Electric fuel pump on 72Z w/carb problems

[Rick Bolus]

Hi Guys, we have a weird problem here, we have a 72 240z in that has a lot of old school modifications, Racer Brown cam, stock exhaust manifold, huge exhaust pipe and Corvair muffler, dual stock appearing su's. Timing and distributor seem ok. We have just finished the full body resto, and are sorting out the mechanicals and have run into this. Car sat for years..34k right original one owner miles, but hes dead. Car had a AC brand electric fuel pump mounted by the gas tank, it was hooked up to a switch on console, stock manual fuel pump on block. We took it off when we replaced the fuel filler tube and changed the gas tank which was kinda rusty on the small metal lines. We have cleaned the carbs, ran corect weight trans fluid and mystery oil mix in them. We did by-pass the non stock AC electric fuel pump, which I have never seen as necessary on SU carb 240z's. Anyway, no matter what we do the car seems to run out of power, and everytime we open the float bowls or max out the float (bend the tab) adjustments, we see little gas in the float bowls. We changed the jet that lets gas into the bowls mounted on the bowl tops, cleaned the screens by the intake lines, replaced fuel filter, blew air back to tank, we even changed the manual pump with another. Today, we changed the carbs to another set of su;s. Still no luck, it seems to run out of gas when you jump on the cars throttle, by time its in second gear its the dreaded "dying" sound. Has anyone run ito this before? I just don't see why this car should have had a manual pump on it, but all signs say it needs more fuel pressure. Any thoughts?

[Ed]

My first guess would be a clogged line somewhere restricting the fuel flow. Have you checked the fuel rail that goes around the valve cover? Try running a fuel line from the fuel rail into a gas can. Then turn it over and see if your getting good fuel pressure to the bowls (4 psi). Another test is to put a gas can by the fuel pump and run a hose to the mechanical pump. Turn it over and see how it runs then.

[Curtis240Z]

You are definitely running out of gas due to clogged lines, tank or pump. Do a pump capacity test to verify. Put one of those glass replaceable filters coming out of the gas tank and you will see it clog up real fast. Plus you can clean it out on the spot!

[Rick Bolus]

Heres what I did, I took a used electric fuel pump and oe mount from a 73z we had in stock and on the shelf forever. Cleaned it and checked that it worked, I installed it in the engine compartment just before the manual pump, this has a factory bowl type filter on it too from Datsun. I hooked it up to the ignition side with the direct kill on/off switch which the car had in it by the PO. Car ran fine and no dead response. I don't see why it needed to be up under the tank as Datsun did years ago on the 73's, but it cured the problem. Had to readjust the rear float one more time so it wouldn't flow out and drip on the manifold! I kept the manual pump and hi-po filter before that one for insurance, problem now is when I hit second gear it doesn't engage seems to hang up and spin the clutch too long, but the clutch is new. Have to work on it and see. Thanks for the advise, Rick

[matria]

Please make sure that you install some sort of automatic shut off to the electric fuel pump, just incase of an accident. Having it wired through your ignition may not be the best way. I would hate to hear of a Z inferno.

My .02

Skip

[Dtsnlvrs]

Check the dimensions on the fuel pump eccentric. Make sure that it is driving the mechanical pump to its full throw. Also make sure that there is absolutly no blockage between the mechanical pump and the carbs. And please place the elec pump back at the tank...they are designed to push gas not pull it...the mechanical pump is for pulling.

[beandip]

For one thing the AC pump is a good pump if you can stand the noise. The stock electric and the one from the early '80s RX- 7 are turbine pumps and are pusher pumps and work the best near the tank and they are quiet. Always install a inline filter before the pump, they run at high speed and crud really messes them up. There is stock wireing on the '72 for a electric pump . you will find it wound up and taped with blue tape , just follow the sending unit wire up the side of the tank. I would remove the screens from the entake of the carbs and leave them out. I am running a electric only on my Z and have no problem. On another note try 20w in the carbs the 5w of the atf is too thin and can cause a lean condition off the line. Just for a split secound. By the way you should be able to find a RX-7 pump at the bone yard for about $15.00. I have tried this pump on a tripple set up and no problem , they put out right at 4psi. If you do the RX pump be sure it is from a carbed car not injected! my2c Gary

[Rick Bolus]

Thanks Guys, I looked for an RX7 pump but had no luck used. It had good flow from the lines, i had cleaned them months ago, but you could see the clear filter empty when it would die out. I am going to relocate the pump back by the tank, not due to noise from it though, just to keep it in the "original" location and as a "pusher". I have to work on an appropriate "kill" safety besides the key and switch on console. Any explanation why this car needed it is up for discussion now that it runs the way it should so any future post readers can learn from this frustrating headache.

[beandip]

One thing to consider is a pressure switch ahead of the oil pressure sensor that will activate the fuel pump above about 7 psi. this way the pump will always shut off if the engine does or looses pressure. With carbs it will start on the fuel in the float chambers. a remote kill switch can also be wired in as a security measure as well. Gary

[=Enigma=]

Is there a stock shut off mechanism built in from the factory on cars with an E.P.?

[Curtis240Z]

When the rpm gets above 400 rpm the electric fuel pump comes on. Similiarly when you get in an accident and the engine stalls the electric fuel pump shuts off.

[=Enigma=]

When the rpm gets above 400 rpm the electric fuel pump comes on. Similiarly when you get in an accident and the engine stalls the electric fuel pump shuts off.

Any idea if this is true for a 73' or if the 73' even came stock with an E.P.?