I just finished rebuilding the carbs on a 280zx motor, did full tune up, did not remove the distributor, replaced all fluids. Now after I've rebuilt the carbs, the car will not start, it just cranks and sometimes backfires. I found that the distributor has some connectivity issues, but that's another problem. The car still won't start, I've already remedied the distributor so I know I have SPARK, so it should leave just the air/fuel problem. Any info to help me out? This is the HITACHI SU carbs by the way.....

so was the car running on carbs beforehand? and the hitachi carbs are the roundtops? 3 or 4 screw? mechanical fuel pump or electric? if electric is it the stock 280Zx unit (these are triggered by the MAF which would have been removed with the stock injection system)? did you adjust the float levels when you "rebuilt" the carbs? did you back the jets out a coupla turns? what weight oil did you use in the carbs? so the carb pistons move freely by hand?did you change plug wires or remove them at all? the dsit on an L6 spins counterclockwise so the plug wires attach counterclockwise from #1, sis you try starting with a shot of starting fluid to verify the problem is fuel and not spark?

get me some answers and we'll get you going

Sorry, I forgot to tell you the story before the problem.

My friend recently bought this 240z w/ a 280zx motor....i think. I believe he said it was the L28 motor, whatever that means. The car ran, the previous owner thought it was a clutch problem. I diagnosed it, clutch was fine. What was happening was the car would surge between 2000-3000 rpm, above 3000rpm it was great. So I was thinking carbs, he says the car has been sitting.

I'm not too familiar w/ the 240z, my first time rebuilding carbs too. When I rebuilt the carbs (yes, the round ones - 4 screws on the adjustment sticker on the intake box), the rebuild kit only came w/ new "jets and springs" and the clip for the fuel cylinder, and gaskets, and the fuel hose going into the butterfly. I checked everything over while the carbs are in the car, everything seems fine, there was even fuel in the fuel cyliners and the floaters weren't sticking. I found out that there was a problem w/ the distributor.

The distributor had a vacuum hose to it, I thought that to be unusual, but I found a vent on the left side carburetor that the hose fits into. The problem was that the distributor has a wire to the top of the cap, it was loose, i fixed it.

Now I think the the problem is going from the fuel cylinder into the butterfly. I dont know what you mean by mechanical fuel pump, but it sure looks like its run from the motor. Does a mechanical fuel pump work after the fuel filter?

One of the carbs weren't moving freely, it kinda stuck downward. Should I pull it and bore the sides a bit to make it smoother?

I did replace the distributor cap and rotor and all the wires along with it. I called a shop to learn that these distributors are counter-clockwise and that the firing order is 153624, correct me if i'm wrong.

When I tried shooting some starter fluid into the carbs, I got it to kinda burp a little bit. Mostly backfiring though, some from the muffler itself...

Thanks for any help you can give me.

ok, which distributor is on the car? stock 240 (points (one wire hookup from the bottom)) ealry 280 (electronic (has a 2 wire hookup)) 280ZX (also electronic(has a little plastic module on the side of the dist that 2 wires hook to))

as fro the carb stuff, the "4 screw" refers to the number of screws holding the large cylinder thing with the black thumbscrew coming out the top, the top of this cylinder is either flat and kinda blocky at the edges (flat top) or it's kinda domes with the top rounding smoothley into the sides (round top), the black thumbscrew has a bit of a dipstick to allow you to check the oil level in the carb piston, if the piston sticks you need to replace the opil with a thinner weight, (ATF is a popular choice but I have heard of anything from heavy weight oil to wd40) careful nto to add too much it only holds a little

the little things to the sides that the fuel lined lead into the top of are your fuel bowls, they have a needle valve in the top where the fuel enters and the float can rise as it fills and stop the flow of incoming fuel, if the valves stick open fuel will come out the vent tube which leads into the back of the orange plate that blts to the carbs and holds the air filter, they have a fuel line coming out the bottom that flows fuel to the jet in the bottom of the carb, you can screw these jets up or down to allow for more or less fuel flow

the mechanical fuel pump means that is is driven "Mechanically" off the motor in this case a cam escentric that bolts to the front of the cam, L28's did not come with this cam escentric as ther were injected and had electronic fuel pumps, it would have to have been added of it would't pump gas at all (check the head casting on the passanger side of the head between the 1st and second flug wires it'll read E31,E88, N42, N47, P79, P90

the vacume line from the dist should be hooked to a timed vacume, should be a nipple just behind the front carb, if it's got all vacume all the time you have full timing advance all the time, this could casue your first problem of stumbling at low rpm

and if it's not firing up on the starting fluid either the enging has no compression, the carbs and stuck shut or you have a spark problem, you got the firing order right are you sure you got #1 in the right position?

