Help nissan 720 sd22 diesel

[plenzen]

Interesting, and I stand corrected.

Perhaps the 720's had inline pumps then.

My D21 had the VE.

[waynosworld]

I have never seen/heard of a diesel 720 with a VE type injection pump in the USA, after the 720 I have heard of the VE type pumps being used, likely because of emissions standards(has computer???), I have never actually seen one myself.

I did import a SD22 with a VE type injection pump from Australia several years ago, I did this to use the VE pump system complete to turbocharge my SD22 engine, but I figured out how to turbocharge my SD25 engines using the inline injection pumps, I described how I did it in my thread, both my SD25 engines are turbocharged now, I will never daily drive one without a turbocharged engine again, they are all gutless without one, but the turbo choice is very important, I turned 71hp into likely into 120hp, maybe more.

The biggest reason I like the inline injection pump is they last for 300,000+ miles, I have heard the VE type injection pumps are good for 60,000 miles before needing rebuilt.

[plenzen]

Sold mine with 343000 Km ( 215000 miles) and only had the transfer pump changed in it, because it started to surge at low throttle low RPM.
Was still going strong and think it still may be however lost touch with the buyer 2 years ago. He drove it the 1400Km from here to his place without an issue.

No computers in the 87 D21. Closest thing to one of them was the glow plug timer under the driver seat.

Had a cold start device on the side of it that was a wax pellet variety that internally advanced the timing a couple degrees in an effort to help it start in cold weather. There are pictures of it on here somewhere
Cold weather to Nissan was -9C . -10C it would not start. Hence the air heater I put on it. A game changer.

Had quicker and hotter glow plugs on it as well as an after glow feature that would reduce the voltage to the plugs after start up and keep them on until it either timed out or the temp sensor in the intake manifold told them to shut off.

No problems with the fuel pump whatsoever. Easy to prime and to time putting back on the engine.


You are absolutely correct about the NA engine.
It was pretty slow and especially living here at 4000 ft it was pretty anemic.
However, putting a turbo on it at such high mileage without doing a head gasket was asking for issues.

I used to love driving it out to the BC coast. At sea level it felt turbocharged to me. Going over the Rockies was however no bueno.
Poor thing was on its knees. 4 way flashers on and on the shoulder to let traffic by. Ignore the single fingers. It's fine.

P

[waynosworld]

Since I turbocharged all my diesel engines in running/driving vehicles, I really only have one thing I have to watch out for, the "exhaust gas temperatures", they rise very fast on uphill grades, my 521 kingcab SD25 turbodiesel does not have an intercooler, my 720 SD25 turbodiesel does have one but I have not driven it daily/much at all since 2011, I drove is some at first, but the intercooler did not seem to change much, the EGTs still got high fast on any upgrade, I did not see a 100 degree difference in the EGTs, since I like my 521 kingcab turbodiesel the most, that is the one I daily drive, on upgrades I limit the EGTs at 1400 degrees, when I get close I back off the pedal, most the time 1300 degrees or less, but even at 1300 degrees on long uphill grades my water temps start to rise also, there is a point where I just give up and downshift and stay to the right.

[plenzen]

There are a couple of mountain passes nearby where I live that rise to 7000 + ft.
I did not have EGT's on mine but I would watch the temp gauge pretty closely on long pulls.
If it got a needle width above the half way mark ( which it rarely would ) I would put the heater on full defrost, full hot, full fan, and open the drivers window. It would take about 2 needle widths off the temp, but if it started to rise again I would just ease out of the fuel.
Mostly happened in summer months as you would think, but there is one pass that would tickle the middle in the early winter ( November)
Good fishing up there at a lake before it completely froze over.

Level ground it was good. About 95 Km/h was where it liked to live. Anything more than that it just seemed I was beating the hell out of it.

[waynosworld]

I like 2300/2400rpms(70ish mph) anymore and I have to start pressing on the pedal more and fuel mileage goes down going faster, but those that drive 55mph can do much better, Larry claimed to get 48mpg with propane injection assist, I just get 30mpg on the freeway as I drive 70mph to 75mph(turbocharged), I am turning 3.3 gears in the rear axle with P205 tires.

Having a turbocharger just changes everything, I will never have a diesel engine without one again.

I did put an EGT gauge on my pre-turbocharged SD25 engine, in less than 2 minutes it would read 1400 degrees on a slight 1 mile upgrade just trying to keep up with the flow of traffic, this surprised me.

[Raptor6717]

20260627_104546.jpg (2.81 MiB) Viewed 421 times

[Raptor6717]

So it turns out it is a North American made truck with the sd22, which I thought didn't exist. 1983.5

I bought it for $900, and here in the southeast, these things are unobtainable with the diesel. Most of them have been scrapped, and I got it cheap. (I live in South Carolina, and the closest one is in Virginia for $7000, and it is not in the shape it should be for the price.) I obviously jumped at the opportunity to own it. The owner said it had rod knock. (It also doesn't have title currently but we can resolve that.) He was a young guy, and it was so loud to him he thought it had rod knock lol. I got it running, it had sat for about a year, runs good no knock. It has a good clutch and brakes.

