Does anyone know what this is

[bucket]

i have an 88 firebird with tbi oil sender is behind dizzy the one in the side is a pressure switch so fule pump wont run with no oil pressure

The oil pressure switch actually sends power to the fuel pump, in the event of a pump relay failure. GM never wired the pumps to turn off with no oil pressure, it's just a common misconception.

 

[Ricko1966]

The oil pressure switch actually sends power to the fuel pump, in the event of a pump relay failure. GM never wired the pumps to turn off with no oil pressure, it's just a common misconception.

Are you sure? IDK about that firebird but I am real sure Vegas, Monzas, and Oldsmobile achieves used the oil pressure switch as the trigger for the pump relay.This is alk from memory but I thunk the sender number we ps64 and having learned on those cars I thought the trucks would be the same.So how are the killing the pump in KOEO?

 

[bucket]

Are you sure? IDK about that firebird but I am real sure Vegas, Monzas, and Oldsmobile achieves used the oil pressure switch as the trigger for the pump relay.This is alk from memory but I thunk the sender number we ps64 and having learned on those cars I thought the trucks would be the same.So how are the killing the pump in KOEO?

Yes, I'm sure. The fuel pump receives power from two different places- the relay and the pressure switch on a separate circuit. The pump relay is normally controlled by the ecm, which is how it primes and then shuts off. The ecm will run the pump for a predetermined amount of time and turn off, unless of course the engine is started before that time. If you cycle the key to let the pump run, they normally only run that one time and won't run again if the key is turned right back on.

If a TBI motor ever has an extended crank time, the first thing to check is for a failed pump relay.

 

[bucket]

That and there's been who knows how many thousands of GM engines killed by running with no oil in them.

 

[Dave M]

The choke has a spring,heat changes the spring tension.Some cars use an electric element to heat the spring which opens the choke,as the spring cools it pulls the choke shut.When the choke is shut the engine can't draw as much air so consequently it draws more fuel so you have a rich mixture for cold starts.There' s also a cam on the choke rod that holds the throttle open a little when the choke is on so the truck will idle cold.

Thanks for the reply, I get all that, makes better sense now that you amended it. My main question is the heater itself, it is powered all the time whilst the engine is running, do they have an inbuilt cutoff when they reach a certain temperature. Are the elements prone to failure/electrical issues/burning. My reason for asking is l am contemplating replacing my Quadrajet and upgrading to the later type, fitted with the factory electric choke, and fitting a dedicated fuse to the power it.

 

[bucket]

Are you sure? IDK about that firebird but I am real sure Vegas, Monzas, and Oldsmobile achieves used the oil pressure switch as the trigger for the pump relay.This is alk from memory but I thunk the sender number we ps64 and having learned on those cars I thought the trucks would be the same.So how are the killing the pump in KOEO?

Stole this diagram from another thread here. But it shows the pump relay is triggered by the ecm. The oil pressure switch receives power from the same fuse as the fuel pump relay, then sends that power to the output side of the relay, which of course is what powers the fuel pump.

You must be registered for see images attach

 

[Vbb199]

In reference to the tbi, they had just 1, im almost certain. Fuel pump relay, and gauge all feed off of the same sensor behind the distributor.

And no, low oil pressure doesnt turn off the fuel pump, at least on the squares.

 

[Ricko1966]

Stole this diagram from another thread here. But it shows the pump relay is triggered by the ecm. The oil pressure switch receives power from the same fuse as the fuel pump relay, then sends that power to the output side of the relay, which of course is what powers the fuel pump.

You must be registered for see images attach

When you brought up the extended crank that turned the light back on in my head,I learned that right about 2000 but been out of the loop so long I had forgotten. Quit /fired depending on who you believe from the GM dealer in 2005


Son of a bitch I think I learned it on that achiva

 

[seniorbear69]

well did any one actual find out whot it wos .i ma have been wrong on how the switch works but i wos tring to help .isent this whot thease forums are about .sory burrban im an idiot and thanks for bukket to pointing it out

 

[bucket]

well did any one actual find out whot it wos .i ma have been wrong on how the switch works but i wos tring to help .isent this whot thease forums are about .sory burrban im an idiot and thanks for bukket to pointing it out

No it's fine, I didn't mean to harp about it. It's just very common for people to think it works that way and I wanted to point out that it's not.

But yes, many trucks have a gauge sender and a pressure switch too. But the locations did flip flop over the years, so there's no definitive answer on which one goes where. It works the same either way.

