Stock location - oil pressure sender?

[focusedontheprize]

Pros: I am 2 for 2 for "Yeses"
Cons: It is based on "Is my truck wiring butchered?"

After rebuilding the carburetor, I realized I need to first fix the engine harness before going forward. I pulled the engine harness today (they had cut a bunch of the wires) and started identifying ones I need to re-wire.

One of them is the oil pressure sender. The wire was never hooked up because the sender did not have the same terminals. I am going to buy this (https://www.rockauto.com/en/moreinfo...61884&jsn=1071), but would like to know where the stock location is to install this. I have read somewhere in the rear of the intake manifold.

Can someone post a picture on theirs? Thank you.

[hatzie]

This differed by year... Assuming it's for the 88 V30

On a TBI engine the large gauge sender is usually on the side of the motor just above the oil filter.
The TBI fuel pump oil pressure switch is between the intake manifold and the firewall.
If it's sporting a carburetor then the oil pressure sensor could've been just behind the intake or down below. Since you're repairing the wiring you can make it reach the location that makes you happy... I'd install it up top.

[kipps]

Originally Posted by hatzie

This differed by year... Assuming it's for the 88 V30

On a TBI engine the large gauge sender is usually on the side of the motor just above the oil filter.
The TBI fuel pump oil pressure switch is between the intake manifold and the firewall.

And just for the record. The TBI engine doesn't actually need the fuel pump oil switch. That was just a backup to power the fuel pump in case the fuel pump relay failed.

[focusedontheprize]

Thanks Kipps. The truck has been converted over to a crate motor (454) so I will take look about that switch.

At the moment, the oil pressure sender is located in the front on the driver's side just above the oil pan.

[hatzie]

Originally Posted by kipps

And just for the record. The TBI engine doesn't actually need the fuel pump oil switch. That was just a backup to power the fuel pump in case the fuel pump relay failed.

Not a good idear to run a TBI without it.

If he has a carburetor that's a moot point anyway. He has a mechanical fuel pump.

[kipps]

Originally Posted by hatzie

Not a good idea to run a TBI without it...

Why? They don't provide a back-up option for modern fuel pump relays. Why should you need one with a TBI?

The TBI computer doesn't see oil pressure at all.

[cerial]

Originally Posted by kipps

Why? They don't provide a back-up option for modern fuel pump relays. Why should you need one with a TBI?

The TBI computer doesn't see oil pressure at all.

It is there so if you get in a accident with you on your side/roof the fuel pump will shut off when your oil pressure drops below 4psi(I think).

Modern fuel pump relays use a inertia switch or a air bag/computer to kill the fuel pump. TBI uses the oil pressure instead of a inertia switch letting you bounce off trees off road and keep going where a inertia switch will trip and shut you down.

The thing can work without the relay once the truck is started and running. But power is run through that switch first then to the relay. This is one of the 10 sensors I replace when I get a tbi truck because if that fails your not going anywhere(unless you bypass it to get home). I have a diagram of the fuel pump circuit with tank selectior that I used to retain this safety feature when running a inline pump/tank. But my image hosting site is messing up so I cant show it to you currently.

[kipps]

Originally Posted by cerial

It is there so if you get in a accident with you on your side/roof the fuel pump will shut off when your oil pressure drops below 4psi(I think). ...

Is this diagram wrong then? it shows the oil switch and the relay operating in parallel. If the switch opens, the relay continues to power the pump, per this diagram.

It's been a couple years now, but I'm pretty sure my '87 was operating quite fine without the oil pressure switch.

[hatzie]

The fuel pump, or the fuel pump via the NL2 dual tank power circuit, gets power from three places.

1. The ECM commands the fuel pump relay closed when it senses the pickup inside the distributor is turning.
2. The oil pressure safety switch Normally Open contacts close when the pressure reaches 4-6PSI.
3. The Hot Fuel module commands the fuel pump to on.

While it will run without the switch you're defeating a safe backup system by omitting the switch. It's not just a backup power supply for the fuel pump. It's backup power with some degree of safety so you can limp home without the fuel pump relay without running the risk of burning the truck down from the fuel pump continually pumping fuel into the fire in an accident.
In an accident where the engine stops the fuel pump should stop because the oil pressure drops and the ECM should stop commanding the fuel pump relay because the distributor stops.

The OP has a carburetor so he likely has a mechanical fuel pump that stops as soon as the engine stops.

[57NAPCO]

Reviving an ol’ thread,

I’m struggling with my original 88 V30, 454, no start.... fuel issue. Ran great until I filled up at the station and then no start. Bed is lifted, pump replaced even thou the old one worked. Took off the tank selector cover on the frame rail and unplugged the electrical connector, with key on I get about 7.4 volts to only 1 pin. Switching from one tank to another makes no difference. The fuel pump relay on fire wall energizes after about 2 seconds of turning key on. I suspected a bad oil pressure switch behind the distributor but can’t locate it. I only suspect because of reading the service manual. I’m very weak with electrical stuff and schematics.

[57NAPCO]

The previous owner put the valve covers on, it’s a stock 454, 22,000 original miles.