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OPS relay question on a 98 6.5

yeah, as long as there is power you dont get the DTC. So bad LP wont trip DTC, but bad relay will. Maybe pull out your LP relay and see if you get the DTC with IGN on when its supposed to power LP.
 
On my 98,key on will run the LP,but it quits when WTS light shuts off,after that,LP will run only when the WTS light comes on,no LP in between.End of glow cycling, still key on,no more LP.
Does'nt that throw a monkywrench in that "redundant" OPS feed the LP line of thinking?
 
bison said:
On my 98,key on will run the LP,but it quits when WTS light shuts off,after that,LP will run only when the WTS light comes on,no LP in between.End of glow cycling, still key on,no more LP.
Does'nt that throw a monkywrench in that "redundant" OPS feed the LP line of thinking?
Click to expand...

x2
 
Thats exactly how its supposed to work, the PCM controls it during WTS/Crank/Operation. Its working as designed, since it is not supposed to run with just ignition on, that whole safety thing that it shuts off fuel when ign is on and engine aint running, like you flipped the truck and lines could be cut/broke. But it primes it during WTS
 
The OPS still provides a power source, but the PCM is also providing an alternate parallel power source. So there is not the same current draw through an OBDII OPS, because it can pull current through the LP relay at the same time during operation. And even if OPS is dead your LP will run off the LP relay, its redundant during operation.

Two parallel power sources during engine running, that is different. The only time the OPS has the load of the LP is after engine shutdown when PCM is not able to control LP relay coil and OPS has not fully bled oil pressure. If LP relay fails then OPS will run LP during operation, but you wont get LP power on the circuit during WTS or crank, so PCM will code.

On OBD 1 if your OPS dies you are screwed if you havent modified the system, this is why its a totally different circuit.
 
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No it wouldn't, that's why the LP runs after shut down until oil pressure drops.
 
How about someone with OBD 2 pulls the connector of the OPS when the engine is running and see if the lift pump stops. If it does, then it must run thru the OPS, like OBD 1. I am curious.
 
That test had been performed, but I'd be interested in someone pulling LP relay out and turning ignition on and see if you get

P0231 Fuel Pump Feedback Circuit Low Voltage

I dont know if its programmed to code when engine is not running so if it doesnt, also unplug the OPS and start her up. This is something I havent heard people discussing when they ask if LP is working.
 
Wiring diagram for a 97 shows a hot wire from ecm-b (hot always) straight to ops , so once oil pressure closes ops should have power to fuel pump thru grey wire going directly to pump . (also shows a parallel grey coming from relay 2nd power source to pump).
 
All year trucks have the hot wire to OPS and parallel power source from the LP relay. But OBD1 LP relays are only controlled by the ignition switch in the start position during cranking. The OBDII LP relay coil gets its source from the PCM, because PCM knows, when your in WTS and cranking and engine running.
 
Sorry if I was off course . Misread Buddy,s post to check for lift pump operation with relay pulled . Was trying to say wiring diagram shows there would be, directly thru ops once ops points closed I guess we all know that..
 
Diesel -T said:
Sorry if I was off course . Misread Buddy,s post to check for lift pump operation with relay pulled . Was trying to say wiring diagram shows there would be, directly thru ops once ops points closed I guess we all know that..
Click to expand...

Yep, you are correct, if relay is dead/pulled, OPS will contiue to function to run the LP once there is oil pressure. But I was wondering if you will get a DTC because the PCM wont get the voltage feedback from the circuit during WTS if relay is pulled.
 
buddy said:
That test had been performed, but I'd be interested in someone pulling LP relay out and turning ignition on and see if you get

P0231 Fuel Pump Feedback Circuit Low Voltage

I dont know if its programmed to code when engine is not running so if it doesnt, also unplug the OPS and start her up. This is something I havent heard people discussing when they ask if LP is working.
Click to expand...


Did that also Buddy I don't recall it setting a code, once this front blows through (heavy rain outside) I'll try it again to see if it sets the code
 
No code with relay pulled,

Relay/PCM control pulled glows cycle per normal, but no lift pump with key on, once engine is started lift comes on

Relay/PCM pulled and OPS pulled, no lift pump, no codes, normal glow function, oil pressure goes out of range high, reading is full off scale past meter face markings

OPS only pulled, no codes, lift pump on, ultra high oil pressure as above
 
Turbine Doc said:
No code with relay pulled,

Relay/PCM control pulled glows cycle per normal, but no lift pump with key on, once engine is started lift comes on

Relay/PCM pulled and OPS pulled, no lift pump, no codes, normal glow function, oil pressure goes out of range high, reading is full off scale past meter face markings

OPS only pulled, no codes, lift pump on, ultra high oil pressure as above
Click to expand...

So, just so I get this right:

The lift pump works without the oil pressure switch connected on OBDII?

In other words, the PCM will power the lift pump even with a bad pressure switch?

:confused:
 
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