Datsun 720 SD22 new owner

[mikecaleb]

I bought a 81 720 with the SD22 engine last night. The man cranked it up for me and it ran like a top. There are a couple things I need to fix first before itll be driveable though. First thing is the battery. I need a new one but i need to know what size and cranking amps and such? I was told that i will need one stronger than the average.

Edited April 10, 2019 by mikecaleb

[wayno]

Get as big as battery as will fit with as many CCA(cold crank amps) as you can find.

I put a Optima red top battery in my 720 with 720 CCA(910 CA) and it works fine for me, it is small but I need a small battery as my power steering pump hose is in the way and I already ruined one pressure hose because of a big battery.

Does your engine start and shut off with the key, or is there a cable to start it and shut it down, do you push a button to warm up the glow plugs or does it happen automatically with the key and a light in the dash?

[mikecaleb]

It will start with the key I believe. Not positive but pretty sure. It was dark out. But you do have to shut it off by pulling down on a lever on the motor. He showed me where it should connect too.  Its just missing a litlle clip. And there is a glow plug button. 

[wayno]

If you have to pull on a lever or push on a arm all the stock electrical stuff is bypassed/not functioning, that is also why you have to press a button to warm up the glow plugs, too bad but it will still run fine without that stock stuff.

What do you think about the power on the freeway?

I turbocharged both my SD25 engines, I wanted more power on the freeway.

[mikecaleb]

I havent been able to drive it yet. I still have to fashion up some sort of cooling fan. The stock one is missing. The slave cylinder needs replacing too. Or so he said. He had told me that once i fix the clip on the rod it will turn on and off with the key. So if thats not true and I cant use the key to start it. How do you start it? 

 

I hardly ever get on the freeway. Maybe once a month. Fastest i ever need to go is about 60 on a regular basis so its not that big of worry to me. I have thought about it though. But from what ive read theres only been one person successful at it and thats you lol 

[hitch]

I still regret selling my 81 720 diesel, good luck with the adventure.  Wayno will be your best resource here, and perhaps I can assist if needed.  Highway travel is not the sd22's best environment, plan to accelerate as you approach even the slightest grade in an attempt to maintain a safe highway speed.  Read all you can here (https://nissandiesel.dyndns.org/) 

 

[mikecaleb]

Thanks man. Is there a good place to buy parts for the motor?  And do they really get 45 mpg like some say? 

[wayno]

I know one guy that said he got 40mpg, he is a semi truck driver also, the guy I bought the engine from in my 720 said he got 48mpg, but he said the engine drove great when I bought it from him, when I test drove it it ran too hot and he said I drove it wrong.

When he said he got 48mpg he was also using propane injection, and he also had a choke knob to shut it down, I believe he pulled on that knob while making that trip to get the best mileage he could by leaning it out on the fly, I would guess his top speed was 55mph on the freeway.

Personally the best I have ever got is 35/36mph, I went under 60mph(all freeway), on the way back home I got 28mpg, I just had to go 70mph.

After installing the turbocharger on my engine in my 521 kingcab I got 30.8mpg going around 75mph, I likely could have got close to 40mpg if I had drove 55mph, but I cannot drive that slow on the freeway.

My friend wants to turbocharge his SD22 so I will get first hand results on that project, also the guy on the Nissan Diesel Forums with "the turbo the bomb" thread did succeed even though his thread has no happy ending, but his way was way more complicated but I would never have succeeded if I had not talked to him on the phone, he made me think about it a different way, and the rest is history.

I have rebuilt a SD22 that ran fine, I got my kit on ebay from a place called Falcon something as I recall, but it was a 5 ring kit, I will use 3 ring kits in the future.

Ebay has lots of parts for the SD22 diesel engine, but you don't see electrical parts come up very often.

Is the clip on rod you are talking about the one that goes from the injection pump lever to the injection pump controller underneath the injection pump, if it is you can likely make a rod yourself, I did that once but since then I have collected a lot of extra parts.

