Thinking about buying a vehicle with a 7.3 Powerstroke? I’ll give my real-world experiences in owning and maintaining Ford’s most respected diesel engine along with some basic history of the design. Ever since reading Robert Pirsig’s ZEN and The art of Motorcycle Maintenance, I have been drawn to works of engineering that posses elements of what he calls quality. I consider the 7.3 Powerstroke to be one of those pieces of engineering. At the very least the 7.3 has good underlying form! Have fun reading!
A brief overview and history of the 7.3 Powerstroke:
The 7.3 Powerstoke is a Direct-injection turbocharged V8 diesel designed and built by The International Harvester Corporation. It first made its way into Ford trucks starting halfway through the 94′ Model year. This new engine replaced the previous 7.3 IDI (indirect injection) models that were found in Ford pickups from 1988-1994 which were also produced by international. The new 7.3 featured a bore of 4.11 inches and a stroke of 4.18 inches making it just slightly Undersquare (Having smaller bore than stroke) and giving it a displacement of 444 Cubic Inches. The engine has a compression ratio of 17.5:1 and came with various horsepower and torque ratings depending on the year and configuration.
Compared to the IDI 7.3 the Powerstroke was equipped with a HEUI (Hydraulic Actuated, Electronically controlled Unit Injector) style Injection system which was largely designed by The Caterpillar corporation but in conjunction with International. This injection system was revolutionary to the light truck diesel engine market at the time, as it allowed more precise fuel metering and injection pressures that were not relative to engine RPM as compared to mechanically injected engines. The Powerstroke Engine uses two separate oil pumps, a high pressure pump for the injection system, and a standard pressure pump for basic engine operating needs. Fuel is pressurized in the injector by hydraulic pressure created by the oil and then sprayed into the combustion chamber when commanded electronically by the computer. This system eliminates the need for an injection pump and is a large contributing factor in the 7.3’s reputation for reliability. Because the injected fuel is metered and controlled electronically, injection timing and duration are precisely administered through the engine control module and its various sensory inputs (MAP, IAT, CPS sensors, Etc.) and because of this, the injection values can be changed on the fly based on these sensory inputs. This system offered more flexibility to varying operating conditions than its mechanically injected counterparts. Because the oil serves two very important operations on the 7.3, it has a very large capacity (close to 16 quarts throughout the entire oiling system). Having a large oil capacity keeps the oil temperatures lower and lessens the breakdown of the oil’s additive package due to the extremely high pressures upon which it is subjected in the injection system. The system also has a very large oil filter to keep the oil free of contaminates and to promote sufficient oil flow without restriction. The 94′-97′ Pickups make use of a mechanical lift pump to supply the injectors with fuel from the tank whereas the 99′-03′ models use an electric lift pump. Furthermore, the 94′-97′ engines use a 15 degree HPOP (High Pressure Oil Pump) instead of the 99.5′-03′ which use the higher flowing 17 degree pumps. Higher oil pressure to the injectors equates to higher fuel pressure which promotes better fuel atomization and therefore a more efficient combustion process. Another thing to note about the injectors is the differences in Single-shot and split-shot models. OBS trucks came with single-shot injectors and 99′-03′ Models came with split-shot, with California compliant OBS truck 97′ year model being the exception as those were split-shots as well. Split shots were an attempt at making the engines more emissions friendly and supposedly quieter. From a performance standpoint, the single-shot injectors are superior in every way, they require less oil to function properly, they produce more power, the are more fuel efficient, and they are capable of metering fuel more precisely.
Turbo and Cooling system
Both new and old body styles of Fords equipped with the 7.3 use Garrett turbo chargers. The 94′-97′ or old body style (OBS) contained no wastegate on the turbo whereas the 99′-03′ Super Dutys did have a wastegate. In the OBS trucks there was no intercooler or charge-air cooler to cool the incoming air before it entered the engine. The 99′-03′ Models did have intercoolers which contributed to slightly more power, lower EGT’s (Exhaust Gas Temperature), and higher efficiency. This is because cooler air is denser and more oxygen rich and since fire needs oxygen to burn you can see how having an intercooler would promote a cleaner more efficient combustion process. Despite the fact that OBS trucks did not contain charge- air coolers, 7.3 Powerstrokes have generally not been plagued with extremely high EGT’s. This is because of the engines very large displacement. Because an engine is essentially an air-pump, a larger displacement engine is capable of moving more air than a smaller one. More air means more cooling and the ability to push hot air out away from the engine. A well maintained cooling system is generally very adequate for cooling the engine during even most extreme conditions. Regular cooling system flushes and radiator cleanings will ensure long cooing system life. 99′-03′ Trucks are equipped with a EBPV (Exhaust Back Pressure Valve) which is supposed to help the engine reach operating temperature quicker in cold climates. You can tell your EBPV is working from the noticeable hissing sound during part-throttle driving while the engine is cold during cold months. Upon the application of more throttle the hissing should subside until once again reaching part throttle conditions. Some people are annoyed by the hissing and opt to disable the feature but the engine should function fine either way. Mine is still intact on my personal truck.
