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Warped · Guest

How do I test that this is working? Also what do I focus on replacing it?

This is the plug that is connected to the air flow sensor, letting the fuel pump knowing upon when to shut off or keep running.

Right now it isn't doing anything to my fuel pump...However I have gotten my fuel pump to turn on...but only by jump starting it with jumper cables...

Thanks guys

Warped

Benski · Guest

I believe the fuel pump relay is also hooked up to the green wire coming from the ignition coil that passes the RPM info. That was the fuel pump will only run when the engine is running.

Of course, this was on an 80... which doesn't have a plug in the air flow sensor. I will double check the schematics tonight and get back to you. You may be able to jumper the connector in order to bypass a non-working sensor.

Benski · Guest

Damn unlabelled older wiring schematic... I can't make heads of tails but it doesn't look like the older fuel pump relays read the RPM, but they do read that sensor plug.

Is it two wires? If so, try jumpering them with a paper clip or wire and then crank the engine and see if the fuel pump starts...

If it's three wires, let me know the colors and I'll trace and see which two to jumper =)

AznDrgn · Guest

The older cars just sense if the air sensor plate is up or not. it should be two wires that plug into the back of the air sensor unit.

-nick · Guest

when the switch is working properly, the fuel pump will only run when the dizzy is spinning. i'm not exactly sure where it gets the info from that it is spinning (perhaps the ignition box?).

with the wire lead unpluged you can turn the ignition key to the run position and the fuel pump will run. with it plugged in the pump won't run in this position.

-nick

924RACR · Posted: Thu May 16, 2002 2:45 am Post subject:

AZNDrgn's right - on your early car, no dizzy hookup, just that airflow switch. If lifting the plate when the ignition's on does not turn on the fuel pump, but jumpering the relay does, you've diagnosed the problem - you just don't realize it! You have a bad relay - 99.9% sure of that. Try swapping in another relay, or just buy a new one. They do go, over time.

As for the stuck plunger - again, worry about it once you've got fuel pressure. Fuel pressure should push it down.

Vaughan

_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

AznDrgn · Guest

When you say "dizzy" do you mean the distributor? if so could the signal for the pump be coming from the two wires that are plugged into the side of the distributor?

AppleBit · Joined: 16 Nov 2002 Posts: 1516 Location: Minneapolis, MN

The wires that come off the dizzy are to the tach....

JvGinPDX · Guest

I have an early 77. I have noticed that I can get the pump to work so I can hear it. I removed the plug from the bottom of the fuel distributer. Then I just need to turn the key to the ON position. Once I confirmed that it did in fact work, I pushed the plug back on. If your pump does work when you jumper it, your problem is somewhere in the wiring that leads to it.

AznDrgn · Guest

AznDrgn · Guest

My pump works fine, I'm just trying to get it so it doesn't run forever when the key is in the on position.

asalmona · Guest

ok the here is the revelation to the mystery switch... having found my connector borken when i bought the car and fixing it (PITA)... when the cables are "jumpered together" or "shorting" it turns the fuel pump OFF .... when the are seprated or not touching they let the pump run... warped if your really deperate to check this here is what you can do but its not pretty: disconnect the connector from the airflow sensor and then go a few inches back from the connector itself and cut one of the wires... this will GURANTEE that they are not shorting at the connector (you may have an ok switch and a bad connector)... if the pump still doesnt turn on when the key is in the "on" postitioon without the car running than the problem lies elsewhere... on the early 924s the distributpor had nothing to do with the fuel pump getting juice, thats why we have the switch at the airflow sensor...

Alex

Benski · Guest

Alex,

Good call on that connector. I don't think any of us realized that it needed to be disconnected for the fuel pump to run.

Warped,

If that doesn't get the fuel pump running, then I think you have some corrosion on the various connectors and wires going to the fuel pump. I resurrected a 924 last weekend (one of my turbos that had sat for years). It wasn't getting voltage anywhere even though all the lines were intact. A dremel tool, a wire brush, and a multimeter got the problem sorted out after about 2 hours.
If you want some help I could give you my home phone number and talk you through each wire connection one by one.

-Ben

Warped · Guest

Oh boy...

Looks like I'm in for some fun times

Thanks guys, I'll get some real time to play on the car tomorrow (Sunday) and I'll check up on a few of these suggestions.

Benski, I might be giving you a call..thanks for the offer

Benski · Guest

Here's what to check for now.

Unplug that air sensor connector.

Turn the key to the 'on' position (so the oil light shows up).

At the fuel pump, test to see if you have 12 volts between the connectors on the wires (on the circular connectors). If you don't, the problem is earlier in the wiring.

If you have 12 volts there, but don't have 12 volts between the two posts on the fuel pump, then you have a corroded connection.

Take the key out and then clean both the connector and the post it goes over with sandpaper, a dremel tool, a wire brush, or whatever. Don't stop until you see bare metal again.

On the 931 I recently ressurected, there was 12.5 volts between the battery posts but only about 0.5 volts between the connectors clamped on to the battery. That's how much damage corrosion can do =)