nelstomlinson
Full Access Member
A friend is planning to travel to Arizona this summer and purchase his first IDI. He wants an older diesel with no computer, so that's a reasonable thing to do. He asked me to tell him what he should know, and this is what I came up with. Does anyone have additions or corrections?
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Engines:
The Ford mechanical, indirect injection (IDI) diesels (the engines were really made by International Harvester/Navistar for Ford) were made from 1983 to 1994. The engines were 6.9L from '83 through '87, and 7.3L from '87 through '94. There is nothing at all wrong with the older 6.9L engines, but the 7.3L engines have some incremental improvements, since they came later.
In '93 and '94 Ford made turbochargers an optional extra on the IDI. The turbo'ed 7.3L engines were built stronger and made a little more power. They are pretty unusual today, and usually go for a premium price.
There are quite a few trucks with aftermarket turbos. If that's done right, the builder will have beefed up the engine quite a bit to handle the extra power, and you can make more power without letting your exhaust gas temperatures get too high. If it wasn't done right, there is a danger of blown head gaskets and so on. Probably, if the conversion was done back when the truck was newish, the problems have already been corrected.
I believe that it was '92 when they went to serpentine belts on the engine. Serpentine belts are nicer, but v-belts are OK.
The earlier trucks use Ford second generation alternator (2G). I believe that they changed to the third generation alternator (3G) in '93, so the '93 and '94 IDIs have the better alternator. The 2G uses two connectors and several wires, and the connectors are weak points. It's worth looking at the connectors on the back of the alternator for signs of melting. That's not a show stopper, but it might be something to fix before you start to drive from Arizona to Alaska. The 3G alternator has a single wire, starts charging at a lower RPM, and is available in higher powered versions. It's a bit more robust and the single connection is much less likely to give trouble.
I plan to slowly upgrade my trucks to use the 3G alternator. I'll begin that with the plow truck, which needs a big alternator to run the electric plow motor.
Things to look for:
The IDI engines have some blow-by, and the oil will be dirty, even right after you change it. Take the dip stick out while the engine is running. If there isn't much air flowing out, that's a good sign. If it spits oil out the dipstick hole, that's a bad sign. My truck that does that will burn about one quart of lube oil in 50 miles.
Look for exhaust smoke. A little black smoke when you are accelerating hard is OK. Loads of black smoke when you aren't accelerating hard is likely to be bad injectors or the injector pump turned up way too high. The injectors and pump should be replaced together, and are likely to need replacement after 100,000 miles or so. Blue or gray smoke is not OK. They indicate dribbling injectors or burning lube oil, or both.
I've mentioned checking the alternator and headlight switch connections for signs of melting elsewhere.
Trucks:
The trucks from '80 through '86 had separate headlights. From '87 through '91, the front clip changed and the trucks had headlights with replaceable bulbs. From '92 through '94 the front clip changed again. The doors may not interchange between the three periods.
For '83 through '86, the manual transmission was a four speed with no overdrive. In '87 the five speed overdrive manual transmission became available. The four speed was eliminated in '89. The five speed manual requires ATF, NOT gear lube!
For '83 through '88, the default automatic transmission was the C6, which is all mechanical and has no overdrive. From '89 on, the default automatic was the E4OD, which is an electronic four speed overdrive. It's not a terrible transmission, and it gives decent mileage, unlike the C6, but I like the standard transmission much better than the automatics.
It's probably a good idea to put relays on the headlight circuit so you don't have the full headlight current passing through the headlight switch in the dash. That switch and its connector are another weak point on the Fords, and it's worth looking under the dash at that switch and connector for signs of melting. Again, not a show stopper. Bronco Graveyard and LMC both sell a plug and play kit to put relays in the circuit.
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===================
Engines:
The Ford mechanical, indirect injection (IDI) diesels (the engines were really made by International Harvester/Navistar for Ford) were made from 1983 to 1994. The engines were 6.9L from '83 through '87, and 7.3L from '87 through '94. There is nothing at all wrong with the older 6.9L engines, but the 7.3L engines have some incremental improvements, since they came later.
In '93 and '94 Ford made turbochargers an optional extra on the IDI. The turbo'ed 7.3L engines were built stronger and made a little more power. They are pretty unusual today, and usually go for a premium price.
There are quite a few trucks with aftermarket turbos. If that's done right, the builder will have beefed up the engine quite a bit to handle the extra power, and you can make more power without letting your exhaust gas temperatures get too high. If it wasn't done right, there is a danger of blown head gaskets and so on. Probably, if the conversion was done back when the truck was newish, the problems have already been corrected.
I believe that it was '92 when they went to serpentine belts on the engine. Serpentine belts are nicer, but v-belts are OK.
The earlier trucks use Ford second generation alternator (2G). I believe that they changed to the third generation alternator (3G) in '93, so the '93 and '94 IDIs have the better alternator. The 2G uses two connectors and several wires, and the connectors are weak points. It's worth looking at the connectors on the back of the alternator for signs of melting. That's not a show stopper, but it might be something to fix before you start to drive from Arizona to Alaska. The 3G alternator has a single wire, starts charging at a lower RPM, and is available in higher powered versions. It's a bit more robust and the single connection is much less likely to give trouble.
I plan to slowly upgrade my trucks to use the 3G alternator. I'll begin that with the plow truck, which needs a big alternator to run the electric plow motor.
Things to look for:
The IDI engines have some blow-by, and the oil will be dirty, even right after you change it. Take the dip stick out while the engine is running. If there isn't much air flowing out, that's a good sign. If it spits oil out the dipstick hole, that's a bad sign. My truck that does that will burn about one quart of lube oil in 50 miles.
Look for exhaust smoke. A little black smoke when you are accelerating hard is OK. Loads of black smoke when you aren't accelerating hard is likely to be bad injectors or the injector pump turned up way too high. The injectors and pump should be replaced together, and are likely to need replacement after 100,000 miles or so. Blue or gray smoke is not OK. They indicate dribbling injectors or burning lube oil, or both.
I've mentioned checking the alternator and headlight switch connections for signs of melting elsewhere.
Trucks:
The trucks from '80 through '86 had separate headlights. From '87 through '91, the front clip changed and the trucks had headlights with replaceable bulbs. From '92 through '94 the front clip changed again. The doors may not interchange between the three periods.
For '83 through '86, the manual transmission was a four speed with no overdrive. In '87 the five speed overdrive manual transmission became available. The four speed was eliminated in '89. The five speed manual requires ATF, NOT gear lube!
For '83 through '88, the default automatic transmission was the C6, which is all mechanical and has no overdrive. From '89 on, the default automatic was the E4OD, which is an electronic four speed overdrive. It's not a terrible transmission, and it gives decent mileage, unlike the C6, but I like the standard transmission much better than the automatics.
It's probably a good idea to put relays on the headlight circuit so you don't have the full headlight current passing through the headlight switch in the dash. That switch and its connector are another weak point on the Fords, and it's worth looking under the dash at that switch and connector for signs of melting. Again, not a show stopper. Bronco Graveyard and LMC both sell a plug and play kit to put relays in the circuit.
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