o/t older ford diesels

i am currently looking at a 1989 ford f250 diesel 4x4 truck with a 7.3 diesel engine are these good reliable diesels, whats the average mpg, and can you do extra performance stuff like chip them?
thanks, chris

The 7.3 non turbo was a good reliable engine, they were a little under-powered but still got the job done, and were much better on fuel than a 460 gas. I would say with the 4x4 around 15-16 mpg empty and less of course depending on the load. No you cannot chip these trucks there are no electronics ie. computer etc. to make it run. its more less like a tractor engine it has a manual injection pump. There are probably ways to make the pump a little "hotter" to help performance but w/o a turbo its going to smoke alot more and there goes all you fuel mileage.

Made by International Harvester. That makes it good to me.

They had a cavitation problem, water leaking into the cylinders through pinholes. I think it was pretty much just a bored out 6.9 so the cylinder walls were quite a bit thinner. Not a problem if they were properly maintained and they could have a sleeve put in during a rebuild if needed. Other than that they were a decent engine just not a real powerhouse unless they have a turbo.

All you need is a good charger and 15 minutes to tweak fuel pump.I used to think they were junk but I got 3 or 4 of em runnin round the farm.Beat the heck out of em and they take it.Alot better then the powerjoke i mean powerstoke that replaced them.Only problem is if glow plugs dont work they will not start.My one truck the glow plugs have not worked for 4 years. I give it some ether and it pops right off.I use it everyday and thought for sure the ether would have killed it by now but its still running strong.

A CHIP??? LOL!

Have FUN with THAT on the Stanadyne mech injection pump!

The 6.9s and IDI 7.3s are very rugged engines. Not very powerful without a turbo though, and not very fuel efficient. Internation Harvester developed them from existing truck gas engines. I still have two. With the IDI engines sold up to mid-1994, the 6.9s and 7.3s are the same engines, but the 7.3 has a slightly larger bore and therefore, thinner cylinder walls. That creates the need to use coolant conditioner to prevent pinholes from cavitation.

One of my trucks is an 85 F250 4WD with extended cab. C6 trans (no overdrive) and 4.10 axles. 260,000 miles and runs perfect, but only gets around 13 MPG on the highway when empty. When loaded, it's not much different. Engine has never been apart.

My other is a 1994 F250 4WD with extended cab. Engine is the 7.3 turbo IDI (last version before the DI Powerstroke came out). It has 330,000 miles and also runs perfect with no engine repairs ever except for routine water pump and injector nozzle changes and injection pump reseals. This truck has the E40D trans with overdrive and 4.10 axles. I drove it around the mountains of New York for years and it never got better than 15 MPG on an empty highway trip. Now I've got it up in northern Michigan with NO mountains to climb, and I've gotten 17 MPG with it. The OEM ATS turbo setup runs around 7 PSI at max boost since the indirect injection limits it.

I'll add that I had many friends that bought Ford diesel trucks over the years since they first came out. I heard a lot of bragging about good fuel mileage - but every one I actually checked myself rarely did better then 16 MPG, and 14 MPG was more the average for highway mileage in a 4WD truck.

Those oem ats turbos were kind of a joke.I have a truck that used to have one. I ran if for a week and pulled it off and put a better charger on it .I can get up to 25 lbs boost now and it makes it run alot better.I did have problems with the seal leaking on the intake untill i figured that problem out.Most diesel shops said that motor would probably not take that much boost without problems but it has 270000 thousand on it now.I did rebuild pump and injectors and new waterpump but other then that no problems.It will out pull any powerstroke around here thats for sure.

Joke or not, that 7-8 PSI boost makes a nice difference. Just about anybody with a background in auto-engineering will tell you that 10 PSI is the max-safe level for an indirect injected diesel with a mechanical compression ratio of over 20-1. That is, if you want it to last a long time. Engines running high boost usually get lower compression pistons.

I've got no doubt that raising boost to 25 PSI on an IDI engine will make it scream. It can also make a time-bomb out of it. If your's has done well for you, it's an anomalie and not the rule. Modern high-boost direct injected diesels usually run mechanical compression ratios of 17 or 18 to 1, to handle that boost (that raises the effective compression ratio).

My Ford ATS factory setup has a wastegate, and I can easily raise boost with a simple adjustment (but I don't want to). If I want to drive a diesel with more boost, I drive my 92 Dodge with the 5.9 Cummins. It's built to handle it.

1993 F-350 4x4 5 speed with 240,000 runs great and much better milage than the 85 F-250 4x4 auto 351w.
You will want to replace the glow plugs, return lines and filters asap doing the injectors would be a good idea and inexpensive $150 for a set of 8 on Ebay.
Great work truck but if you want power and upgrades a 12v cummins is the ticket.I am saving parts now to power a 50s truck with a Cummins and D60 axles.

We have a Ford cutaway with a 7.3 that has well over 300,000 mi and no engine trouble. My brother has an 89 F-250 4x4 diesel with about 285,000 on it and it still gets 17-18 mpg empty. they are very tough engines. aside from Ford trucks, they were used in a lot of International trucks and school buses.