eighty_six_720 Posted March 25, 2014 Report Share Posted March 25, 2014 So I've been having what I'm fairly certain is some carburetor woes over the past few months and I was hoping you guys could shed a little light on the situation. It'll start up and idle just fine and even when I rev it up everything sounds fine but when I'm driving its very sluggish and starts popping and backfiring when it hits around 3000 rpm, sounding like It's starved of fuel, however after driving for maybe a half hour or so itll run fine until I stop and then Itll act up again. I took the carb off and installed a rebuild kit and removed a fair amount of silt from the bowl and when I took it for a test drive it ran better than it ever had for a little while but as soon as I stopped at a red light and took off again It was back to its old ways. I've been searching around the internet and havent really found much so any help would be appreciated. thanks. Here's the truck as it sits today Quote Link to comment
datzenmike Posted March 25, 2014 Report Share Posted March 25, 2014 Replace the fuel filter. It should be between the tank and the electric pump which is on the outside of the frame just forward of the pass side rear wheel. Quote Link to comment
eighty_six_720 Posted March 25, 2014 Author Report Share Posted March 25, 2014 I put a brand new filter in after I found all that crap in the bowl but no dice Quote Link to comment
MicroMachinery Posted March 25, 2014 Report Share Posted March 25, 2014 Before I even go back and read anything that you wrote, I must say, if that truck in the pic is yours, that's bad ass. Ok, now that I've gone back and read, do you have an electric choke? If so, is it adjusted correctly? Quote Link to comment
eighty_six_720 Posted March 25, 2014 Author Report Share Posted March 25, 2014 haha yeah its rougher than it looks right now after thrashing it in the desert. I do have the electric choke but I have no idea whether its adjusted correctly. It does tick when the key is turned to on so it works but could that be whats causing all this? Quote Link to comment
MicroMachinery Posted March 25, 2014 Report Share Posted March 25, 2014 If the choke is taking too long to open up, then it will definitely affect the way your truck runs until it has a chance to fully open. I readjust mine when it gets warmer in the spring/summer, then again in the fall/winter when it gets colder. The best way to do it is first thing in the morning(when the engine is cold), go out press the accelerator pedal down once or twice. That will set the choke. Now make the adjustment to where the choke plate just barely closes off the throat of the carb. Tighten the adjustment cover back up and you're set. Quote Link to comment
datzenmike Posted March 25, 2014 Report Share Posted March 25, 2014 The timing is 3 degrees before TDC. The Z24 is very forgiving of too much timing but it will run poorly. With eight spark plugs it's very easy to mix up two wires so check and be sure they are going to the correct plugs. At some point pull both coil wires off and hold near a ground and crank the motor over. They should both spark. If one is not firing, replace the first fuse on the far left of the fuse box. Replace it, don't trust looking at it. The timing is set for both coils working. If one quits it will act severely retarded. Z24s need the head bolts re torqued at least once a year to prevent the head gasket blowing at around 100K miles. Do this in the morning when the motor is dead cold. Do only one bolt at a time. Loosen fully and immediately torque to 60 ft. Lbs. Now do the next one. Do in any order you like but only one at a time. Check and set the valve lash with the motor hot. 0.013" on both intake and exhaust. A tight valve can cause backfiring. Inspect the stainless steel tube running from the back of the exhaust manifold to the EGR valve on the back of the intake manifold behind the carb. Is it full of holes and corroded? It has to be air tight or oxygenated outside air will get into the intake and the mixture will be run lean.. Quote Link to comment
eighty_six_720 Posted March 25, 2014 Author Report Share Posted March 25, 2014 I'll check out the choke tomorrow as well as the EGR which sounds like it could definitely be the problem. I've definitely got some electrical/timing issues but because this seems like its an on/off problem so I'm not sure thats whats causing this piece of the problem. But then again I'm no expert so just tell me if I'm wrong. Thanks for all the responses! Quote Link to comment
datzenmike Posted March 25, 2014 Report Share Posted March 25, 2014 Well there is no EGR when the motor is cold or when idling. As this problem happens when warmed up and revved up.... could be it. Quote Link to comment
eighty_six_720 Posted March 25, 2014 Author Report Share Posted March 25, 2014 it certainly does sound like that EGR could be the issue so thats the first thing I'll check. Though strange part is that it randomly decides that it wants to work it doesnt seem to matter if its hot or cold. And when this problem is happening its a major issue like 40 mph top speed sometimes 30 if I'm going up even a slight grade, So Its not been freeway worthy in a while. I was told by some people it could be the secondary not opening in the carb but those were just guesses. Quote Link to comment
