Engine I.D. and Help

[Dweano]

Hey guys, I recently bought a 1984 Nissan King Cab (720 I believe it is also called?) with a Diesel in it. I believe it is either a SD23 or a SD25? I need help identifying it. How would I do this? I need to order parts and I want to make sure I get the right ones.

Also...it won't start! The battery is weak, wiring is sketchy, but even when boosted it turns over slow. I am thinking I will get a new starter. Also the glow plugs were not getting power when I checked with a multimeter. When I jumped a wire from the battery to the glow plugs it turned over and fired a little bit but still didn't start. So here is what I think I will do:

New Glow Plugs
New Glow Plug Relay
New Battery
New Starter
Fix any wiring problems I can see.

Should help eh? It was running when I bought it and I drove it home (1 hour plus) and it ran pretty good. So its not a massive problem like the injection pump or anything. But I cannot for the life of me get it started again. I think the guy used starter fluid to get it started, then I drove it home. I also restarted it when warm but since then I have not been able to get it started...this is what leads me to believe it is glow plugs. Any replies would be greatly appreciated! I need to know how to ID the engine, I can't find any identification on it

Thanks!

[plenzen]

Welcome!
You have a project ahead of you for sure.
Most importantly DO NOT USE STARTING FLUID on these engines. It will damage the pre-cup in the cylinder head. No No NO ! If your just trying to get it going then try using a heat gun or good quality hair dryer and blowing hot air down the intake for a minute or more and then crank. Starting fluid is BAD !
Putting 12 V for a long period of time to the glow plugs, especially if they are the OE type may burn them out. So beware of that. You may also want to remove them and bench test them to see that they are ALL working. Even 1 burnt out will casue starting issues. Be careful when removing them as some may have blistered the sides and be tight to get out. Massaging them carefully to get them out may be in order. Just yanking them out if they are tight might cause one of the tips to break off causing some drama there, and a whole new project that quite frankly SUCKS. There are a couple of posts here on that little event as well.
The engine may be an SD22 or SD25. There are some posts in this forum on where the identification number is located. I believe it's on the passenger side of the block near the fuel pump but you can search it here. I think your truck is right where Nissan started to switch from the SD22 to the SD25 but I could be wrong on that.
A good strong battery is essential for these little guys as turn over speed also plays a role in how well it starts. The engine WILL NOT START without a glow sequence either so cranking without that event will only burn your starter out. Once there is heat in the engine it will start considerably easier but will still work better with a glow sequence. There are numerous posts in this forum on how the glow system(s) works etc. It is important to know what system it is that you have. There are 2. The older trucks had a pretty straight forward type of system and the later trucks have a "Quick Glow/After Glow" type that is controlled by a timer that is located under the driver’s seat. The types of glow plugs that you buy are specific to the type of system you have.
Good luck, and look through this forum using the “Search” feature. There is tons of info here to cover 99% of the issues you may run across.
You may also want to update your profile as to your location.
HTH
Paul
EDIT: See here for location of engine model # :
http://nissandiesel.dyndns.org/viewtopi ... ght=serial
Scroll to the bottom of the page and there is a photo of a FSM page there with the location.

[Dweano]

Thanks man! That post helped alot. I found out I have an SD 25. Would you recommend I go ahead and order all those parts then?

Also...the engine has seen better days I bet. What should I do in terms of a tune up? I know what to tune up on gas engines but diesel is new to me? I took the air filter off and it looked clean but the throttle body (these are throttle body injected engines correct?) looked caked with gross stuff. That would be a good place to start probably eh?

Thanks for the help! Hopefully I can get this truck running!

[Glegor]

Thanks man! That post helped alot. I found out I have an SD 25. Would you recommend I go ahead and order all those parts then?

Also...the engine has seen better days I bet. What should I do in terms of a tune up? I know what to tune up on gas engines but diesel is new to me? I took the air filter off and it looked clean but the throttle body (these are throttle body injected engines correct?) looked caked with gross stuff. That would be a good place to start probably eh?

Thanks for the help! Hopefully I can get this truck running!

no, its not throttle body injected.

the fuel is indirectly injected to the cylinder.. not throttle body injected. the throttle body is only for operating the throttle, nothing more. the fuel is injected by the fuel injectors on the other side of the engine..

[plenzen]

First off, the engine is injected by 4 fuel injectors located on the passenger side of the cylinder head. Those things that have the steel lines running to them from the fuel pump. The throttle body is merely a means to get air into the engine. As for a "tune up" per say, other than setting the valves and the standard filter changes there is really nothing more to be done. The gross stuff that you see in the throttle body is most likely “blow by” from the rings and, unless it's caked and clogged, then there is really nothing to be done. If you feel that you want to clean it out then I suggest you remove it from the engine as anything that you clean it with will end up in the engine intake and diesels don’t take kindly to things in there other than air. If it’s really caked and clogging then the engine may be worn and your compression may be low. Something to keep in mind before you spend too many $$$’s on it. It may not be worth it. Valve check/set is probably one of the more important things that you can do. They are to be set/checked hot at .014 for each of the intakes and the exhaust. If you have not done that before there are posts here as to how to go about it. Find out what kind of glow plug timer and glow system you have. A multi meter is a must to see what is going on with the glow system and will give you a starting point (no pun intended). Remove and check each of the glow plugs to see if they are working and also check them to see what kind you have. A lot of people that had issues with hard starting just went and bought any glow plug that would fit in the hole. There are, as stated, a couple of different kinds. Some people that had issues with the timer etc simply bypassed it and put in some generic 12V glow plug to get the danged thing to start. If you get further into it then replace the fuel filter as well as clean out the pre filter screen that I think is mounted on the firewall. (my truck is a different model and has a different filter system on it but I think all the 720’s were the same) Not too sure if there is a separate water trap on your truck or not but if there is, remove it and check/clean that as well. There is a procedure for the fuel filter change as well and the air will have to be purged from the system. This is also posted here. A service manual will be real handy if not a must to have as well and they are usually available on EBay and, you may even find someone on this forum that might have one they want to sell. Go into the “Peddle or Procure it” section and post in there. A compression test may be in your future and there is special tester for that. There are a couple of guys on the forum that may send/lend you one to use with the appropriate deposit.
Diesels are a bit different in how things are “put into motion” from gas engines. Their fuel systems are very expensive to repair and are real sensitive to water dirt etc. Just be real careful as to cleanliness etc. when dealing with them.
I guess to make a long post even more boring I think the best advice I can give you is to get the glow system working first before I spend a lot of $$’s on it. Once you are sure they are working then check the valve settings. Valves that are too tight will make it hard to start as well. Once those things have been checked and you can get it started easily then buy a battery and filters, and at least 2 cans of hand cleaner .

EDIT: Perhaps update your profile and put in where you are.

Paul