screwhead

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Howdy. Thanks to everyone on this forum have helped me out a lot already.

I recently purchased a 1993 7.3 idi non turbo as my first diesel vehicle. (Odometer is out and both me and previous owner have no clue what that mileage is. Dumb move maybe, but she is very fun to drive) Drove from Arlington to Austin as soon as I got it and it rode fine, started up every time, could definitely go it’s max speed or more but I’ve been trying to be nice to it for now at least. Fluids were all at a decent level and seem to have been at least half ass maintained.

Day after I got home it started doing some strange things, blue/whitish smoke, randomly would lose power and have a hard time maintaining any kind of highway speed (switching between fuel tanks actually seemed to help with this which I thought was very strange), and after driving it back from the mechanic first time I had him look at it died on me multiple times on the short and slow drive home.

Mechanic did compression tests, etc and is telling me that the rings on three pistons are going out/need replacement and that’s the biggest problem along with it (1, 2, 6) He said that other than that the motor is in pretty good condition. I have had the transmission serviced. I did an oil change, cleaned up batteries, and am about to do a coolant flush and change.

He also told me that the injectors 4 and 6 need replacement and two of the glow plugs are going to or need replacement soon. My biggest question is should I go ahead and replace all fuel injectors and glow plugs, do whatever else I feel I’m mechanically skilled enough to do and wait a little while to have the pistons serviced or should I just wait till I can get the pistons serviced at the shop and change glow plugs, injectors, etc then. Also any idea what it would cost do get something like that done?

Other questions I have are about possibly upgrading the pistons, would like to put a turbo in it one day but not sure what I can or should start upgrading to be able to handle the turbo.

Any advice or thoughts would be appreciated. Happy truckin
 

gnathv

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Did your mechanic give you numbers on your compression test? When you take off your oil fill cap while idling, how much blow by do you have? These engines do have some.
 

screwhead

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No numbers on the compression tests, should be sending me them ASAP along with quote for piston work.

If I take the cap off, set it back in there without threading it the cap spins a little but doesn’t come off, can definitely feel some strong air flow coming out but I guess that is somewhat expected?
 

screwhead

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Let it warm up in the driveway for quite a while, oil cap will still sit in there (seems like it wouldn’t if any more air pressure) and it whistles like a tea pot about 20 seconds from boiling.
 

Nero

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A compression test does not tell you if your rings are bad, or your valves. If you have low compression, you also need to do a leak down test, to see if you have air leaking past your rings, or valves.
Hopefully it's just a valve and you don't have to mess with the rotating assembly
 

screwhead

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@Nero I’m pretty sure the mechanic did one, that’s how he would determine what actually needs to be replaced right?
 

Nero

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I wouldn't assume, but I'd hope he did it that way.
 

gnathv

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Has the truck sat for a long time or only used for transportation and not worked (loaded, trailer towing)?
Diesels like to work and generate heat. I would check fuel pressure and volume also.
 
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screwhead

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From what I understand it was a daily driver until pretty recently. The guy I bought it from only had it for 6 months and was using it some but not much. I have no idea what original owner did with it but it does have a goose neck hitch.

Trying to talk to mechanic about it more but won’t be able to until Monday. Guess I’ll try and post what he says for some clarification.
 

