81 Datsun 720 SD22 Diesel

[Hawk_91119]

Hey guys, I have a 1981 Datsun 720 sd22 that has been sitting for many years and I'm trying to revive it. I was able to jump the starter solenoid and spin the engine over,but the engine turned over slowly. I used a 700 CCA battery and put some diesel down the air tube, but it didn't fire. It may be because it is turning over so slow or I flooded it. It may have a bad ground ( the truck is rusty) and the starter did not engage all the time ( the starter is probably bad) , but just spun without engaging. I also couldn't turn the ignition switch on because the key was misplaced, and that may be a problem as well (like glow plugs or something idk), but what do you guys think is the issue?

 

Also, what size battery is recommended for the diesel motor?

[ggzilla]

Unbolt the ignition switch from the back of the key barrel, then turn it with a screwdriver. There is only one screw holding it on

1 hour ago, Hawk_91119 said:

couldn't turn the ignition switch on because the key was misplaced,

 

 

For suspected ground problem, use jumper cable from Battery Neg terminal to any metal engine part

 

jumping the starter solenoid is problematic. If you only connect the two big terminals it will spin without engaging the flywheel. If you jump the small terminal to the battery cable it should engage, unless ... the solenoid contacts are corroded inside, which is somewhat common problem

[ggzilla]

The factory battery was 80ah for the diesel engine, which is much larger than the 60ah for the gasoline engines

This is about 600 CCA, however CCA means how well it does in cold temperatures, while AH is more about how long it will crank

 

Bottom line: today's batteries are far better than 1981 batteries

1 hour ago, Hawk_91119 said:

what size battery is recommended for the diesel motor?

[wayno]

1 hour ago, Hawk_91119 said:

Hey guys, I have a 1981 Datsun 720 sd22 that has been sitting for many years and I'm trying to revive it. I was able to jump the starter solenoid and spin the engine over,but the engine turned over slowly. I used a 700 CCA battery and put some diesel down the air tube, but it didn't fire. It may be because it is turning over so slow or I flooded it. It may have a bad ground ( the truck is rusty) and the starter did not engage all the time ( the starter is probably bad) , but just spun without engaging. I also couldn't turn the ignition switch on because the key was misplaced, and that may be a problem as well (like glow plugs or something idk), but what do you guys think is the issue?

 

Also, what size battery is recommended for the diesel motor?

 

There is more involved when it comes to starting a SD22 diesel engine, the glow plugs need to be warmed up first, it will not likely even try to start.

 

You first need to get the key working, find the key!

 

I will describe how to start the engine, turn the key on and wait for the glow plug light to turn off, when it turns off then try to start the engine, do not pour diesel down into the intake, it is not a gas engine.

 

If you like a powerful truck/car, this truck/engine is not likely for you, the SD22 engines are only rated for 61hp, it takes time to get up to freeway speeds.

 

It has been sitting for many years, I have started engines that sat for years, the owners were amazed I got it started so easy, but I ask them if it was running the last time it was started(running, not tested with either), if they say yes, I do my thing, I first test the glow plugs to see if they are working by turning the key on, if the light turns on and turns off I prime the pump, and then try to start it, sometimes it takes a minute to start trying to fire/run, if the glow plug light does not come on I bypass the key and warm the glow plugs up using a large wire for the battery to the rear glow plug for a minute, then I get in and turn the engine over as fast as I can.

 

Another thing you have to keep in mind is that the diesel electronics move the injection pump to the off position, it will never even try to start in this position, the key has to work so when oil pressure is built up the electronics move the injection pump to the start position, when it starts it moves to the run position, you need the key to work, there are ways to bypass this also, but tell me why it was parked in the first place.

[Hawk_91119]

Thanks guys for the imput. It was parked in 1994 due to (in my approximation) the fuel pump going out near the tank. The previous owner does not remember why, but he said it wouldn't start anymore.  I have a fuel pump and diesel can, but haven't had time to rig it up, so I dumped some fuel down the air tube to see if it would fire up and jumped the solenoid.  (The ignition switch may be bad because when I had the key, I tried to turn it over but the injection pump relay clicked or something and the starter would not do anything.) I was told it was messed with about 10-15 years ago and started up with ether. 

