Common issues with 7.3 liter IDI Diesel engines - Ford and International Harvester

Overview of issues common to 7.3 IDI Diesels.
- Cracked heads causing loss of compression and white smoke
- Injection Nozzle wear, leakage and uneven spray pattern
- return line issues - worn out o rings and broken return caps
- Fuel filter housing sealing issues
- Coolant service intervals & cavitation against cylinder walls
- Oil leaks - oil pan, timing cover, crank seals, valve cover gaskets
- Glow plug burn out
- Glow plug wiring issues - connector ends become whored out
- Turbochargers causing bottom end damage
- Ether damaging prechambers and burning out glow plugs
- Piston ring wear and piston skirt scoring
- Main bearing wear uneven due to running engine too hard (too much power, boost etc)
- Weak injection pump causing hard starting and lack of power
- Dual Mass flywheel can wear out

[@ramblerclassicman221]

Real.

[@anthonymazzone6463]

Thanks so much. This is absolutely the best explanation I've seen on KZbin.

[@ramblerclassicman221]

My condolences!!

[@sabbath7081]

Everything is true what you say about these blocks the 6.9 and the 7.3. I grew up with these engines around in my teenage years and they got a bad reputation but they were actually a great engine I had a 91 with a 7.3 and a 5-speed now I have an 86 with a 3-speed C6 4:10 gears and a Ford installed Banks gentle boost kit. The previous owner hauled a huge fifth wheel with draft horses in it.

[@ramblerclassicman221]

Forgot to mention - early 6.9 idis have weak castings near the block heater on the right hand rear of the engine. I don’t remember what casting numbers you’re supposed to avoid though.

[@mikematthews916]

Very Very Thorough & Informative! Thanks So Much For Taking the Time To Share Your Knowledge! I bought an !D! 7.3 1994, been a learning curve from working on Mopar Gassers!

[@ramblerclassicman221]

Injection pump was weak in this truck thus the hard start.

[@brendonmasters]

Thanks for all this free education.

[@ramblerclassicman221]

✝️

[@Mikael5732]

Excellent video.

[@soldaten2474]

Excellent video

[@redneckarmitage770]

Very helpful video thank you

[@andrewmunchkin7212]

Very good video presentation. 🏆🤓👍 thank you!

[@anthonywychock3449]

Great video

[@Mikael5732]

When my glow pug relay clicked on and off I just replaced my glow plugs as they were very old. Clicking went away. That was 6 years ago.

[@bobhanke6401]

I'm looking for an IDI truck now and i really appreciate the tech tips. Power and speed of are less concern for me than computer and sensor issues of the later trucks.The mechanically driven fuel pump is a better option for me than the HPOP driven pumps on the Power Stroke engines that replaced them. Thank you for giving us the benefit of your experience.

[@ramblerclassicman221]

Ultimately a p pump intercooled 12 valve swapped in an obs aeronose extracab or crew cab ford backed up by an nv5600 with a gear drive dana or new process t case and a 4.10 ratio dana 60 front axle plus gen 2 sterling 10.25 will be the best setup. Longer stroke mills, more torque and waaaaay more aftermarket support. Itll cost between 10,000 and 15,000 for a decent body cummins+tranny swap if you put in the work but brining an old idi truly up to speed generally takes a few thousand anyhow, for a non turbo mill. But IdIs are good for screwing around and having fun! Theyre pretty unkillable, tho ive had em throw a rod through the side of the block if theyre run with turbos. The 7.3 idi turbo is specifically designed with different block, rings etc to handle the boost. They pit out about the same hp and torque numbers as a p pump 12 v cummins though.

[@DB-jo4se]

Usefull thanks... Putting a 7'3 navistar..in a ex petrol econoline E150 in Netherlands.. having some "glowplug" and "fuel cut" problems...😌.. so change glowplugs to "beru" hope its the good one..

[@ramblerclassicman221]

Beru is absolutely the only glow plug manufacturer I use for these engines, the tips swell and burst off autolites or densos. I’d also recommend looking at your lift pump, take it out and make sure the armature is secure in the lift pump body. Make sure it pulls a good suction. I’ve had multiple lift pumps fail, the armature can fall into the oil pan (what a nightmare to get out!). Hopefully the 150 frame and driveline are stout enough to take the massive power of stock Navistar IDIs ;)

[@Mikael5732]

That is the only glow plug to use. I replaced my old ones 6 years ago with Beru and still cranks up immediately. German glow plugs are the best.

