Datsun l18 engine carburetor adjustment

[Sergio146]

I am doing the adjustments on this carburetor and I just can't get the idle to go down to 750~800rpm. Some facts about the truck: 1980 Datsun 720, 4x4, has had an engine swap at one point i'm assuming (L18), seems complete with factory setup, hitachi carburetor, points ignition. Oh also, valve lash has been done to 0.10 and 0.12 hot settings for intake and exhaust. I have sprayed the base of the carburetor with carb cleaner to see whether there is any change in idle but there is no vacuum leak. Float seems to be level. Timing is ~ 10 degrees before TDC. Does anyone have any ideas as to why I am not able to lower the rpms to the desired settings? Also, off the subject, the dipstic seems to be cut out and just wanted to know if the dipstic is from the wrong engine since it seems like the previous owner intentionally cut out a section of it to make it fit.

[datzenmike]

Make sure that there is a very small amount of slack in the throttle cable so it can close.

 

Check that the secondary barrel is completely closed. May be sticking.

 

 

 

 

The two bottom left hoses looping up to the top left.... pull them off and seal the ends. The top hose is totally wrong and connected into the vacuum advance line to the distributor. The bottom hose connects the BCDD to the EGR, also wrong. I have no idea what this might do to the BCDD so remove and seal

 

The single hose just above the throttle cable going to the intake near the brake booster hose connection... remove and seal the intake end.

 

See if that helps for now.

 

 

 

Have a look on the distributor body for the 10 digit part number. The first 5 are 22100. Need the other 5 digits. This will tell me (and you) if this is an L18 distributor but also what it came from. I see that this is an '80 so it should have an EI (electronic ignition) In this case it should be a matchbox, I can't tell from the pictures. If it is an L18 points distributor then an EI coil is going to draw more power through the points shortening their life. 

 

[Sergio146]

Now that you've mentioned that it may have had a matchbox distributor, does the connection with the white and black wire is where it would go? 

[datzenmike]

The '80 truck had an EI and L20B engine. If L18 was swapped in they may have kept the EI distributor but as you have now posted, it does not. Those points look ok but check the gap.

 

 

Only need one wire to the distributor. Power goes from the ignition switch to the positive terminal of the coil, through the coil and out the negative terminal and to the points which open and close like a switch to ground. If it fires up for 45 min then it's wires correctly.

[banzai510(hainz)]

whats the idle now?

turn the speed screw out all the way so the trottle is slack. then adjust the mixture srew in out till best idle.

 

Maybe idle jet is dirty and somebody increase the speed screw to bypass the idle jet?

 

maybe the wrong oil pan is on and they cut the dipstick?

 

1980 will not have the hot start wireing for the ballast ressistor

maybe you got a 3 ohm coil? does the points burn out quick???????

Point coi lin there or EI coil?

 

Convert that distributor to  Pertronixignition  and 3 ohm coil

 

Love a 720 4x4 with a L motor!!!!!!!!

Edited October 19, 2023 by banzai510(hainz)

[Sergio146]

For an update, this is what the points look like and how the float looks like while it is running, coil is a "Standard Plus" brand

[Sergio146]

Also what i've noticed is that the temperature gauge is a bit high for the truck and oil pressure is low

[DwayneOxford]

I'd get new points. 

[banzai510(hainz)]

Standard PLUS brand dont tell us the ohm reading of that coil.

Really has this motor ran with this coil say for a few months OK? driving fine?

 

To Me points always use a Ballast resisitor(about 1.5ohms) and a higher resisitance coil say 1.5ohms  . My 510 is 1.6+1.6+3.2

During START the ballast is bypassed to give more current to the coil via the points. But this is only to give more current as its cold ect.. then once the key goes to ON current goes thru the ballast then to the coil with a total of 3 ohms 3.2 or close to that.which will be a lower amount and not burn the POINTS up.

 

a 720 that I know of ,Dont have a HOT START by bass wire from the factory. actuall the guy went backwards on this and could have just used the L20 dist and mount if it was still good from the last motor and put it on the L18. Just make sure its timed correct.

 

You can get a HIGHER volt pump from Amazon OUP0023 I think the number is for the Hitachi made one(about $60 and up). Dont get the 30$ ones as they made in China.

also full the pump with oil before install. But do this after you get this running good.

 

put maybe a napa oil filter in and see if oil pressure up. Whn warm it can drop. But the stock ones do seem low when using a gauge.

pertronixballast.bmp matchbox.bmp pertronix 3ohm.bmp

Edited October 20, 2023 by banzai510(hainz)

[banzai510(hainz)]

I only suggested the Pertronix(as if fits inside asingle point distributor)  if the coil is a 3 ohm you just put the pertonix and and hook to Neg and the Postive to the coil and your done as the coil is hooked up already.

Now if the coil is from the 720 which is a low ohm type and made to run on Full voltage it not good for the points and the motor pops and stumbles ect.

 

Or if you have a Matchbox dist and have the 720 coil in there thats a EZ hook up. and go by the link above for the Matchbox to the coil.

 

 

Key is was this running OK before with this set up

 

 

Edited October 20, 2023 by banzai510(hainz)

[Sergio146]

The thing is Hainz that I haven't driven the truck because I am in the process of replacing the cv axles so I have an unknown history behind this truck's condition. For the most part everything from the factory wiring seems original.

[datzenmike]

What is the build date on the driver's door jam??? An '81 would have a Z22 engine with two coils and wiring for it and the 8 plug distributor. An '80 720 at least had an L20B and an L18 would drop right in. An '81 would need  to change the throttle cable, transmission, radiator and more. The brake booster looks like an '80

 

 

See the engine tag over on the passenger inner fender below the hood hinge by the wiper motor? What does it say on it for the engine??

[Sergio146]

This is the engine tag info.

[datzenmike]

That would only be found on an '80 720 chassis.

 

HGY is Nissan for L20B, long bed, 4x4.

 

2,815mm wheel base is a long wheelbase truck. Also used on the king cab but this isn't a king cab

 

Chassis number 374,328 is almost certainly late in May '80. The last one made in May was 374,396

 

 

The 80 hood (though they can easily be swapped) should have louvers cut close to the back above the air filter.

 

What does the build date say on the door jam???

 

 

[Sergio146]

[banzai510(hainz)]

Getting the motor running is a EZ fix. just take your time.

I would get it running first before getting CV in case the motor already bad.