 

[wayno]

This is the thing about this, the injection pump has its own fuel pump, it does not need one near the tank, 720 diesel engines never had an electric fuel pump.

 

You can connect a remote fuel source(fuel can with diesel fuel), you just connect it to fuel line from where the tank comes from to your fuel source, then prime the pump, but when you do this all the extra fuel goes back to 720 fuel tank via the return line.

 

In the end I do not believe you know enough about these engines, it is difficult to explain things if you do not know what every part/filter is for, it likely has 4 filters, maybe a pre-filter also, certain things have to happen for the engine to start, one is the injection pump controller has to move to the run position for it to start, second is the glow plugs have to be warmed up, the electrical system has to function properly for it to do that, it also has to oil pressure for the diesel electronics to let it start.

 

It took me a while to understand how this diesel engine system works, my 720 diesel truck still does stuff I do not understand and I have had it for 15 years.

 

 

 

[Hawk_91119]

thanks wayno

 

[Hawk_91119]

*UPDATE* The key was found. The diesel engine electronics seem to work, as I can see the glow plug light turn on and off and hear the glow plug module clicking. It will try to run on starting fluid. The issue is the fueling. There are many different fuel hoses coming from the tank, going to the fuel filter, and to the injection pump. This may sound dumb, but which lines are for the return and and which ones are the fuel suppliers? This may be hard to explain, but there isn't much information about these engines, so please bear with me. And also, should I try to hook up a auxiliary fuel system or should I use the original tank, because the truck has been sitting for so long? And is the thing on the side of the injection pump a manual hand pump?

 

[ggzilla]

Detailed diesel information is in the Datsun 720 factory service manual

 

from $20 to $100 on eBay or Amazon

[wayno]

You can try to use a remote fuel source, the lift pump on the bottom of the injection pump goes to the remote fuel source, the return line going back to the engine should go to the fuel source also.

 

The metal fuel line going to the lift pump is fuel coming from the tank, the other line next to it is the return, that line comes from the back of the fuel filter.

 

The thing is if that fuel filter is not full it will not start because it is sucking air out of the fuel filter, the fuel comes from the top, you do not want to put unfiltered fuel into the injection pump.

 

All the air has to be out of all the lines for it to run properly, there are filters in a few places, the pre-filter on the firewall, the screen in the banjo fitting that is on the bottom of the fuel lift pump, the fuel filter itself.

 

When I prime the fuel lift pump I start at the start, first I make sure the fuel filter is full by cracking the banjo fitting that feeds the injection pump and pump the primer until only fuel comes out, then I crack the fitting on the front of the injection pump and do the same, there are ither fittings but if it starts I let it do the rest as it runs.

[Hawk_91119]

Thank you guys so much. I will get back to you when I hopefully get it running.

[Hawk_91119]

Hey guys, I was able to get back to the truck. I hooked up the fuel line to the fuel source with an auxiliary fuel pump and tried to start it. It did not start, I cranked it many times and eventually the battery died. I cracked an injector line but was only getting small drops out of the lines, and it didn't seem pressurized. What do you think is going on, it is still probably not getting fuel.  

[Hawk_91119]

I have read threads about the lever on the injection pump staying in the off position or the fuel filters being clogged. I tried getting the main fuel filter off but the truck is rusty and it is pretty well on there. 

[wayno]

OK, you need to prime the pump/system, this could take a while, but you have to be using the stock fuel pump to be able to do that as the primer is part of the fuel pump/lift pump.

 

You also need to warm up the glow plugs, it will not even try without the glow plugs being warmed up.

 

You can disconnect the injection pump controller arm from the injection pump, this will allow the injection pump to move to the run position, but to stop the engine from running you will need to either put it in gear, hit the brakes and kill the engine using the brakes, or move the injection pump towards the firewall to the off position/cut off the fuel.

