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Goofing around with my truck this morning and removed the fuel pump relay when the truck was running and to my not so surprised mind it keeps on running.
Turned it off and restarted and drove around the block fine with the relay removed.
It should not do that with the relay removed correct?
I did check the three blk/wht ground wires at the ecu by probing them to a ground and it made no difference.
I know i have a electrical issue and 2 shops have not fixed it so im going to need to do it myself. Problem is im not a auto wiring guy at all really.
I have a test light and a multimeter but that should be enough i think.
Where should i start?
That is exactly what it should do.
That means that your oil pressure sensor is working correctly.
The system is designed to continue to power the fuel pump through the oil pressure sensor if the fuel pump relay fails.
That is a safety feature that keeps the engine running so it cant shutoff and cuase you to loose power brakes and power steering because the relay failed.
In other words, congratulations!
Your oil pressure sensor is working.
The real halfass way to test this is to wait untill the truck is stone cold.
Key on untill the pump stops then key back to run.
Not off, only back to run.
carefully pull the relay so you dont short anything.
try cranking it again.
It may momentarily fire but it should stall
Like Richard said you should expect a really long crank cycle while the oil preesure sender builds pressure.
The idea behind the key on sequence is to fool the system into thinking that the fuel pump relay has failed.
If you go back to key off you are starting from scratch.
If you really want to get nutty about it.
Put the relay back in.
Wait untill it is stone cold.
Start it and get it up to temp with all systems in place and warmed up.
While it is hot and running, pull the connector of of the oil pressure sensor.
It might stumble and run like poo for a bit but.
It should stay running.
You will get a check gauges light for sure.
There is this nutty idea across a lot of TBI forumns that spread this theory that they are designed to stop running if they dont have enough oil pressure .
That is just not what happens.
That
That check guages light and stall means that your fuel pump relay and your oil pressure sensor are failing.
Often times they have dualing heat related failures.
This is where it stalls and you wait awile and it starts again and then stalls once more?
No matter what anyone tells you the TBI system is not designed to shut off due to low oil pressure.
It will shut off if you have a bad fuel pump relay and a bad oil pressure sensor.
But not because of low oil pressure.
It fails because both paths to the fuel pump have failed.
The check gauges light and the low oil pressure reading are just low voltage inputs .
And the factory oil pressure gauge is not only useless. It also doesnt read where the factory manual claims it should.
My 1994 owners manual tells me to expect 28 psi cold and 7 psi hot.
It reads at 60 cold and 10 hot.
It actually has 45 cold and 25 hot.
25 hot on worn a small block chevy at idle is good enogh for me
I think at 270k shes a bit crudded up
Dont sweat the load over factory gauges.
If you run a small block chevy bone dry you will hear all about it.
As long as you dont beat the snot out of a stock engine and you change the oil,
They just dont explode.
They wear out the rings and valves untill they cant compress anything long enough to start.
Look at it this way my friend.
Fixing your truck and learning how to do it is just something you need to look into and learn.
It can be a bit intimidating and thier are quite a few people who will try to shoot you down for trying.
**** them little boys.
The best thing you can ever do for yourself is to learn how to repair cars.
A new truck is about 70 to 80 grand.
The resale is about 30 percent of that tops.
And they all do zero down crap trade in and a five friggen year float.
That is not an 80 grand truck stupe.
That is a 120 thousand dollar truck.
Meanwhile, back at the ranch.
You buy an old chevy truck and you have some apprehension because you are not familiar with how to fix it.
But you reached out to try to do it yourself
That is such a great and grand thing to do.
Every dollar that you dont send to the finance company and every damn dollar you save by figuring out how to do on your own is another dollar towards buying your house or putting your kids through college or putting in your retirement fund or making sure that your wife has enough money when you drop dead.
Im getting kinda old these days.
But I sure as **** never thought that people would pay house prices for a damn pickup truck without people looking at them like they were ****** idiots.
