I just purchased a 1985 F250 6.9idi 4 speed 4x4, it's got 55000 miles. I was wondering what all I should watch out for since this is my first idi. Any wise words would be greatly appreciated

 

Welcome to FTE
Is that 155K and not 55K? Not that 155 is a bad think on a diesel.
I had 230K on a GM 6.2 and at 100K I added a Gail Banks turbo kit.
I will let the diesel guys answer but I dont see anything you really need to look out for other than do service when it is due.
Dave -----

 

The early diesels like yours had a fuel/water separator on the firewall that always gave problems, letting air into the fuel. Even with only 55,000 miles, yours has probably already been deleted but if it hasn't, bypass it.

You most likely have the early glow plug controller. But maybe they also upgraded it. If you have the old controller system, it will be screwed into the back of the engine. The newer version mounts on the top rear of the engine. The original units are prone to sticking on and burning out the glowplugs. Do some research, maybe the replacement screw controllers are ok, I do not know. Or you could convert to a manual pushbutton switch for the glowplugs, making it pretty much bullet proof as far as failures.

 

An 85 should have the older style glow plugs. The controller is in the back of the driver's side head. If you turn the key to RUN the Wait to Start light on the dash will cycle and you'll hear the glow plugs click ON/OFF a few times (about 12-20 seconds). Then it should start.

If your glow plugs don't work properly don't bother replacing the controller. I tried that and the new controller only lasted a few months. You'd want to follow one of our threads to install a pushbutton for the glow plugs. Also, make sure you only use Motorcraft glow plugs if they need replaced. Others are known to swell and the tips break off in the head.

x2 on bypassing the OE water separator on the firewall. I made the mistake of pulling the ring to drain the water and caused killer air intrusion when I first bought the truck.

 

I haven't encountered a swollen glow plug yet, but as mentioned some cheap glow plugs are known to have that issue. I was thinking of starting a thread over on the IDI forum about this issue. It seems the tips swell and break off when trying to remove the glow plug. I think if you encounter a swollen glow plug rather than trying to remove it, reinstall it and leave it wear out some more. When a tip breaks off it should be removed and that process is tedious involving removing an injector and using every trick in the book to get the tip out. Shop vacs, shop air and other tricks. Hopefully you will only encounter one or maybe two of these troublesome glow plugs. They may not energize fully but if you have 6 or 7 good ones energizing that should be enough to get the engine started. I feel that the swollen ones will continue to deteriorate and eventually you can get it out without losing a tip. I wouldn't try to force one out if you can help it. That's how tips break off. This is my opinion on a stuck glow plug. Others may have a different view.

I also use a manual momentary button to operate the glow plug relay. And the water separator has been bypassed as well.

 

I've heard the same thing about the glow plug tips and just leaving them alone once they start swelling definitely sounds like the safer move compared to forcing them out. The manual glow plug button setup seems to be pretty popular on these older IDIs too.

Have you been running that setup long term without any issues?

 

I've been running the manual pushbutton for years with hardly a hiccup. I recently had to replace my glow plugs. 15 out of 16 Motorcrafts that I had tested bad.

Here's a hi speed glow plug push button kit. Of course, you can do it cheaper yourself (just run switched 12V to your glow plug relay). I actually have to think about getting this kit. I like the heavy duty harness. 🤔 I've ordered from CDD before. A+ on customer service and parts.

https://classicdieseldesigns.com/pro...conversion-kit

I suggest reading this thread on counterfeit glow plugs. It has some good videos too.

https://www.ford-trucks.com/forums/1...zd-28-a-3.html

 

I've been on the manual button for decades. In fact I wore out my first momentary button. It was cheap junk. I replaced it with a better one that looks more robust. Been installed for 4 or 5 years now. The first one came apart and wouldn't make contact. Not like the contacts wore out. It was the mechanism that failed. Look for a well made momentary button and you are good. I also have a splice in the wire that I can undo a wire nut and touch the positive battery terminal with it. That came in handy the day that the momentary button failed.