[Hawk_91119]

*NEW UPDATE* OK, I was able to work on the Datsun truck. It was getting fuel past the fuel filter and Into the line before the injection pump. The actuator for the injection pump does not move. It will not try to move fuel at all. I tried to move the lever manually but it only moves backwards slightly towards the firewall. The lever will not move forward. There is a spare motor in the garage and the lever only moves forward (away from the firewall direction) and then springs back (which I believe is normal). As you said, the pump would normally move back to stop it and forward to run and start, but the pump in the truck does not move forward. What would cause this? Is it stuck from sitting? And also, is there a different variation of Kiki pump where it has a different actuation process on sd22s,or all of them the same on these trucks? 

[wayno]

OK, the injection pump controller is not working, there are a lot of reasons for this to happen, oil pressure is not building up so the electricals are not letting the injection pump to move to the run position, the other electronic parts are not working properly, try disconnecting the oil sensor wire from the sensor, then turn the key on, does it move to the run position?

 

If it does not move to get it running disconnect the injection pump controller arm from the injection pump, don't lose any of the parts(spring/washers/clip), then the arm should move to the run position on its own, it should start this way, but if it has not run yet in all of them years, it may take time to start if all the other things are working properly, sometime when I start an old engine I have found I squirt a very small amount of ether, and I mean small amount to see if it is trying to run.

 

Another thing to keep in mind is the glow plugs have to be warmed up for it to start when cold(engine not run over night), there are a lot of things about diesel engines to learn when you own one.

 

A few times I have had people call me saying the engine will not start or shut off without disconnecting the injection pump controller, I tell them to disconnect the injection pump controller from the wiring harness and plug it back in a few times to scrape the connections or use electrical contact cleaner in the plugs and blow the cleaner out with compressed air to dry them out.

[Hawk_91119]

Thank you, wayno. It did try to run on ether the last time I tried. It is funny because the oil light comes on in the dash, so I added some oil, but it didn't change anything. I tried starting it with ether, but this last time it would not start. The battery was almost dead. The glow plugs do work correctly. I will try to do what you have suggested when I get back out there.

[wayno]

OK, remove the wire going to the oil pressure sender, have someone turn the key on, the injection pump controller should move to the run position, if it does not move it will never start as it is not getting fuel.

In the case above remove the arm coming from the controller to the injection pump, try starting it then, I am assuming that it is all primed and all the air is out of the system.

[Hawk_91119]

OK, so I was able to work on the Datsun truck and I made progress. When I first hooked up the battery, I immediately sprayed ether into the engine and it was firing. I hooked up the fuel line from the auxiliary tank and began cranking the engine. The injection lever was not moving. When the battery was dying, I got a jumper box and hooked it up. I think the extra amps jolted the electronics, and the injection motor started moving. I did not have to unplug the oil pressure sensor. The electronics are slowly coming back around. It was trying to fire, and I was getting fuel out of some of the injector lines. But then the lift pump lost prime, and the positive terminal started smoking, so I quit for now. I know it is not recommended, but I think next time I am going to hook a fuel pump directly to the injection line from the auxiliary tank. I have to hear this thing run. The pump does have a filter attached to it. 

[wayno]

8 hours ago, Hawk_91119 said:

OK, so I was able to work on the Datsun truck and I made progress. When I first hooked up the battery, I immediately sprayed ether into the engine and it was firing. I hooked up the fuel line from the auxiliary tank and began cranking the engine. The injection lever was not moving. When the battery was dying, I got a jumper box and hooked it up. I think the extra amps jolted the electronics, and the injection motor started moving. I did not have to unplug the oil pressure sensor. The electronics are slowly coming back around. It was trying to fire, and I was getting fuel out of some of the injector lines. But then the lift pump lost prime, and the positive terminal started smoking, so I quit for now. I know it is not recommended, but I think next time I am going to hook a fuel pump directly to the injection line from the auxiliary tank. I have to hear this thing run. The pump does have a filter attached to it. 

