98 is starting sluggishly

A couple of days ago, my 98 Cherokee wouldn't start right away. I turn the ignition, and it cranks for a few seconds without starting. Right when I'm about to let off the ignition, it starts. However, sometimes it doesn't start, but on the 2nd try it will. It appears to be a battery problem. I went to autozone, and they did a battery test that said I had a bad battery. I replaced it, but it's still doing the same thing. Someone else thought it might be a fuel filter problem, but I found out that the fuel filter is located inside the gas tank and is part of the fuel pump.

After discussing this problem yesterday with my dad, we both thought that the spark plugs and wires might be an issue. I'm going to replace those today to see if that's the problem. I have a 98 Cherokee Sport 4.0 liter 4x4, 4 doors, and I've owned it for a little over 2 years. I really have no idea when anything was last replaced, so it looks like I get to start replacing things piece by piece. The battery that was "bad" appeared to be the original battery, and I'm assuming that the spark plugs or wires have never been replaced.

One other thing, it seems that the longer I let it sit, the harder it is to start. If I turn off my enginge, and then restart it within 20-30 minutes, it will usually start again just fine. However, if I let it sit for an hour plus, it starts in the way I just described. Also, one of the guys at Autozone thought that there might be a short in the ground and this might be causing a leak. Does that sound right, and if it does, how do you fix that? Any words of wisdom would be much appreciated. Thanks.

I disagree it is either a battery or a ground problem, and probably not related to ignition wires. The symptoms are of a fuel problem.

My guess would be leaky injectors. The fuel rail is pressurized with gasoline. When you turn the engine off, the fuel pump stops running. Gradually, over a period of a half an hour or longer, the fuel pressure will bleed off, but it should hold at 30 PSI for 10 minutes, and 20 PSI for 30 minutes. A pressure gauge (an old A/C gauge works well) will tell you if that pressure is holding.

Leaky injectors allow the fuel pressure to bleed off, but unfortunately, they bleed it into the cylinders, which, in effect, floods the engine. This makes it very hard starting. If you try a restart within 2-3 minutes of shutting it down, they have not had time to flood. If you leave the vehicle off for an hour or so, they will have drained down and the gas in the cylinders will have evaporated, so the cylinders are no longer flooded.

One quick test without a pressure gauge may help. After running the vehicle, shut it down. Wait until it would normally be hard to start (5 minutes or so) Then, without turning on the ignition switch, push the accelerator pedal to the floor and hold it there. This does exactly the same thing it would do on a carbuerated car - it opens the air path to the cylinders, and allows gasoline to evaporate. Hold the pedal down a full two minutes or so! Then, while still holding the pedal down, turn on the ignition and try to start the car. If it starts much better than it normally would, you have leaky injectors. All it takes is one or two.

Of course, you can also, even without a pressure gauge, check the 'apparent' pressure on the fuel rail. Shut the engine down. Press in the needle valve on the fuel rail and see how much gas fluid pressure you get. This is for comparision with the next phase of this test.

Then restart the engine, let it run a moment, then shut it down again. This time wait ten minutes - a full ten minutes, by the clock - then press the needle valve again. You should get a very healthy squirt of fuel. If you do not, (1) the injectors are leaking (2) the pressure regulator is bad, or (3) there is leaking back into the fuel tank past the pump check valve.

I will definitely try that. I'm leaning towards it being a fuel problem as well. I'm also finding that I'm getting horrible gas mileage as of late, so that might have something to do with it also. Thanks for the help, and I'll try those tests.

One other thing that is interesting to note is that the other day, as I arrived at work, my fuel tank was showing as empty. However, at the end of the day, when it came time to go home, the gas was up at an 1/8 of a tank. A similar thing happened the next day when I went through a drive-thru and put the car in park. All of a sudden there was more gas in the tank then previously had been indicated. Does this point to anything?