[hitch]

I've got to say, mine was a rare low mileage great runner, but it never saw more than 35 mpg in daily driving.  Perhaps if cruising at 45mph and no more you could see that.   Seems I was usually at full throttle in any driving until into 5th just to stay out of the way.

[wayno]

I averaged 25mpg in the city no matter what, and around 27/28mpg on the freeway, I only got that because I also was floored most the time on the freeway trying to do 70mph, and hills/upgrades drove me crazy, I then found an SD25 engine, I could do 75/80mph all day long on level ground, but again hills/upgrades drove me crazy.

Since installing a turbocharger I have come to the conclusion I will never drive a Nissan 720 diesel again without a turbocharger, it makes driving my diesel trucks a pleasure, the way they should have been built in the first place.

 

[mikecaleb]

Yes thats the rod im talking about. The rod is still there it just needs a clip on it to stay there. I kinda figured they didnt get that great of mpg. But thats still decent. The truck only has 183,000 miles. From what ive read thats nothing for these deisels. 

 

[wayno]

There is a reason the rod was disconnected, I don't know what that reason was but it likely would not start, there are a lot of reasons why it might not start, and until you get to know the engine figuring out the reason that time is like walking around in the dark, you might stumble into the reason, but unless you try to start it every time you touch something you may never figure out what the actual issue was.

I have had people call me telling me there engine will not shut down with the key, 95 percent of the time it is the injection pump controller stuck in the run position(doesn't move anymore), they come over here and I unplug and plug back in the wiring for the injection pump controller and it starts working, I tried to explain to them what to do on the phone but for some reason they do not understand what I am talking about, they think they need a new DPC Module, well when they replace that module they have to unplug it and plug the new one in, well doing that also fixed the issue, it's just easier to unplug and plug back in the IP controller itself.

Now if the injection pump was re-timed for one reason or another(hard to start maybe) sometimes the rod your talking about gets out of adjustment and binds/screeches, this could be one of the many reasons the rod was disconnected, my 720 would not start and I spent hours trying to figure out why, if I disconnected that rod it started fine, and once the engine started the IP controller moved to the run position every time, well in the end I figured out if I disconnected the wire from the oil sensor/sender on the side of the block everything worked fine except the oil light on the dash, so I put an oil gauge in the truck as every time I connected that wire it would not start, it's not supposed to start until it sees oil pressure, well I have lots of oil pressure, I just have not taken the time to pull the wiring harness apart to see which 2 wires may be melted together if that is the reason at all, I have changed out every diesel related component without positive results, so I am still learning also.

The rod is held on by a small spring, 2 washers, and a cotter key, this is how it came stock, mine are held on by safety pin(hillman safety pin).

I would suggest you never use starting fluid on these engines, it is very hard on them and can mess them up.

I may have forgotten to mention how the start/shut down system is supposed to work, when you get in the truck to start it you turn the key on and a light is supposed to come on on the lower right corner of the dash, this is the glow plug light that tells you the glow plugs are warming up, when the light goes out you start the engine, now I have no idea what was done to your truck when the button to warm up the glow plugs was added.

Another thing I will mention is if the alternator is not working properly(charging) the glow plug light doesn't work properly, also when you start the engine it will not show a charge until you hear a click, then it should be charging, I know this because all my trucks have volt meters and oil gauges, if the fan belt is not tight until it starts charging the belt may squeal, it's a goofy setup if you ask me, I have no idea why they set it up to do all these shit, I go thru a belt every year or less on the 720, it appears that the alternator is harder to turn until it starts charging, goofy setup.

 

 

 

[mikecaleb]

Alright well im going tomorrow to buy a battery after that I'll be able to look into all of that. 

 

Would a fan from a z22 motor fit onto the fan clutch on the sd22? I can find a new clutch but cant seem to find the actual fan.

