MadMungo

I believe I have a problem with the fuel pump relay. I purchased a new fuel pump and installed it. Cranked the engine and nothing. Checked the fuel pump plug with voltimeter and nothing. I should have did this first before purchasing a new fuel pump (pissed at myself)! Can anyone tell me where the fuel pump relay is located??? I have a 85 RX7 GS with the stock 12A. Thanks.

snivley whiplash

iTrader: (4)

see link
http://foxed.ca/foxed/index.php?page=rx7manual

coldy13

It's under the drivers side of the dash, if I remember right it's a 4pin relay just a bit to the left of the fuse box. Might as well check all the fuses while your down there, ohms or continuity(beeps if the fuse is good) on the multimeter and touch the probes to both sides of the fuse.

ALWAYS check for power and good fuses first. The shop I used to work at always gave me the "hard" problems to diagnose after the other guys f'ed up the diagnosis and their parts didnt fix it. 90% of the time it was a bad fuse or ground wire, the other 10% was a bad relay or ECU not grounding the relay.

MadMungo

Okay,...I found the fuel pump relay and got it out. Not too difficult. What's next? How do I check to see if the relay is bad?

coldy13

Find the wiring diagram for the fuel pump in the link snivley whiplash posted, and you've got a voltmeter....Did you check to make sure the fuse is good and you have power at the fuse?

Relays are an electrical switch, on the plug side with the key on 1 terminal is grounded through a switch to activate it, 2 should have constant power, 1 goes to fuel pump.

MadMungo

On the plug, I checked the two that should have constant power and they both registered 11.85V. So am I to assume that the fuel pump relay could possibly be bad since it has good power going to it? Or should I be checking something else? Sorry for the questions....I'm not very good when it comes to the electrical componenets. Thanks again.

coldy13

Have you found the wiring diagram yet? Relays are easy to test, put the multimeter on ohms and the probes on the switching side of the relay. Apply voltage to the control side and the meter should go from infinity to 0. Any resistance is a bad contact inside the relay, take the cover off and look at how it works

If you have power at the relay and no power at the fuel pump, either the relay is bad or the wire between the relay and fuel pump is bad. To test the wire use the meter on ohms and put one probe in the relay plug and the other in the fuel pump plug, might need longer wires for the meter to do this. In a live circuit you can use voltage to test connections, .1v drop per connection is "allowed". Testing from power to ground will show 12v dropped, a good wire/connection will show 0 from end to end.

74RX4

iTrader: (10)

The fuel pump relay is attached to the right side of the steering column, under the dash. If you attach a jumper wire between either of the Black/white wires and the Blue/white wire in the harness plug you can bypass the relay. The fuel pump will run anytime the ignition is turned on. Very common problem.

Kentetsu

One other thing that would cause the pump not to run would be loss of the trailing ignition. Check for spark on the top plugs to rule this out...





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RustyRacer

Not sure if you have a similar wire harness as my '80 but I found out that I didn't ground the pump at the tail lights. Not sure if the FB is similar. I had no power at all to my fuel pump.

coldy13

On cars of this age everything is a common problem, because all components are past their intended life span. Either learn how to properly do the work yourself or pay someone to do it for you, guessing will end up costing you more in the long run.

A bad ground doesn't mean there's no power at the fuel pump, power is there it's just not flowing since it's not a complete circuit. If you test only on the plug for the fuel pump's power and ground the meter will show 0v, test from the + on the plug to the - bat terminal or any CONFIRMED good ground and it will show 12v. Grounds are the easiest thing to test, check from the - wire on the fuel pump plug to any clean bare metal on the car(if the - bat terminal to chassis wire is good) and the meter should show 0ohms. But for certain problems you need to remember that 1 good strand inside a wire will show 0ohms, but can't carry enough power to run a fuel pump.