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Testing Fuel Pump Relay
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924RACR  



Joined: 29 Jul 2001
Posts: 8298
Location: Royal Oak, MI, USA

PostPosted: Wed May 06, 2020 9:49 pm    Post subject: Reply with quote

Yeah, those 1000 and 1500Ohm wires are the ballast resistors/wires.

Definitely confine your investigation to the wires to and from the relay. Odds of a new relay being NFG are low, if not zero. Testing all the leads should resolve the issue.

If that pesky green/white wire has zero resistance to the tach and coil as shown on the wiring diagram, that should be enough.

One thing I'm not completely certain you've checked: can you verify you have +12V on relay terminal 15 when ignition switched on, and a good ground on pin 31 of the relay at all times?

In addition to needing the tach signal, those are the control circuit for the relay; very easy to have a break there.

Finally, might also help to share pics of the wiring diagram printed on the side of your fuel pump relays (both original and replacement) - make sure those are correct and match the wiring diagram...
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Vaughan Scott
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winddude  



Joined: 15 Jan 2020
Posts: 41
Location: Vancouver Island

PostPosted: Thu May 07, 2020 4:05 am    Post subject: Reply with quote

924RACR wrote:

One thing I'm not completely certain you've checked: can you verify you have +12V on relay terminal 15 when ignition switched on, and a good ground on pin 31 of the relay at all times?

In addition to needing the tach signal, those are the control circuit for the relay; very easy to have a break there.



I get 9.6v from 15, the ignition terminal with ignition on. I get 1.2v from the tach signal with ignition on.
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winddude  



Joined: 15 Jan 2020
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Location: Vancouver Island

PostPosted: Thu May 07, 2020 4:11 am    Post subject: Reply with quote

Original relay, I believe, and the replacement KAE 3.300.300
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924RACR  



Joined: 29 Jul 2001
Posts: 8298
Location: Royal Oak, MI, USA

PostPosted: Thu May 07, 2020 4:26 am    Post subject: Reply with quote

winddude wrote:


I get 9.6v from 15, the ignition terminal with ignition on. I get 1.2v from the tach signal with ignition on.


But what about the ground?
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Vaughan Scott
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winddude  



Joined: 15 Jan 2020
Posts: 41
Location: Vancouver Island

PostPosted: Thu May 07, 2020 9:36 am    Post subject: Reply with quote

The ones near the relay board are a little corroded, I'll have to work on getting in there to clean them. However I was checking voltage off of that ground terminal.

Engine to body is a little corroded might need to be replaced.

Also interesting battery to body, goes battery to engine...

The green and white wires I have <1ohm between the coil and relay board and tach and relay board.
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924RACR  



Joined: 29 Jul 2001
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Location: Royal Oak, MI, USA

PostPosted: Thu May 07, 2020 9:31 pm    Post subject: Reply with quote

Definitely clean your grounds before going any further.
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Vaughan Scott
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winddude  



Joined: 15 Jan 2020
Posts: 41
Location: Vancouver Island

PostPosted: Wed May 20, 2020 6:44 am    Post subject: Reply with quote

cleaned all the crounds, and terminals on the back of the relay panel. That was a big job on hooking all of them and getting them back up.

I did resolve the issue. I had the tach hooked up backwards... opps. Working now.
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924RACR  



Joined: 29 Jul 2001
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Location: Royal Oak, MI, USA

PostPosted: Wed May 20, 2020 8:41 pm    Post subject: Reply with quote

Good job! Well done...
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Vaughan Scott
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