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Old 04-29-2014, 05:38 PM   #1
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reliability of old 7.3 engines pre Powerstroke. (1990-1993)

I have never viewed any topics regarding the older IDI 7.3 engines from pre 1993 SMB's.
Mine is a 1993 Quigley Extended SMB with the IDI 7.3

I would like to know if the older IDI 7.3 engines are worthwhile to have and keep going forward for years to come. I read that the HP and torque is low by comparison to the newer power stroke models but I can live with that. Seems they have less HP and torque than the newer 5.4 models.

For me I only have $18K into it and am the 2nd owner.
Mine now has 170K on the ODO in perfect mechanical shape and super clean under carriage. I only tow a light weight 18ft runabout.

Besides being loud and slightly smelly when compared to newer models, it works fine.

My mechanic tells me it is much easier to fix and less costly than power stroke models or 6.0
He thinks it will run forever…….

Downside is that it does look dated when compared to other fellow forum members newer rides.

Kindly advise….

Copes
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Old 04-29-2014, 05:49 PM   #2
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Re: reliability of old 7.3 engines pre Powerstroke. (1990-1

I think we need pictures to give accurate feed back.
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Old 04-29-2014, 05:58 PM   #3
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Re: reliability of old 7.3 engines pre Powerstroke. (1990-1

You can make a lot of upgrades for just one year's payments on a new one.

If it meets your needs, I say stick with it.


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Old 04-29-2014, 08:09 PM   #4
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Re: reliability of old 7.3 engines pre Powerstroke. (1990-1

I am an idiot savant regarding diesels. Meaning I know a little about my 7.3L Powerstroke and am a total idiot about any other diesel. But here's what I would do if I were in your circumstances. Read the 6.9L/7.3L IDI FAQ here:

http://www.ford-trucks.com/forums/10290 ... r-faq.html

And then post your specific questions here:

http://www.ford-trucks.com/forums/forum117/

But this is my favorite IDI thread so far - The IDI Myth Thread:

http://www.ford-trucks.com/forums/12654 ... hread.html

It includes such gems as:

"Myth: the 7.3L IDI is so legendary that God used it to start the rotation of the earth.

This ones likely true. Scientists just haven't proven it yet..."


and:

"Myth: "IDI fuel injectors are expensive to replace."

Fact: You can replace an entire set of IDI injectors for the cost of one PowerStroke injector. Live it up!"


As a Powerstroke owner I can personally testify to the sad fact of this statement.

Dang that was a good read! PM speedwrench72 over at ford-trucks.com. He posted in the myth thread and his signature shows an IDI van. And he and his son (a Marine) appear to have multiple IDI's. Probably they like them for a reason...

My guess is that they will say that the 7.3L IDI started it all. That it was the simplest and most reliable of the diesel engines in the Ford lineup. And that all the add-ons to the later Powerstroke versions were really attempts to make a more civilized, more powerful, consumer acceptable diesel. All of which have attendant weaknesses.

I know one poster who sold his late model 7.3L Powerstroke and went back to the earlier Powerstroke (not IDI) because it is not regulated by CARB and he can modify it anyway he wants.

Perspective from the Myth thread:

"I see the IDI in particular this IDI as a the perfect combination of attributes between a big block gasser and a tough diesel.

For starters fuel is fuel, heat is heat, and pressure is pressure. That said it's not fair to compare an electronically fuel injected diesel to a mechanically injected diesel in comparing DI to IDI. In comparing mechanically injected diesels between DI and IDI the only shortcoming in the IDI design is a slightly larger surface area in the head that sucks the heat out of the cylinder into the coolant instead of doing work.

However there are many other advantageous attributes created by the IDI design. Chief among them is that because the initial BANG is contained largely in the pre-cup the rest of the structure of the engine can be built much lighter for the same amount of displacement and power. This allows for an overall much lighter engine that can rev faster making it much more practical for pickup applications. Secondly because the fuel impacts and is contained in the pre-cup on injection they aren't sensitive to injector issues like even fine atomization of the fuel making them much more durable and tolerant. This combined with the quinch mentioned above and the swirl it creates in the pre-cup makes for a very complete burn without the added and tempermental complications of other engines.