[@foothillsreadiness]

I saved this video to my 7.3 IDI vids. A lot of very useful information. My 7.3 IDI Is in my 1989 F-250 4wd XLT Lariat Regular Cab. It has the factory automatic. It was a very unexpected gift from my dad. I want to resurrect it and put a slide in camper in it for coastal fishing here in nc. Any tips for an initial start after the truck has been sitting for about 3 years? Also, who to get an injection pump/injectors, larger fuel tanks from or upgrade from another series of vehicle? I don’t particularly care for rolling coal, I want reliability and more power if I can swap parts or bolt it on. I would like to figure out worth of switching to a manual transmission over the factory one and which manual to look for. Any help is greatly appreciated. Have a good’un! Semper Fi!

[@sabbath7081]

Personally I like to start mine gently, when it does fire to hold it around 1,100 to 1,000 RPMs until the rat tat tat bang bang rattle rattle calms down, the timing cam on the fuel control makes the noise less with the pedal down a tiny bit, and then let it idle down rather than jabbing the pedal assuming the oil pressure is still rising and filling the gallies.

[@user-xs5od7wo2d]

I own a 7.3idi 89 350 4x4 dually diesel. Useful video. Just after I fix something seems like something else goes wrong lol. I got it back from the shop and it eventually started having very rough starts. Long cranks, but would eventually start but rattled the engine a bit. I noticed the water and fuel light come on which makes sense because of the diesel additive, I drained about 3 water bottles worth of it the orange liquid. Came back maybe a few days later and it was the same old hard start, but the light was gone. I’m thinking maybe I need to drain it until the green diesel comes out? Maybe it’s still a hard start cause there’s some left. Shop also said no issue with starter or alternator, and I repeatedly asked. However from this video I noticed that my glow plugs click like someone mentioned in the comments which makes me want to get better ones. I’m hoping maybe just continuing to drain the fuel filter separation will help the starting. Maybe someone else reading this is experiencing the same thing as me.

[@jameslafountain]

Did you ever figure it out?

[@user-xs5od7wo2d]

@@jameslafountain yeah, I just went ahead and kept draining it even more this time with a proper setup for draining and a tank for collection etc. Idk how much additive they put in but it’s usually the entire bottle which is a lot, so it makes sense it would just take awhile to drain. I drained a whole bunch of it and it was all good starting up just fine like normal again.

[@johnnyohness]

Great video. I have a 94 F250 with a 7.3 IDI turbo diesel. This is the first diesel I have ever owned so I am still learning. You pointed out the vacuum pump, and I wonder what exactly this pump does. At this point, the truck runs great, but I am wondering what the function of that silver pump is and how I will know if it dysfunctions? I know that is a mouth full but would appreciate some knowledge of its basic function if possible Thanks.

[@ramblerclassicman221]

