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'89 R3500 Crew Cab 2wd to 4wd conversion & beyond

Started out with 2wd TBI350 with SM465 to current 4wd with 454, 700r4, NP241
Overview Gallery Discussion
skunked said:
I was going to add a dummy light. I wonder if the other port above the oil filter is an option?

Edit, the smaller port to the left. Mine is plugged...

ccrp_1102_07_o%20demon_engines_low_buck_454_engine_build_part_iii%20tapped_oil.jpg
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I'm guessing it would. They must be using it for something in the picture. There are also the ports above the pan rail like the one you can see in the image above.
 
Truckman4life said:
It's really easy to get a pressure sensor for say 10 psi or whatever you want and just wire it to the ground side of your relay so it cuts the pump if oil pressure ever goes below that pressure and you won't get fuel pump until you crank a little to build pressure either.
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Yeah, I'm thinking it would be easy to wire up my own setup. I've been reading over at Thirdgen about what people are doing when swapping from TBI to carb. Many of them are keeping the TBI system in the vehicle and using the existing fuel pump relay. You keep the oil pressure switch, ECM, and change the input on the green and white wire into the fuel pump relay. Nice thing about this is the ECM will still send the signal to run the fuel pump during cranking.

Some people are also using a momentary switch to run the fuel pump during cranking.

With the 2 tank setup added to the mix I'm thinking it might be easier to keep the TBI components to maintain the fuel supply setup. I don't know tho, I'd really like to pull all the TBI wiring out. Although on the other hand, if it stays in the truck it would be easier to switch back to TBI if I ever wanted to.
 
Interesting info added here for anyone searching in the future and as a reminder for myself. The fuel pump power feed from the Sniper harness will shut the pump off at 0 RPM. It will also run the pump for a short bit when key first turned on and then shuts off until it gets a tach signal.
 
That will work then!
So I assume that the TBI stuff is all coming out now?
 
Hopefully so. I hate having new systems layered over the old. It would stink to have the ECM fail and cause the pump not to run when the ECM would just be in there to keep the fuel system wiring as is.
 
the simplicity of these new EFI systems is too cool to clutter up with old TBI wiring IMO.

You're running two tanks with two in tank pumps and a selector valve right? If so, couldn't you have a toggle switch so when you switch tanks you also switch to the other fuel pump?
 
skunked said:
the simplicity of these new EFI systems is too cool to clutter up with old TBI wiring IMO.
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Truth

skunked said:
You're running two tanks with two in tank pumps and a selector valve right?
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Correct

QUOTE="skunked, post: 3757632, member: 73997"]If so, couldn't you have a toggle switch so when you switch tanks you also switch to the other fuel pump?[/QUOTE]
The tank selector valve does that for me. It has 1 input power wire for the pump and the tank selector valve routes pump power to the tank selected.
 
mrk5 said:
The tank selector valve does that for me. It has 1 input power wire for the pump and the tank selector valve routes pump power to the tank selected.
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ah yes, duh it has TBI pumps :doah:

That should be pretty slick.
 
So I was wrong, it's the tank selector switch that chooses the pump.

Below is the wiring diagrams I pulled from the book. The green highlighted is the pump feed. I marked where I can cut that wire and tap in the wire from the Holley.

I also labeled the wires on the factory fuel pump relay a person would need to change if they were going to keep that part of the TBI system. This is most common for people converting from TBI to carb.

Fuel-Pump-Circuit.jpg
 
What perplexes me - and why I like the idea of totally removing the TBI wiring - is why there are 2 other places power is fed to the tan/white. One comes from the fuel pump oil pressure switch and the other comes out of the ECM.

I'm guess maybe the lead comes from the ECM so the computer can run the pump in special situations. :dunno:

Then I really don't understand how the oil pressure switch works. Unless the switch grounds out to the motor when pressure is low. Otherwise I don't see how the switch can stop the fuel pump when it's still getting power from the fuel pump relay.
 
The relay is not a real reliable long term power distribution option for the pump. The oil switch is direct to the battery once the pressure comes up, for reliable power.

Not too sure that wasn't the issue on my tank selection. I did not have the oil switch in yet, think it burned the solenoid on the selector valve
 
Ah interesting. I would have guessed it was the other way around. Does the computer ultimately kill the ignition trigger to the relay? If so then I can understand how low/no oil pressure would kill the motor.
 
mrk5 said:
Ah interesting. I would have guessed it was the other way around. Does the computer ultimately kill the ignition trigger to the relay? If so then I can understand how low/no oil pressure would kill the motor.
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Yes it shuts off the ig module
 
Thanks, that clears up my confusion. Except the tan/white output off the ECM.
 
I can honestly say that oil pressure switch works. I cut an oil cooler line on the crank pulley one of the last times I was out. Didn't notice the pressure gauge was 0 for longer than I would prefer to admit, would not start. Looped the line and it fired right up.
 
I suppose it's good insurance for thinkers like those of us on this site. No matter how careful you are mistakes/oversights happen.

Seems like I could wire the factory oil switch into my plan.
 
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