dan121

all right i need some help just bought a 77 datsun 280z 2.8l 4 speed manual, car was missing and wouldnt stay on, i tought it was fuel pump so replaced it when i replaced it though i noticed new wires going to it, realised it had switch to the pump,k so i flipped switch, car starts but still missing, replaced wires, spark plugs rotor , cap and fuel filter,.seems not to misfire now but now it will run for a couple minutes then shut off, i have done what i can maybe main relay, i noticed if i leave the pump switch on it goes to 40psi if i leave the switch on it will die if i sit there and flip the switch on and off so the psi doesnt go over 20 the car will stay on.....so my main question is is the function of the relay to switch the pump on and off? or is there another reason the car wont take that much psi?

dan121

ok i took the car out for a spin wont really drive its like bearly accelerating...with fuel pump switch on or off so maybe the airflowmeter? come any suggestions?

NismoPick

Welcome to ZDriver!

I saw your post the other day, but couldn't make much sense of it.

So there is a switch for the fuel pump? And if you leave it switched on, it will stutter, and if you switch it off, it will die?

I suggest downloading the FSM (Factory Service Manual) from www.xenons30.com/reference to get the wiring & relays all tested. Also check all sensors & connections. Check timing, spark, etc...

dan121

thanks for responding ok the car has a manual switch to the fuel pump, if i sit there and play with the switch as in switch it on and off the car will stay on if i leave the switch on it will bog and if i leave it off it will eventually die so has to be low pressure fuel for it to stay on...but in gear, driving car has no power at all will barely get to 35 or 40...one question is does the pump having a manual switch affect it?or should it be ok? do i have to fix the relay for the car to work normally?as in does the fuel injection work electrically with the pump?and is it the main relay underneath the steering wheel?i have done fuel pump spark plugs ,wires, cap and rotor spark is good from coil air flow meter seems to move when accelerated put new fuel in it...have the manual but im a little slow with diagrams hahaha

JSM

Being that you just got the car I would drop and clean the tank unless you know it was done prior. My 78 that I got was sitting for quite ahwile. I got similar readings and running conidtion as yours. I dropped the tank and the rust and gunk were unbelieveable.

dan121

ok i replaced the main relay and hooked up the fuel pump to original it started right up and after a good couple revs it slowly starts to backfire and bog down, i notice when it starts to bog down the air flow meter does not move from the idle position so maybe its the air flow meter thats bad? or does the temp sensor affect it?

dan121

ok another short one got the car had the fuel pump rigged or relay bipassed and car didnt run for shiz unless i played with the switch as in on and off, i figured relay was bad so i replaced it and hooked up the fuel pump to its original manner now the car started and accelerated great but a couple revs into it it started slowly bogging and backfiring, and it will only idle, if i try and accelerate it the airflow meter doesnt move with the throttle my guess its the airflow thats bad, and fuel pump is new with filter, is there any way i can check the air flow meter with out buyng a new one any tests ? since the cheapest one i see is 300?

NismoPick

Yep... stick your finger in there & see if it moves.

Also, click: https://www.zdriver.com/forums/240z-280zxt-s30-s130-tech-tips-275/js-how-rebuild-your-afm-15277/

dan121

replaced afm, fuel pump theres spark just wont run smooth and cuts out after a while what else dropped the old fuel any sensors maybe temp sensor

dan121

ok i have been tryng to get the temp sensor but the ones at my local shops are differnt then the one i have they are smaller, same connector but thread is smaller any idea on were i can get one or if im ordering wrong its by the thermo housing in front of engine 2 prong?

theramz

Back firing is caused by unburned fuel in the exhaust. One cause can be the cold start valve or injectors being stuck open. An easy way to test them is with a 9volt battery and jumpers to each one with engine off. You should hear an audible click. Spark plug wires crossed, check firing order. Check your throttle position sensor, there are 3 positions, idle, off idle and wide open throttle. Check the afm per the fsm. When you switch off the pump you are creating a temporary run out of gas situation making it lean out and masking the problem. It could be very simple.

dan121

well its not back firing anymore its actually popping through intake it was backfiring before i did the main relay i rewired the pump and its good and all but its weird it runs good for a few secs then it starts to bog down then it pops through the intake, i realised when i play with the temp sensor as in move the wiring at the pig tail it will accelerate good so i wanted to get the sensor and pig tail but no one has the correct temp sensor. what do u think

theramz

If it's popping through the intake it is to far advanced or you have 2 plug wires crossed.

theramz

If you don't have a multi-tester and know how to use it then get one and step through the FSM. For the temp sensor and thermotime sensor go here
http://motorsportauto.com/products.html

JSM

You have never tested the fuel pressure have you? It is very important to the operation of the car. If too low, it won't run or to high.

dan121

i have tested the fuel pressure its at 38psi,ok i got the temp sensor pigtail huge difference it starts right up and seems to be iddling fine not 100 percent though once i begin to accelerate it will start moving smooth then it will slightly bog and then suddenly keep moving like nothing is wrong no backfire no lean pop just seems to slightly bog, but its better and its running rich like alot i havent gotten the temp sensor and thank you theramz i will order one... do you think i should also get the thermotine? and i believe the timing should be set at 10 correct?

dan121

wtf just went on the website for the coolant temp sensor and the sensor looks like the one off of a 300zx?

JSM

Alot of the parts are shared for different years.

If you don't have the CTS hooked up the ECU will never come out of its "i'm cold" mode and u will continue to run very rich and eventually fowl the plugs.

Good job getting this far. I bet it feels great!

theramz

The thermotine switch turns on/off the cold start valve. Makes it run rich if it's bad. Carefully check your intake boots for leaks. There is a valve on the bottom of the tb that opens during enrichment to make it idle faster. If you get fast idle after warmup this valve is bad and you can plug it from inside the tb.

dan121

feels awesome i just wish i had more time but im stoked on how its driving if the bog stops and rich il be the happiest guy

dan121

hahah just found out the sensor i have been tryng to get is not the coolant temp sensor but the thermo time?in front of engine in between intake and cylinder head? now to my credit i was able to put the new pig tail on it and has ran better so now i must locate temp sensor and still replace thermotime switch?

dan121

got worse now it wont even stay on......starts then dies ....looking to get the carb conversion theres a set on ebay for 240 off a 260z 74 looks complete besides new fuel pump what would i need for conversion as in is there any sensors on the carbs or is it basic wire to ignition ?

dan121

alright guys did a complete swap off of another 77 280 it came with injectors and a 5 speed trans and walla car starts revs fine but under load it drives but takes for ever to pick up like for ever.....no load revs fine load real sluggish what can i look for