Why would the engine loose compression? Due to the carbs sticking? The rear (4,5,6) carb is the one that's sticking. The front carb is the one that is bleeding off the fuel from the vent tube. What should I do about that?

I was told that since the 456 carb is sticking, that may be the cause of my no-start.....

The distributor only has 1 wire, and I've recrimped that so its not a problem anymore.

Ohh, and the head is an e88.

ok, the E88 is a low compression L24 head, also smaller valves than the N42 and newer heads, what code is stamped on the block?should be on the drivers side just to the front of the engine mount, should read E30, N47or F54, you have a L28 head lets see which block you have

the carb sticking would not cause a loss of compression, I am simply saying if the spark works and it won't fire it's either a timing issue, a compression issue or a fuel issue, kinda hard to diagnose from 1000 miles away but I have to know what you've got and whats changed to help figure it out

now then one wire from your dist should be going to the negetive side of the coil and you should have a Start/Run hot on the positive side, I don't remember which trigger the early dist used at the moment but it's not important

if the front carb is bleeding fuel off the vent tube the needle valve is stuck on the open postiion, you need to open the fuel bowl and replace if need be mbut most likely just needs adjusting, and if it's bleeding off fuel then I am gonna assume your fuel pump is working fine

did you back the jet off on the front carb? did you shange the oil in the rear carb to a ligher weight?

I dont see how I messed up the timing, the car was running great before I did the tune up besides the stumbling. The needle valve in the fuel chamber, how do I adjust that? Do I just back it off? Or should I adjust the nut that goes into the fuel line on top of the fuel chamber?

I didn't put any oil in the top of the carbs, not sure if I should as I might need to disassemble the entire thing again.....

If I put oil in the rear carb, would that allow the plunger to slide more? I doubt it will, feels like the whole thing is really seized.

I know there's spark because I arced the plugs to the body, I dont think I'll have to troubleshoot the distributor anymore. The vacuum line for the distributor, would it matter if the line doesn't secure into the vent/nipple properly?

PS - as far as I know, the motor (block) is out of the 280zx, the L28, not the L24.
Modified by RatedR at 8:40 PM 2/13/2006

the cylinder head you have is from an L24, if you tell me the casting number on the block I can tell you for sure if you have an L24 or an L28

the oil in the carbs goes into the thumbscrew on the top of the dome on each carb, it only holds a tablespoon or so and it is intended to dampen the action of the pistons rising to engine vacume, ATF is the most commmon replacement oil used for this, and if your piston is sticking with no oil in it you have a real problem and the carb is gonna need to be taken apart and find out why it's binding

as fro adjusting the float level you'll need to remove the 4 screws holding the top on the fuel bowls, it will lift right off after the gasket seal is broken (these gaskets tend to be reusable, once you lift off the float/lid assy, you'll see the needel valve in the incoming fuel line resting on a little metal finger goming off the float, you'll need to adjust this so thatwhen the float drops the valve opens adn when it rises it closes, right now it's not closing which is why fuel is coming out of your vent line

while you have the float bowl open, pull the fuel line from the jet on the bottom of the carburator and make sure all the fuel in the bowl flows right out the bottom, if the fuel doesn't run out with the line off the jet then you have a clogged fuel bowl (pretty common) you can cleat it with a small pic the hole is right in the bottom of the fuel bowl

the thing that concers me is that the car was running before you "fixed" it this is pretty common it's just a matter of tracking down a silly mistake (god knows I've made enough of them) ti stands to reason that if it's not running now it's because you messed something up, you said the car would only sputter on starting fluid which woud suggest the timing is way off or not in the correct order or a lack of spark, the fuel coming out of the vent line is dangerous and could cause a rather nasty engine fire

