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Lift Pump Relay Upgrade - '94-'95

SnowDrift

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I don't think there has been a full write up on this, so I'll try to put something together. I wasn't a fan of cutting the factory wire harness on my truck, so I wanted to find a way to do this upgrade without having to cut wires. I was able to buy the parts and use my old non-functioning OPS by cutting it apart. By doing this, I was able to avoid cutting the gray wire, named in the schematic. I, basically, am just using the terminals to make a jumper to plug in the harness from my truck pigtail to the new OEM OPS.
 

SnowDrift

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Here is the end result of cutting apart the OPS. I used a tubing cutter to make a nice, perfectly round cut. I am left with the portion you see here with just the metal terminal spades left in the housing. They're loose, so be careful they don't drop out. Note their orientation, in the event any fall out, so they can be replaced properly.
DSC_0461.jpg DSC_0462.jpg

My new OPS is the 1924-4501 shown here. This is not the one the dealer called for. The one they said I needed was a 1924-4500, which did not function at all for my application, although I don't know why. I returned it and asked for this one, instead, after talking with Bill Heath and he told me which P/N they use for this. The pigtail shown can be had from Amazon or your local parts dealer. They range from $4-5 to $30 or so.

I tied the loop in the wire to join to the gray "glow plug on" wire, so I didn't get them switched by accident.
 
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SnowDrift

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I purchased two relays from a manufacturer in the USA. http://www.pokornyrelays.com/page3.html They were hard to find, but I understand they might be the only ones making relays in the USA. These were a sealed unit for a Ford application. These are also a weathertight relay, but the socket is not. Later, I'll show how I mounted them so they retard water intrusion. They only came with four wires/terminals on the matching sockets they provided so I had to add one to one of the sockets. I had bought another socket for this project earlier and didn't use it, so I robbed one terminal/wire from it. It is the yellow wire you'll see later on.
DSC_0466.jpg
 

SnowDrift

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The two remaining bare wires on the made up harness got male and female connectors that could be connected and disconnected. I put opposite ends on them and did the same on the mating wires they attached to, so I couldn't get them mixed up if I had to remove anything in the future. It would only go back together one way. I also filled the cavity in the modified OPS with hot glue to keep the terminals from moving around. It didn't turn out as pretty as I hoped it would, but it got the job done. I think if I have to do it again, I would coat the terminals at the bottom with the hot glue and then fill the rest of the cavity with some self leveling silicone.
DSC_0468.jpgDSC_0469.jpgDSC_0471.jpg
 

SnowDrift

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I wired everything together temporarily with butt connectors, just in case I got anything wrong, I still had plenty of wire to re-wire and repair. This is a nasty spaghetti mess.
DSC_0472.jpg
 

SnowDrift

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Here is the final harness with the corrected wire lengths, all the proper eyelets, heat shrink and such. I've taken some close up shots so wires can be followed and traced down. Here you see the yellow wire I mentioned in the one socket. My reds are power, the blacks are grounds, the yellow connects the two relays together, and you can see where the blue terminals plug and how I mentioned the male/female so they can't be connected wrong.
DSC_0491.jpgDSC_0492.jpgDSC_0493.jpg
My tile shown is 12" tile. I had plenty of wire for everything. I might make some shorter if I had to do it over, but this gives you an idea on some lengths. I had measurements someplace, but I'm not sure what happened to them.
 

SnowDrift

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This shows the new harness tucked back in the back. Again - no wires have to be cut with this new harness. The whole thing, here, ends up with one harness to go between the OPS and the truck harness and a separate harness that contains the relays I'm adding.
DSC_0494.jpgDSC_0495.jpg
 

SnowDrift

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Here is how I routed the harness along the firewall - you'll notice the nice shiny black loom - that contains my wires heading out to the relays.
DSC_0496.jpg
 

SnowDrift

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Here is the bracket I made up that I mentioned earlier. It keeps the relays so the socket is facing downward. If any water should come in, it would drain out. It's just a small piece of 10 ga. I bent up and poked a couple holes in. My relays had mounting tabs by choice. This was the reason for the tabs. The first set I ordered didn't have tabs, so I sent them back to the supplier. Finding the exact relay I wanted with mounting tabs was a challenge for me. The owner, there at Pokorny seemed to be top notch, though.
DSC_0497.jpgDSC_0498.jpgDSC_0501.jpg
 

SnowDrift

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I grounded to the mount bracket for the ABS module. Mine is a '95 and I'm not sure if the '94 was the same or not. Basically, though, I looked for a ground that was out of the weather, water and that was accessible in the event I needed to check it in the future.
DSC_0502.jpg
If someone needs better shots of something, just let me know. I did this update several months ago but I'm just now getting time to post all these photos, so I hope I didn't miss any critical steps.
 

SnowDrift

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These relays have the diode or something that was mentioned. I believe AK suggested that to me. I forgot to mention that in the thread when I was talking about the relays. That was the other part that made them hard to find. Easy to find relays with any combination I wanted made in china, but seemed hard to find brand names and/or better yet, made in the USA. I'd have bought Tyco or Bosch, though.
 

Burning oil

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Mine will have the diode and surge protection.
Its going to be a very high quality harness.

You did a good job on yours.
 

Chevypoor

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Nice job. Looks good. GM missed the mark on the lift pump wiring on these trucks. After mine left me sitting twice I put mine on a manual switch. The 93 6.2 parts truck was very difficult to start and then would cut off and would be even more difficult to start. Same problem the lift would not run or only run intermittently.
 

SnowDrift

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In post #12, above, I provided a link for Page 3, showing a wiring schematic I used when wiring up my relays for my lift pump. Page 3 is no longer there. At first, I thought I mistyped it, but then I noticed the link, itself, has "page3" embedded.

where did it go?
 
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