The engine internals are very robust on 7.3 Powerstrokes. The cylinder heads feature two valves per cylinder which, although generally don’t flow as well as three and four valve designs, maintain a simpler and more reliable valvetrain. The 7.3 also has six head-bolts per cylinder which promotes a very consistent and even clamping force on the cylinder head gaskets. Because of this, head gasket failures on stock well maintained engines are rare. All OBS trucks and 98′-into 00′ build date trucks had forged connecting rods. Somewhere during the 00′ build date years, International started using compressed powdered steel connecting rods which are weaker. This really only affects the horsepower freaks out there who are looking at modifying their trucks to make more than 400RWHP (Rear wheel horse power). 400RWHP seems to be the point where there is no guarantee of them holding up, although some have pushed it farther with no failures. On a stock or slightly modified engine, the powdered steel rods offer no disadvantages or threats to reliability that I’m aware of. On the 00′-01′ model years it can be tricky to tell if you have forged or PMR rods. It seems as though mid October of 2000 build date is when they started using the PMRs for sure. Although there some examples of trucks made after that date that used forged rods.
Early 99′ Models
Early 99′ year models were kind of bizarre. They were like a cross between the OBS motors and the Super Duty ones. You can sometimes tell an early 99′ Model because generally the Powerstroke diesel badge will be on the fender instead of the bottom of the front doors like the late 99’s. Another way to tell is when activating the cruise control on a late 99′, a green cruise light will illuminate in the instrument cluster whereas there will be none on the early 99’s.
There are some subtle differences between the early and late 99’s. Early models had a slightly different turbocharger housing and wheel. Also the up-pipes, Y-pipe, turbo pedestal, and intake manifolds are all slightly different it seems. Early models had the old 15 degree HPOP instead of the 17 Degree. The injectors on the early 99’s are slightly smaller at 130cc instead of the late 99’s at 140cc. As far as a stock motor, the power difference between the late and early 99’s is negligible. However the late 99’s are more mod friendly if your goals are making substantially more power.
7.3 Powerstroke Maintenance:
Diesel engines are very rewarding to own. Many diesel trucks are owned by businesses and construction companies because of their workhorse nature and their high level of efficiency. When driving a diesel it just feels like there is something more going on under the hood. The feeling of using torque instead of engine RPMs to get up to speed is very addicting. That being said, Diesels are not very forgiving of poor maintenance. If you buy one and expect to treat it like a teen’s first Honda Civic, neglecting maintenance and care, you will have a very unfortunate experience. But if you treat your diesel engine with respect, attending to regular maintenance and reasonable driving habits, I assure that you will get many many miles of satisfying and rewarding use from your vehicle.
As we discussed earlier, oil plays a very important role in your Powerstoke engine. Not only does it lubricate and cool internal engine parts but it’s also the hydraulic force behind pressurizing fuel in the injectors. Because of the high demands placed on the engine oil in the 7.3, regular oil changes are a must. I use only Motorcraft filters and and that is all I can recommend that you run as well. Ford designed the filters to work with the engines that are in their trucks and covered under their warranty. I’m sure there are other filters out there that will work fine but for the price the Motorcraft filter is hard to beat and like I said it is made by Ford. The filter for the our trucks is the Motorcraft FL-1995. When it comes to oil you have a lot of options. I recommend a name brand oil, either synthetic or traditional. I personally run Rotella’s T6 synthetic 5W-40 Diesel oil. I live in a colder climate (South-Western Montana) so the thinner oil is great for those cold starts on winter mornings but I run it in the summer as-well. Whatever you do, make sure you run a diesel oil instead of a traditional oil. Diesel oils have higher levels of Zinc and phosphorous and other heavy duty additive packages which are made specifically for our applications. Regular gasoline motor oils are required to be lower in zinc and phosphorous due to new government regulations in the name reducing pollution. Our diesel oils are exempt because of their viscosity. Anything from Motorcraft, Rotella, Delo, Royal Purple, Schaffers, or Amsoil would probably be a safe bet. What really matters is that you change your oil. I change my oil and filter every 5000 miles on the dot. I feel that 3000 mile intervals are unnecessary most of the time and on our engines with HEUI style injection, I just don’t feel comfortable going 10,000 miles. One way to be certain is to have a sample of your oil sent off for analysis. Blackstone Labs, Schaffers Lubricants, and Amsoil all do oil analysis for about the cost of two of our filters. This is a sure-fire way to see how your oil is wearing and possibly pinpoint other problems in your engine like trace amounts of coolant in your oil. You could just as easily take the easy route and do the 5000 mile oil change interval. I always change my oil after the engine has been running for awhile. I like getting the engine up to full operating temperature for at least half an hour and then draining the oil while its hot. What this does is suspend all of the soot and dirt particles in the oil so when you drain your oil pan, they come out with the oil. Otherwise the dirt and soot will settle to wherever they fall in your engine and stay there until the engine is hot again. It’s not a completely necessary practice but again is something I recommend. Some people choose to drain the HPOP reservoir when they change their oil but I don’t find it necessary for people who change their oil consistently. Before you screw your new filter in, be sure to fill it up to the top with oil. The filter holds over a quart of oil, so if you can lesson the amount of time the engine runs without oil pressure upon initial startup, the better. Don’t forget to coat the rubber seal with oil before you tighten the filter down.
