I jumped into the 720 world about 4 months ago with a 1 owner 1985 720 4x4. She's got 114k miles and the original owner had everyoption nissan had at the time on the truck which all still work. I love the truck but she has some quirks. . .

The main one is that the truck won't idle when I start up from cold. I usually pump the gas twice before trying to start (as was recommended to me) and then as I engage the starter I give it some gas and hold RPMs around 1500-2000 for a minute or so. If I take my foot off the gas at all the truck simply dies. After temp comes up the truck will idle and I have the idle set screw giving me around 800-900 rpms. So my first question is how do I get my truck to cold idle? I assume I need to adjust something on the choke???

Now once I'm at temp the truck runs pretty good unless she sits for around 3-4 minutes. After that the RPMs change and drop to around 500. It clearly sounds worse like its starved a little bit. The truck stays at 500 until I take off again and them the cycle repeats, doesn't matter how long I've been driving. What could be causing this and is there anything I can adjust? Do I need a new carburetor?

Any advice is greatly appreciated. I'm no mechanic but I have the tools and with a good tutorial I'll dive into anything, I'll just need a "paint by numbers" kinda explanation if you're so willing. Thanks!

for the idle - have you messed around with the idle screw on the carburetor?

as for your running problem, try draining/dropping the tank and get it hot dipped at a radiator shop. mine was having similar problems randomly and we traced it to rust in the fuel tank.

semi-fly wrote:for the idle - have you messed around with the idle screw on the carburetor?

as for your running problem, try draining/dropping the tank and get it hot dipped at a radiator shop. mine was having similar problems randomly and we traced it to rust in the fuel tank.

I already dialed in the idle screw to around 800-900 rpms once the truck is warmed up but it won't hang there when it starts up cold and it still drops to 500 rpms once the truck sits for around 3 minutes.

Can you explain why dipping the tank would fix the rpm drop? I already replaced the fuel filter. Could it be a fuel pump issue?

bylzebub wrote:
Can you explain why dipping the tank would fix the rpm drop? I already replaced the fuel filter. Could it be a fuel pump issue?

there may be rust in your fuel tank, causing the pickup to clog. you COULD buy a new tank, but getting it dipped is wayyy cheaper

Can anyone give me some choke adjustment tips? I'd like to play with that first I think.

fine, ignore the advice from the person that was having THE EXACT SAME PROBLEM.

semi-fly wrote:fine, ignore the advice from the person that was having THE EXACT SAME PROBLEM.

Dude... Chill much???

Where do you get the impression I'm ignoring you? I read your advice and I'll look at the tank. If I'm having a rust issue though I'd think it would either shut down the truck completely or randomly choke out, neither of which are happening.

Instead it only drops RPMS exactly 3 minutes into idle which sounds like a carb stage problem so I was ALSO looking for some carb adjustment advice.

You seriously must be the most insecure person on the Internet.

I have the same truck same problem. it is a vacuum problem in the tank lines that involves the breather line that runs to the charcoal canister up front and vents the tank. take the gas cap off or half off and drive see if that don't fix it also TEMPORALY hook up a fuel can in back bed to the fuel pump to check it also

also the choke has a relay on the passenger side of the cab under the dash above the speaker. the bigger relay there with it is the fuel delivery relay. if you go to ROCKAUTO.COM for parts it will list a choke relay it is 17.00 there is a so called UNIVERSAL relay that is the same for 4.00 check the pics look at the pins. there are 2 more above the fusebox and 1 more up by the battery total of 5 I changed them all thru rockauto.com otherwise they cost a lot at the parts store. if you could obtain a FACTORY SERVICE MANUAL that would be great for you . I was lucky the guy I bought mine from gave me 1 with the truck and boy have I needed it!!

well I ran the outboard gas tank on my 84 Nissan 720 pick up and she ran fine, so the problem is at the tank. drop her down see whats going on