This brings up why it's unfair to compare the IDI to modern electronically injected engines(even though they are better) In these later engines the stress of the BANG is minimized by limiting the initial injection.

So to me it's all about an engine that gets close to the size, weight, and revving/rpm ability of a 460 with the torque, toughness, reliability, and fuel tolerance of an old school mechanical diesel all in a very efficient package."


The fact that your mechanic says it will probably go forever, would probably make me want to keep it forever.

As far as aesthetics go, I agree with TexGX. Post pictures and these SMB gurus will have great recommendations for you to spruce it up.

If you do post in the IDI subforum on ford-trucks.com, let us know what the consensus is.
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Old 04-29-2014, 11:55 PM   #5
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Re: reliability of old 7.3 engines pre Powerstroke. (1990-1

The IDI motors really don't have that much that can fail. Common problems include glow plugs and glow plug relay (both are pretty easy, but at this point the glow plug wire harnesses are all brittle and can need some TLC too) and the rubber fuel lines on top of the motor need to be upgraded to nitrile to handle the biofuels being used now. The big item though is cavitation if supplemental coolant additive has not been used. Not a common failure, but if it gets bad it is non-repairable. Really they are easy motors to work on, and there's a whole lot more space around them than the newer powertrains.

The auto transmissions did not last forever, but probably better than other autos from that time. If it were ever rebuilt, it probably received some of the newer updates to help it last longer.
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Old 04-30-2014, 08:48 AM   #6
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Re: reliability of old 7.3 engines pre Powerstroke. (1990-1

You should put in a special coolant.

This is the way I understand it. Diesel engines are subjected to more heat and stress in the cylinders than gasoline engines. The cylinders are sleeved. On the other side of the steel cylinder sleeves are water jackets which bring water to the sleeve to cool it. Air coming out of the coolant called "cavitation" can, over time, eat away at the other side of the metal cylinder sleeve ruining the cylinder sleeve, and, thus the engine.

So diesels require a coolant with an anti-cavitation additive. So, you can use green coolant and use an additive ("SCA") and then periodically test for adequate presence of the additive.

There are some that suggest that you can use ELC (Extended Life Coolant) which doesn't cavitate. From the above IDI FAQ:

"Coolant capacity is 8 gallons. It's HIGHLY suggested you use a ELC (extended life coolant) since it has the proper SCA additives already added. For the other 4 gallons, distilled water is recommended. If the thermostat needs to be replaced, DO NOT use a run-of-the-mill part's store one. It will make the engine run colder, these diesel's like to run on the hotter side (helps completely burn the fuel also). The correct motorcraft part number is E5TZ-8575-C. The only other place to buy a replacement thermostat would be directly from a International dealer."


And there are some that say NO don't use ELC in an IDI:

"There is a little debate over what ELCs can do to an engine. If you run a newer engine such as a Powerstroke, ELCs that have chemicals in them to protect against cavitation are perfectly fine. However, if you run an older engine such as an IDI there may be problems. The older rubbers and materials in the cooling system of the IDI may be susceptible to failure when in the presence of ELCs. It is a take at your own risk kind of thing. From what is gathered though, they do protect against cavitation, as long as it says on the labeling, but just because you don't get any damage from cavitation doesn't mean you won't have problems in other areas of your cooling system. There are many that run ELCs in IDIs and claim to have no problems. The advantage is you need to change your coolant far less often. But for me, why risk it? I'll just change my coolant every 30,000 miles or so and be happy with my engine."

Regardless, EVERYONE SAYS YOU CAN'T MIX ELC WITH STANDARD COOLANT (EVEN WITH SCAs) SO A FULL FLUSH IS REQ'D!

Check the IDI FAQ above for additional recommendations. Or check with your mechanic. Or hopefully carringb will be by here again. He can probably tell you what coolant to use from memory.