So for the jets, I'd just have to turn it counter clockwise until it stops fuel when the float is up right? I dont know why the piston on the carb is sticking, when I had everything pulled apart, the plunger would just stick when I slide it on its own in the roundtop. I think the thing may be warped or something.....

it the piston is bone dry I could see it sticking and jamming, just add a bit of light weight oil and see if it improves

as for the jets, you screw them clockwise all the way up with the piston down and then back them off about 2 full turns, this will be a good starting point, you can treak and tune them with a unisync after you get it running again, you can't make them stop the fuel flow with the piston all the way up unless you managed to get the needle put into the pistons upside down which I don't think is possible but then I havn't tried

The piston isnt jamming because its bone dry, I've tried adding a bit of ATF to get some lube going, still sticks. The carb w/ the fuel spewing out is the carb that IS NOT STICKING, this carb seems to be fine when I compared it w/ some rebuilding tips for carbs. The only one that sticks is the one w/ no fuel coming out of the relief valve.

I'll try backing them off 2 turns, but wont the gasket for the needle not seal?

the needle should seal around the needle should keep the fuel out when not running and if the seal is damaged or gona it'll only loose a bit of gas as the fuel bowls just don't hold very much

as for your sticking piston, I am gonna suggest you pull it apart and find out why it's sticking, it's only 4 screws adn pull the top off revealing the spring and piston, pull out the pistong and remove the needle and put it back together just to see if it moves more easily, you could have damaged your needle causing it to bind, if thats it just grab a new needle, if the seal is slipped over and dragging fix it etc.

Okay, I've solved the spark problem, now the car won't get fuel. My friend just decided to buy new carbs off ebay, so I'm presuming that they're still set as far as the adjustment screws on the bottom of the carbs. Now I just can't get fuel into the carbs. I replaced the fuel pump w/ a new unit, but is there a special way to install the fuel pump on these motors? Its mechanical, so I presume that there's a special stabbing proceedure. When I have the pump out and I manually pump the fuel, it works. Just not when its installed in the motor.

the fuel pump lever needs to be angled up as you insert the pump, if you pull the valve cover you can see the pump arm resting on top of the pump escentric assuming of course that it has the cared car pump escentric on the end of the cam, is there fuel coming out of the ful pump when you crank the motor? easy enough to test just take the line that feeds the carbs and run it into a cup and crank the engine, if you have no fuel then you have a bad pump, clogged pickup ir some other problem

you said you solved the spark problem, what was it?

Good thread!

The car won't spew fuel w/ the pump attached to the motor, but when I manually pump it, it works. This tells me that I have it installed wrong. I did install it w/ the arm upwards, but I'll check again.

I found a bad ignition coil for the spark problem, but now the spark is only consistent before the distributor. Sometimes there's spark w/ the #1 spark plug wire, sometimes there isn't. I think the distributor is going out....

if the spark is intermitant which dist are you running? if it's the 240Z type could use new points? or if it's the 280ZX it could need a new module, you might want to check the wiring sonnectors as well

back to your pump, pull off the valve cover, it's only 8 10 mm bolts won't take but a few mins, you can see is the pump arm is engaging the cam excentric or not, I am condcerned that someone removed the cam escentric from the E88 head, you said it was pulled from a 280, which would have been injected, and had no need for the pump escentric, someone could have removed the excentric as it wasn't needed in their application, and now you need it, it's only one bolt to pull the escentric and you can pull it from the sylinder head of the engine you removed

I didn't remove a motor or a cylinder head. I did however fix the spark problem. The car ran fine for a while, but now the car wont start because there is no fuel coming into the carbs. But when I pull off the pump and manual prime it again, the car runs and starts fine. I'm not sure about the cam eccentric that should be engaging the fuel pump. I'll try and look that up, but the only thing I know that could be wrong is that I pulled out the fuel pump w/ the tank almost full even tho the manual says not to......I think there may be air in the line, not sure how to get it out

just pop the valve cover off and you can see the pump arm and it's position on the pump escentric, sounds like your getting the arm under the escentric instead of on top (actually it rides to the side as I recall)