OPS relay install

[Schwind]

I finally got around to doing my OPS relay today. I found in the search that there weren’t any pics of this so took my camera along and snapped some. The first pic is of the OPS location. The second pic is of the OPS plug and the wire colors. The third pic is of the items I used to do the project. The fourth pic is of the wires cut and crimped.

The length of the extension wires were 24“, I removed the convoluted tubing from the OPS wires before I started cutting. my wire colors for the relay extension were :

Orange for the hot: I cut the orange wire from the OPS plug about 3” from the plug and tied in the orange extension wire. Crimped and shrink wrapped it.

Gray for the OPS plug: approximately 2.5” from the plug I cut the gray wire. The wire from the OPS plug I connected the gray extension wire. Crimped and shrink wrapped.

Light purple for the LP: on the cut wire going to the LP I connected the Purple wire. Crimped and shrink wrapped.

Brown for the ground: The brown ground wire is much shorter because it is just ran to the relay’s mounting screw.

My pics don’t show the shrink wrap installed on the wires (I thought I had took one but this was the time the grandson decided to interrupt me). The fifth pic is of the wires from the OPS re-loomed and the relay wires Loomed. I decided to mount the relay under the electric shroud pic # 6 on the passenger’s firewall pic # 7 . It seemed to be the most likely place to put it. Being that the factory saw fit to have already put holes there and the other relays were there as well. I mounted the ground with the same screw I mounted the relay with. Then replaced the shroud.

The relay is numbered and the extension wires hook to the relay in this order. #30 is the orange power wire (by the way this wire is hot with key off don’t let it ground out. Please don‘t ask how I know). #85 is the brown ground wire, #86 is the gray wire from the OPS and #87 is the purple wire to the LP. Post 2 has the rest of the pics

 

[Schwind]

Remaining pics

Here are the remaining pics. the board would not let me post more than 5 at a time.

 

[matuva]

Good job.
Mine is on the way, scheduled for next week-end.
You're lucky, your OPS is close the glow relay. My truck being a 1996, my OPS is under the intake 10:

 

[Schwind]

Yeah OBD-I is the easiest I guess. I didn't have to take anything off other than unplugging the OPS and removing the electrical shroud.

 

[JMJNet]

On 95, it does not have electrical shroud.

 

[JiFaire]

Thanks, Schwind! Another picture tour of a common install is now in the 6.5 Turbo Diesel Technical Library... Thanks for taking the time to document, photograph, and write this up for us!

Jim

 

[Schwind]

Thanks, Schwind! Another picture tour of a common install is now in the 6.5 Turbo Diesel Technical Library... Thanks for taking the time to document, photograph, and write this up for us!

Jim

Thank you Jifaire. Just thought it might help someone else. The tasks at hand take a little longer taking pics but it helps to have them later.

 

[Schwind]

Here is the wiring for the bosh relay.

 

[gmctd]

The large relay there on the firewall to the left of your addition is the real Lift Pump\OPS relay, replete with clamping\filtering for computerized vehicle circuitry - certainly hope that Bosch aftermarket relay has the same, so inductive kickback spikes don't get into your electrical system - that can really mess with IP operation..............

 

[matuva]

Is that an OBDI setup only? I don't have this large relay on firewall on my 96 OBDII

 

[JMJNet]

Is that an OBDI setup only? I don't have this large relay on firewall on my 96 OBDII

That is a 94. Yours is probably on the fuse/relay box.

 

[matuva]

Thanks JMJnet.
I just finished the relay mod, and I wired mine (no name) exactely like schwind describes.
That works fine.
Funny is to hear the lift pump still running now after you shut down the engine, just time for oil pressure to drop---
Hope this will be fine for ECM circuitry---

 

[Schwind]

The large relay there on the firewall to the left of your addition is the real Lift Pump\OPS relay, replete with clamping\filtering for computerized vehicle circuitry - certainly hope that Bosch aftermarket relay has the same, so inductive kickback spikes don't get into your electrical system - that can really mess with IP operation..............

Can you elaborate on this point GMCTD.

All I did is use the relay to carry the voltage from the hot to the OPS straight to the LP with the gray from the OPS to trigger the relay.

My understanding of the factory relay is for the ECM to operate the LP till the OPS is in operation by the oil pressure.

 

[RadioMan]

GMCTD - I'll try to save you a bit of typing...

GM uses a resistor (value unknown by me) to quench the kick back when the relay releases. A diode works great too and can be picked up at Radio Shack for a few cents (well - maybe a buck or two, but only worth a few cents).
This will explain it Inductive KickBack Elimination.
The kick back usually isn't a big deal, but under the right circumstances can be like a lightning bolt hitting your circutry. Protection is cheap & easy - Go for it.