FYI:

https://en.wikipedia.org/wiki/Cavitation

"Cavitation is the formation of vapour cavities in a liquid – i.e. small liquid-free zones ("bubbles" or "voids") – that are the consequence of forces acting upon the liquid. It usually occurs when a liquid is subjected to rapid changes of pressure that cause the formation of cavities where the pressure is relatively low. When subjected to higher pressure, the voids implode and can generate an intense shockwave.

Cavitation is a significant cause of wear in some engineering contexts. Collapsing voids that implode near to a metal surface cause cyclic stress through repeated implosion. This results in surface fatigue of the metal causing a type of wear also called "cavitation". The most common examples of this kind of wear are to pump impellers, and bends where a sudden change in the direction of liquid occurs. Cavitation is usually divided into two classes of behavior: inertial (or transient) cavitation and non-inertial cavitation.
...
Since the shock waves formed by collapse of the voids are strong enough to cause significant damage to moving parts, cavitation is usually an undesirable phenomenon. It is very often specifically avoided in the design of machines such as turbines or propellers, and eliminating cavitation is a major field in the study of fluid dynamics."
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Old 04-30-2014, 10:25 AM   #7
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Re: reliability of old 7.3 engines pre Powerstroke. (1990-1

The current 5.4L has more HP, but less torque. For the last year of IDI production in the van (1994), it was rated 185HP and 385lb-ft of torque. If you can find a used turbo kit for these vans, it really wakes them up. Banks and Hypermax both made kits.

I had one that had no issues whatsoever, aside from killing the E4OD transmission every 100,000 miles like clockwork.
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Old 04-30-2014, 11:10 AM   #8
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Re: reliability of old 7.3 engines pre Powerstroke. (1990-1


Quote:
Originally Posted by copescobra

Downside is that it does look dated when compared to other fellow forum members newer rides.
It's the newer body style - You'd be surprised at what a difference in looks it would make to swap wheels and tires, remove the running boards and add fender flares. If you're in to that sort of thing. If you've got some cash burning a hole in your pocket, add some bumpers too!

I've got a loud smelly 6.9L, which is essentially the same engine. As mentioned above, checking the coolant for SCA's will be your primary task in keeping this engine going for a long time - other than that they are pretty dang sturdy. Expect to replace the injectors and injection pump every 100k-125k if they are showing signs of wear.

These engines are super sensitive to injection pump timing. Having the pump timing off by a little bit can make a big difference in mileage, excessive smoke, starting, and driveability / power.

How does it run now? Start pretty easy? How is your fuel economy?

It sounds like you've got a great rig.

For more info on the IDI engines, check out oilburners.net too.
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Old 04-30-2014, 11:24 AM   #9
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Re: reliability of old 7.3 engines pre Powerstroke. (1990-1

Rockbender: I get it, you grabbed that image from Copes' gallery? GoodOnYa!

Copes: That is a sweet looking rig. With a great engine. IMO it doesn't look dated, at least it doesn't look any more dated than my 7.3LPSD. We have the same body style. I would like to eventually replace the front fenders, hood, grill, etc. on mine with the new body style but not because of looks, but because it is 6 inches longer which will provide more engine bay access (for installation of different intake filter, etc.) which you shouldn't need. You've got a great looking rig there in my opinion.
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Old 04-30-2014, 11:27 AM   #10
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Re: reliability of old 7.3 engines pre Powerstroke. (1990-1

Quote:
Originally Posted by E350
Regardless, EVERYONE SAYS YOU CAN'T MIX ELC WITH STANDARD COOLANT (EVEN WITH SCAs) SO A FULL FLUSH IS REQ'D!
[/i]
I called Zerex directly about this issue. Radiator shop added a few gallons of green to the Zerex ED/ELC red that was already in there (this was in a Peterbilt). Zerex said it would not cause any problems or react, it just loses its long life properties and should be changed on the standard service schedule instead of the extended life coolant schedule.
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