AGING WORKHORSE TURNED SPRING CHICKEN, PART1:

UPGRADED FUEL SYSTEM, INJECTORS, AND TURBO ON A ’95 F-350

As a general rule of thumb, the earlier the electronically controlled diesel, the less horsepower potential you have to play with. Take the ’94.5-97 7.3L Power Stroke for example (not to mention the ’98.5-02 24-valve Cummins). Its mechanical lift pump only provides 40-45 psi of fuel pressure, the injectors ow a measly 95cc, and the turbo runs out of steam in a hurry. The good news is that upgrading all of these components won’t force you to close your bank account, and it’s exactly what we have in mind for this 22-year-old, 160,000- mile ’95 F-350.

DW-1706-OBSFUEL-02 — Before any mods took place, we strapped the truck to the rollers at Tri County Diesel in Godfrey, Illinois. While aboard the company’s Mustang chassis dyno, we ran the old Ford (which is equipped with the ZF-5 manual transmission) in fourth gear and ended up with 181 hp and 315 lb-ft at the wheels. While it wasn’t impressive by any stretch of the imagination, we knew it was only the starting point. With the engine rated at 215 hp from the factory, a 15% drivetrain loss is feasible, so we believe we achieved an accurate baseline.

DW-1706-OBSFUEL-03 — Irate Diesel Performance’s OBS fuel system comes with everything you need to add electric fuel to your ’94.5-97 Ford. From the selector valve forward, the kit includes a Walbro GSL392 lift pump pre-assembled on a 304 stainless steel mounting bracket (complete with fi lter bases and Baldwin fi lters), Irate’s regulated return system, all wiring, 3/8” Parker fuel hose, and all necessary fi ttings. The system can support injectors as large as 250cc (and with a 200% over nozzle) and retails for $1,000.

DW-1706-OBSFUEL-04 — The Walbro GSL392 lift pump has been known for its performance, reliability, and affordability in the 7.3L segment for more than a decade, so we completely endorse Irate’s use of it in its OBS fuel system. This little pump is capable of supporting up to 600 rwhp, so it should have no problem keeping up with the demands of the 238/80 hybrid injectors we plan to run.

DW-1706-OBSFUEL-05 — Tackling the electric fuel system fi rst, the guys at Flynn’s pulled the upper radiator hose, factory air intake assembly, the Y-inlet for the turbo, and taped off the openings in the intake plenums. Then the drain valve in the factory fuel bowl was opened and allowed to drain into a 5-gallon bucket while the factory lift pump to fuel bowl lines were disconnected. Once all fuel lines running to the fuel bowl were separated, the injection pressure regulator (IPR) wiring harness was disconnected and the factory fuel bowl was removed

DW-1706-OBSFUEL-06 — After a 1-1/4” wrench was employed to break the banjo bolt at the rear of the factory lift pump free, its mounting bolts were loosened. From there, the 22-year-old lift pump was pulled from the lifter valley and discarded (the aforementioned Walbro pump will take over fuel supply duties and will be mounted along the framerail). While these camdriven mechanical pumps can live a long time, asking one to support a set of larger injectors is never a good idea—especially when it’s already borderline on supplying the stock injectors with ample fuel.

DW-1706-OBSFUEL-07 — Next, the freeze plug Irate Diesel supplies in its OBS fuel system was installed where the factory lift pump used to protrude into the block (directly above the camshaft). The freeze plug installs just below the surface of the block. Then the lifter valley was doused in brake cleaner and given a longoverdue cleaning.

DW-1706-OBSFUEL-08 — Because the supplied fuel fi tting we needed to install in the rear of the driver side cylinder head wouldn’t clear the factory up-pipes (and because we were upgrading anyway), the factory turbo was the next item to be removed. To ease the process, all turbo bolts were drenched in Liquid Wrench prior to being loosened. Once the turbo was out, the factory turbo pedestal was on its way out, too.

DW-1706-OBSFUEL-09 — Here you can see the fuel fi tting at the rear of the driver side cylinder head being removed. The factory fuel system on ’94.5-97 Power Strokes squeezes diesel through tiny 5/16” lines. This is why—in addition to adding an electric, higher-fl owing lift pump to the equation—Irate Diesel’s fuel system increases the size of the fuel lines and fuel fi ttings to 3/8” diameter.

DW-1706-OBSFUEL-10 — A little extra labor was required when installing the supplied #6 JIC 90-degree fi tting in the rear port of the driver side head. To gain enough clearance to thread it into the head, the up-pipe bolts had to be loosened at the exhaust manifolds and the up-pipes pushed back against the fi rewall. Permatex thread sealant was used on all fi tting threads for an optimum seal.

DW-1706-OBSFUEL-11B — As for the passenger side cylinder head, the factory rear fi tting was much easier to access (especially with the turbo out of the way). It was replaced with the #6 JIC straight fi tting, installed here.

DW-1706-OBSFUEL-12 — In order to gain access to the fuel fittings located at the front of the heads, the accessory drive bracket, A/C condenser, power steering pump, and vacuum pump had to be moved out of the way. Here you can see one of two supplied #6 JIC 45-degree fittings installed in the driver side cylinder head. The other 45-degree unit installs in the passenger side head, but both fittings have to be pointing up once installed. We’ll also note that caution must be used when installing fittings in the 7.3L’s cast-iron heads. If you over-tighten them, the head(s) will crack.

