How to Convert a Nissan 720 (1980- 86) truck to Z24i (fuel injection) from a D21 86.5 - 89 truck.
My old 85 720 4wd (was 2wd) with an 87 z24i swap. 4.88 Nismo gears. 2" Jim Conner Triple shock lift.
When it was a 2wd and a z24.
I bought most parts used from junk yards (some new) and did all the work myself. These steps could be used on any old car or Truck with some work. I used all Nissan Parts for simplicity.
1986 was the last year of the carb. The z24i was introduced in small numbers in 1986. So in theory you can use all 1986 720 parts. I heard only 200 trucks were made with z24is. Production date 4/85 is when z24i was started. I have pictures in a magazine of the reviews of the engine in a 4wd 720. This was before the big debut of the all new D21 in1986.5, the "Hardbody". All D21s made or sold in US are z24i or VG30i TBI (Throttle Body Injected) injected. I really wanted a V6 but did not know how to weld yet. I have met a guy who had put a VG30 in a 1985 720. But used a carb and points and condenser 240z distributor and homemade motor mounts. Pretty cool though. He was in the process of trying to add the Stock Fuel injection and electronic ignition. 1990 the ka24e and vg30e were introduced. E means Multiport EFI.
I used primarily 1987 and 1988 donor parts you could use slightly newer parts.
I was having problems with the stock computer controlled Carb. Weird idle speeds, stalls and sputters after engine warms up etc. I tried a few aftermarket Weber and Solex 2 barrel carbs. The carbs were xlnt for power gain but the adapters were high maintenance. I had a carb fall off once. The throttle return springs were a constant nightmare. I tried every type of spring I could find. But had a lot problems with sticky throttle and high idle not too mention the smog issues. I decided the only legal and reliable way to go was Fuel injection. There is no aftermarket versions available. So I decided pure Nissan parts was the best way. Unfortunately 1986 was the last year of the 720. But I found out the 86 720 was available with the z24i motor just before the D21 (Hardbody) came out. I decided that if Nissan made a Fuel injected 720 I could convert mine. The big problem is there is no 720 z24i parts laying around in junk yards. So I used all D21 (86.5+) parts with the exception of the fuel pump, hoses and throttle cable. I have received a few emails on how I did this so I will try to be more detailed on what I used and how I did it.
This picture is from a stock 720 with z24i. Very rare. (Not mine)
Step 1. collect all the parts. If possible go to a junk yard that lets you get the parts yourself and get most from same vehicle.
Mandatory Parts needed: Assuming the old truck is a 720 80-85 z24 and new is 87-89 z24i. Note the i means fuel injected.
Step 2. Lay used wiring harness on floor and connect all the parts to the appropriate connectors. Just make sure you have all the pieces and they fit.
Step 3. Remove all black tape and cut away all extra wires. This includes 87 fuse box, headlight stuff, heater, park lights etc..YOU DO NOT HAVE TO CUT ANY WIRES THAT GO TO THE COMPUTER. Leave these as long as possible to integrate into the 85 harness if possible.
Step 4. You will need to integrate a few wires into your 85 harness. These wires come from the 87 computer and "tap" into the 85 wires so leave as long as possible. You do not need to buy or extend any wires.
z24 wiring schematic
1988 z24i wiring schematic
1988 ECCS wiring
z24 sparks plugs and z24i Sparks plugs
New z24i VACUUM layout. The carb version is more complicated.
EGR cut solenoid is different between z24i and z24. The ECU controls EVAP and EGR as of z24i. z24 is thermal controlled.
z24i Vacuum layout. z24 is very similar.
Step 5. Re tape harness.
Using black electrical tape rewrap the wires coming from computer. This will make it easier to install through firewall and will protect wires. Just leave the few bare ends for the "integration" to 85.
Step 6. Remove old parts:
Step 7. Install new/used parts:
Step 8. Mount black plastic relay box to inner fender well (drill a hole for big screw) and connect battery. In this 87 relay box you should have a fuel pump relay and I think 1 or 2 ignition relays. blue and orange if I remember. The rest you can remove.
Step 9. There is 2 wires that connect to the trans neutral switch and 4th gear switch. I never got around to connecting these. The neutral one I read is to prevent stalling during deceleration and the 4th gear is for timing adjustment. or something Truck ran xlnt without both.
Step 10. Start the truck check the timing and adjust idle speed if necessary. Check the computer codes for codes. 44 is no errors on 87 engines. 88+ engines are code 55. If the engine does not start check for gas and spark. The engine should still start even if one of the electronics are bad. It will just run poorly. The distributor and computer are the heart of the system the rest just "fine tune" the engine. You should be able to hear the fuel pump "prime" when you turn the key to "on".
Note: If your truck has power steering. You have to modify the 87 EGR control bracket to mount next to 85 power steering (if you have power steering). 87 uses the old L series fuel pump location for the EGR control bracket. 85 is part of the intake. 87 mounts half of the power steering pump to fender and mounts pump were 85 does. The 85 engines uses water to control EGR operation, 87 uses the computer with the new intake temp sensors. The engine now has 2 separate temp sensors one on the 85 side for the Driver in dash and one for the 87 computer.
This was my first fuel injection conversion, I was told it could not be done. The hardest part was cutting a 2 inch hole in the firewall for wiring harness. The computer is too big to fit under the seat of a 720 truck. So I installed it in my custom 5 foot long center console. Overall It was quite easy to do. I want to put an Infiniti V8 in a Truck next complete with all the electronics.
If anyone wants to do this, please Email me with any questions.
Done in 1995. Just before I started my first website that same year. I wish I had taken pictures..