The cooling system another extremely important but often neglected area of your engine. Coolant ,just like oil, deteriorates over time and will need to be replaced. Coolant contains additives which prevent corrosion of engine internals and the rest of the cooling system. These additives also combat electrolysis which is an electrical charge throughout the cooling system which speeds and causes cooling system corrosion. Over time, corrosion builds up in the cooling passages much like plaque in artery and inhibits flow. This same buildup can block the smaller passages in your heater-core and radiator resulting in poor heater performance and engine overheating. Because of these negative consequences it is important that you service your cooling system with the same gusto as you would your oil system. Regular coolant flushes and replacements will contribute drastically to your engines longevity. Dealing with coolant is nasty and a lot of people will opt to let their local diesel shop handle the task. I just had mine done the other day to the tune of $145.00, not bad for not having to deal with disposal of the used antifreeze. Generally a cooling system flush will involve a series of drains and fills. The first fill might include a flushing agent or cleanser which will help to remove some of the debris and corrosion followed by a fill with just tap water and then two or even three more fills with strictly Distilled Water. With each fill, the cap is replaced and the system is allowed to reach normal operating temperature before it is once again drained, this aids in the removal of deposits and rids the system of any remaining old coolant. Some flush kits include a T-fitting which goes in-line with one of the heater hoses, this allows you to run the engine while you pump in fresh water with a garden hose. This is a fine strategy as long as you remember to do the last few fill and drains with distilled water. Tap water is high in minerals and is of varying Ph levels which will contribute to corrosion of the system. Once you’re done with your flush be sure to replace your coolant with a quality brand. Our 7.3’s came with both standard (Green) and ELC (Extended life coolant) which is orange. Whichever you choose to replace yours with is fine. Some people choose to stick with the style their engine came with but switching coolants should pose no risks. If you use green coolant, a flush and replace would be a good idea every 25,000 miles or so. Some ELC’s claim that 100,000 mile intervals are fine with their coolants but I feel that 50,000 miles is a much safer bet. Any of the heavy duty coolants from Prestone, Rotella, International, or Motorcraft will be fine. Some people say that the Motorcraft Gold coolants are no better than the rest and some will use nothing but Motorcraft Gold, it doesn’t matter, just change it. The total capacity of our systems is 8 Gallons so get 4 gallons of undiluted coolant and top the rest off with distilled water.
Modern day ULSD (Ultra-low-sulfur Diesel) is very hard on your diesel’s fuel system. ULSD is once again an attempt by our Federal Government at reducing exhaust emissions. The problem is that diesel engines get a large percentage of their lubrication directly from the fuel, this is one of the reasons why diesel engines generally last so much longer than their gasoline counterparts. Diesel-fuel is essentially an oil whereas gasoline is more like a solvent. Sulfur is one of the components of diesel that gives it is lubricating properties. The modern diesel just doesn’t protect the fuel system like the old stuff. It also doesn’t contain the same amount of energy per the same quantity as the old stuff. To combat the pitfalls of modern fuel, many people add fuel treatment products to every tank of diesel. Some people will add one-half to a quart of automatic transmission fluid to every tank. I cant vouch for this method but I’ve never heard of anything ill coming from it. I do however add a 1/3rd of a bottle of Stanadyne fuel treatment every time I fill up. Stanadyne makes a great product and are recommended by many. Cenex also offers a version of diesel that they call their “Roadmaster” blend. It is also known as premium diesel and aims to counteract come of the pitfalls of ULSD fuel. It generally costs about 10-15 cents more than regular diesel but I use it in conjunction with Stanadyne and my engine seems to run much smoother. As far as fuel filter change, I always change my fuel filter every two oil changes or 10,000 miles. This is another one of those situations where I will only use a Motorcraft filter. Some aftermarket filters come as the fuel filter and fuel bowl cap all in one. The Motorcraft filters use the original detachable fuel bowl cap. If someone swapped in an aftermarket filter like they did on mine, you will have to go pick up a fuel bowl cap along with the Motorcraft filter. I think mine was about 15 bucks at my local O’Reillys.