This is how i think of it, could be wrong: The vacuum pump performs a few functions - primarily it provides supplemental vacuum to the braking system and secondarily to the hvac system and cruise control. These trucks (IDI and T444 diesel f250 and f350) have vacuum assisted juice brakes - combination drum and disk brake vehicles which require both proportioning valves and power assist. The proportioning valve acts to siphon most of the braking power of the hydraulic system to the front brakes under normal load conditions, preventing rear wheel lockup as weight shifts forward during braking due to inertia. The large pistons of the front disk brakes require more fluid and subsequently braking pressure than do the wheel cylinders in the rear. The area encircled by the front disk brake pistons is probably 6 to 9 times that of the rear wheel cylinders (which are 1:1 roughly with the bore diameter of the master cylinder), diameter is 2 to 3 times greater for each of the two pistons in each caliper pi*(radius)^2 = area. This means the force required to actuate the brakes is, per example 1:1 for the rear wheel cylinders but 1:9 for the front cylinders (9 times the force required to push the large piston using the small piston in the master cylinder and 1/9 the distance travelled by the large piston compared to the small piston). Thus the force applied by the drivers foot is divided by 9 for each piston in this example on both front wheels. 1/36 the total force is delivered to each caliper piston in this example. This is why the brake pedal is rock hard when the engine is off. The average person simply cannot supply enough force to the relatively small bore master cylinder to force the pistons in the front caliper out and agains the brake pads. Cars built prior to 1967 in the U.S. had single pot master cylinders feeding 4 wheel drums. This meant that with properly adjusted and bled brakes, drivers did not require any form of assistance to effectively stop their cars, as the wheel cylinders each took 1/4 of the volume of fluid displaced by the pedal. Thus there was no difference in the pressure required to actuate drums front and rear. This came with drawbacks suck as rear wheel lockup which some manufacturers modulated with early load proportioning valves. With the introduction of front disk brakes and dual pot master cylinders, cars needed a way to assist braking effort. Traditionally this was done using engine manifold vacuum (generated beneath the throttle plates by the pressure differential between atmosphere and intake.) Diesels (of older vintage, modern diesels may differ for emissions reasons) lack throttle plates meaning they have no way to generate the pressure differential required to operate a diaphragm style vacuum brake booster. Ford solved this problem in two ways: 1) an externally mounted belt driven diaphragm style pump which generates ‘vacuum’ (negative pressure). 2) using a ‘hydroboost’ piston style assist pump run off the positive hydraulic pressure generated by the power steering pump (used primarily on super duty models and heavier 11,000 gvwr and up). Our trucks use vacuum generated by the sucking action of the vacuum pump to pull a diaphragm in the booster toward the master cylinder. This lends a lot of force to the braking action and greatly reduces braking effort.

[@idahopotato5837]

My 89 had a vacuum pump that would constantly loosen up and then there was no power assist on the brakes. Happened when towing once. These motors love to vibrate. i finally removed the standard bolts that tightened into the block with bolts and nuts on the through side of the block. Never loosened again.

[@sabbath7081]

Wish there was a way to install the rest of the road ranger that goes with that hockey puck shifter knob.

[@ramblerclassicman221]

Absolutely! I think the thirteen speeds are a bit wide but 8, 8ll and 10 speeds have been down even on 4wd trucks.

[@flatbroke68]

I have the 7.3 idi and it dumps a ton of black smoke when I’m on the pedal hard. Possible problem??

[@ramblerclassicman221]

Turbo or non-turbo? What altitude you run at? Hows the injection pump doing? Hard starts when hot? Tested the injection nozzles lately? IDIs smoke black when at full fuel. Turbo and non-turbo trucks smoke about the same amount. Excessive smoke usually indicates a faulty injector overfueling a cylinder. High altitude means the trucks run comparatively richer for the same fuel volume.

[@flatbroke68]

It’s non turbo. I believe it’s probably over fueling. Thank you for your time

[@shespractical7272]

Hence, the saying "Rollin' Coal".

[@mikeingalsbee2959]

What glow plugs do you recommend?

[@ramblerclassicman221]

Motorcraft zd9 or (updated) zd29 bullet style plugs. Beru is the german plug manufacturer, you can get em directly from them. Update the connectors on the harness to bullet style if urs are the older spade type.

[@travistillman611]

What state are you from?

[@ramblerclassicman221]

The best one

[@ramblerclassicman221]

Lol im from montana. Its nice up here but folks keep flocking here from the coasts and its sure fucked my local community lol

[@chrisduhaime5689]

If one glow plug goes open the relay won't stay on as long 2 go open it will drop out before the warm up and will burn the starter and battery down before it will start. The reality is they don't last long . It's a chronic problem running this engine. Fond generally when you lose one pull them all the ones that do show .5 ohms are still good put them on a drill and sand of the carbon! one's that show .7 ohms or more about go open and are not getting as hot plus contribute to the relay short cycling . Inaddion that carbon on the good ones acts like a insulation / this system is a high mantaince pain.

[@okiedoke6373]

Glow plugs aren't supposed to cycle if glow plugs are cycling it's either cheap glow plugs you have a bad glow plug Warrior wiring is faulty 1 cycle on and then it'll cycle off at the end of duration a lot of the times two little clips that are installed at the Factory are lost or whatever and not on the glow plug that will make things glow plug relay cycle can you turn the key it will click on at the end of the cycle it will click off not click click click if it does that you have an issue

[@Mikael5732]

Exactly. My relay used to cycle and replaced my glow plugs with new Beru and the cycling stopped immediately. That was 6 years ago. Still starts up immediately now and no cycling.

[@Barrymckociner074]

But idi means indirect injection