z24i to z24 conversion

[powderfinger]

I have an 86 720 4x4 z24i. I just recently put the engine out of a running z24 truck in it. I left the weber on the z24 engine I put in the truck and at first I swapped the distributor out for the crank angle sensor in the z24i and got the truck running using the factory z24i ignition setup but it was never running correctly. Had absolutely no power at all. Maybe this wasn't the best move but I decided to simplify things by swapping back to the standard vacuum advance distributor setup like the z24 has. I used the coil packs from the other truck and wired in the distributor and coils figuring now the trucks computer is out of the equation and the motor should run fine...and now I can't get it to run.

 

I have verified there is spark, I was able to check timing while my son was cranking the engine over and it is very advanced for some reason, past the timing scale on the block by quite a bit. I tried rotating the distributor as much as possible but still very advanced. I then tried rotating the wires one spot on the distributor (intake to next closest intake spot and exhaust the same way) in case I could get the timing close enough like that to get the truck to fire. No dice. 

 

The shaft that drives the distributor is installed correctly so, not sure why the timing is off so much and even so it seems like I should have been able to get it close enough to at least attempt to start. On top of that it now seems my timing light isn't working so there's that.

 

Is there any reason swapping the distributor and coils over like I have wouldn't work? Seems like it should work fine, I have verified I wired the the distributor correctly.

 

 

[DuallyDatsun]

I believe, if you have a tbi setup (I think the z24i was tbi) you have to run the tbi. Mainly because of the computer system used to run the injection. 

 

However, I've only seen people swap to a tbi system and haven't seen anyone swap one out to a carb setup.

 

Does seem weird though, because you would think the carb setup would be easier to set up and run. Especially since the only computer ish thing I remember on those was to the o2 sensors to tell you when to change them.

[datzenmike]

Use the coils the Z24 distributor works with. You'll have to wire them in as the CAS is wired to the EFI computer. The computer sets the advance and it will probably add to  the vacuum advance on the Z24 distributor.

 

You need a power wire that's on with the ignition, going to both + terminals of the coils and the Brown wire to the Z24 distributor to power the ignition module inside. The other two wires Red and White/Blue go to the - terminals on the coils. Use the Z24 coils.

[powderfinger]

That's exactly how I wired it using the Z24 coils. Not sure what's going on yet but it definitely won't start. Doesn't help that my timing light is acting up now. 

[Logical1]

[Logical1]

I just swapped a 84' z24 with a weber into a 86' 720. I discarded all the 86' crap and moved every part to the 86' wired it as shown. Runs like a top.

[datzenmike]

1 hour ago, powderfinger said:

That's exactly how I wired it using the Z24 coils. Not sure what's going on yet but it definitely won't start. Doesn't help that my timing light is acting up now. 

 

Well if the timing is way off then the spindle is set wrong. Easy fix though.

 

Turn engine to TDC compression on #1 cylinder, lift distributor out and you should see this...

 

 

Note there is a small and large side.

[powderfinger]

Thanks for the replies. It seems I have everything correct. Going to go back out to the shop today and double check everything again.

[bottomwatcher]

Remember there are 2 TDCs. Compression and exhaust. Make sure you are on compression. I may have made that mistake more than once.

Edited March 21, 2022 by bottomwatcher
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[powderfinger]

I got it running. I believe my distributor must have failed at some point during troubleshooting this issue. Caused me to think my timing light was acting up. I swapped the distributor out with another one I had and it fired right up. Power is a little down especially once I am in 3rd gear and higher. I still need to check and make sure the timing is advancing like it should. Also the weber was jetted for a truck with a header, no catalytic converter, and a turbo muffler. This truck has full stock exhaust so I guess it's possible it could be running a little on the rich side. I'll check the plugs and see how they look.

[datzenmike]

Timing is 3 degrees BTDC.

 

Lack of power is another indication that the engine is only running on single plugs. Check both sides are firing. Single plug will act like the timing is retarded and lack power.

