29th Jun 2008, 00:41

Just to let you know, I am a mechanic working for an International truck dealership. We service many Ford diesels ranging from the 6.9 & 7.3 IDIs, and the Powerstrokes.

Between my father and I, we have put nearly 400k on an '84 F250 with a 6.9L IDI. It has never had an internal engine failure, the only problems that we have ever had with the engine has been injection pump failures. We have replaced it 4 times so far. We have worked it hard since the day my dad bought it new. Bullet proof motor.

I also have a '90 F250 7.3L IDI that I bought used. It did not have the best of care before I acquired it. After replacing a couple of badly worn valve rockers, rebuilding the E4, and repairing the badly neglected brakes, it has been a rock solid vehicle for over a decade.

As for my experiences at work, they are generally positive.

Until very recently, there was a public school district in the area that still ran a fleet of International school buses with 7.3L IDI's. Very good track record for the engines, the rest of the buses were falling apart though.

The one major cause of engine failures of the 6.9/7.3 IDI's made before 1990 is engine oil contaminated with coolant. The usual cause is due to the intake manifold/valley pan gasket corroding from corrosive enzymes building up in the coolant. This also causes serious pitting in the block and heads and will cause major problems if left uncorrected.

Coolant enzyme/corrosion is a problem for pretty much any diesel engine and is easily and cheaply monitored and controlled.

The problem with the pre '90 models' intake manifold/valley pan gasket is that, even though coolant does not circulate through the intake manifold, as with gasoline V8's, there is still a water jacket port in the heads between each intake port. If the enzymes in the coolant are left unchecked, over time they will corrode the tin in the intake manifold/valley pan gasket and will seep water internally. In '90 thru early '94 7.3L IDIs, this port is sealed off with a small freeze plug and is not a problem.

Also, never get one hot. They do not take heat well!

As for the 7.3L PS engines, there are 2 variations. The early models have two injector harness "pass-thru" connectors in each valve cover. On these particular engines, they are notorious for the glow plug wires to come into contact with the valve push rods, which will then rub through the insulation. Then, when the glow plugs cycle, there will be a direct short to ground, which will almost always melt the pass-thru connector, shorting out the injector power circuits. When this happens, the injector driver detects the short and cuts power to that bank. Cylinders 1, 3, 5, and 7 (right bank), or 2, 4, 6, and 8 (left bank), will all be dead.

The second variation only has one injector pass through connector in each valve cover and the above mentioned problem was remedied.

Another common failure plaguing both variations of the 7.3 PS (and most other International diesels, for that matter) is the cam position sensors. While they don't fail at an alarming rate, they are most often the cause of a "no-start" or intermittent engine stumble/stall. It was so much of a problem, that International redesigned the sensor. The new one looks totally different than the factory original, the Ford replacement, and aftermarket sensors, and is considerably cheaper than any of the others.

Overall, these are very durable and dependable engines. The IDI models are far cheaper to maintain, however.

7th Apr 2009, 14:21

Greetings, nice site.

I've been troubleshooting my F250 brake system. The pedal is soft until it gets to the floor. then it stops the truck. I've centered my efforts on the Anti-lock brakes. I've seen that you were able to disassemble and clean the RABS. Could the RABS be my problem. I've already replaced my Master Cyl, and completely flushed the lines. Can you help me with the RABS?


30th May 2009, 12:25

I have an 89 f-250 7.3 IDI. I have a question for anyone who cares to comment on it. It actually involves the transmission. As of late, I am having trouble keeping the thing in gear, since it tends to want kick itself out of gear as it gets warmer. I have a lot of trouble even getting it into a gear. It started just with the reverse, but now has moved to all gears. Like I said, it's not so bad when it is cold, but changing gears is hard after she warms up. I have to hold the lever down in order to keep it from kicking out. Also, I have noticed my clutch does not engage until almost the floor. Is this just a time for a clutch job or do I have bigger issues in the tranny? Thanks anyone for any input.

6th Jan 2010, 22:53

My 92 F250 7.3L IDI has 256,389 miles and is running great. The body has had some abuse, but the motor is still running strong. I'm getting about 16 on the highway and 13 in town, and was wondering if that could be due to worn out injectors or possibly a worn fuel pump. If you anybody has any ideas on how to get better gas mileage, please let me know, brownie839@yahoo.com

27th Mar 2010, 23:24

Great, well written, detailed article!

I just completed installing a fuel pump in the forward tank on my 1993 F-250 5.8 L (351 c.i.) truck. I realize that the majority of you guys have the diesel version, but I will have to say that I have thoroughly enjoyed my F-250.

I have always pretty much been a GM man, but Ford builds a great truck! Especially when you opt for a 3/4ton or larger. I like the stiffer ride and the "bulldog" stout feel it has on the road. My truck has 167,500 miles and was purchased several years ago needing a E40D rebuild. I have since, pulled trailers and hauled some very heavy items. As for the E40D, my recommendation is to change the fluid & filter every 40K miles. Also, the most important thing to remember, is to disable the Overdrive while towing. This is very important, due to the fact that the OD is a weakness of the E40D Transmission.

I like the power and takeoff the 351 gas allows. If need be, this truck will really get up and go! I have a F-450 Rollback with the 7.3 Diesel. So, I'm able to get my 'Diesel fix' through the use of that truck.

Other than the Transmission, there have not been a very long list of items to repair on my F-250. I am very particular about having a solid dependable truck to tow and haul with, so it is imperative that I keep this truck in top notch condition. I can't afford to have a disabled truck several hours away from home.

I've yet to touch the engine other than routine maintenance i.e. oil changes, air filter, fuel filter, and coolant flush. I yet, have the need to perform service on the brakes, body bushings, or front-end ball-joints/bushings. The suspension appears to be in phenomenal condition for a truck of this age.

The work I have done is body related i.e. repaired the door striker/handle assembly (s), replaced tailgate handle, replaced wiper motor, repaired spare tire carrier, replaced front fuel pump and brass float attached to the sending unit, left and right tie-rod ends, alignment, changed the differential fluid, and of course, several tires.

So, for a 18 year old truck going on 200 thousand miles, I'd say she's been a great truck! I'll tell you this much for sure, I wouldn't hesitate to buy another one...

Chuck Rogers