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OPS relay install

Jess_sr said:
You can use the same kind of relay as the one you already have for your fuel pump.
Click to expand...


I think thats the one in my OPS that I'm trying to get away from. I believe you may have a hanging one on your 93 or a flanged one as they say...kinda what I'm looking for. I've read you should stick with ones of same year...so yours might be out of the question since it probably doesn't have the diode built in. I picked up a 200v 1amp diode at R-Shack to install on a regular one in case i cant find a built in one(I hope that the 1 amp is enough)

....Currently I'm looking for a Pre-Made Plug.... so as to if its ever serviced by someone else, or shall I ever grow old and forget the wiring...It can be hooked up with no fear of Shorts.


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The one in my 93 is also the same one I used on my sons 95.
I did the mod on both trucks.

I also belive it's the same relay that is used on a gas truck for many years.
 
The stock LP relay is not the same in the 93 and 95. It is the same from 92-94, then in the model year 95s they went to fuse centers under the hood that had the fuel pump relay in it. You can use the same cube type or whatever on both OPS relay mods.

I think you are doing well looking for one with an internal diode, but amazing you cant find any local. I guess I already oder most things online. I had worked up a diagram of how I would make mine also do LP priming during the GP/WTS and came up with the attached options.

The 1 amp relay should work for the quenching one, but if you ever use one inline on the LP power I would get something like 5 amp tolerant.
 

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Thanks for the wiring diagram Buddy! I like the second one with the single relay dual contacts. Since my post I have hunted down several sources now for relays and even the connector. I now am TRYING to take it one step further and go with the newer weatherproof connector and relay..but am falling short of ones would diodes in them. I am currently looking at hella and omron as i don't think (or haven't found) any Bosch relays in that design. Looks like most are called Bosch type (pin-outs i suspect) relays. I also found a hella waterproof with diode and resistor...not sure about the resistor though.

So to clarify the pump uses 5-8 amps and thru a relay i would be reducing the ops down to 1/4 amp load. Putting the 5-8 amps on the relay. So would using anything above a 10 amp relay be ok. I'm assuming that the higher rated 30 or 40 or even higher would be even better (more durable - longer lasting?)

Second looking thru the diodes they come in a flavor of protection voltages ( PIV or peak inverse voltage, I believe) Ive got a choice from 50V- 600V. I think I read somewhere that I probably should be using a 400V piv diode ( i picked up a 200V guess i have to go back). Also would a 1 amp forward current diode be acceptable seems wrong because of the 5-8 on the pump...but again thats the pump?

Lastly, I beleive I should be pointing the diode arrow towards the positive coil terminal on the relay. Ive seen them attached (soldered) right on the terminals....wont attaching your wires (parallel) to the terminals just circumvent the diode?

Not trying to beat this topic to death...I just want to do it right the first time...I'm kinda like that.


Thanks.
 
My diagram was specifically for also adding automatic WTS/GP priming for the LP. You can also do that with a momentary switch directly from a battery source, through the switch to the 87A NC contact of the 5-pole relay. Then anytime you push switch LP will run to prime it.

The protection or rectifier diode on the relay coil is only coil amperage. V=IR, so whatever the coil resistance is, you are going to drop 14.4V across it. So coil amperage going through OPS will be 14.4/R=I. Assume the coil resistance is 100 ohms. The the amps through the OPS through the coil will be 14.4/100= 0.144 amps.

So yes OPS amperage will be more like 1/4-amp. Your coil resistance can be measured, and is likely between 80 and 100 ohms. So if its 80 then current would be 0.18-amps.

The diode forward current then depends on the voltages. The protection diode is to dampen the transient spike on shutdown, which could be 1000V. If you only have an 80ohm coil to disperse it though then the current is going to be high (13 amps) for just an instant. However a 200V 6 amp diode would be fine in most cases, even though it sounds inadequate, they can handle a lot more (5-10 times) instantaneously than they are rated for actual opertion. Otherwise you can find 15 amp 600V diodes are just as cheap. The resistor in series with the protection diode is to cut that current down and will be better overall for the relay. Say you put a 220 ohm resistor in series with the protection diode then your current would fall big time to just a couple amps. Diodes alone will pass the higher current back to the other side that it could cause relay wear or damage. Our relays are big and dont get a lot of switching compared to one in a computer or something. The PMD is something that switches really fast, so it gets hot, but this relay just switches once per drive so there not a whole lot of concern and even the diode protection is just a bonus. Here is a chart of different types of supression and effects http://www.kilovac.com/kilovac/appnotes/fig48.asp

Any 10-40 amp relay would be fine, but I would not always associate higher voltage with more reliability. In some cases all the parameters of something are more precise and what not on lower tolerant devices. You wouldnt want to use a 10watt resistor on a 1/8 watt system, because the higher the watts the more error it can have.

