oil sending unit

[redbeard]

Hi. I am back with more quesitons. I finally am getting it all together to install that electric fuel pump. I talked to a tech rep at Airtex, maker of the fuel pump. It's Airtex pump part #E8012S. He told me that particular pump won't need a relay since it runs at something like 1.6amp. He recommended a part (Airtex part # OS-35 they make (cant' sell retail) to install in place of the oil sending unit. He said I can get a 'T' to install and put the sending unit and their part in there.

Powering the pump from the oil sending unit insures the fuel pump will only run when engine is running. Also helps to prevent the fuel pump to keep running incase of a crash.

My first question is where is the oil sending unit?
next, rather than the 't' and part and all, can I just splice the fuel pump power wire to the wire coming out of the oil sending unit?

For those of you wondering what took so long. Um mainly 2 things, weather and my health. Foot of snow 3 weeks ago was a surprise. ahh, springtime in Colorado..

Thanks for the help.

Myles

[712edf]

First of all which engine are you talking about. On most mopar V8 gassers its on the back of the engine on top where the bellhousing connects to the block. Second does this fuel pump have its own sending unit? If so I'd go with the "T", just to be safe. Different sensors have different parameters to operate within.

[redbeard]

oops to which engine oil pressure sending unit.

Thanks for pointing out that necessary informaiton. This is for a 1977, M880 with the 318ci V8, auto tranny. I guess that's all the needed info.

I was able to order that part suggested by Airtex from Rock Auto. $20 delivered UPS ground. Now, where does it go again? LOL, I will look at that suggested area tomorrow. As of now, it does not have a sending unit. I thought that was what I was ordering. Replacing the oil pressure switch with the sensor I ordered. They said to find a place to install he pump , ground wire to ground (duh!) and power wire to this part.

Next question is where do I get that kind of 'T'. When the part arrives, I can match threads to make sure it's right when I find it. Should I use brass? galvanized? I would like to use the 'T', I think it is important to have a working oil pressure gauge.

Thanks,
Myles

[712edf]

As of now, it does not have a sending unit. I thought that was what I was ordering. Replacing the oil pressure switch with the sensor I ordered. They said to find a place to install he pump , ground wire to ground (duh!) and power wire to this part.

I may be missing something here, but the stock oil pressure gauge sending unit does NOT have or produce any voltage. All it does is provide a GROUND for the oil pressure gauge which gets its voltage from within the instrument panel wiring/circuitry. The more oil pressure that its "sensed" by the sender then the more ground continuity is produced within that sender which moves the needle higher in the instrument panel. Not sure how your fuel pump should be wired, but if it involved the oil sender then it maybe should have to do with the ground circuit of the pump.

The "T" fitting is a NPT (national pipe thread) of a certain size (can't remember, somebody jump in here any time) which aftermarket gauge makers like AutoMeter should carry. Or try plumbing/hardware section that carries small fittings. I think you want brass.

[DODGEBOYS]

the SENSOR he,s talking about is a LOW oil pressure cut-off switch and can be had at NAPA fairly cheap

[712edf]

the SENSOR he,s talking about is a LOW oil pressure cut-off switch and can be had at NAPA fairly cheap

Aha! That makes sense. My rigs are too primitive to have such a device.

[redbeard]

fuel pump cut off switch

OK, I am still at a loss. I checked back with the fuel pump manufacturer and again, they said pull the oil pressure sensor (low or high, I have no idea) and install this switch.

The base of the switch is a fine thread of about 1/4" diameter and there are 3 electrical terminals on the top. the wiring of these 3 terminals are:

1. to fuel pump pos wire.
2. to starter solenoid
3. to a 12v connection only hot with ignition on

The purpose of the switch is that if the engine stalls, the electric fuel pump will stop pumping.

Regarding the location of the senosr, I looked at the rear on the intake manifold and there is something threaded into it in front of the distributor and slightly to the right (driverside) of the distributor. There is a vacuum hose going from it to the vacuum boost(?) cover that the brake fluid reservoir is attached.

Does any of this help or make more sense of what it needs?

Decided to wire the pump to the battery and check the pump to be sure it's what's needed. We were able to get the truck to run when we poured fuel into the carb. Also, no fuel came out into the carb when we tried to start. sounds like a fuel supply problem.

will be back with test results

RED

[712edf]

What you've found on the manifold is a vacuum port. The oil sensor unit will not be on the manifold, but on the block. Usually they are on the back of the block close to the firewall, less than 2" from the transmission bellhousing. Yours is probably behind/below the distributor. You will have to nearly crawl on top of the engine to see it.

[redbeard]

oil sending unit

We were wondering about the vacuum line going to the sensor. It almost ran today when we 'hot wired' the pump. Still didn't have good flow. I think we will go back to the beginning and pull fuel lines and blow them out, re check rubber hoses for holes, and probably replace the ones that haven't been replaced anyway. If I can get it to run as far as Colorado Springs, I'll take it in and drop the tank, AGAIN, and clean it and sending unit.

about crawling in and sitting on the engine, well, I have to do that anyway. I keep a folding step stool in it just in case I need it to get to the engine. Darn good think I don't have set timing by rotating the distributor. I would have to pull the hood or risk laying on top of a running motor. OUCH!.

thanks for the info on that sending unit, we will see what happens.
Myles