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Should the fuel pumps run all the time...

Hi guys
Trying to troubleshoot the yellow relay.
With key on engine off should the fuel pumps run indefinitely ?
89 turbo
Thanks

Old 05-01-2012, 03:30 PM
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No they should shut off as soon as the engine stops. The CDI box will run for about 10 more seconds to burn off residual fuel. There is a cutoff switch in the fuel head that is supposed to stop the fuel pumps from seeing any electrical power when the engine is off and the CIS metering plate is on its stop.

I editted this post to say CDI not CIS box.....

Also thanks everyone else for expounding on my explanation.....the wiring diagram should explain it really well.....a picture worth a thousand words.

Fred
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1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max
---"When you're racing it's life! Anything else either before or after, is just waiting"

Last edited by fredmeister; 05-02-2012 at 03:02 PM..
Old 05-01-2012, 04:07 PM
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How about if the key is in #2 position ( key on engine off )?
Thanks
Old 05-01-2012, 04:34 PM
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The pumps should only run when the engine is running. And as
Fred said the engine will run on for a few seconds when shutting
off the engine but the fuel pumps will be off. If you turn the key on
and pull the green connector off at the metering plate housing the
pumps will run when the metering plate is depressed.

This might help you chase down your issue !!!!!







Cole
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Cole - 80 930 "The Old Sled"
Mods: TurboKraft Custom IC, 934 Headers, GSX 61, Zork, Port Work, SC Cams, Air Mod Fuel Dist Relocated, Water Meth Injection, BL WUR, MSD 6530, Greddy EBC, Synapse Bov, Short 2nd & 3rd with 8:37 R&P, Wevo Shifter, Coupling, and Mounts, MTX-L SSI-4, Big Brakes, Rebel Coilovers, Bilstein Sports.

Last edited by cole930; 05-02-2012 at 08:57 AM..
Old 05-01-2012, 05:24 PM
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Quote:
Originally Posted by cole930 View Post
The pumps should only run when the engine is running and as
Fred said for a few seconds when shutting off the engine. If you
turn the key on and pull the green connector off at the metering
plate housing the pumps will run continusly. Cole
Just a smidgen of clarification: The pumps should shut off instantly when shutting down a running engine (a safety feature to keep your car from becoming a pile of molten goo in the event of an accident, keeping the pumps from spewing liquid fire when the engine is dead). It's the CDI electronics (i.e., spark) that will continue for a few seconds in order to burn off residual fuel in the lines. I always have to think twice about this every time the topic comes up....
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Old 05-01-2012, 06:37 PM
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Thanks Mark !!!!!

Cole
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Cole - 80 930 "The Old Sled"
Mods: TurboKraft Custom IC, 934 Headers, GSX 61, Zork, Port Work, SC Cams, Air Mod Fuel Dist Relocated, Water Meth Injection, BL WUR, MSD 6530, Greddy EBC, Synapse Bov, Short 2nd & 3rd with 8:37 R&P, Wevo Shifter, Coupling, and Mounts, MTX-L SSI-4, Big Brakes, Rebel Coilovers, Bilstein Sports.
Old 05-02-2012, 08:33 AM
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Hay Cole:
When you figure out whats going on let me know. My pumps run when the engine is off as well. I think something on the car has been bypassed. Mine is a 89 as well.
Old 05-02-2012, 11:33 AM
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Guys:

I'm going to be s o l on the later models with the infamous Yellow Relay.
Mark may have some ideas there as his car is a later model and he has
experience with Yellow Relay woes. The only thing I can offer is pull the
Yellow Relay, clean the pins and socket, then spread the pins slightly and
try it. There are a ton of posts on here referencing it, just do a search on
yellow relay.

Cole
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Cole - 80 930 "The Old Sled"
Mods: TurboKraft Custom IC, 934 Headers, GSX 61, Zork, Port Work, SC Cams, Air Mod Fuel Dist Relocated, Water Meth Injection, BL WUR, MSD 6530, Greddy EBC, Synapse Bov, Short 2nd & 3rd with 8:37 R&P, Wevo Shifter, Coupling, and Mounts, MTX-L SSI-4, Big Brakes, Rebel Coilovers, Bilstein Sports.
Old 05-02-2012, 01:12 PM
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In order for the pumps to run when the engine is off and the key in the first detente the connector at the air meter assembly must be unplugged or the fuel pump relay jumped. The fuel system may also be wired directly to the battery via the aux switch.
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Old 05-02-2012, 01:26 PM
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You guys have covered it. All I can offer is a nice little picture that will show you how to bypass your yellow relay in the event it fails and your pumps won't run as a result.


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Old 05-02-2012, 03:16 PM
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