98 sw2 problems starting bad mpg

[Tommm]

I bought a saturn sw2 a few weeks ago and have a fixed a few issues with it and now have a new problem. car has 103k on it. I replaced the spark plugs, new air filter. Water pump went out on it so replaced that, serpintine belt, coolant flush, replaced the valve cover gasket. It was starting rough when I bought it so put in new fuel filter and it solved the problem. So after all that seemed like I was good to go. Now out of nowhere a new problem. I ran in the store quick and when I came out to start the car it didnt want to start. It took 10 min of trying to get it started. Started fine for 3 days then same problem today. My mpg went from 31 mpg to 27 mpg. Any ideas what the issue could be? I know the muffler needs replacing soon. I was thinking maybe cat is clogged or something happened when I changed fuel filter?

[td1238]

Check for spark. Check CPS for 700-900 ohms resistance. Look for thin yellow and purple wires at PCM. I can't remember which plug they go to, and there are a number of yellow and purple wires, though I remember the ones for the CPS being near eachother.

Fuel filter/pressure regulator can cause starting problems, so it's good that you replaced it. Check for fuel pressure at the Shrader valve after you shut the engine off. However, since the car is very hard to start even after much persistence, it is highly unlikely to be related to the pressure regulator. It is most likely the CPS, though it could possibly be a failing fuel pump, too. Actually it could be a whole lot of things. Lack of fuel pressure would indicate pump, though you could disconnect the return line from the pressure regulator and note whether fuel was flowing. If it was, that might indicate a failed regulator, if no pressure was available at the Shrader valve.

[Tommm]

So an update to my starting problem.

When the car is not starting I can push in the schrader valve (just a quick push) and the car will start right up?? I have no idea why it works, I just let out a little pressure and gas and it pops right over. Does this pin point my problem?

[magtec]

what fuel filter did you use? 98+ requires a very specific filter.

[td1238]

Very strange.

I think I remember which wires are the crank sensor wires. This will make testing it easier, since otherwise you must jack up the car. I believe that the wires are on the brown PCM plug. There are 3 wires at one end of the plug: a purple, yellow, and purple wire. I believe, if I remember correctly, that the yellow wire and inner purple wire are the crank sensor wires.

Does the car not start when you don't depress the Shrader valve, and does it start perfectly every time you do depress the Shrader valve?

...And it is good to know which fuel filter you have.

[Tommm]

The car always starts cold. So the first start of the day I have no problems. But if I try to start it when its been drivin in the last 20 or 30 minutes it will not want to start 90% of the time but when this happens I tap the schrader valve and starts right up. I got the fuel filter from pep boys and all the fuel lines matched up but the mounting bracket was different.