I've got a similar problem as crs46 on my 97 XJ sport. I will definitely try your suggestions Edbrooks. Thanks

As an update, I think I've narrowed the problem down to my oil pump. Does that sound like it could be the culprit? The fuel pressure is not dropping off, so a mechanic who looked at it thought it would be the oil pump.

This is the exact symptoms I had when my fuel pump was going.

It is normal for the fuel pressure to drop to 0 after the vehicle sits for some time, this is because the fuel contracts as the vehicle sits, but within a half a second after the ignition is turned to the on position, it should get better. But it may not.

I'm going to stick with fuel pump.

Yes, but I have now been paying more attention to my oil guage when I start my car, and I've been noticing a noice (I'm assuming it is the oil pump building the pressure), which after it stops put the needle at 0, instead of below 0. If I make sure the oil guage is set before I start the car, I don't have any issues in starting it. All of this has led me to believe that the oil pump is starting to go.

I guess it could be, but the oil pump is a mechanical unit that is driven by the crankshaft, and typically oil pressure won't build until the motor is running. This is why starts are so tough on vehicles.

Another thing. The oil pressure gauge is driven by a sending unit that is on the side of the block, not by true oil pressure. I had to replace that sending unit at about 95,000 miles.

I was worried about my oil pressure, so I had a mechanic hook up a mechanical pressure gauge to the thing and we discovered the oil pressure was fine, and the sending unit was bad.

As an update, I think I've narrowed the problem down to my oil pump. Does that sound like it could be the culprit? The fuel pressure is not dropping off, so a mechanic who looked at it thought it would be the oil pump.

HI, ARE YOU SAYING THE OIL PUMP OR DO YOU MEAN FUEL PUMP THE OIL PUMP HAS NOTHING TO DO WITH THE FUEL SYSTEM. IT COULD BE THE FUEL PRESSURE REGULATOR. GET A FUEL PRESSURE GAUGE PUT ON IT AND SEE WHAT KIND OF PRESSURE SHOULD BE AROUND 39LBS.SHOULD HOLD AT LEAST 20 MIN. HOPE THIS IS OF HELP DALE [email protected]

HI, ARE YOU SAYING THE OIL PUMP OR DO YOU MEAN FUEL PUMP THE OIL PUMP HAS NOTHING TO DO WITH THE FUEL SYSTEM. IT COULD BE THE FUEL PRESSURE REGULATOR. GET A FUEL PRESSURE GAUGE PUT ON IT AND SEE WHAT KIND OF PRESSURE SHOULD BE AROUND 39LBS.SHOULD HOLD AT LEAST 20 MIN. HOPE THIS IS OF HELP DALE [email protected]

What I'm saying is that I've ruled out the fuel system since the fuel pressure is just fine. The mechanic who looked at the fuel system thought it might be the oil pump, since the fuel system didn't seem to have any problems.

if your "mechanic" thinks that an oil pump has anything to do with your starting problem i would seriously consider a new mechanic.listen to what people are telling you,the fuel pressure has to hold after the engine is off.just because it good while its running doesnt mean you can rule out the fuel system.

As I stated previously, the fuel pressure does remain stable AFTER the car if OFF. I never said anything about it being fine while the car is running. That wouldn't make any sense. The fuel pressure remains constant for at least a good hour or so after the car has been turned off. Are you saying that you still think it's the fuel system, even though the fuel pressure if fine AFTER the car has been turned OFF?

no we are just trying to tell you that the oil pump has nothing to do with it

Yes, it could still be the fuel system.

Yes, it could still be the fuel system.


Hi, Like xj and i stated the oil pump has nothing to do with it starting sluggishly. i've had fuel pumps that worked as long as you didn't make a demand on it, like kicking it into passing gear. just changed one that had 38 lbs. at idle, if you snapped the throttle open quickly it had 17 lbs. The fuel pressure regulator snaps on to fuel pump module, you have to lower tank to change but you don't have to remove fuel pump assembly. dale [email protected]