2ndgenrx

When I turn my key in the on position the fuel pump will not come on, but when I jump it from the yellow plug in the engine bay it does come on. My pump is a rewired walbro.

Also I checked my ignition coils for power because my tach would not move when I turned the engine over. Both the coils had power but arent producing a spark. It seems like both the coils are shot but it just seems odd. Anything else I could check to make sure?

Any ideas as to what I should check next would be very helpful.

Thanks

Icemark

Fuel pump wil only run on a S4 if the AFM is connected and working seeing air go through it. Just turning the key on, won't turn on the fuel pump unless the diagnostic plug is jumpered.

The tach is from a summed signal on the trailing coils. The car will start without the trailing coils even connected.

and you didn't mention what car you have, and your profile says you have a 240sx... not exactly the same thing as a FC.

Of course my answers are for a FC

NZConvertible

The system is working perfectly then. The fuel pump won't run unless the engine is cranking or running, or the check connector is jumpered.

HAILERS

Your know something. Some people say the S5 are different. Yes they do indeed. *They* say if you turn a S5 key to ON, the fuel pump runs for a few moments, although the S5 FSM says different. What say S5 owners?

2ndgenrx

Sorry for the misunderstaning, I have a 88 Tll and I was trying to say the fuel system wont prime when I turn the key in the on position.

Icemark

Fuel pump will only run on a S4 if the AFM is connected and working seeing air go through it. Just turning the key on, won't turn on the fuel pump unless the diagnostic plug is jumpered.

HAILERS

Some people think S5 *prime* when the key is turned to ON. Anyone know if this is the bullshit I think it is?

2ndgenrx

im not sure about the S5 but i know the S4 fuel system is primed when the key is in the on position.

Icemark

NO, that is not correct. How many times do we have to tell you???

It "primes" when either the key is in Start, or if the Key is ON and there is air flow through the air flow meter.

IT DOES NOT PRIME BY JUST TURNING THE KEY ON....

for the 4th time

2ndgenrx

On/ Start position, same thing. I think you know what I meant you.

Icemark

No ON and Start are two entirly different things and two different postions of the Key.

That is like saying ACC and ON are the same thing.

I'll make it more clear for you.

The ignition key has 4 positions

OFF
ACC
ON
START

In the Off position nothing has power unless it is wired to the battery.

In the ACC position, the accessory circuit (radio, part of the climate control, Etc) have power. This is the position that when you are sitting parked you can listen to the radio.

In the ON position, the accessory circuit, the ignition 1 & 2 circuits have power. This is the position that when you are driving the key is in.

In the START position, the Starter and the Ignition 1 circuit has power. This is the position that when you are cranking the car, trying to start it, that the key is in.

ON... completely different than START.

2ndgenrx

So Ice, what do you think is going on if I have power at the pump and the key cylinder and the pump wont prime?

Icemark

So you have jumpered the plug, under the hood, and turn the Key to the ON position, and the pump has power and ground and there is no fuel flow???

Then the pump is bad.

But if you are just turning the key to ON, and have not either jammed open the AFM, or jumpered the Diagnotsic plug no fuel will flow.

HAILERS

If you go to START and the Circuit Opening Relay does not pull in and *prime*the fuel rail, so what?????????

I delibertly disabled the so called *prime* coil in the circuit opening relay and a empty, and I mean EMPTY rail will pressurize in less than two seconds. Once pressurized the rail stays pressurized for over twenty minutes.

I disabled that so called *prime* circuit and noticed no difference in starting at all. I left it that way for the better part of a year until I remembered it a few weeks ago and put the black/red wire (memory here) back in the relay plug. NZCONVERTIBLE might remember the thread where I mentioned disabling the *start* coil in the circuit opening relay.

Here's a jpg of a series four turboII circuti opening relay. See the two coils in the circuit opening relay. One coil gets energized from the START circuit to energize the relay when the key is put to START. On a non turbo its a black/red wire and on a turbo its a black/white wire that pulls the coil in. It holds the coil in as long as the key is HELD to start and drops out if the key is returned to ON https://www.rx7club.com/forum/attach...postid=1398836

Icemark

yeah, that's only an issue if you are loosing rail pressure due to leaks or a faulty check valve in the pump.

and I don't know if the S5 is the same way (locking out pump operation unless there is air flow through the AFM). You know I try and stay away from the damm S5 models

NZConvertible

Different method, same purpose. There is no switch in the AFM, instead the pump is controlled by the ECU, and the ECU will only turn the pump on if the engine is running (CAS signal). The start signal and check switch work the same as on the S4.