FUEL PUMP TEST 2: Using Starting Fluid
Checking to see if your car (or mini-van starts) with a good dose of starting fluid is the most common way to get the ‘ball rolling’ when troubleshooting a bad fuel pump.
Using starting fluid is not the most accurate way of testing the fuel pump but it doesn't mean it's not effective.
I've used this starting fluid test with good success, along with a few other tests, to verify if the vehicle I'm working on is not starting because no fuel is reaching the engine.
OK, to get this show on the road, this is what you'll need to do:
- 1
Remove the intake air duct from the throttle body.
You don't have to completely remove it, since you'll have to reconnect it in one of the next steps. - 2
Open the throttle plate, manually, and spray starting fluid down the bore.
- 3
When you have sprayed a good squirt of starting fluid, quickly reconnect the air duct to the throttle body (you don't have to tighten the hose clamp).
Reconnecting the intake air duct is important because your 3.1L or 3.4L Malibu (Venture, Monte Carlo, Grand Am, Century, Regal, etc) may be equipped with a MAF sensor. Also, it's a very important safety precaution in case you get a back-fire thru' the intake. - 4
Have your assistant, inside the vehicle, crank the engine once the intake air duct is back on the throttle body.
- 5
You'll get one of two results with this test:
1.) The engine will start momentarily and after a few seconds will die.
2.) The engine will only crank but not start at all.
OK, let's find out what your results mean:
CASE 1: If the engine started and ran for a few seconds. This means that the reason your Skylark (or Impala, Lumina, Monte Carlo, Achieva, Alero, etc.) is not starting is due to a lack of fuel.
Usually, this also means that the fuel pump is bad. But since we don't live in a perfect world, this could also mean a few other things like: the fuel pump fuse is blown, or the fuel pump relay is bad. Now, don't worry about this too much, because you can test this by:
- Removing the fuel line that connects to the fuel injector rail (this is the one that delivers fuel from the fuel filter) and place it in a container. When ready, have your helper bump the starter motor while you verify if fuel comes out or not. No fuel coming out of the fuel line further confirms a bad fuel pump.
- Making sure that the fuel pump is getting power (12 Volts) when you crank the engine. How? By tapping into the wire that feeds the pump power and making sure it's feeding the pump with 10 to 12 Volts when your helper is cranking the engine.
NOTE: There's a good chance that anti-theft system on your vehicle is behind the no-start problem. For more info, go to: Is The Anti-Theft System Causing The No-Start Condition?
CASE 2: The engine did not start, not even momentarily. This usually means that a lack of fuel IS NOT the reason your car is not starting.
Now, remember what I said about this test not being very accurate? Well, I suggest you do one more test.
This is to remove the fuel line that connects to the fuel injector rail and place it in a container. Then have a helper bump the starter while you check to see if fuel comes out of the Line and into the container. This way, you can visually see if there is or there isn't fuel coming out of the fuel line.
A no-start condition can be caused by a number of things (yeah, I know, life's a bitch), so my recommendation is to see take a look at this tutorial: How To Troubleshoot A No Start (GM 3.1L, 3.4L).
Is The Anti-Theft System Causing The No Start Condition?
PASS-Key/Passlock system failures are very common (especially the ignition key lock cylinder malfunctioning and not sending the correct key signal to the PCM or BCM).
The end result of these failures activating the anti-theft system is a no-start condition. This no-start condition can seem like it's due to a bad fuel pump.
To explain this a bit further: The anti-theft system is designed to disable the fuel injectors (when it activates) the 3 seconds after the engine starts. This causes the engine to stall and if you use starting fluid, the engine will start (and of course die when the dose of starting fluid you just sprayed gets consumed).
This may lead you to believe that the fuel pump has failed (when it hasn't). To help you tell the difference between a bad fuel pump and an anti-theft system problem, take a look at the following chart:
| Anti-Theft Versus Fuel Pump | ||
|---|---|---|
| Symptom | PASS-Key / PassLock | Fuel Pump |
| engine cranks but won't start | YES | YES |
| engine starts with starting fluid (momentarily) | YES | YES |
| Ignition system delivers spark | YES | YES |
| Anti-theft MIL flashes on instrument cluster | YES | |
| Engine starts momentarily then stalls | YES | |
| Fuel pressure at spec (as checked w/ fuel pressure gauge) | YES | |
| PCM disables fuel injectors a few seconds after the engine starts | YES | |
Related Test Articles
If you enjoyed and/or found this ‘How to’ article helpful, I have written several more 3.1L and 3.4L specific test articles. You can find them all here: GM 3.1L, 3.4L Index Of Articles.
Here's a sample of the tutorials you'll find in the index:
- How To Test The MAP sensor with a multimeter (GM 2.8L 3.1L, 3.4L).
- How To Troubleshoot A No Start (GM 3.1L, 3.4L).
- How To Test The Ignition Coil Packs (at: easyautodiagnostics.com).
- How To Test The Ignition Control Module (at: easyautodiagnostics.com).
- How To Test The MAF Sensor (at: easyautodiagnostics.com).
- How To Clean The MAF Sensor (at: easyautodiagnostics.com).
- How To Test The Throttle Position Sensor (TPS) (at: easyautodiagnostics.com).
If this info saved the day, buy me a beer!