The issue is it is not charging, does this have an external regulator? I would assume just to replace the alternator, would this be correct? I can't think of anything else. It sits at 12.7 v while running and the battery light is on.

[Raptor6717]

And what true fuel economy do these engines get? I'm not planning to go over 65mph, or put it on any highway as of now, most of the speed limits in my area are around 40-45

[plenzen]

I believe that it was mid 83 they changed the name to Nissan from Datsun.

The alternator will have an internal regulator.

If you have a local rebuilder then that might be an option to look at.
There are replacements out there (ebay etc) but it seems that some folks on here ( IIRC) had some issues with their longevity/compatibility etc. Plug fitment for one.

Yours will have vacuum pump on the back of it so bear that in mind if you go shopping. I think there are some out there that have the pump affixed to them, or cheaper without.
Perhaps open your vacuum pump up and check its condition before you buy one.

I believe that Al ( forum manager ) or perhaps it was some other forum member replaced the alternator with a standard type and mounted an external electric (12V) vacuum pump. This allowed for a more robust alternator to be used. The internal regulator on these is their weak spot.
I had mine rebuilt 2 times for this very thing.

A good battery is essential as these are really meant to maintain the charge after start up and not really to charge a dead battery after needing a boost. Boost jumping another vehicle is another thing to be careful with.

I think there is a post on this forum someplace ( I think by Al actually) that had some answers or experimentation with regulators, or diodes, or solutions that he came up with. Search alternators on the general forum.

I cant recall now what regulator the last rebuilder put into mine, but said that he used something different that "fit". ( a different Hitachi application I think)
That said I believe that alternator for the D21 was slightly different. ( but it's been a minute )

My D21/sd25 would usually get around 8L/100km +/- ( 30 mpg/us gal).
Some folks on here said they got more some less.

Gears in the 720 both transmission and rear gear are different as well

Wayne can give you numbers that are more in line with what you have as that's what his fleet is.

The speeds your talking about of 40- 55 mph is right in the "happy place" for these little guys.

If your looking for VW TDI numbers it isn't going to happen.

Good luck

[waynosworld]

The best mileage I ever got was 35mpg with my SD22 powered 720 diesel truck without a turbocharger, that was going around 55mph to 60mph on the freeway, it dropped to 27mpg when I drove 70mph, the worst mileage I ever got was 22mpg towing another 720 diesel home behind my 720 diesel, I never checked what kind of mileage I got towing a 720 diesel with my SD25 powered 720 dually, this dually was never meant to haul weight, the dually was for looks, it towed fine as long as I kept in mind that the dually rims are held on with an adapter I had made, one time the inside lugnut's got loose that held the adapter onto the H190 axle, I did this because the C200 dually axle's best freeway gearing is 4.11, I turn 3.3 gears in my diesel trucks using H190 axles, this keeps my rpms down below 2500rpms which gets me around 30mpg at 70mph, I just cannot drive 55mph.

My biggest issue with charging is the fusible links connectors to the battery post, the connectors get loose/wore out and do not make good connections, all 4 of them connections have to have power, you can see in this photo the connector to the battery post is melted slightly, my 720 connector is worse.

[Raptor6717]

I also have another issue. The truck will crank and crank until it starts, and after a day of sitting it will not start unless I spray something in it, then it will go. It seems to miss for a while until it warms up. Is this glow plugs? What do you guys think

[hayat]

I would check the glow plugs and make sure the glow plug controller is actually powering them before chasing anything else. If they all test good, the next thing I'd look for is a small air leak in the fuel system since those symptoms can show up after the truck sits overnight.null's brawl на ios

[plenzen]

Remove all the glow plugs and test them individually with 12V.
They should all turn red within 15 seconds or so, and start to "smoke" pretty much immediately.
It only needs one glow plug to be out to cause a hard start.

And agree with what hayat said about fuel and the timer.
Hook a meter on one part the daisy chain that hooks them all together and see that your getting 12V.
That will tell you if the timer is working.
Time it to see how long it comes on for.
Wayne or hayat can tell you how long the 720 timer should run.
Mine was different and was engine/ambient temp sensitive so I cant help you there.

Or search the forum, there has to be a post on here somewhere that tells how long it should run.

As previously stated be very careful what you "spray" into it. Head damage can occur.

Better yet, remove the air cleaner and try a heat gun on medium heat for 30 seconds or so right down the throat, or a hair blow dryer on high a good minute and see if she'll fire.

It sounds more like a GP issue to me, compression could be down a bit as well.