ggzilla Posted March 25, 2014 Report Share Posted March 25, 2014 Sounds like the tank has crud in it and its getting past the filter. What I would do is remove the float bowl cover, let drain and fit yet another filter. Drain the tank, and pour only the clean top layer of gas back in the tank. Quote Link to comment
datzenmike Posted March 25, 2014 Report Share Posted March 25, 2014 Fuel may be ok as it runs fine when cold. This is when the choke is on and fuel is used at a higher rate than when warmed up. The primary jet could still be part plugged (again) and the choke being on could mask this until warmed up. Quote Link to comment
eighty_six_720 Posted March 26, 2014 Author Report Share Posted March 26, 2014 so today I disconnected all the electronics including the choke and took it for a spin and it seemed to run just fine. Any Idea why that would be? or is it just a coincidence? Quote Link to comment
datzenmike Posted March 26, 2014 Report Share Posted March 26, 2014 If the choke heater is disconnected the choke won't shut off fully. This will cause it to run rich. This says the carb is running lean normally when the choke is off. Quote Link to comment
eighty_six_720 Posted March 26, 2014 Author Report Share Posted March 26, 2014 okay so do you think the EGR could be causing it to run lean and with the heater disconnected its running rich which is cancelling it out? because If I'm right about what the EGR is then the piece that it was bolted to was pretty corroded. Quote Link to comment
datzenmike Posted March 26, 2014 Report Share Posted March 26, 2014 It's a process of elimination. You can look at the EGR tube or unplug the hose going to the EGR itself which will disable it. Try it and if it doesn't help that probably isn't it. Quote Link to comment
eighty_six_720 Posted March 26, 2014 Author Report Share Posted March 26, 2014 alright I'll give that a shot in the morning Quote Link to comment
discobandaid01 Posted April 26, 2014 Report Share Posted April 26, 2014 hello everyone, just bought my first 720 4x4 '85..haveing similar issues..reuilt the carb ran better..sitting can rev up sounds great..going down the road is another story..have to easy the throttle..can give it to much or it stutters..today it acted like it ran out of gas..after i walked a mile to get a gas can and gas and out it in ..it ran again ..not a mechanic but am able to work on a car ..i rebuilt the carb no problem..any help would be awesom..oh..checked the oil and the fuel pump..the oil was a little low but didnt think that would couse it to act like it ran out of gas.. Quote Link to comment
datzenmike Posted April 26, 2014 Report Share Posted April 26, 2014 Fuel filter may have done it's job and is plugged. They are cheap so just replace. The filter is between the tank and the pump, which is mounted on the outside of the frame just forward of the right rear tire. You are using gas faster that what can get through the plugged filter. Float set to low and not allowing enough gas in for driving. Next time it stutters, as quick as possible shut the ignition off to kill the electric pump and pull over safely. Look at the small round glass bull's eye on the front of the carb. Fuel level should be at the dot in the middle. If not, and the fuel filter has been checked or replaced, the float will need adjusting. You are using gas faster than it can get into the carb. Quote Link to comment
bryant2482 Posted April 26, 2014 Report Share Posted April 26, 2014 hey Mike, just throwing this out there on re-tourqing the head bolts but isnt it likely that by doing that it will disturb the head or head gasket and make it more prone to blowing it? Quote Link to comment
discobandaid01 Posted April 26, 2014 Report Share Posted April 26, 2014 ok..swaped out the filter..think i adjusted the float ..right? ..but still has a little stutter when giving it more peddle at speed..kinda like im in a higher gear at slow speed and you give it to much gas..any other ideas or maybe tell me which way i need to adjust the float..i couldnt see any gas in the window so maybe i went the wrong way?? Quote Link to comment
datzenmike Posted April 26, 2014 Report Share Posted April 26, 2014 hey Mike, just throwing this out there on re-tourqing the head bolts but isnt it likely that by doing that it will disturb the head or head gasket and make it more prone to blowing it? The gasket compresses over the life of 100k of heat/cool cycles. The aluminum head expands twice as much as the cast iron block so the gasket is also subjected to a shearing action too. Effectively the clamping force lessons as the gasket deteriorates. The re-torque is advised in the Nissan FSM as a prevention to premature gasket failure be keeping the head firmly clamped. It applies to the Z24 motor. Quote Link to comment
discobandaid01 Posted April 27, 2014 Report Share Posted April 27, 2014 dont know how but i messed up the set screw for the fuel line..now it is leaking fuel..cant find a replacement..help?! Quote Link to comment
ggzilla Posted April 27, 2014 Report Share Posted April 27, 2014 Just fit a generic hose clamp. Go to autozone and get a 1/4" fuel line hose clamp. Quote Link to comment
discobandaid01 Posted April 27, 2014 Report Share Posted April 27, 2014 wish that would work but it screws into the seat for the needle above the float Quote Link to comment
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