Was wondering if you guys could help me out here.Ive got a pic of the fuel pump wiring and neede to know if the small plug with the gray and blk/wht wite goes to the oil press. cutoff switch and the large plug goes to the fuel pump?What am I missing here?im going to be running a walbro 255 and not sure on the wiring.Thanks in advance.

 

Oh yeah also do you know where I can find the jumper harness to go from the MAT sensor to the wiring harness?Thanks again.

 

I can build you a new section. Is this what you're looking for?



Please email me if you're interested.

 

ANyone know about the fuel pump wiring?Thanks s10 wildside that is the harness im looking for.I e-mailed you.

 

The connector on the left may be for the A/C pressure switch. It is definitely not the oil pressure switch.

 

Can you post a pic of the oil pressure switch plug?Sorry for all the ?'s but im trying to wire this motor up and all ive got is some diagrams i got from a haynes manual and what ive found on this board.Do you know what the big plug is for with the orange and red wires?Thanks again.

 

Where is connector located under the hood? What year car? Cooling fan possibly?

 

Well its in a rock crawler,but its out of a 1991 f-body with a 305.
The problem im running into is there are sooooo many different wiring diagrams out there.Some match the colors Ive got and some dont.What Ive done so far is started at the ecm and did continuity checks between the ecu and its respective sensor/plug.
And going by my diagram for the ecm pinouts these arent for cooling fans and they arent for the a/c.How many wires go to the fuel pump and sending unit?Im assuming theres a body harness that goes to the fuel pump.This is what I need to duplicate.

 

If I am not mistaken, the 91 V8's had the oil pressure sender and switch integrated into one unit, not sure if it was 2 or 3 wires. the wiring would go down towards the oil filter.

The round connector you have in your hand looks just like the A/C pressure switch connector and the connector next to that looks like the fan harness connector.

Fuel pump connector will have 4 wires, 2 orange and 1 black and 1 grey I believe with the orange wires on the outer edges of the connector.

The harness that goes to the fuel tank will have 3 wires, one grey, one black, and one pink.

Most of the wiring stuff I mentioned above is from memory, but I will double check tomorrow for accuracy.
kinda worn out after finishing up my Holley Stealth Ram install.

I should know all of this by heart since I myself did a carb to TPI swap a few years ago.

Also, the oil pressure/fuel pump switch is a backup for the fuel pump relay. It is designed and wired up so that if the relay ever fails the oil pressure switch will activate the fuel pump when 3-5psi of oil pressure is detected. It does not cut off the fuel pump if oil pressure drops.

 

Very true...some have this confused. A quick look at the wiring diagrams will show this functionality. In fact, I don't have to use a fuel pump relay when I test the TPI harnesses I build and test because cranking the engine will produce the oil pressure needed to power the fuel pump on startup.

 

I'm running short on time this morning, so I can't post a pic. This is the best I can do for now. The oil pressure switch connector is gray with three wires going to it:
16ga Orange: This is tied into battery power (protected by 20amp fuse)
16ga Gray: This is tied into your fuel pump power.
18ga Tan: This goes to the oil pressure gauge

Hope this helps:



***EDIT***
This is the Oil Pressure Switch connector.

 

Hello , i put a tpi system on my truck and it was from an 87 iroc. the plug with the two wires you have in the pic (red+orange) looks to be the same as the plug i have which was used as an auxillary power for alot of the accessories on the front of the car. my plug is still hanging from the harness. if it is this plug you dont need it. i went to GM school for training on all the efi systems thru 92 and have GM diagrams and descriptions if you need them. david

 

Go to this link. www.diy-efi.org/gmecm/ecm_info You'll find schematics for most all years.

 

Hey CHEVYTPIMAN If you dont mind send me some diagrams for the fuel pump wiring and relay wiring for a 91 350 TPI.Id really appreciate it!ALso the oil pressure switch,is it the same thing as the oil pressure sending unit?I went to autozone and both were the same P/N.Are there 2 of these switches or are they smoking crack?

 

Hey CHEVYTPIMAN If you dont mind send me some diagrams for the fuel pump wiring and relay wiring for a 91 350 TPI.Id really appreciate it!ALso the oil pressure switch,is it the same thing as the oil pressure sending unit?I went to autozone and both were the same P/N.Are there 2 of these switches or are they smoking crack?