Need the advice of experts on the fuel system
 

hey guys so i was out working in the cold on my car and i have been trying to figure out the problem as to why my car doesnt run anymore , so i sort of narrowed it down , the fuel system. i checked the fuel pump ( which was good but i bought a new one anyways ) i check the resistance and if the fuel pump sending unit was getting power , no , when i turn the key it doesnt get power, but when i plug the battery directly to the sending unit i can get my fuel pump to pump fuel. so where do you suggest i start figuring stuff out ? i hate not driving my car and it pisses me off more that i worked for a year and now it stopped ERGH !! lol .

On a series four car the fuel pump does not run if the key is just put to ON.

The fuel pump on a series four works if the key is HELD to START (power from the start circuit energizes the circuit opening relay).

The fuel pump on a series four works if the engine actually starts and runs. ( a gnd signal from the afm pulls in the circuit opening relay).

The fuel pump on a seires four car works if the key is ON and the yellow two pin fuel pump check connector is jumpered. (jumpering does the same as just above)

If the ENGINE fuse is blown the fuel pump will not work under any of the above conditions.

Series five are a bit different than the above. Not much different.

Here's the S4 information (your profile says S4 n/a).

https://www.rx7club.com/attachment.p...1&d=1264651812

https://www.rx7club.com/attachment.p...1&d=1264651861

thanks for the info , i keep asking but nobody tells me the exact location of the circuit opening relay for the fuel pump , i think its under the dash ? correct me if im wrong .

yup

ok i was just under the dash and is it the green/yellow one with a black top ?

I don't remember the color, but you should be able to identify it by the 5 wires, and the wire colors. It's usually mounted just to the right of the steering column. I can find/unplug the thing by hand without looking, but I'll be damned if I can remember what it looks like underneath there.

In my minds eye the chance of the circuit opening relay to be the culprit is minimal.

The reason is that the relay has two coils that can pull it in. One coil has a gnd on it all the time and is just looking for batt voltage from the Start circuit to make that coil work.

The other coil in that relay has batt pwr from the ENGINE fuse all the time if the key is to ON and is looking for a ground from either the afm or the jumpered two socket fuel pump check connector.

So you should get fuel pump power if the key is HELD to START or if the jumper is installed in the two socket fuel pump check connector (both acts do the same thing...put a gnd on one of the circuit opening relays coils to pull it in).

The large BLUE wire on the fuel pumps electrical connector is the one that feeds power to the fuel pump. Thats the blue wire on the rear harness side of that connector. The pigtail harness of the pump has a black/white wire that mates with the Blue wire of the REAR harness.