel, albeit less volatile diesel fuel. Nonetheless, you want to minimize the possibility of fuel leakage. On the ’98.5 and ’99 trucks the filter is in a housing and the housing drops down from a horizontal filter bracket. On top of the bracket are two ports that are tapped and plugged with a 1/8 NPT plug. The innermost plug is the clean side of the filter. Remove the innermost plug and install an electric Westach fuel pressure sending unit. Because the Westach fuel pressure gauge does not always match other gauges that owners have installed, the gauge can be mounted at the bottom of the kick-panel in a rubber donut mounting kit. This keeps the gauge hidden and unnoticed. Because the Westach gauge is electric, the chance of fuel leakage is minimized. There are no fuel isolators to malfunction, and therefore no fluid can leak into the cab. The Westach gauge is also the least expensive and least prone to give the customer a problem. Low cost and dependability—an unbeatable combination.

The Westach fuel pressure sending unit mounted on a ‘98.5/’99 model engine.

For the ’00 to ’02 trucks the fuel filter assembly was changed to make fuel filter changes easier to perform. To change the fuel filter one simply removes a plastic cap and the filter comes out of its housing. For those wanting to install a fuel pressure gauge this presents a problem, as tapping into the fuel system is no longer as easy as removing a 1/8 NPT plug. The first solution that we offered called for replacing one of the fuel system banjo bolts with a bolt that was drilled and tapped to accept a 1/8 NPT pressure sending unit. Unfortunately, none of the banjo fittings are located in a vertical position. Common sense dictated that mounting a 6-ounce sending unit that is on an angle into a fragile banjo bolt on an engine that vibrates is not a good idea.

At first we suggested that customers purchase a 1/8" NPT hydraulic “whip hose” for a grease gun and use the hose to plumb from a tapped banjo bolt to a mounting point for their Westach pressure sending unit.

As the technique evolved, TDR member John Holmes developed a hose that would screw onto the Schraeder-valve, test port and also screw onto the 1/8 NPT male Westach pressure sending unit. After several generations of hoses, the Geno’s group now offers a universal hose kit to access the fuel system’s pressure.

The Westach fuel pressure sending unit mounted
on a '00/'02 model engine.

Customer: Wow, that’s a story! It is now easy to understand the answer for 24-valve customers.

GG: For ‘98.5 and ‘99 owners all that is needed is the Westach electronic fuel pressure gauge and an acceptable gauge mount. The ‘00 to ‘02 owners should purchase a universal fuel line, a Westach gauge and an acceptable gauge mount.

Customer: Do you have any suggestions about transfer pump replacement for the ‘98.5 to ‘02 owners?

GG: Okay, this is another of our favorite topics. Many TDR members have added aftermarket fuel pumps to work in tandem with or in lieu of the existing factory pump. The drawback to any aftermarket accessory is that the owner is now responsible for installation of the product, special parts and tools to support the installation, and parts necessary should the new-and-improved accessory fail.

Admittedly, the original fuel transfer pump has been problematic. However, before I would recommend going the aftermarket route, I would suggest the keep-it-simple-stupid solution. Purchase a spare Cummins transfer pump. Yes, the part number has been superseded numerous times (the final kit number: 3990082). The current price at a Cummins distributor is $160. Next, read (and copy?) and understand the previous article showing how to replace the fuel transfer pump. By using the factory parts you’ll not have to worry about special aftermarket parts that may not be available to complete the repair when the truck breaks down.

Better yet, consider the ‘98.5-’02 transfer pump relocation kit from Vulcan Performance and Geno’s Garage that allows you to change- out the transfer pump in five-minutes or less.

Customer: What should I tell my friend with the ‘03 and newer HPCR engine?

GG: The HPCR fuel system is entirely different. First and foremost, the fuel transfer pump is of a different design than the fuel transfer pump on the 24-valve engine. Although we are early in the ’03 and ’04 engine’s life cycle, there are not reports of widespread problems with this newly-designed transfer pump. For ’05, the transfer pump has been moved to a unit located in the fuel tank where the pump pushes fuel to the engine rather than pulling fuel from the tank. On the HPCR engine, the fuel is pressurized by a gear pump and loss of fuel pressure from the transfer pump does not equal an expensive fuel injection system failure. The gear pump is not fully capable of pulling fuel from the tank, so should a transfer pump fail, the worst scenario is that the truck does not start due to loss of fuel prime. Should you spend money on a gauge to tell you that the truck is not starting?

Customer: Is there enough pressure to support higher horsepower settings with the ‘03-’07’s fuel transfer pump?

GG: In Issue 47, page 60, “Technical Topics” authors Doug Leno and Joe Donnelly had this to say about the HPCR fuel system: “It is not the purpose of this article to repeat the multitude of experiments showing the limitations of the stock lift pump and low pressure fuel system. This series of tests was done simply to validate that the stock fuel system is sufficient for power enhancements delivered by the boxes we tested (100 horsepower and below). We found no stumbling, hesitation, or other performance problems using any of the tested boxes; the power was smooth and predictable. As for actually measuring low-side fuel pressure, we hooked up the boost channel of the SPA Technique EGT/boost gauge to an SPA pressure sender on the Bosch CP3 fuel pump inlet. For the most aggressive power increase we tested, the low-side fuel pressure dipped to a value that is nominally equal to atmospheric pressure (gauge pressure read zero). This means that the low pressure fuel system is at the limit of its capacity, and from this we concluded that for the power levels tested, the low-pressure fuel system was sufficient, although barely so. Zero gauge pressure simply means that the CP3 inlet is not drawing (or pulling) fuel under vacuum.”

Okay, should you spend money on a gauge to tell you that the truck is not starting? Will you be increasing the engine’s output by a number larger than 100 horsepower? I can’t answer these questions for you. I can suggest a combination of parts (a fuel cap and a Westach gauge) to make the installation on a ’03 and newer truck easy to do.

Go forth and make an informed decision.