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OPS relay, worth while?

6.5TD Burb

6.5TD Burb

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Location
Wendell, NC
Is it a worth while mod doing now that my lift pump is on its own circuit? The original cause of the mod was to lift some of the electrial burden off the switch if the lift pump relay failed, correct or am I misunderstanding? It has no direct effect on the ops itself?
 
I am glad I did mine because I like to have the lift pump pushing fuel before the engine is started. As far as the load goes, I suppose it helps that out, too. Maybe I just got a bad part when I got my last one - not sure.

I'm really leaning toward Heath's OPS, since it's USA made and is said to be superior to the ACDelco design. It's pricey, though, but so is a calling for a hook on a holiday weekend. Their guy I spoke with that said he wrenches on the trucks most of the time told me he's never changed one of their units out. I think he said he's been there 7 years.
 
That would be correct. Right now it's wired to a constant hot circuit, on a switch of course. This week it'll be wired to an actual relay. I've noticed my oil pressure gauge moving with the turn signals lately which got me thinking about the mod.
 
Fix your grounds! Also add a new ground strap from the body to the engine and engine to frame. The Voltmeter is ok to move with signals, but, not the oil pressure. I do get slight movement with headlights.

If you hot wired the lift pump to the ignition, bypassing the GM oil pressure safety cut off, leave it alone as you don't need a relay. Just more krap to F up say when a ground falls off the relay and kills the engine at 70 on the freeway. Many of us have thousands of trouble free miles like that. Now if I could just get a lift pump to be that trouble free. (The Walbro is close, but, I killed one and rebuilt the other due to bad fuel. I won't even touch a low lifetime OEM type. Not worth the time for me to swap it every 2 months...)

Otherwise go back to the OPS powering the LP with the relay mod.
 
SnowDrift said:
I am glad I did mine because I like to have the lift pump pushing fuel before the engine is started. As far as the load goes, I suppose it helps that out, too. Maybe I just got a bad part when I got my last one - not sure.

I'm really leaning toward Heath's OPS, since it's USA made and is said to be superior to the ACDelco design. It's pricey, though, but so is a calling for a hook on a holiday weekend. Their guy I spoke with that said he wrenches on the trucks most of the time told me he's never changed one of their units out. I think he said he's been there 7 years.
Click to expand...

WHy are you thinking about changing the OPS?

What exactly is Heath's OPS? Is it custom made? Is it a rebadged product?

What do you have on it now for an OPS?

We have had a total of 8 - 6.5 diesels ranging from 1989 to 1998. I only remember changing 1 OPS in the 2 million miles plus that we have put on them. We also seem to go through fewer lift pumps than what I see posted.
 
6.5TD Burb said:
The original cause of the mod was to lift some of the electrial burden off the switch if the lift pump relay failed, correct or am I misunderstanding? It has no direct effect on the ops itself?
Click to expand...

It is to relieve the OPS from carrying the current to the LP.
The original design only OPS carry the current to LP.
In other words, the LP relay have no effect on 93-95, only OPS carry the current.
OPS still needs to be there, though.

At least that is the way I understood it.
 
jrsavoie said:
WHy are you thinking about changing the OPS?

What exactly is Heath's OPS? Is it custom made? Is it a rebadged product?

What do you have on it now for an OPS?

We have had a total of 8 - 6.5 diesels ranging from 1989 to 1998. I only remember changing 1 OPS in the 2 million miles plus that we have put on them. We also seem to go through fewer lift pumps than what I see posted.
Click to expand...

I already changed the OPS. Previous ACDelco part got me an estimated 2000 miles in a little over 2 years time. New OPS is the exact same model and brand and country of origin.

Heath's guy told me theirs is a premium design to the ACDelco unit. Supposed to have more windings and is made for them, here in the USA, not Mexico like the Delco part. I've not talked with Bill, directly, about it yet, but I have no reason to doubt what I was told by one of his guys.
 
JMJNet said:
It is to relieve the OPS from carrying the current to the LP.
The original design only OPS carry the current to LP.
In other words, the LP relay have no effect on 93-95, only OPS carry the current.
OPS still needs to be there, though.

At least that is the way I understood it.
Click to expand...
The reason the OPS needs to be there is the safety aspect. It shuts the lift pump down if there is a loss of oil pressure - Such as in a wreck.
 
I never got how that matters on a flow on failure pump. lift pumps burn out and people keep driving it, just hard starting and loss of high rpm power...
 
Will L. said:
I never got how that matters on a flow on failure pump. lift pumps burn out and people keep driving it, just hard starting and loss of high rpm power...
Click to expand...
The theory is that if you have it direct wired and by pass the safety cut off of the OPS and you get in a wreck and your fuel line comes lose on the pump will pump diesel all over the place until the connection is broken or the battery goes dead. With the OPS it will only pump fuel until it loses oil pressure
 
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