94 chevy astro oil pressure switch problem

I put the oil pressure switch in and its still the same thing. I still get the 12v+, the oil gauge 6v and the 12v to the pump untill warm. Then it just dies and won't start again. I don't lose the 12v+ but the wire out to the pump reads 0v as soon as it dies. Its not like I'm losing oil pressure. The cluster reads around 40 psi.

Did you ever wonder why the relay was melted?

Could it be that the fuel pump has a problem where when the pump runs for a while it shorts out or otherwise draws too much current?

Ted

As far as the pump relay being de-energized after oil pressure builds, I've never seen any published information, stating that. I've worked on alot of GM vehicles and I have never seen that.

There should be a fuel pump prime connector. You can run B+ to that connector and the pump should run. You don't have to use the key, you don't have to worry about the oil pressure switch in the fuel pump circuit, you can try this after the vehicle warms-up and dies, just turn the key off.. This is just for a test, you can see if the pump runs and check fuel pressure. I didn't notice a fuel pressure spec listed in your post, maybe I missed it.

If the system was holding oil pressure for a long time, that o/p switch in the fuel pump circuit, would remain closed, meaning the pump would run, until either the oil pressure drained off or the key was turned off.

If there is a red wire coming off the relay, that should lead to the fuel pump prime connector. That connector is usually on the same side of the engine compartment as the battery, that doesn't mean it is close to the battery. The connector can be in different locations on different models. Sometimes their close to the relay. You could take the pump connector loose, then run B+ to the prime connector and check for B+ and ground at the pump connector. Usually you can get to the pump connector without dropping the tank, you'll have to look.

Like TED suggested, your pump may be having a problem.

I just wanted to add, if you use a jumper on the prime connector, you might use a fuse on the jumper.

Never mind about the oil pressure switch. As usual, you've been led down the garden path by whover told you that the oil pressure switch disables the fuel pump relay when you get oil pressure. That is not what happens! The circuit through the oil pressure is designed to provide a "another" path for current to flow to the fuel pump "if" the relay packs it in. It is "not" designed to "turn the engine off" if you lose oil pressure.

Ian

Its a decently new pump. By decently new I actually mean 2 years old which really isn't new at all. But would that cause me to lose voltage out of the oil switch but still have 12v+ in? And the1 2v to the relay is most certainly controlled by the ecm/pcm which I watch cut out. Its a new computer... I checked all +v in and both grounds all is good. I guess I'm gonna take a closer look at the pump. Do you know the proper amp specs by any chance??

thanks Chad

I'll try the pump prime tomorrow. There is published info on the oil pressure switch/fuel system in Haynes repair manual. Thanks for everyones input so far...

Are you saying, according to the manual,once the oil pressure rises, the fuel pump relay is de-energized?

I just looked at a wiring diagram on your vehicle, the computer has no way of knowing what your oil pressure is doing and no connection to that o/p switch in the fuel pump circuit.

I have an old 88 GM vehicle. I have two oil pressure switches, one is located by the oil filter, that is for the lite or gage on the dash. The other is located on top of the engine, that o/p switch is in the fuel pump circuit. In the past I have unplugged that switch, the vehicle started and ran just fine, the pump was getting voltage through the relay. I plugged that switch back in and unplugged the fuel pump relay, just let the connector dangle. The vehicle started and ran just fine. The pump was getting voltage through the oil pressure switch.

How old is the fuel filter and what is the fuel pressure spec. Maybe you listed fuel pressure and I missed it. My generic info for a GM TBI system, says the pump should draw 2--4 amps. If you check amp draw using the prime connector, I'd use a fuse on the circuit.

Thank you Ted and jdl for all of the info. I apologize for the delay. I have had a constant headache between Christmas, my other car being totaled and work. I checked the amperage draw (which was almost double maximum allowable amperage) thought about what jdl said and put a pump in. So much for Napa fuel pumps. The new dealer pump should keep me in business. While I was under there I cleaned up and moved the ground a bit closer to the tank. Thanks again to everyone and have a safe and happy holiday.

Chad