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Help - Grand Am Hard to start in mornings

I have a 1991 Pontiac Grand Am (2.5l, 102,000 miles) that can take several minutes to get started. 3 or 4 times out of 5 it starts fine. If it's going to have a hard time starting, it will be the first time (cold start) of the day. Subsequent times throughout the day won't be a problem.

In those times, the car turns over but just doesn't start without a lot of cranking. After it starts, it idles as smooth as ever and doesn't stall. Problem is at least a year old.

A guy at the auto parts store suggested the O2 sensor. But isn't the O2 sensor ignored on starting a car because it has to be warmed up before that even works ? What about the Throttle Position Sensor ? Also, fuel pump and fuel filter were mentioned but if these things were failing wouldn't the problem be more consistent ?

Thanks,

Eric

Reply to
Eric Gooden
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Can you hear the fuel pump run for a few seconds with the key in the On position with the engine stopped? If not, the fuel pump relay may be bad - the pump will still get power when the oil pressure switch closes, but this will take some cranking.

Reply to
Robert Hancock

As in the post above suggests, listen for the pump. It should light for 2 sec. in key on position before start. If it doesn't, check the relay to see if it is activating during cranking. If so, & I've seen a few of these, The ECM isn't exciting the relay at key on. If you have a pressure guage this scenario is easier to see. Watch the guage, it should come up to spec. (35-40psi I think) at initial key on. If it doesn't, crank the car & if it comes up to pressure slowly then starts, your pump & relay are doing their thing correctly & your ECM is the culprit. Good luck.

Reply to
PA-ter

The ECM is basically the computer, is that correct ? So basically I think you're saying that I can check the relay terminals that are normally triggered by the ECM (not the terminals on the relay that go to the pump) and if they don't have any voltage then it could be the ECM.

I know that I am missing some basic understanding and have a question. So, at key on (car not started) the pump will normally run until the pressure is up to spec. Then when the car has started and is running the pump pressure is maintained by the same method (relay engaged when more pressure is needed). Okay, what I'm not clear on is if it happens to be the ECM (or the relay) at fault how does cranking the car (for several minutes maybe) eventually start the car. In other words, is the relay finally engaging or is there a second way that the pump can work (another electrical way or maybe a mechanically driven way) ? I think that Robert in the previous post mentioned oil pressure, but I didn't understand that.

Thanks,

Eric

Reply to
Eric Gooden

The fuel pump will run for 2 seconds after the key is switched to on, then stops if no RPM reference pulses are received. It also will stop after 2 seconds if the engine stalls. With the engine running, the fuel pump will run continuously.

Many vehicles have the oil pressure switch wired in as a second power source to the fuel pump, but it will take some cranking (till the oil light goes off) to close the oil pressure switch.

Reply to
Robert Hancock

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