 

I do not understand, "I am going to hook a fuel pump directly to the injection line", what line is that, to start it just disconnect the injection pump controller arm connected to the injection pump, it will rest in the run position then, and having oil pressure is out of the loop, but you better have oil pumping threw the engine.

 

If the engine tries to start but won't continue to run try using the starter fluid, just very short shots while turning it over, do not just spray it in steady, just very short squirts, you do not want to blow it up.

[Hawk_91119]

I meant the fuel line directly into the injection pump that feeds fuel into it, not the ones coming out of the pump. I also said that the injection pump lever began working properly, probably because of the extra amps from the jump box. 

[wayno]

I have a 1980 Datsun 720 diesel truck that stops working properly if it sits too long, it does all sorts of weird things, the controller stops moving the arm on or off, so I have to put it in gear and kill it with the brakes, to start it I have to remove the controller arm from the injection pump, after doing that a few times it magically starts working for a while, another thing my 720 does is when I turn the headlights on they are on brights, I have to sit there till it warms up(the relay) and then it drops into regular mode, but if you hit the brights it takes time again for it to return to regular mode, eventually it will work properly again if the truck is used enough.

 

I would not use unfiltered diesel fuel directly into the injection pump, it needs to be filtered properly, eventually you will plug up and injector, that is a major job once you figure it out it is plugged, the fuel has to work as the system was designed.

[Hawk_91119]

OK, I still cannot get this thing to run. I hooked the electric fuel pump from the auxiliary tank into the fuel filter, so the fuel would have some filtration. Fuel was getting to the injection pump. The injection motor lever that moves the injection pump positions works consistently now. The glow plugs are still working as intended, and the engine will fire off of ether. It will not run on its own, but I am getting drops out of the injection lines, so I closed those up. I now have the original owner's manual, and it says to push the accelerator pedal down all the way until it starts, which I was not doing. I also know what fitting to crack now to bleed the injection pump to get the air out, so I should try that correct? It is the one with the flathead screw on the side of the injection pump near the first injector line. So why won't this thing run, does it need to crank and bleed the air out more? And also what size battery do you use in your diesel trucks? The one I have been using has 880 cranking amps, and it is not sufficient. 

[Hankford]

Not knowing what I needed, I went to Napa and the sold me this. No issues so far with it and the CCA is less than what you are using. Hopefully someone else chimes in. I've started by truck a handful of times and moved it around the driveway without issues, but it's not finished/driving yet.

[wayno]

21 hours ago, Hawk_91119 said:

OK, I still cannot get this thing to run. I hooked the electric fuel pump from the auxiliary tank into the fuel filter, so the fuel would have some filtration. Fuel was getting to the injection pump. The injection motor lever that moves the injection pump positions works consistently now. The glow plugs are still working as intended, and the engine will fire off of ether. It will not run on its own, but I am getting drops out of the injection lines, so I closed those up. I now have the original owner's manual, and it says to push the accelerator pedal down all the way until it starts, which I was not doing. I also know what fitting to crack now to bleed the injection pump to get the air out, so I should try that correct? It is the one with the flathead screw on the side of the injection pump near the first injector line. So why won't this thing run, does it need to crank and bleed the air out more? And also what size battery do you use in your diesel trucks? The one I have been using has 880 cranking amps, and it is not sufficient. 

I do not understand, the fuel needs to go thru the lift pump on the side of the injection pump, the primer is on it, that line goes to the top/side of the spin on fuel filter, this is the lift pump.

 

 

This is the lift pump removed from the injection pump.

 

 

This is the banjo fitting on the bottom of the lift pump.

 

 

If you remove the banjo fitting on the bottom, carefully pull the filter out and see if it is plugged full of crap, I will repeat, carefully remove that screen, it is easy to break as you can see the broken one in the photo, these parts are old!!!.

 

 

I am not saying this is your issue, but putting fuel in any other way is not likely going to work, the air in the system has to be cleared out using the primer pump.

 

The housing of the injection pump only has engine oil in it to keep this lubed.

 

Edited April 12 by wayno