Engine starts then shuts off immediately

Hello,

To me this sounds like an issue with the Mass Air Flow Sensor or MAF for short. The engine’s computer can’t determine the amount of air entering the engine, so it doesn’t know how much fuel to add.

Check out this link to learn more about MAF Sensors:
https://www.2carpros.com/articles/how-a-mass-air-flow-sensor-works-maf

The quickest thing you can do to test is:
1. Make sure the key is off and removed.
2. Go to the MAF and unplug the connector.
3. Now try starting the car and see how it goes.
If it started and ran fine, then the MAF is sending the wrong signals to the engine's computer. This is happening because the sensor is worn, dirty or both.

These things aren’t cheap so it’s best to try and clean it. Here is a link to an article on cleaning the MAF. The sensor in this article probably won’t look like yours but it is the same idea. You need to clean the element with Mass Air Flow Sensor Cleaner.
https://www.2carpros.com/articles/mass-air-flow-service

I have included a picture of the brand I prefer. Don’t cheap out, get good stuff and follow the instructions. Be very careful not to touch the element and wear clean gloves.

*Make sure the sensor is completely dry after cleaning before plugging it back in. Do not blow off compressed air since air lines and compressors have oil in them and we don't want to risk getting any of that on our freshly cleaned sensor. *

After re-installing your sensor make sure the rest of your air intake and duct work are all tight and there are no leaks.

Let me know how it goes or if I can help in any other way.

Thanks,
Brendon

Hmm, that’s too bad. If you hit the throttle, will it stay running or seem like it wants to? Since the vehicle has high mileage and is 22 years old, I would still clean that MAF sensor just so we can make sure to rule it out and it definitely won’t hurt anything.

Then next I would check your key-on-engine-off fuel pressure. I have added a picture of your fuel rail. This is what delivers fuel to the injectors. I have also added a picture of a fuel pressure gauge. I know you said you changed the fuel pump, but it doesn’t mean there isn’t a problem with the harness going to it. I will also add the spec for the fuel pressure from the manufacturer.

Fuel pressure testers are really that expensive. I would buy one instead of renting it from the parts store. While it is convenient, they get banged around and mistreated which could throw off your reading.

What you want to do is relieve the fuel pressure. You can usually stick a small screwdriver and push in the valve. I have highlighted it on the picture below. Make sure to have a few rags around and also around the end of the valve because once you push on that valve it’s going to spray everywhere. Also, I recommend safety glasses because if you get gasoline in your eyes, you will definitely wish you had.

Make sure all fuel has dried that came out and that it isn’t pooled up somewhere.

Now attach the gauge to the valve on the fuel rail and press the button to relieve and additional pressure. Have an assistant turn the ignition to the key-on-engine-off position and watch the fuel pressure rise, note how long it takes and if it has reach the specification 48-55 PSI.

Here is an article with more information about testing your fuel pressure.
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

If the pressure isn’t within the specification, it is possible you have a bad ground or excessive resistance somewhere in the fuel pump harness. This will decrease the power to the pump. Even though the pump can pressurize the fuel rail to start the vehicle it might not be able to keep up with demand. So, we can rule out any fuel issues.

Also check the fuel pressure regulator. Normally if they are bad fuel will be in the vacuum line when you pull it off, it should be dry. I have included a picture from GM for the fuel rail, injectors, fuel pressure regulator, and other components.

I also found a TSB or Technical Service Bulletin on the fuel strainer that is on the fuel pump. I will attach a picture from the GM catalog as well as a generic picture of this part. I am just wondering if a new one came with the new pump or not.

According to the TSB they can clog and restrict fuel. GM recommends part number 88891094. If it has been changed that's good, we can rule that out. If it were reused from the old pump, it could be the issue, but I would just keep this in the back of your mind and continue to test the more likely issues.

I think we should check these things and see what you come up with.

Let me know how you make out and we will go from there.

Thank you
Brendon S