[wayno]

As I recall the SD series fans are offset towards the block while the Z series is offset towards the radiator, I just looked at my 720 and the fan is very close to the radiator, I am not sure if it will work, if I were to guess looking at my 720, no the Z22 fan will not work.

OK, the type you need is on the right in the photo below.

In this photo you can see how the mount surface/holes are near the front of the fan, this sets the fan blades back towards the engine.

In this photo below you can see the mount surface is near the back of the fan, this offsets the fan towards the radiator, I would likely be an inch into my radiator using this fan, I believe this fan comes from a Z22 or Z24 block.

If you cannot find what you need I have a few extras and I could sell you one, all my diesel fans have 8 blades.

Edited April 11, 2019 by wayno

[mikecaleb]

Well that sucks. Ive got one for a z22 i aint using. How much would you want for one of them? 

 

[wayno]

If you had to you might be able to reverse the Z22 fan, it would likely still work although the blades would not likely move as much air as the curve would be backwards.

Do you need the clutch part also?

[620slodat]

Wayno, I don't have the fans in front of me, and in my mind I couldn't picture the whole thing. But, if the fan on the left was flipped over would it work on the SD22.

 

You just posted as I was pecking (two finger typing) out my question. You answered my question before I even got to ask you, which was exactly what you posted. Thank you for answering my question. You are a wizard.

 

Don

[mikecaleb]

Yeah i do. Rockauto has the clutch. But how much for both of them? 

[mikecaleb]

Well i picked up a battery earlier today. I got one with 750 cca and 935 ca. That should be plenty. Im a little worried it's going to be to tall though. Maybe not. I'll be able to hook it up tomorrow morning and see what itll do then. I sure do appreciate all yalls help. Being this is my first actual datsun truck and its diesel i sure do need it. 

[wayno]

There is room for a tall battery, just put the negative post towards the fender, hopefully the negative post will be towards the rear/firewall when the battery is in place.

Having room and getting it in position is another story though, but you likely don't have power steering like I do, no power steering leaves a lot more room.

[mikecaleb]

Awesome the negative will be beside the fender and towards the fire wall. And your right no power steering. 

 

I may end up having to but a new ground cable and a new positive battery cable end. They look pretty rough. 

[wayno]

That positive cable is long, if the ends look bad put another end on it.

Also no matter how bad the fusible links/plugs look, if they work use them as there are no replacements unless you know how to make them.

[mikecaleb]

I got the battery in and replaced the cable ends this morning. The light for the glow plugs on the dash comes on and goes off as it should. I tried a few times letting them warm up and couldnt get it running. I even tried primeing it up a little bit. 

 

The belt looks awful and is very loose. Ive already got a new one on the way. Could this cause it not to run?

 

 

[wayno]

There are a lot of reasons why it would not start, and I am not there to see what is going on, I could start asking questions but miss some important piece of info.

It has to get fuel and the glow plugs need to warm up, either issue and it will not run even if the rod is disconnected, now if the rod was connected it could be a bunch of things keeping it from running, alternator not working, oil pressure sender bad, fusible link bad.

First thing you need to do if it ran the way it was before is to make sure the glow plugs are warming up, you need to either check it with a test light or volt meter, when you press the button is there power to all the glow plugs?

If you have a laser temp gun you could try checking the temp of them before(not been started that day) and after you warm them up(not starting the engine), if they show warmer then they probably are working, I have never tried this, it may not work, I do know that if the glow plugs get too hot they can be ruined, I was sold the wrong set once, they only worked once.

If you push that lever you used to shut the engine off towards the radiator/front that is the richer start mode.

[mikecaleb]

Alright im off work tomorrow so ill be able to check all that out. The man who sold me the truck said it had sitting for a couple years. All he did to get it running was pumped up the prime button a few times. It wouldnt start at first but he gave it a small squirt of starting fluid and it fired right up. Ran good too. I know now starting fluid is really bad for them. Only wish he knew that too.