fuel problem

[Robin260z]

Hi guys,

i am having a problem with the fuel part of my car.

I few weeks ago i have driven my gastank too empty and i guess there has become sludge in my fuel lines, fuelpumps and fuelfilter and carbs. I have already cleaned the carbs, en the fuel lines from the filter to both the carbs.

What i have experienced is that when i try to start the car it will start with a small amount of choke. ( thats normal when starting the car when cold ) when i am going to drive and put in the gaspedal the car will stutter and bangs out both the carbs ( the first carb more ) and out of the exhaust back.

this continues all the way untill i loose the pedal and put it half way. the it drives almost smooth.

when i pull the choke to 2/3 open the car drives fine when i hit the gas. when i loose the gas i drowns ( didnt know the exact word ) in gas. when i pull the choke more than 2/3 it also drowns but that is normal because it is running too rich then.

I have already read some topics here and studied several manuals and i think it has to be sludge in all the fuel lines.

What it think i have to do is:

- remove the gastank and drain it.

- remove all the fuel lines from tank to filter

- remove all the fuel lines from carbs back to tank

- Replace all the fuel lines ( when working on it is seems better to me to replace them all)

- clean/ replace the fuel filter

- clean the carbs again.

But what i am thinking of now, and what i have read about is that there are 2 gaspumps.

An electrical and a mechanical. could this also be full with sludge?

And could it also be possible that one of it fails.

I read something that the electrical runs during the start and when driving and the mechanical only while driving. Maybe the mechanical is failing so that the car gets not enough fuel.

But where can i find these pumps?

Please can someone help me and try to eliminate some of my guesses or give me an idea where to look or what i could be?

thank you

robin

[SteveJ]

Robin,

The electrical fuel pump is in back by the tank. The mechanical is in front and mounted on the cylinder head. If the European 260Zs are close enough to the North American 260Z, you should download the 74 factory service manual from XenonS30 and read through the fuel system pages. The fuel filter is near the electric fuel pump, but there also could be a screen filter before the fuel pump, and there should also be screens at the carburetors if I remember correctly.

Anyway, if the filters are working correctly, the fuel pumps should not have sludge.

As for operation, the power to the electric fuel pump is interrupted by a relay when starting the car. I have attached a simplified drawing of the circuit. The mechanical pump is operated by the camshaft.

[240ZGL]

It's not fuel lines or the pump, it's running, on the choke. It's your carbs, probably got some junk in them. Clean the fuel bowls. Would be a good idea to clean the filter in the pump and change the fuel filters.

[Robin260z]

Well guys thank you for your answers.

I got an update.

I dont have a electeic fuel pump. from the tank there are two hoses that go straigjt to hardlines.under the.car.to the feont.

Fuel filter is replaced with a new one and the carbs are clean. when i pull the fuel line off while running the fuel blows out off the line. so the fuelpump is working ok.

What i can think off now is that the ignition isnt working right.

I had a leak at the cap of the radiator and i think water has came in the ignition.

Tomorrow i am going to open up the ignition and clean it. i think the carbs are stuttering because the spark isnt ok

the sounds off the exhaust are regular bangs so that can be evidence off a not right sparking ignition.

[SteveJ]

Are you sure you're getting enough fuel? A mechanical fuel pressure gauge would be helpful here. Since you have to choke the carburetors to get the engine to run when you increase RPMs, that indicates that your mixture is lean. Add to that the fact that your engine loads up at idle with the choke on, and I would guess that you have an issue with fuel flow. If you install a mechanical gauge in the line before the fuel rail, you can see if your fuel pressure drops. A drop in fuel pressure would indicate an inadequate fuel pump or an obstruction in the line.

[Robin260z]

Well there was one fuelline frome the floaterpart to the carb which was leakibg. i have replaced it some i have too check it.again while dricing iff it helsp when i use the choke.

What will be a commen problem with mechanical fuelpump iff it is a problem with the.pump?

[CW240Z]

Robin,

I have had fuel problems with my 240z as well. I had dropped the tank, cleaned and sealed it, replaced the fuel pump, checked the fuel lines on my car, and the carbs, all was good and clean. However, when I start my car it is starved for fuel for about 20 seconds, then fuel comes gushing out. Further research showed I had a cracked and broken fuel outlet line on the top of the tank. Anyways i would suggest checking for sufficient fuel pressure, or just go ahead and get a new fuel pump. Mine "gumped up" from junk in the tank, and a new one only cost about $28.00. I also added a second filter on the car next to the tank, that way I can see if i still have a dirty tank or dirty lines. That's my 2 cents on the topic.

[Bruce Palmer]

Did "cleaning the carbs" include pulling the final filters out of the float bowl lids and cleaning them? They could be partially plugged restricting fuel flow into the float bowls. Running low fuel levels in the float bowls would show up when you pull the chokes on dropping the nozzles farther down where the fuel level is, making things run better.

Hard to diagnose from half way around the world.

[Robin260z]

Well bruce thank you for that. i didnt clean them. i ve just did it and the car is doing better but there is still the problem. ive also rebuild and cleaned the mechanical fuel pump. got a new fuel filter and cleaned the fuel rail.

I havent clean the lines under the car to the tank. maybe here is also some sludge in.

how can i check if it is not the ignition that has changed? I guess i could s

ee this during idling? Idling is ok.

[Robin260z]

well i got an update again.

Today i cleaned both the fuel lines from the thank underneath the car to the front.

I replaced the fuel filter, cleaned the complete fuel rail, cleaned and checked the mechanical fuel pump.

( cant find anything that was or could be broken ) cleaned the filters bruce told about and cleaned the needles and fild the carbs with oil. I did notice that the oil in the carbs have to be fild very often.

the only thing i now can think of is something with the ignition or with the carbs.

Ignition is strange because while idling the runs fine.

While driving the car still stutters en blows ( small blasts ) out of the exhaust ( thats why i think its the ignition )

But it also blows ( small blasts ) out of the airfilters on te carbs.

While driving and using the choke te cars is going to run better but still not normal.

A few months before the car runned very good and fast.

Things that happen between then and now is a drove the fuel tank to far empty and cooling fluid was gushing out of my radiator cap due too filthy stuff inside the cooling system.

I know it is hard too give the answer when you cant see or here it, but it almost give me bad dreams about my car.

Would it be usefull when i make a video?

thanks so far for the help guys

[Bruce Palmer]

Carbs only need to be filled often if you are overfilling them. I drive mine daily and add ATF maybe twice a year. Top of the inner tube only, not up to the threads. Anything above the tube that rises and falls with the piston just gets sucked into the engine and burnt.

s'pose we'll have to go over this a few more times.