IDIBRONCO

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Mechanic did compression tests, etc and is telling me that the rings on three pistons are going out/need replacement and that’s the biggest problem along with it (1, 2, 6) He said that other than that the motor is in pretty good condition.
I find it hard to believe that three cylinders could have bad rings that are going out or need to be replaced and that "other than that, the rest of the motor is in pretty good shape". Nor impossible, but hard to believe. It's also hard to believe that you have three cylinders that are "bad" while you're able to drive it to it's max speed. I assume that you mean that it has plenty of power to drive as fast as you want to down the road and then some. If you have three bad cylinders, I tend to doubt very much that you'd have the power to drive it that fast.
He also told me that the injectors 4 and 6 need replacement
How did he come to determine this? The only way to tell for sure is to pull them out and pressure test (pop test) them all to see what pressure they fire at.
two of the glow plugs are going to or need replacement soon.
This is believable, but again, how did he come to this conclusion? You can use a test light to see if glow plugs are burned out, but that's it. Like a switch that's either on or off, they are either burned out of not with this method. Since you mentioned that it started right up every time when you first got it, Hopefully one of these starts was with a cold engine. If it started right up and ran smoothly, then you probably don't have bad glow plugs.
My biggest question is should I go ahead and replace all fuel injectors and glow plugs,
I think that you should at least pull the glow plugs out and look at them. If they are anything but Motorcraft/Beru, then you should replace them all. If they are Motorcraft/Beru (they are the same thing just different names) then you can test them to see if they're good or not. As for the injectors, I don't think that you should make any descisions on those before you do some more trouble shooting.
wait a little while to have the pistons serviced or should I just wait till I can get the pistons serviced at the shop and change glow plugs, injectors, etc then.
Don't jump to any conclusions here until you get more, better information.
Other questions I have are about possibly upgrading the pistons, would like to put a turbo in it one day but not sure what I can or should start upgrading to be able to handle the turbo.
A N/A (naturally aspirated/non turbo from the factory) engine can handle a fair amount of power increase without anything extra being done to it internally. The only thing that I would recommend, and only if you're wanting to run a good amount of boost, would be to install head studs.
If I take the cap off, set it back in there without threading it the cap spins a little but doesn’t come off, can definitely feel some strong air flow coming out but I guess that is somewhat expected?
Don't try to judge the amount of air coming out here. Since the oil cap will sit in the hole loosely without blowing off, you don't have any abnormal amount of crankcase pressure. That also most likely means that you DO NOT have three bad cylinders (pistons with bad rings). This is a VERY important clue. These engines do have a large amount of blowby when you remove the oil fill cap with the engine running, but that's by design and is perfectly normal.
Let it warm up in the driveway for quite a while, oil cap will still sit in there (seems like it wouldn’t if any more air pressure) and it whistles like a tea pot about 20 seconds from boiling.
I'm assuming that you are saying that there's a lot of noise coming from underneath the oil fill cap with it removed and the engine running. That's also normal. These engines are completely gear driven at the front end. from the bottom up, you have the oil pump, crankshaft, camshaft, and then the injector pump drive gear on the top. Since these gears all mesh together, you do get a lot of gear noise from them turning.
Overall, I would recommend not putting much, if any faith in what this mechanic tells you. As for myself, he would NEVER be touching my truck for any reason unless he volunteered to change a flat tire for me for free. A lot of diesel mechanics don't want anything to do with these trucks and they don't know very much about the engines because they are so old. Most of them don't want to do any real diagnosing, they just want to plug their scanner into them so that it will tell them what's wrong. The main thing to remember about these engines is that underneath the fuel system (glow plugs are included here), they are just basically the same as any old fashioned V8 engine (350 Chevy, 302 Ford, 318 Mopar for some examples). Machanicly, they are very simple and are actually very durable engines.
 

screwhead

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@gnathv The only problem I noticed on that 200 mile drive was that if I was driving on the rear tank the pick up seemed to have a harder time maintaining 75 especially on a incline (even a very slight one) whereas if I was on the front tank it could do more. Rest of these problems started the next day or over the following week it did not die on me till after I got it back from mechanic the first time. I’ve also noticed it seems to die on me when I first start driving it, maybe multiple times but after that it won’t till maybe the next day. (After quite a few hours of not driving it) I guess I’d have to drive it more to find out but just been using it to pick up parts from auto zone or whatever.

@IDIBRONCO thank you for all the information. I have not been able to talk to the mechanic a lot as I work past when shop opens and closes, when we initially spoke he told me he was going to do a list of tests on it, multiple compression tests and leak down test, not sure what he did for glow plugs, only information the shop gave me was what I posted and I told them I’d have to talk to him more about it but he wasn’t in at the time. Also have a general distrust of mechanics but definitely don’t know enough about diesels to diagnose this problem and don’t want to cause further issues by continuing to drive it.

However I will take your advice, already been looking for a more reputable shop to go to hopefully with someone more experienced working on old pick ups. I’ll also pull the glow plugs probably tomorrow and check them out.
 

screwhead

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Just to clarify it does start right up, probably about to take my girlfriend to get some ice cream in it right now, but if it dies on me while driving I have to pull over and takes a minute to get it going again.
 

screwhead

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Another thing, I got the feeling the guy I purchased it from was doing more or less the bare minimum for it. I was planning on changing glow plugs and injectors anyways just because I have no idea the last time it was done, guy who owned it last didn’t do either, and didn’t know when the last time it was done and I have no problem taking some extra steps to make sure she runs well.
 
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