DW-1706-OBSFUEL-13 — Next, the hard lines included in Irate Diesel’s OBS fuel system were attached to their respective rear fittings. For the passenger-side hard line to install correctly, the factory engine eyelet had to be removed.

DW-1706-OBSFUEL-14B — After that, both hard lines were connected to the supplied #6 JIC T fitting, located just behind the high-pressure oil reservoir. The barbed fitting (installed in the T) is where the 3/8” supply hose from the lift pump will hook on. From there, fuel will enter through the rear fittings. Once through the heads, leftover fuel will return to the tank via the fittings located at the front of the heads, and after traveling through the regulator (which is not yet installed in this photo).

DW-1706-OBSFUEL-15 — With the supplied hard return lines connected to the return fittings in the heads, the included Fuelab adjustable fuel pressure regulator was installed. The driver side of the regulator incorporates a #6 O-ringed 90-degree fitting, while the passenger side required a straight #6 JIC fitting.

DW-1706-OBSFUEL-16 — A 100psi liquid-filled Marshall fuel pressure gauge is also included in Irate Diesel’s electric fuel system, which makes it easy to set fuel supply pressure at the regulator. The guys at Flynn’s told us the regulator would be set between 65 and 68 psi once the truck was up and running.

DW-1706-OBSFUEL-17 — Moving toward the lift pump install location, the factory return line was disconnected near the driver-side front tire. This is where a short section of the supplied 3/8” Parker hose will span between the regulator and the OEM hard line.

DW-1706-OBSFUEL-18 — Up in the valley, the factory return and supply hard lines were cut off. As previously mentioned, a short section of return line would be made up of the supplied 3/8” Parker hose, and the entire fuel supply hose (from lift pump to engine) would entail using the 3/8” hose.

DW-1706-OBSFUEL-19 — With the supplied 3/8” fuel hose attached at the T in the valley (feed) and the regulator (return), the accessory drive bracket, A/C compressor, power steering pump, and vacuum pump were bolted back into place. The guys at Flynn’s took care that plenty of clearance existed between the driver-side head and the accessory drive bracket (namely the A/C compressor), and that the fuel hoses weren’t pinched off in any way.

DW-1706-OBSFUEL-20 — Because we were installing Irate Diesel’s fuel system on a regular cab truck, the lift pump and filter assembly had to be mounted on the outside of the frame rail (on super cab and crew cab models the system mounts to the inside of the frame rail). We chose to mount ours under the bed (where the frame transitions upward), just behind the driver-side door. The assembly was installed by first clamping it in place on the frame, drilling the appropriate holes, and then bolting it in place using the supplied hardware.

DW-1706-OBSFUEL-21 — An added benefit with Irate’s fuel system is that it works in conjunction with the factory selector valve, which allows customers to continue to utilize both fuel tanks on OBS Fords. Tapping into the selector valve required disconnecting the factory hard lines, installing the 5/16” brass barb fitting supplied in the Irate kit, and connecting the new 3/8” fuel hose. When routing the 3/8” fuel hose along the frame rail (between the selector valve and engine), it was anchored to the old factory hard lines via zip ties. From there, the system was wired up.

DW-1706-OBSFUEL-22 — Moving on to the injectors, the valve covers were unbolted, the UVCH harnesses inspected, the glow plug spades, glow plugs, and oil spouts were pulled, and the oil rail plugs were removed. Then the injector hold-down bolts were broken loose and the injectors were pried out of their sleeves.

DW-1706-OBSFUEL-23 — Because it was wearing all black O-rings, we believe the truck was sporting the 22-year-old factory injectors. The fact that we made a relatively strong baseline horsepower number (181 rwhp) told us these injectors were still in tip-top shape given their age. It’s proof that practicing good maintenance (namely oil changes) goes a long way with a 7.3L.

DW-1706-OBSFUEL-24 — The 238/80 hybrid injectors we went with came from Unlimited Diesel Performance. Known as standard hybrid, they flow a maximum of 238cc of fuel and come equipped with brand-new 80% over nozzles. Capable of supporting more than 500 rwhp, they’ll have to be de-tuned a bit in our stock head bolt, factory-based turbo application, but a solid 425 to 450 rwhp should still be on the table. We’ll go into more detail on the tuning side of things in Part 2.

DW-1706-OBSFUEL-25 — Once the injectors were in, the hold downs were torqued to spec and the oil spouts and oil rail plugs (shown) were reinstalled. After that, the engine was bumped over to remove oil from the cylinders, a set of new glow plugs went in, and everything was buttoned back up.

Over the course of our two-part series, the first-generation 7.3L Power Stroke will be graced with an electric fuel system from Irate Diesel Performance, a set of hybrid injectors and 66mm turbo from Unlimited Diesel Performance, and a DieselSite Adrenaline highpressure oil pump—all courtesy of Flynn’s Shop in Alexander, Illinois. We’ll walk you through the fuel system and injector install this time, and the turbo and high-pressure oil pump upgrades will be highlighted in Part Two. We’ll also be heading back to the chassis dyno in the second installment, so make sure you tune in next month for the finale.

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Pinaki Bhattacharya

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