 

[gmctd]

Retired electronic engineer here, RadioMan (or, is that really you, Tesla?) - all the relays in your truck(s) are spec'ed for PCM\ECM systems, and are constructed with the counter-emf suppression (also called snubbers, commutating diodes, etc) circuits built-in the relays - don't believe it? - look at the imprinted circuit conection diagram on your oem relays: notice the rectangle connected across the energizing windings = suppression circuitry - particularly so in the GM\Stanadyne system, any emi\rfi noise causes erratic operation of the FSD\PMD - any added relay must have the emi\rfi supression built-in, or installed externally

Schwind, look on the top of that LP relay there next to your addition - if your addition does not have that small rectangle across the coil terminals, you will need to add a 1n4004 silicon diode and a 0.1ufd capacitor for suppression - better to get the appropriate relay, IMO - most better a\m relays are now oem-equipped with the circuitry as part of the assembly

The Lift Pump is a solenoid\shuttle type configuration, but the drive is SCR with buffered tickler coil feedback to shut the pump off when operating pressure exceeds flowrate spec, so the LP needs no protection on the relay contacts - however, for pristine system operation, the coil on any installed relay should always have the snubber installed - that includes any accessory relays.

Word up, dudes.....................

 

[Schwind]

Ok ya’ll are expanding my mind, with your knowledge and teaching me things I didn’t know. With the information you are giving me here, but I am no engineer. Just a layman trying to make things better on my truck to improve longevity of the items known to give problems. It is also why I posted this here to get the feed back from the more knowledgeable people on the forum. The point of the relay needing voltage suppression has never been mentioned before in what I have read.

I don’t quite understand the theory but I get the concept of the voltage suppression on shut down. That is that the magnet builds voltage in the coil and then when its shuts down releases the voltage into the circuitry. Is this the correct analogy?

GMCTD Could you explain your acronym?

EMI/RFI?
SCR
UFD

I will look for the proper relay at the auto parts with the resistor built in. The one I currently have doesn’t have the resistor. I am not looking to cause more problems just improve the ones I/we have with the OEM systems. If I can’t find one here in my area I will try to put the 1n4004 silicon diode and a 0.1ufd capacitor on the relay externally. Can this be done by just looping them between the coil pin connectors of the relay?

My reasoning for putting the relay in line with the LP is/was to remove the 5amp load of the LP from the 2amp switch in the OPS. Which is what causes the OPS to fail? This is information that I acquired from post in multiple site on the web. If my thinking on this is not right please say so.

I respect your opinions, knowledge and help. Thank you

 

[gmctd]

Correct on the voltage spike - computers are particularly susceptible to damage from that

ElectroMagneticInterference resulted from the electromagnetic spikes caused by motors, relays, solenoids, etc
RadioFrequencyInterference caused by various electronic devices such as the FSD\PMD, alternator, electric motors, etc
SiliconControlledRectifier - a transistor-like switching device
FuelSolenoidDriver\PumpMountedDriver - 6.5 nemesis

Adding the relay is not a bad idea - using an un-snubbed relay is a bad idea - the snubbed relays are commonly available everywhere, just look for the small rectangle across the coil terminals - if you run the commutating diode, the band on the diode goes to the terminal where you connect the positive wire - that method can be used with any relay used in a dc circuit - ac circuits use a resistor\capacitor snubbing circuit

 

[vail426]

The wiring diagram for a 94 ( on my all-data ) shows the orange wire as " hot at all times" and the purple wire for the tank sending unit for the fuel gauge. This diagram shows the LP and sender in the tank. It almost looks like you are by-passing the OPS and your pump would run all the time. Some one correct me if I am wrong.

 

[matuva]

Orange is hot at all time, even on my 1996, connect to pin 30 (input of power line in relay).
Yes, you're bypassing the OPS if we talk about the power line to the lift pump, the grey wire coming from OPS being used only to trigger the relay(pin 86) and is no more carrying power to LP.
Your lift pump will not run at all time as the relay will be opened as soon as the oil pressure will go down, and so the relay will open, cutting the power circuit (pin 87 output relay connected to the grey wire portion to the LP)

 

[Schwind]

The power wire is hot constantly but the relay is tripped by the OPS switch for the LP so that it doesn’t run all the time. The OPS sends the trigger to the relay in order to send power to the LP without running the voltage through the OPS. Thus the relay is carrying the voltage to the LP with little as possible amperage through the OPS.