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Jumping and testing Fuel Pump Relay [pics]

 
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Global AT  



Joined: 05 Jun 2009
Posts: 4
Location: Newport

PostPosted: Mon Jul 27, 2009 1:41 pm    Post subject: Jumping and testing Fuel Pump Relay [pics] Reply with quote







The two images are of the fuel pump relay relay I pulled from under the dash; and the last of the light bulb continuity checker. To properly check a relay to see if it's still working, what should I connect the (+) & (-) wires of a 12v source to, and what should I connect the light bulb wires (volt meter) to? From what I understand there should be a clicking sound when the relay closes the circuit to let the juice flow through then I should get light.. I heard no click, and didn't receive light.

The four big ones are 30, 87, 15, and 31b. Top, Bottom, Left, Right respectively. And there are two small ones at the top right and top left; 31 & 50.

I just brute forced it to make sure. I used a positive and negative lead from my battery *good, solid connection throughout testing* and the light bulb connection ends *doesn't matter which end takes in positive or negative*. And after trying every possible scenario with each of the big leads I received no light what-so-ever.

Now that wouldn't be such a big deal, meaning it's just a bad relay, but I thought I would at least get dim light, seeing as when I have the relay in the box, the pump will turn on and go, but will whine and die out *surging*. I asked a Porsche specialist in KY today and he told me the symptoms lead toward the relay, and not the distributor (which is what I thought might have been the problem originally). Obviously he told me this before I started to check the relay, which is where I am now. Tomorrow I will jumper the relay, 30 & 87 and see if the problems persist.

After searching how to fix it on youTube I found this guy's video of his bike:

http://www.youtube.com/watch?v=9HVwTBmGF5g

Mine did the same exact thing.

[img]http://www.youtube.com/watch?v=vtfEKHA1FDE[/img]

So, what do you guys think? It's a 78 Porsche 924 non-turbo. Oh, and keep in mind that I had the idle rpms upped at 2k *don't ask* and I did not touch the accelerator while recording the latter half. Skip to 4 minutes in to see the important part. Thanks guys!
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datatrain  



Joined: 15 Sep 2007
Posts: 441
Location: Osoyoos, British Columbia

PostPosted: Mon Jul 27, 2009 3:12 pm    Post subject: Reply with quote

Fuel pump relay socket pins 30 and 87 are the relay fuel pump connections. If you place a jumper across these two the fuel pump will run continuously with the key on. If it doesn't check the pump. If it does replace the relay.
At least that's the way it works on mine.

DAve
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dpw928  



Joined: 02 Nov 2002
Posts: 1860
Location: owasso, ok 74055

PostPosted: Mon Jul 27, 2009 11:22 pm    Post subject: Reply with quote

datatrain wrote:
Fuel pump relay socket pins 30 and 87 are the relay fuel pump connections. If you place a jumper across these two the fuel pump will run continuously with the key on. If it doesn't check the pump. If it does replace the relay.
At least that's the way it works on mine.

DAve


Jumping the 30 and 87 connections will power the pump continuously, key on or off. Before replacing the relay, make sure it is getting voltage on the 15 circuit.

Dennis
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emoore924  



Joined: 13 Apr 2004
Posts: 2790

PostPosted: Mon Jul 27, 2009 11:41 pm    Post subject: Reply with quote

30+87 agreed.

Just a comment: You need to be ready to remove the (-) lead from the battery because yes, with the jumper in, the fuel pump will run key on or off. Whether you want it to or not

I pull the negative (ground) from the battery, put in the jumper, then put the neg lead on/off the battery to control running of the pump.

IMHO it is safer that way. 'Specially when you're messing with the fuel system. Just be aware you might get a tiny spark when attaching. So you don't want any fuel/fumes around when you start things up.
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Rich H  



Joined: 10 Jun 2007
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Location: Preston, Lancs, UK

PostPosted: Tue Jul 28, 2009 12:47 am    Post subject: Reply with quote

The relay is far cleverer than a normal one, it looks for a pulsed negative from the coil to ensure the engine is running, it looks for asomething like a freq of 1/2Hz or so IIRC. The UK spec relays have 4 big pins adn one little (The coil signal) Engine stops, dizzy stops, coil sig stops fuel pump stops. Cuts the fuel if you stall or crash - very good idea.

Jumpering it is not a good idea except for testing.

Without the coil signal it'll do nothing.

You say you have 2 small pins I dunno what they both do...
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Global AT  



Joined: 05 Jun 2009
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Location: Newport

PostPosted: Tue Jul 28, 2009 1:07 am    Post subject: Reply with quote

Thanks a lot for the fast replies you all! Oh, btw; should I use a fuse to jump them? Or just wire?



Thanksk again!
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RC  



Joined: 25 Mar 2007
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PostPosted: Tue Jul 28, 2009 1:23 am    Post subject: Reply with quote

All useful info above. As Rich says, these are not a simple relay. The ignition signal type he describes are fitted to later 79 or 80+ models. The earlier models, like yours, rely on a switch at the AFM to trigger the relay. IIRC these relays have 2 smaller pins. There should be a wire with a blue plug connected to the side of your AFM, so that the pump only runs when air is flowing. Unplugging this connector with the ignition on, and relay installed, should activate the relay & FP. Reconnect to resume proper operation.
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dpw928  



Joined: 02 Nov 2002
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Location: owasso, ok 74055

PostPosted: Tue Jul 28, 2009 1:42 am    Post subject: Reply with quote

Global AT wrote:
Thanks a lot for the fast replies you all! Oh, btw; should I use a fuse to jump them? Or just wire?



Thanksk again!


A 15 amp fused jumper would be safer if you onl have a single pump. Two pump systems should use a 25 amp fuse.

Dennis.
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Rich H  



Joined: 10 Jun 2007
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Location: Preston, Lancs, UK

PostPosted: Tue Jul 28, 2009 2:16 am    Post subject: Reply with quote

You miss my point, if you have an accident the fuel pump will not stop.
Jumping it is not a good idea for driving on the road - testing is fine though clearly!

FP is protected by a fuse anyway isn't it?
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dpw928  



Joined: 02 Nov 2002
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Location: owasso, ok 74055

PostPosted: Tue Jul 28, 2009 3:16 am    Post subject: Reply with quote

Rich H wrote:
You miss my point, if you have an accident the fuel pump will not stop.
Jumping it is not a good idea for driving on the road - testing is fine though clearly!

FP is protected by a fuse anyway isn't it?


Thought this whole thread was about testing the relay. Even during testing it still runs a risk of causing a fire or hdrolocking the cylinders.

Not sure if the 87 circuit runs through a fuse before or after the relay. The fuse is still a good safety valve in either case.

Dennis
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Rich H  



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PostPosted: Tue Jul 28, 2009 4:28 am    Post subject: Reply with quote

Fair enough!
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Buwani 931  



Joined: 31 May 2004
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Location: Napa California

PostPosted: Tue Jul 28, 2009 7:20 am    Post subject: Reply with quote

Heres one I made up with a switch ,fuse and enough wire to use it up front



A short wire with male spade terminals will do the job.
Shawn
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