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rbbertsch

Fuel Delivery Problem 1972 240Z

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My nice running '72 with 115k would not start one morning. Fuel was not getting to the carbs (SU-type) and the there was no fuel in the filter. Replaced the fuel pump without effect. Checked the fuel line and it was clear and unplugged. The engine starts with "starter fluid" but is not drawing fuel from the tank. I tried priming the system by adding fuel above the filter. This fuel drained OK to the tank. Carbs are "dry."

My service manuals do not have a next step. Any ideas to try next? Thank you, RB

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if you're SURE the lines aren't clogged and the pump is operable, then it's the tank/tank outlet to the hard lines. there really isn't much else to the system: tank, tank lines, filter, mechanical pump, fuel rail,carbs. could be crud in the tank clogging the outlet

OR did you run out of gas? :)

Edited by 7277

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Ditto on what 7277 said with an underscore on the word "sure". I speak from experience when I suggest that the gauge reading may not be the best information available related to how much fuel you have. How much gas is in the tank? Also, it's not uncommon to have a clog at the tank, and sometimes the fuel pick-up in the tank will rust through allowing the system to draw air instead of fuel if the level is 'low'.

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Fuel is OK. Line from the outside of the tank to the fuel strainer/filter is OK. Looks like the problem is with in the tank. Appreciate the comments about the fuel pickup. The reason the lines are clear is that I added fuel at the filter and and through "gravity flow" the fuel could be heard entering the tank. Looks like the next project will be to remove the tank and inspect/repair.

Can I assume that if fuel is pumped from the tank to the SU carbs, that carbs will pre-fill to the correct level to function?

Thanks for the comments and ideas. RB

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RB,

Adding fuel at the level of the filter does not answer the question as to whether your fuel rail between pump and carbs is clear, at least that's how I read your reply. Not too common for those to get clogged, but it's possible. When you say your carbs are "dry" does that mean you checked the float bowls and there is no fuel?

I've not heard of the fuel pump lobe on the cam going bad, but if everything else doesn't fix it, then.....

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to help on the basics of troubleshooting....

use a 1gal metal (metal-for safe grounding) tank (Auto-zone, or whatever you choose to fill your lawnmower) and place it (filled) besdie the car with a length of fuel hose going into it. crank the engine to prime the system.

pull off the hose to each carb at the float bowl and see if they're peeing fuel...connect them back on and try to start the car. if that works, the problem is in your tank.

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RB "replaced the fuel pump"

I suggest removing the valve cover, spin the engine over a revolution or two and see how far, if any, the fuel pump arm is moving. If the arm is not making proper contact with the eccentric, it won't pump fuel.

Bonzi Lon

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Just be aware that the pickup line in the tank does not have a screen over it and small bits of debris can block fuel from passing.

Tom

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7277: You were "spot on". The car started with a fuel line direct from the fuel can to the pump. Next step will be to try to clear the line that enters the tank. I suspect that is the cause and hope it can be cleared without dropping the tank. Again, thank you! RB

P.S. Thanks to the other for ideas...RB

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Consider this one closed. I clean the line into the tank with 60# monofiliment fishing line, added fuel and started the car. Up and running again....RB

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However, you have a good bit of crud in that tank. Better look after it or a similar problem will return.

The 2 Liter I had 30 years ago had so much junk in the tank it would starve the engine. The vacum would hold the rust scale against the pick up opening on the tube inside the tank. Fuel would flow again after pulling off the fuel line thus breaking the vacum and allowing the rust scale to fall off the inlet. This only happened under full throttle.

Solution was a full steam cleaning of the tank.

Good luck.

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7277: You were "spot on". The car started with a fuel line direct from the fuel can to the pump. Next step will be to try to clear the line that enters the tank. I suspect that is the cause and hope it can be cleared without dropping the tank. Again, thank you! RB

P.S. Thanks to the other for ideas...RB

you're welcome :) glad it worked out for you

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I had the same problem in my '72 a while back. Thought you might be able to glean something from my story. My clog was self inflicted as I'd dropped a piece of duct tape in the tank and hadn't bothered fishing it out. The adhesive disolved and the individual fibers sloshed around forming little balls of fuzz that would occasionally plug my fuel line.

I, of course, didn't know this at first and wondered what was causing my car to suddenly die at random intervals. I tried the same stuff, new fuel filter, swapped fuel pumps, etc... I finally narrowed it down to either an obstruction at the tank end, or in the hard line between tank and fuel filter.

I tried blowing compressed air through the hard line from the back to the front, and that solved the problem for a few days, but eventually another little piece of fuzz clogged it up again. If it stopped running, then all I had to do was pull off to the side of the road, unscrew the hose from the intake side of the filter, blow on it to clear the obstruction then reattach it. Needless to say it wasn't the best solution.

Finally I got the car up in the air to take care of the problem once and for all. I had already had the tank out in the past, so I knew it wasn't rusty inside. I took off the gas cap (to relieve pressure) and blew compressed air through the hard line from the front then drained the tank. I replaced the drain plug and filled the tank up with the same gas, but this time I strained it through a rag. This only got some of the fuzz so I did it a second time. I made sure to blow some more air through the line to swirl and mix the gas throuroughly. When I drained and filled the second time I got even more fuzz, and two big fuzzballs which stayed behind in my plastic gas can and had to be fished out with a coat hanger.

Expensive lesson to learn, don't let stuff fall in your tank, and if you do then fish it out immediately.

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