The factory air intake system is very adequate for a stock or nearly stock truck. The paper style filters are very good at filtering the incoming air to your engine. I am not a big fan of aftermarket oil-able filters such as the K&N style. These style of filters don’t filter the incoming air as well and have the potential for dusting your turbo blades. Your turbocharger spins at speeds greater than 120,000 RPM’s so even the smallest particles in the air have the potential to damage the fins on your turbo, leaving them looking like the leading edges were hit with a sandblaster. When replacing the air filter in my stock intake system, I always go with the Motorcraft paper filter. If you are looking for an air intake system that flows much better than stock and filters better as well, look into the Ford AIS intake system. It is Ford’s “Extreme Duty” intake system for the 7.3. The AIS uses a Donaldson filter which is very similar to the stock intake system on the 6.0 Powerstrokes. It is a quality setup that flows better, filters better, rarely needs servicing, and has a cost that is inline with or cheaper than most aftermarket intakes.
Common 7.3 Powerstroke problems:
Although the 7.3 Powerstroke is generally an extremely reliable engine with many people getting upwards of 400,000 miles without any major problems, it is not without it’s little quirks.
Camshaft Position Sensor (CPS)
Camshaft position sensors on 7.3’s tend to fail at random. This will show up as the engine randomly “Cutting out” while while driving or cruising at a steady speed. But sometimes the engine will die and wont restart until after a cool-down period. Replacement of the sensor is about the only fix. Luckily they aren’t very expensive and only require the use of a 10mm socket to replace. Many 7.3 owners keep both 10mm socket and an extra CPS sensor in their glove-boxes just in case. Make sure you get a sensor directly from Ford as some of the aftermarket ones have found to be defective right out of the box. There is also some debate as to which color of sensors seem to run the best. Some say black and some say dark blue. I’m not sure on color really but I’d definitely get the Ford or International part.
Leaky Exhaust up-pipes
Over time the stock exhaust up-pipes start to leak slightly. This usually isn’t a huge reliability issue but could result in slight loss of performance or the aroma of exhaust upon startup. The stock up-pipes use an exhaust doughnut which wears down over time causing the leak. You can replace the doughnuts for the fix but there are also companies who make aftermarket up-pipes with a crush gasket in place of the exhaust doughnut. This would make for a more permanent fix.
Under Valve-Cover Wiring Harness (UVCH)
The under valve-cover wiring harness is what delivers the electrical single to both the injectors as-well-as the glow plugs from the main wiring harness. The wires on the UVCH are prone to fraying and chaffing because of the vibrations associated with the diesel engine. This will show up as an intermittent miss and possibly a check engine light or you could even lose the whole bank and be left with a very rough running 4CYl engine. The UVCH can be check by removing the connector and measuring the resistance between the leads. The terminal positions are G G I I C I I G G. Measure between the center C terminal and each Glow-plug/ Injector to see if you are getting a consistent reading. If there is no connection or extremely high resistance, then the harness is most likely the culprit. UVCH’s are about 60 Bucks from online retailers and UVCH and valve-cover gasket are one piece so no need to order a separate gasket.
- G= Glow-Plug
- I- Injector
- C= Ground
Fuel Bowl Heater
When changing your fuel filter, if you look down into the bowl after draining the fuel, you will see a circular wire soldered to three pads. This is the fuel bowl heater wire. This wire isn’t generally soldered very well from the factory and can break off from the pads when changing fuel filters. If this occurs and it touches metal housing of the fuel bowl, it can blow fuse #40 which also controls the electric lift pump. If you just replaced your fuel filter and suddenly your engine wont start, this is where I’d look. The plate that the wire solders to can be removed and re-soldered and the fuse replaced if this occurs.
I hope this Article gives you a little insight if you are thinking about purchasing a 7.3 equipped vehicle or already own one and just wanted to know a bit more. The 7.3 was one of the last of the great simple diesel truck motors. It’s because of the combination of great technology and the simplicity of the day that the 7.3 Powerstroke has such a cult following. Many people and organizations have gotten many many miles of reliable service out of their engines. In addition, the 7.3 is fairly fuel efficient in the right situations. I routinely average 18-19MPG mixed highway and city and over 20MPG strictly highway driving with my personal truck. If you choose to own one of these engines, I know with the proper maintenance and care, your experience with your 7.3 will be very rewarding just like many others. Thanks for reading.