# spark plugs keep fouling!!



## skeen (Mar 25, 2007)

I have a 86 nissan with a z24i 4cly engine. the plugs keep fouling and I can't figure out why. can anyone give me some advice?
thanks,
Scott


----------



## bkea (Feb 4, 2005)

I'd say you have oil leaking by the rings or down the valve stems, or your injectors are way too rich. How does the truck run? Any smoke from the tail pipe? 

What plugs are you using? I only use NGK.


----------



## skeen (Mar 25, 2007)

I don't think oil is leaking by the rings I think it is just burning rich. the truck runs really good till the plugs foul. some times there is black smoke from the tail pipe and some times there isn't any smoke at all. I have been using autolite plugs. could somthing just be wrong with the carburetor?


----------



## dvdswanson (Nov 6, 2005)

check for codes on the ECU.


----------



## skeen (Mar 25, 2007)

it doesn't have a ecu. do you have any other suggestions?


----------



## dvdswanson (Nov 6, 2005)

are you sure, could have sworn my 86 720 had one. do you have a TPS, IAC or temp sensor?


----------



## skeen (Mar 25, 2007)

well I took a 86 engine and put it in a 84 truck and the 84 didn't have one. and some one told me that if I used the peripherals from the 84 I didn't need a ecu. there is a temp sensor. do you think some thing is wrong with the carb? I really need some help I have spent allot of money on plugs!!


----------



## golfer (Aug 21, 2006)

Maybe the Autolite plugs are too cold ... try NKG.


----------



## bkea (Feb 4, 2005)

OK You said you have an 86 with a Z-24i engine. That would be a D-21 with fuel injection. Do you in fact have a 720 with a carb? If so, that is probably the problem. They seem to go bad quite frequently. Most folks go with the weber replacement, which isn't without problems either.

And put it some NGK plugs.


----------



## skeen (Mar 25, 2007)

no it is not fuel injection they didn't start fuel injection till 86 1/2. yes it has a carb. and what goes bad quite frequently?


----------



## bkea (Feb 4, 2005)

The carbs are somewhat electrically controlled I think. I'm not sure what wears out, they just seem to go bad after a while. I don't think they can be rebuilt like the good old days. If you can find a new one it will be expensive. 

BTW, I've been told there were a few of the 720 trucks made with FI before Nissan went to the HB.


----------



## skeen (Mar 25, 2007)

the only thing electronically controlled is the anti-dieseling solenoid. I don't think it is the original carburetor and I have already rebuilt it. is there anything ells I can check before I buy a new carb?


----------



## dvdswanson (Nov 6, 2005)

are all 8 plugs fouling or is it just intake or exhaust?


----------



## skeen (Mar 25, 2007)

um... yeah I'm pretty sure it is all 8.


----------



## dvdswanson (Nov 6, 2005)

check your voltages to the coils to make sure they are putting out the right voltage, and like golfer said switch to NGKs, Nissan's dont like any other plugs to well. check the plug wires to make sure they are not breaking down as well.


----------



## skeen (Mar 25, 2007)

I just go new plug wires. why are NGK's so much better?


----------



## 88pathoffroad (Jun 6, 2004)

Is this on the same engine that you can't get the timing set on? 

I'd work on getting the timing right before asking myself why the plugs are fouling.


----------



## skeen (Mar 25, 2007)

yes it is the same engine.


----------



## Nitobare (10 mo ago)

Hello. This temporary solution helped me lots till I could tear down the engine and rebuild for a more permanent solution.


----------

