Moe Greene

iTrader: (2)

Hi guys,

While i was cruising a few days ago my car suddenly stopped running and the battery light came up on the dash. I have diagnosed the problem to be lack of fuel from the fuel pump. How do I go about checking the fuel pump and relays for the fuel pump? So far I have used the diagnostic box and hooked up F/P and ground and turn the key to the on position and no fuel flows. Before I go and order another fuel pump I want to make sure something is not wrong with the relay or wiring of the car. Also the fuel pump is only 1 year old with less than 400 miles on it.

The car is on stock ECU and the fuel pump is an upgraded walbro 400


Moe Greene

Red94fd

iTrader: (5)

Check the voltage going to the fuel pump at the connector. If you have voltage that means your relay should be good,.

DaleClark

iTrader: (55)

The battery light coming on means there's something going on with the charging system. You may have had your alternator die and voltage dropped enough to shut down the pump.

The only way that battery light will come on is something with the charging system.

You can easily test the voltage getting to the fuel pump at the connector as stated.

Dale

Moe Greene

iTrader: (2)

So I checked out the voltage directly at the pump with the ignition on the On position and got nothing
I even hooked up the diagnostic wire to F/P and ground and check voltage.. nothing

What should I check out next?

Dale what should I check on the alternator?

Red94fd

iTrader: (5)

Check the fuse box for any blown fuse.

DaleClark

iTrader: (55)

Put a multimeter on the battery - car off should be around 12.5 volts. Car running should be around 14v with a healthy alternator. If the voltage with the car running is the same as off, the alternator isn't happy.

Regardless, see how your battery is before testing further. Also, you will only get voltage at the fuel pump connector with the F/P and GND terminals in the diagnostic box jumpered. The ECU tells the fuel pump to run and it only runs when you're cranking or the car is running.

Dale

Moe Greene

iTrader: (2)

Moe Greene

iTrader: (2)

I tried cranking the car with the fuel lines disconnected and everything connected to see if fuel flows, got no fuel flow at all. After that the batter read 12.0v. I took the alternator to autozone to get tested, and it failed. My question is would a bad alternator cause no fuel to flow form the pump when cranking the engine or jumping the diagnostic box?

I would like to get everything sorted out for a cruise that i'm going to this weekend with some fellow RX7 owner, I want to get everything fixed and sorted, what else do you guys recommend I check so that I can have the parts in before saturday.

Thank you all so much for the help,
Moe Greene

armans

iTrader: (2)

Have you already checked the fuel pump fuse?

Moe Greene

iTrader: (2)

Its the EGI main and EGI 30A right? Do I just check to see if I get any resistance with a multimeter?

armans

iTrader: (2)

20A fuel pump fuse, it's in the cabin fuse box.

Moe Greene

iTrader: (2)

Bingo! fuse is blown, Im going to replace the fuse, checked out the main relay and 30A fuse aswell to make sure they are good. With that said, should I still get my alternator replace? Autozone said it failed, but prior to my shutdown my car was running fine. Also why would the fuse blow? I would like to make sure it doesn't blow again while driving.

armans

iTrader: (2)

So did it all happen at the same time? A bad alternator means either brushes are too short (you can open the alt case and have a look, this is easy to do), bad diodes (you can check this with a multi-meter), or a bad voltage regulator (a short in the system may cause this).
Be careful, if that's a short that blew both the fuse and the voltage regulator, you have more to dig into.

armans

iTrader: (2)

Also a bad voltage regulator may itself be the cause of the blown fuse - this is because alternator may produce more voltage than what is needed.

Moe Greene

iTrader: (2)

Red94fd

iTrader: (5)

Good that you found the fuse. Yes, replace the alternator. , maybe the alternator has internal short or other issue. Pay attention when you put your new alternator.

Moe Greene

iTrader: (2)

Will do! Just ordered a replacement.

alexdimen

iTrader: (13)

As you suspected, fuses don't just blow for no reason. There may be something going on with the fuel pump circuit in addition to the alternator.

Do you still have the stock pump and wiring?