 

[WebMonkey]

my truck has both.

one is just a switch (on/off).
the other drives the gauge (variable resistance rather than binary on/off).

both are plugged into a T then in behind the distributor.

lots of answers, i don't know nothing myself.

my truck had a hose/fluid line someone put on the other side of the T to drive a non existent mech gauge.
pulled that out and put the correct unit in and plugged in the wire from the factory harness.

gauge works.

 

[Ricko1966]

The oil pressure switch actually sends power to the fuel pump, in the event of a pump relay failure. GM never wired the pumps to turn off with no oil pressure, it's just a common misconception.


Are you sure? IDK about that firebird but I am real sure Vegas, Monzas, and Oldsmobile achieves used the oil pressure switch as the trigger for the pump relay.This is all from memory but I think the sender number we ps64 and having learned on those cars I thought the trucks would be the same.So how are the killing the pump in KOEO?

Stole this diagram from another thread here. But it shows the pump relay is triggered by the ecm. The oil pressure switch receives power from the same fuse as the fuel pump relay, then sends that power to the output side of the relay, which of course is what powers the fuel pump.

You must be registered for see images attach

https://images.app.goo.gl/ASQhzMYCBLvTkwq38

This is how I learned it, and it stuck in my brain,and sometimes fail to remember just because one car was one way doesn't mean all cars are the same way. But you are correct on the chevy truck . I've gotta try to remember to only post on exact same stuff I've done not similar stuff. Sorry to anyone I confused.

 

[bucket]

The oil pressure switch actually sends power to the fuel pump, in the event of a pump relay failure. GM never wired the pumps to turn off with no oil pressure, it's just a common misconception.


Are you sure? IDK about that firebird but I am real sure Vegas, Monzas, and Oldsmobile achieves used the oil pressure switch as the trigger for the pump relay.This is all from memory but I think the sender number we ps64 and having learned on those cars I thought the trucks would be the same.So how are the killing the pump in KOEO?




https://images.app.goo.gl/ASQhzMYCBLvTkwq38

This is how I learned it, and it stuck in my brain,and sometimes fail to remember just because one car was one way doesn't mean all cars are the same way. But you are correct on the chevy truck . I've gotta try to remember to only post on exact same stuff I've done not similar stuff. Sorry to anyone I confused.

Well, I'm curious... what cars are you remembering? The fwd cars I messed with were done the same as the trucks, and the F-body too.

 

[Bextreme04]

just to clarify, this really only matters if it is an engine block or head or intake maniifold casting "ground-through" type sensor.. which would be a single/terminal/pin/wire type sensor.

this type design of sensor will simply allow engine block ground through itself and into the terminal/wire on/in it.
and so with these sensors they DO indeed need to be grounded through the threads- clean with no sealant at all- to the engine block or part casting that it installs/threads into,. yep.

a good example of this are the single-wire CTS sensors. you defiitely never should thread seal a single-wire CTS. but the two terminal TBI ones yes thats fine, can thread seal those no problem.

This is not necessarily true either. The thread sealant fills in the gaps between the two thread surfaces, but if tightened properly the thread ends are biting into each other through the sealant. If you don't use sealant it will almost always leak. I've never seen a factory 1-wire sender installed without sealant of some kind. I generally prefer the liquid thread sealant.

 

[Bextreme04]

Stole this diagram from another thread here. But it shows the pump relay is triggered by the ecm. The oil pressure switch receives power from the same fuse as the fuel pump relay, then sends that power to the output side of the relay, which of course is what powers the fuel pump.

You must be registered for see images attach

Thanks for posting that diagram, I keep hearing that it is just a secondary power supply to the pump, but couldn't figure out what the purpose would be until seeing that diagram. I wonder what pressure the switch is set to? My take on this is that it is there to prevent the truck from just shutting off while driving due to a failed relay. It keeps the fuel pump running as long as the engine is running. So, if you are driving and the relay fails mid drive you would never knw until yo uget to your destination and shut it off. Once oil pressure bleeds down, the switch disengages and the pump turns off. Then when you go to start it back up again, you have a failed relay, you will get the fuel prime on key-on, but wouldn't get fuel pumping when you go to start(unless maybe it cranks fast enough to build enough pressure to engage the switch).

What do those relays look like on a TBI truck? Is there a bunch of them like a modern car? Its pretty common to have a fuel pump relay cause a car not to start, you can usually just swap it with the horn relay that is almost always right next to it(and easy to test) to verify the problem.