High Pressure Fuel pump install

[Grit dog]

Also found this little gem on LMC’s website. I haven’t seen something like this for sale anywhere else.

https://www.lmctruck.com/fuel-system/fuel-pumps/fuel-pump-control-module-15

Still no motor in the truck yet, but I will be sure to follow up when I get this done and running!

They work great. I didn’t get it from LMC. I dont recall now but there’s several similar options out there.
My carb 454 is a gen vi so cant run a mechanical pump. This little gadget is the ticket to safe operation.

 

[Ricko1966]

Also found this little gem on LMC’s website. I haven’t seen something like this for sale anywhere else.

https://www.lmctruck.com/fuel-system/fuel-pumps/fuel-pump-control-module-15

Still no motor in the truck yet, but I will be sure to follow up when I get this done and running!

Not as simple and easy as just buying this thing from LMC but cheap and no truck down time if one would fail. 2 simple 4 prong relays from your local parts store,or even 1 simple relay and a diode. 1 relay runs the fuel pump,relay trigger is the original choke wire or an oil pressure switch. Second relay runs the fuel pump only in cranking position. Solenoid wire is the trigger. Even simpler is solenoid wire to a diode to fuel pump,again runs pump only in cranking position. The 2nd circuit is necessary to run the pump while the engine is cranking,the diode or 2nd relay is necessary to keep the fuel pump from backfeeding the solenoid and keeping the starter engaged after the engine starts. If a four prong relay fails you are only dead for a few minutes,you can cripple it back up a couple of different ways to get to the parts store to buy another 8.00 relay,not waiting for the mail to send you a new part. Also many oil pressure switches can be used to power your fuel pump,mid 70s Vega is one example. I think they were standard ignition number ps263. Didn't trust my memory,did a little quick research it's a ps64. Here's a wiring dighram for you

 

[Broken85]

It’s EXPENSIVE but it works
Holley #12-308
I bought 1 tried it out then bought 2nd later (had 3 of the in-line fuel pumps fail)
Install in your existing tanks
Works with existing fuel tank switch valve
Wired to valve so tank switch still works
No regulator needed
No return line
Works with factory fuel gauge
Been running them for 3 years now,
never had any problems

I think I maybe going to this set up sooner than I thought. I don’t think the inline can pull the fuel.

Question, when you wired the in tank pumps, how did you switch power between the two pumps? Did you use a relay and if so, what did you use to trigger it??

I will need to power them from the designated pump relay from the sniper two, so I am looking for the best way to provide that power to the selected tank. I thought about a two pole ground trigger relay to the sending unit of one tank, but I don’t think that is going to work. Potentially a tank switch valve off a 1987 would work since GM had to have solved this problem when they went to a TBI.

 

[Red3833]

Sorry Broken, haven’t checked in lately,

Relay…
There is a blue power wire in the sniper 2 harness
that powers the fuel pump. I believe it comes from pre installed relay.
That wire will switch places with the power wire on your
dual tank switch, just cap off existing wire (forget which color), diagram says pink…

Fuel pump power…
Power wire from your fuel pumps will splice into Dark Green and light green somewhere before selector valve harness connector. I used test light to verify which was left and right
I just used butt connectors, two wires in one side and one out the other. You’ll do this for each tank. (supposed to be temporary ended up being permanent) With this setup you won’t have to add anything and your stock tank switch will control both tanks

The second diagram is from Holley website, it’s basically what I did.
PS.. I’ve been really happy with this setup, hope this helps

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[Broken85]

Thanks for the reply. Interesting solution. I didn’t think of powering the pumps through the switch from the sniper. I had it in my mind that some how I was going to have to use a relay so that I wasn’t pulling power through the stick wiring. The 12-308 says they need a minimum 12guage wire (which is weird, because their wiring harness is only 14guage) but I didn’t want to pull a 30 amp circuit through the stock 16guage wire on the truck or the switch.

The thing that stumped me the most was how to trigger the relays because the stock switch on an 85 K10 is momentary, not constant. Then I realized, I don’t have to solve this problem because GM must have solved it on the 87 TBI V10. So I replaced the stock sector switch with a 1987 constant version ($10 from LMC). You will have to take the nub off one terminal with a die grinder to get it to fit in the stock harness.

I don’t think I had to do this, but I also replaced the switch valve. I could find anything that said the 85 and 87’ valves were different, but I was worried about adding constant power to a valve that from the factory was only getting momentary power. Plus, when the tanks were out and I had all the original hoses off, it was a $90 no brainer.

I attached a wiring diagram below of my beautiful mind (don’t make fun of my art work). I figured I could do this with one relay and one trigger or two relays. I chose the two relay option because if one tank relay ever burns out I will have an independent circuit and relay to get me home on the other tank.

This worked immediately and fired right up. Full disclosure, The right tank is running perfect. The left tank will only make 30lbs of pressure so I think I have a bad pump. But when I figure out that problem and the solution I will post it also.

Adding my diagram below.

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