[powderfinger]

Timing is at 5deg right now.  I haven't checked to make sure both plugs are firing yet but I'll do that this evening. It looks like I am going to have to rewire the fuel pump. I put a low pressure pump on and it comes on for the initial 5 second prime but never comes back on when the truck is running like it's supposed to. I checked the wiring diagram and the fuel pump relay on the z24i is connected to the computer which gets a signal from the crank angle sensor that let's it know the truck is running and the fuel pump should be on. (At least that's how I interpret it) Since there is no crank angle sensor it doesn't know it's running, maybe I can connect that to the coil just like the tach is connected? Otherwise I can simply wire my own relay in or break the connection back to the computer on the existing fuel pump relay and either ground it or tie it to ignition depending on which it needs, I'll have to check wiring diagram.

[powderfinger]

Intake and exhaust plugs are firing. I took a look at the manual, then cut and grounded the wire going from the fuel pump relay to the computer. That fixed the fuel pump issue, only issue with that is there is no safety mechanism to shut off the fuel pump in case of an accident now. If the truck happened to be laying on it's side not running the pump would spew fuel out the carburetor until the fuel level was below the pickup tube.

 

Power still seems too low compared to what it did in my 2wd. I realize this truck is heavier but I think it's a little more than just the extra weight. I also believe I have a bit of a wiring issue which could be affecting how the truck is running. I noticed when I first start it up the battery light is flickering and the voltage gauge bounces around. After it has been running for a bit the light seems to stop flickering but when I put the truck in reverse the light comes on and I can see the voltage drop from 14V to around 12V on the gauge. What's strange is it doesn't do it when I turn the headlights on, only in reverse.

 

Regardless I am thinking my ground connection at the battery box might need to be redone. That connection looks pretty rusty and I have already had a connection problem with the corroded wire on the ground terminal of the battery that I had to clean up.

[Crashtd420]

11 hours ago, powderfinger said:

Intake and exhaust plugs are firing. I took a look at the manual, then cut and grounded the wire going from the fuel pump relay to the computer. That fixed the fuel pump issue, only issue with that is there is no safety mechanism to shut off the fuel pump in case of an accident now. If the truck happened to be laying on it's side not running the pump would spew fuel out the carburetor until the fuel level was below the pickup tube.

 

 

You could always add an oil pressure switch for the fuel pump...

They make the power connection when the starter is cranking or when the oil pressure is over a certain psi...

The one I'm using is around 7psi where it turns on and off....

 

https://www.ebay.com/itm/Carter-A68301-Oil-Pressure-Safety-Switch-/193947552578?mkcid=16&mkevt=1&_trksid=p2349624.m46890.l6249&mkrid=711-127632-2357-0

[powderfinger]

3 minutes ago, Crashtd420 said:

 

You could always add an oil pressure switch for the fuel pump...

They make the power connection when the starter is cranking or when the oil pressure is over a certain psi...

The one I'm using is around 7psi where it turns on and off....

 

That's a good idea, I'll likely do that, but where did you mount this? It looks like the only place it would thread into is the where the sending unit currently is.

[Crashtd420]

13 minutes ago, powderfinger said:

 

That's a good idea, I'll likely do that, but where did you mount this? It looks like the only place it would thread into is the where the sending unit currently is.

Yes that's where you wanna put it....

Just be careful I'm not sure if the z24 motors are still a bspt thread vs npt.... 

Easiest way is to add a line off the block to a tee then install both sensors...

[datzenmike]

All Nissan are BSPT.  Just use the oil pressure switch. It closes below about 8 PSI. and grounds to the block to turn the warning light on. It's open above this. Use it to open a relay to the pump to shut it off.

 

 

Nissan 720 choke heater relay... has normally open and normally closed contacts. Wire pump through the NC terminals and power through the two coil terminals to the oil pressure switch. When pressure drops below 8 PSI the switch grounds, the coil energies and the NC opens shutting the pump off

[powderfinger]

That's a great idea Mike, I think I'll do that.