If wiring up to get priming during WTS/GP then the diode forward current on the one coming from GP power should be rated for at least the coil current which you already know is 1/4 amp, so a 1 amp diode would be fine in that case. You can also install one on the line going from the OPS to the relay.

For calculating power, that is P=VI, or also current squared times resistance, and the units are Watts.
 
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What went wrong?

Ok, i finally got to do this mod....not without some problems though ;)

I ditched the weatherproof connector (gasketed) idea, and went with the standard old setup (picked up a harness and relay for about 6$ each). I was unsuccessful at finding (at a decent price) a hanging relay with built in diode...so I basically learned thru these pages how to do it on my own.

I used Buddy's diagram in post 63... as my template printed and all ( a little different pin-outs from what Matuva summarized up so well :) ....but should work the same none the less).

Ok following the diagram that Buddy Made I made some changes...(my first mistake I bet) I had gotten a single pole double throw (SPDT) relay (unknown amperage at this time) with A RESISTOR built in it. I measured 80 ohms across the coil.

I installed a diode in parallel to the coil (1N4005... or a 1amp 600v ...across 85 and 86) in accordance of the diagram.

I installed a second diode of the same type in series between the OPS and terminal 85 on the relay (grey wire that i cut) and fed it with a 4Amp fuse( its all I had at the time.... will be changing to a 1 amp).

I then wired the other end of the grey wire to terminal 30 on the relay (which goes to the pump).

I grounded pin 86.

Okay here is were i deviated from the diagram aside from the extra diode & fuse protecting the OPS from the relay (85).... I grabbed power (12V all the time) from the Glow plug controller lug, using a 10 amp fuse and landing it on 87 of the relay.

I wanted to do a prime on the pump during glow plugs....and decided to grab the power (as described in the diagram ) from the glow plug controller (other lug) using a 1N5404 3amp 400V diode and another 10 amp fuse (which I'm blowing) and instead of landing it with the OPS on 85 I INSTEAD landed it on the N.C. 87a thinking it might be better isolating it from the OPS (and it was available).


So...after all that I turn the key for Glow plugs...GREAT pump is running with the glow plug cycle....then start. After shutdown Pump runs until oil pressure drops GREAT, all is well....and this was with the OPS that stopped working after 3k miles (ac delco).

Well I went to show off my work....(murphys law), and then found out that I'm not getting the fuel pump with the glow plugs before starting because of a blown 10amp fuse. So I changed it out for another 10amp and cycle the glows half a dozen times and the pump runs each time ....until i restart then same blown fuse again.


So whats causing the fuse to blow? Its happening between cranking and after shutdown?
 
dazed said:
Okay here is were i deviated from the diagram aside from the extra diode & fuse protecting the OPS from the relay (85).... I grabbed power (12V all the time) from the Glow plug controller lug, using a 10 amp fuse and landing it on 87 of the relay.

I wanted to do a prime on the pump during glow plugs....and decided to grab the power (as described in the diagram ) from the glow plug controller (other lug) using a 1N5404 3amp 400V diode and another 10 amp fuse (which I'm blowing) and instead of landing it with the OPS on 85 I INSTEAD landed it on the N.C. 87a thinking it might be better isolating it from the OPS (and it was available).

So whats causing the fuse to blow? Its happening between cranking and after shutdown?
Click to expand...

I dont quite get this one.

Getting your power source from the always hot controller lug is OK, However one lug is always hot and the other is ground. The line for priming should come from the output of the controller which goes to the plugs. smaller green wire from the harness.

I think you are putting NC of the relay on the ground and NO relay contact on the battery terminal, so off the bat you are grounding the contact that is connected when there is power going to the lift pump via the actual stock LP relay. so the fuse blows on that direct short during cranking when stock LP relay has power.

I suggest dual coil input, only so you dont draw another 2-3 amps through the controller. Which is also why I would have used another battery source not to pull more current through the wire that already does the most work next to the alternator wires. Although that is a pretty good sized wire.
 