 

One way to get a swollen glowplug out is to loosen it all the way, of course it won't come out but just leave it. Then crank the engine. I have never tried it, I have all good ones in it now, but I have heard it works, just a little hard on the hood insulation.

One thing I never liked about the controller, 1 bad plug or a couple corroded connections on a few glowplugs, it will not glow enough to start the engine. You are dead in the water. I have run the manual button for years, had 3 glowplugs bad during one winter, and I was still able to start the engine with the manual button. It wasn't too happy about it, but it did start. I did not have time to fix it right away, we had a big snow storm that year.

 

Every IDI 6.9 or 7.3 we ever had poured a leak from the right side head-gasket back near the firewall.

Of course, we worked the devil out of them pulling loads of cattle in big gooseneck trailers for thousand-mile-plus trips load after load after load.

We used those big jumbo bottles of Bars Leaks by the case.

Replacing the affected head-gasket was a waste of time and effort as the new one would be leaking within a week in exactly the same place as always.

The 6.9 is the superior engine to anything Ford used later so far as being bullet-proof and lasting and bringing you home - so long as you keep the coolant topped off.

Keep a couple cans of Ether in the tool-box - not in the cab with you.

The best thing I did to the 6.9 with Hypermax Turbo System in my 1985 F-350 was to replace it with a 6BT Cummins; I did that in 2006 and now the Cummins has more hard miles on it than the 6.9 did and I easily expect it to double or triple that; the Cummins has none of the short-comings of the IDI engines or any of the V-block engines for that matter --- over twice the fuel mileage and easily ten times the power.

Why on earth Ford ever thought it was a good idea is beyond me; but, they put a T-19 4-speed behind the diesels instead of a "Bulldog Gear" T-18; the T-19 1st gear is way to high for launching big loads and very hard on clutches; however, the T-19 4-speed will last forever and has none of the failures of the Z-5 and Z-6 of the later Ford diesels.

All that being said, anything diesel is better than anything gasoline and you should enjoy your truck and come to appreciate the reasons why a diesel engine is superior to anything gasoline.

 

Interesting, I never read that the T19 first gear was too high. If anything, I've read that the T19 granny 1st would pull a stump out, or house down at idle.

Mel Gibson should have used a Ford IDI in the Lethal Weapon 2 scene in which he pulls down a mountain house with his truck, but they didn't want him to get hurt.



A 6BT Cummins! Have you found your other 2 cylinders yet!?

Actually, I read that there was a TSB or documentation back in the day to retorque head gaskets on the 6.9l when it came to the dealer. The back of the head gaskets are known to weep, but as long as you have good compression. You can put head studs on a 6.9l but there are folks on our forum with hundreds of thousands of miles on a turbo 6.9l with OE head bolts.

 

The T19 has two or three different gear choices. Some have a deep granny.

 

I do know for fact that the T-19 that came behind all the 6.9s is the one with the high 1st gear and make for a lot of riding the clutch to get launched when actually loaded and not just with a few sticks of firewood and some tools in the bed.

As per HERE = "The T-19 was offered with a granny low 1st gear, but this version was not used behind the 6.9L IDI diesel."

1st gear in a T-19 behind the 6.9 is 4.02:1

 

I'm pretty sure if you ordered the truck build you could get one of the lower range T19. But yeah the normal one for the T19 was not a deep granny. You probably had the 4.10 rear but hauling full cattle trailers is a special loading. I have the 3.55 rear and it's given me all the pull I've needed. And I also have 4WD and the low range 1st gear I could have slipped the clutch and ran around the truck in Chinese fire drill fashion.

 

When I had my C6 rebuilt I considered swapping to a T19 or ZF5. My truck has the 3.55 gears.

I saw a Bullnose parts truck in Tulsa, OK that supposedly had a ZF5. Conveniently, the shift **** was missing.