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Old 03-20-2016, 04:43 PM   #1 (permalink)
Duratys
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93 lift pump issue

Ive read through the FAQ list but its still unclear to me if the OPS is the reason for the lift pump to be inop, will the op gauge on the cluster still work?

I don't hear the LP when the key is turned on nor does it run when the truck is. I can "hotwire it" at the relay by jumping the orange/grey terminals and I've confirmed it does run then. Am I a candidate for a new OPS?

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Old 03-20-2016, 04:51 PM   #2 (permalink)
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Sounds like it.

ACDelco OPS only D1808A, IT IS HARDLY AVAILABLE LOCALLY.

There are 2 circuit on the OPS, one control the LP and one send signal to the gauge.
The one that control OPS can be bad without the other being bad.
They are sort of independent of each other.

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Old 03-20-2016, 05:01 PM   #3 (permalink)
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Ahh. Figured if it wouldn't run the lift pump it shouldnt register on the cluster either.

You guys generally buy the OPS online then with local sourcing being scarce?
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Old 03-20-2016, 05:42 PM   #4 (permalink)
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RockAuto or stealership.
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Leroy Diesel Flight System PMD
Leroy Diesel Oil Cooler Line
4" Warpspeed Exhaust
Kennedy Diesel LP/OPS Harness
Bosch Duraterm GP
Heath Turbo-Master
AD244 Alternator

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Old 03-20-2016, 05:58 PM   #5 (permalink)
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You should strongly consider doing this mod: https://www.dieselplace.com/forum/63-...di-trucks.html

This mod takes the LP power load away from the OPS.
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Old 03-20-2016, 07:02 PM   #6 (permalink)
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Thanks. Ill look into the dealer tomorrow and see what they have.

Working on the relay mod right now.
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Old 03-20-2016, 08:29 PM   #7 (permalink)
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The relay mod will not work without a working OPS.
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Old 03-20-2016, 10:53 PM   #8 (permalink)
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I understand that. I had time today to tackle it so its ready when i get the new OPS in.
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Old 03-22-2016, 04:45 PM   #9 (permalink)
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Got a new OPS in and did the relay mod. Started it up and it worked however the pump didn't run when the key was on, only when the truck was running and had built oil pressure. Took it for about an hour drive and when I got home the pump wasn't running again. WTF. Looks like I'm wiring the pump to a keyed source and screw this OPS setup.
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Old 03-22-2016, 07:26 PM   #10 (permalink)
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LP on a 93-95 never runs when cranking. It ran solely on oil pressure.

That is the feature from the factory, called GM.

If you want, you can make the relay to run the LP during WTS by connecting the "normally closed" pin to a "ign ON" fuse.

If the LP is not running when engine is running and you have done the mod, check the mod, make sure it is connected properly.
If they are connected properly, then the LP is bad.

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1995 GMC Suburban:
PMD in Bumper
Leroy Diesel Flight System PMD
Leroy Diesel Oil Cooler Line
4" Warpspeed Exhaust
Kennedy Diesel LP/OPS Harness
Bosch Duraterm GP
Heath Turbo-Master
AD244 Alternator

Last edited by JMJNet; 03-22-2016 at 07:27 PM.
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