[Crashtd420]

32 minutes ago, powderfinger said:

That's a great idea Mike, I think I'll do that.

Just make sure you use a switched ignition source for the power to active the relay or it will stay active... also make sure the power going to the pump is a switched power source... because the default of the relay is to leave the power wire to the pump connected... 

It will work though...

 

I was trying to remember why I didn't do it that way.... 

I basically didnt like that the relay remained active .... I believe I was using battery power to feed the relay though...

So I used the sender I posted then added a relay to turn the dash light off... 

 

[datzenmike]

You can use the power to the pump at the initial start as the supply for the one side of the relay coil instead of running a separate wire.

[Crashtd420]

10 minutes ago, datzenmike said:

You can use the power to the pump at the initial start as the supply for the one side of the relay coil instead of running a separate wire.

I agree he should just be able to use the same pump power wire to trigger the power side of the relay coil...  

I just like to verify things if I'm unsure..

[datzenmike]

LOL after printing that and posting I stopped and went back and drew a picture to be sure. Not the first time I have wired a relay that back feeds the input. Once on it can't be shut off.

[powderfinger]

Well, I drove the truck to work today but it is still underpowered. I think the jetting is pretty close because the plugs look good, although I didn't check every cylinder yet but I don't expect any surprises because I know the motor is solid. The truck also idled into my shop and ran for a second before checking so I guess the jetting could still be off at higher throttle. It's pulling to the left some so maybe it's possible the brakes are dragging some. At only 100hp it wouldn't take much to make an impact I wouldn't think. As it stands the truck will not maintain highway speed around 60mph in 5th. As soon as I hit any sort of hill at all I have to downshift. I did notice when installing new shocks that the inside of the front rotors were thinner than the outside. Sounds like it's time for a better brake/brake line inspection. 

[datzenmike]

You should be able to maintain 60 on the primary barrel and level road. Minor uphills should be do able even in 5th. Fifth is not advised for passing or climbing grades or even into strong head winds. Always use 4th to take the strain off the transmission.

 

Take a wrench with you and go for a drive of at least 15 minutes to self clean the plugs, get the truck into neutral then shut off engine, pull over safely. Check the plugs. They will show what your fuel mixture is for the last while. A light tan/cream is good enough.

 

You mean the caliper pads are worn uneven??? or actually one side of the vented rotor? Either, could be that the calipers are not free to shift sideways on their pins to center themselves as the pads wear down. Often just removing them and taking apart will fix them. I think the pins they slide on have a special coating so don't wire brush them. I think you can lubricate them with brake grease.

 

Pulling to the side could also be the alignment. A slight toe in or out. Adjust the front wheel so it is straight ahead. Look horizontally towards the rear tire and set one of the front tires so it perfectly lines up with the rear using all 4 side walls. Now go to the opposite side and look. If you sight down the front tire side walls and can't even see the rear tire then it's toed in, if you can see the rear tire tread then it's toed out. If you can't see much difference then it's probably ok. My rule of thumb is... if you can see a difference then it probably needs an alignment.

 

Yes, possibly a dragging brake could be causing a pull to one side. Raise each wheel front and back, and spin by hand and if one is dragging  it should be evident. The '83 and up 720s have self adjusting rear brakes.

[powderfinger]

I bought a wideband sensor and gauge mainly because I have been wanting one anyway and figured this was good excuse to get one. I am starting to think the truck is running as it should and maybe I have expectations that were a little too high. The AFR gauge tells me the truck is jetted fine and it accelerates decent on level ground through all gears. It certainly maintains 60mph on flat ground. Only issue is hills but I think I may have been spoiled by the 2wd, I haven't driven an early 80s 4cyl 4x4 in a long time. In addition to that my tires are 235/75/15 which is 1.2" taller than stock and that isn't helping matters.