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Hmmm Funny I checked those 2 lugs with voltmeter prior....One was hot all the time and the other had 12V while the glow plugs cycled.

Im Pretty Sure it was the Controller....Had Boots on the wires Right next to the OPS and Fuel Filter and thought the wires (2) were grey(maybe orange) on copper Lugs...
 
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Well they are Grey (fusible link Wires) attached to 2 Orange ones.....

So I grabbed the Meter for the lug on the controller that feeds the glow plugs and guess what....I get continuity to ground...WIERD...since It also feeds 12V to the glow plugs ....so thats probably what was shorting the fuse after cranking.

I pulled my stuff of the Glow plug controller and Ran The Hot all the time contact to an accessory post of the fuse panel in the engine compartment....just to get off that glow plug circuit.

I checked My manual and found that there are 3 wires ( pink, yellow, and black) that also hook up to the Glow plug controller via connector. So I guess until I can figure out what went wrong attaching it to the controller ( which when powered off, goes to ground), I'll leave it off....since I don't really want to do a T-tap there.....maybe I have a shorted out glow plug or bad controller.
 
That may be what I was thinking, its normally grounded, until the controller flips it to the 12V battery supply. Its been a while since I checked that. So the GPs are normally just grounded until PCM commands controller to switch it to battery power.

The diode was supposed to protect any current from passing that way though, so I dont know why it blew the fuse.
 
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I installed diodes in the middle ....like between the fuse and the relay...

example ...with the current flow It was GP controller -> fuse -> Diode -> Relay.

Are you saying that the Diode has to the the ABSOLUTE First thing in the added on circiut??

Im pretty positive about how i did the Diodes.....White band towards relay....otherwise It wouldnt have primed in when WTS Light was on (in theory...if its supposed to go only one way with the diode)
 
The way you have it should be fine.

The only problem would be if the diode was defective and allowed current in both directions.

Assuming its not a Zener diode, and the resistor in the relay is in parellel with the coil.

can you see if the fuse pops right after starting the truck? And if not then shut it off and see if that is when it pops. That relay contract should not be a completed circuit as long as the OPS has oil pressure.
 
I know the fuse blew before shutdown....but cant pin point any better than that...other than it was blown within 15 secs after starting....Its a epoxy Rectifier diode (1N5404 3amp 400V diode ). I checked it with the Battery & meter before Installation to check polarity and it read voltage only one way.

Is this Diode Ok for the Job?

The package came with 2 diodes....I can series another ( just to test) and see if it blows that way.... or get another one (that was the biggest one RS had).


In theory the 87a contact should be fine for this appliation ...would you agree?

Also the Relay is a 20amp AR143
 
I agree that it should work, just that it draws more current through the GP controller.

Test the resistance through the diodes each way. You should have little bit one way and a huge amount to no continuity the other.

That diode should work fine, there is a 5amp fuse on my LP and it never blows. A 3amp diode should be fine, escpecially since it was working during WTS over and over, although they typically fail shorted.

Can you verify your protection diode on the relay is not shorting out any pins, such as pin 87a that it travels over between 85 and 86.

Or perhaps try without the protection diode on the relay, and just let the resistor protect it.
 
Diode on relay is not shorting anything....have it wired on the outside of relay harness... Its all soldered ... and I'm positive it s not shorting.

Maybe...just Maybe its the pump failing? I ordered a Walbro FRB-5 pump from lubrication specialists. The one on it is original.....so who knows. Maybe the resistance on the pump is high??

I have noticed the pump used to be louder...and i can almost not hear it...and I don't know if thats due to the 2 stroke or the pump just going....its time for a new one by now even with 75k miles. So at least I'll have pretty much all new, well thats if the pump wasn't shortening the life of the New ac/delco OPS (3500 miles).

Like I said before pump was not running before this, and only shortly after installing a new one. Then I took the truck out for a short drive and noticed pump wasn't running again after shutdown (didn't have time to check the fuses yet...and GP circuit is removed).

If the Pump was bad maybe the OPS is also shot....I m feeling like a ca$h station lately with new exhaust and crossover mods and PMD, and now new LP...all within the last six months and 3500 miles....thats why I need this to work before I be changing the injection pump next :shots:

I wont even mention drooling over that KOJO thread.....Thanks for all the support everyones offered, ESPECIALLY buddy!:thumbsup:... hopefully i can get this resolved before I want an ATT.:eek:


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