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Just for clarification...

normburns

normburns

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think of this in your mind to the old little kids ditty...
the LP is connected to the relay...
the relay is connected to the ops...
and ops is located to the... uhhhh, ahhhh where?

Decided to roll under the truck yesterday to check some voltages before I get into replacing the lift pump, etc. My voltages were taken with the lift pump still connected to the wire harness, because I read somewhere that disconnecting the pump could give faulty readings. My readings were about 8-8.4vdc spinning, and just a touch over 3vdc running. That just does not sound like enough to properly run the pump. My plan is to replace the ops, which is located where? I also plan to add a relay to the circuit, that will fire the LP whenever the engine is turning over/running. Does that sound like a good plan? I have also read about bleeding the fuel system via a brass t-handle valve. This valve is located where?

Thanks for all the tips guys! I need to get it running right, and soon. My little crippled up buddy needs to be moved from Oliver Springs to Rockwood in about 4 weeks, and I would like to have the truck running right by then... and I will give you two guesses who will be doing the move.
 
OPS just above bell housing flange at rear of driver side head. On a 94 its a PITA. I have an extension hose kit on my site you may like.
Drain is on the tstat housing.

Voltage sounds low to me also. The relay should fix you up.
 
The only additional consideration is to add a dual pod solenoid that will power the LP during the GP cycle also, so it will run during the GP cycle just like OBD2. This helps add some supply pressure the the IP before you hit the starter.

Search the sticky section there was a schematic with details from Buddy posted some time ago.

HTH's
 
The old OPS can be butchered since it is bad anyway.

The OPS is right underneath the GP controller.

i posted the link for double relay in the original post.
 
They aren't much fun to get at in the valley under the FFM either... not sure if a Crows foot or faucet wrench are good tools to use on the 94's but here's a shot of the back of the motor with the local identified by the DeWalt Bit.
OPS-Rear.jpg
 
On the 1995 Tahoe I did the double relay upgrade and used the bad OPS. The bad OPS put out enough juice to trigger the relay. It's been running fine like that ever since. I still have the OPS in the counsel.

If and when I do change it I will get the extension kit.

If'n I wasn't broke, I would order that to have on hand also. Seems like when you have a problem there is no time to wait for parts.
 
They aren't much fun to get at in the valley under the FFM either... not sure if a Crows foot or faucet wrench are good tools to use on the 94's but here's a shot of the back of the motor with the local identified by the DeWalt Bit.
Click to expand...

Many have had luck with a "Crows foot."
 
That's a problem, LP should see 13.8 vdc. Check the ground, and then start tracing back to see where the voltage drop is happening. Got 13.8 at the hot side of the relay? How about on the load side? May have a bad relay.
 
Just do the double lift pump relay update first and if your lift pump runs you shouldn't have to worry about the OPS til there isn't enough juice coming from the OPS to open the relay

Guster said:
That's a problem, LP should see 13.8 vdc. Check the ground, and then start tracing back to see where the voltage drop is happening. Got 13.8 at the hot side of the relay? How about on the load side? May have a bad relay.
Click to expand...
 
Well, I finally had a chance to break loose, and do a little with the truck. Just for grins, I put power to the old LP that I replaced. I have an old 30A power supply from my r/c racing days, and I used that to put power to the old LP. I went black to ground, and orange (more like a baby poop yellow, imho...) to 12vdc. It did absolutely nothing. I wonder if that had anything to do with my low voltage readings? Well, I have the new LP installed (for a couple of weeks now). I am sitting here doing a wiring harness for the relay I am going to put into the system. I will let you all know how it goes. I am hoping to get it done tomorrow. Since I am uncertain regarding the OPS, or the original relay, I will be feeding my new relay with a fused 12vdc from the battery, through the relay to the pump. For the trigger, I will be using a key on 12v source, also fused. Since I am using all new wire, on a different circuit, if I should ever decide to go for stock style, I will have all of the wiring intact.
 
There is no original relay that works with your stock OPS. Its a simple circuit, battery power to the OPS, oil pressure switches OPS to on and power goes to LP.

The relay in a 94 provides power only during crank when the key is in the start position. There is a fuse next to that relay which goes to the LP, its positioned after the two separate power sources merge (crank relay and OPS). There is also a fuse under the steering column called CRK (for crank I guess) that allows the ignition power to reach the relay to power the LP during crank.

The common mod, is to just let the output of the OPS trigger an added relay, which would switch 12V to the LP. This is to maintain the safety of no fuel pumping in the event fuel lines are severed in an accident. No oil pressure, no fuel pumping. That said many people have triggered it off an ignition source, just have to realize that its always running with key in the on position.

The dual relay method in the sticky provides what OBD2 trucks have, priming during the WTS/glow time and operation while the engine is running, and will shut off if engine dies.
 
My truck has the lp connected to be on with key on, It is currently wired like this:

Wire with inline fuse plugged into a fuse tap located on the 4wd fuse. This wire leads straight to the Lp, originally this wire was used for either fog lights or some other add on.

However I plan on adding a relay to this setup for safetys sake.

So the new wiring would be as such:

Lead from 4wd fuse with inline fuse to relay
Relay to Lp

Does this sound like a good idea? Maybe I should tap into a different keyed on fuse?

Sent from my SGH-T959D using Tapatalk
 
I would use the wire coming off the OPS connector to trigger the relay then send a 10ga wire to LP from load side of relay.
 
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