Does this sound like a bad fuel pump?

Hey Jady, I'll giver a shot!

I work in the auto biz, but in the parts department, so diagnosing is not exactly my forte.

I would guess either a fuel or spark (ignition) problem would give you a similar problem, so you may be on the right track.

You don't have a check engine light on at the moment do you?

This is a 6 cyl motor?

When was the last time it was tuned up?


I'm at work right now and have access to Car Quest's online catalog and it looks like the fuel filter is not in the tank and easy to change. You could give that a try if you want first.

Also, I would check things like your spark plugs, distributor cap, rotor, and wires.

While you're at it, check the air filter too. If it's really dirty the engine could be starving for air, but it has to be pretty damn dirty for this to happen.

Take out one of the spark plugs and check the electrode. If it's worn down or covered in oil, that would make your engine hard to start. Also, pop off the distributor cap. You should be able to do this without removing any of the plug wires. Take a look at the electrodes on the inside of the cap and see if they are worn or heavily pitted.


Whelp, that's the first things I would check. If you've had a tune up in less than 30,000 miles it should all be good though.

 

Could definitely be the fuel pump. Find the fuel tank and get as close to it as possible, then have a friend turn on the ignition. You should hear the pump turn on. If you don't, there's your problem.

 

Even if the pump runs it might not be pumping anything. Take it in. Save a whole lot of hassle. Assumptions be damned!
Josh

 

Pump

Plugs or distributor

Timing (if Check Engine light comes on)

 

Yes.

 

Hold up, Could also very easily be the ignition switch aswell, my friend had a similar problem, turns out the switch was completely worn out, causing a no-start. just throwing that out there.

 

^^^ If that was the case it wouldn't be cranking.

Check for spark. While you're at it, check to see if fuel is getting into the cylinder as well.

 

Crank the engine, then stop and pull the spark plugs. If the pump is working and the injectors are spraying fuel, then the spark plugs will be somewhat wet with gasoline; that will indicate that the ignition isn't working. If they are dry, then you know that the fuel system is at fault.

 

Even better, there is a test port on a fuel line. Turn the ignition on, and see if there is pressure in the system. You might take it to a parts store, and ask to borrow a fuel pressure gauge, or ask them to help you. If it tests low, you know it's the fuel pump. You probably also need to change the fuel filter and do a tune up. 3 years is getting a little long (IMO).

 

I'm a jeep tech. Your jeep could have several problems that would intermitantly keep it from starting. Older ZJ jeeps such as yours sometimes have a problem with the check valve in the fuel pump not holding fuel/pressure in the lines and the rail causing a hard start/extended crank situation. Usually it doesn't take a couple of minutes of cranking to get the pressure back up and the engine to start though so it's not a given by any means. One thing you can do since I'm assuming you don't have a fuel pressure gauge is to find the service port on the rail and after it sits for a little while depress the schrader valve and see if there's any fuel pressure there. Do this with caution because I dont' want you starting a fire. There should be a decent amount of pressure in the rail. If it just dribbles a tiny little bit of fuel out with no pressure then that might be your problem. The fuel pump should start pumping as soon as you start cranking the engine so it shouldn't take very long to get fuel pressure back up. Unless it's just on it's last legs alltogether. When's the last time you had a tune up becuase it could be secondary ignition (plugs, cap, rotor, ignition wires). Could even be a problem with the crank sensor especially if it's a four litre. Then again it could be a problem with the ignition module or even the pcm......Basically it's hard to diagnose the problem over the computer. You have to be able to figure out if it's a spark or fuel problem to start off with. If you had an old spark plug (or a new one) you could take a wire off of a plug, put the new plug in it and lay it on the engine, it has to be grounded so what you lay it on has to be metal, crank it when it won't start and see if the plug fires. Between that test and the fuel pressure in the rail you should be able to get an idea of what's not happening, as good an idea as you can get with no tools or test equipment. Do that and get back to us.

 

Sounds like a plug problem to me. I had this problem with my motorcycle, changed the plugs and starts right up now.

lowsound

 

Had this EXACT problem last year with my 96 4.0 liter Cherokee. I even started a thread about it. Mike N, resident mechanic of TB suggested it was the crank position sensor.
Sure enough, that is exactly what it was.

IF you hear a slight "buzz" when you switch the key to "on" before cranking, your fuel pump is working.

Best of luck to you with your Jeep.

 

That sounds like a fouled plug. Does the jeep belch out a cloud of black smoke when it finally starts and then run rough or barely at all untill it clears itself out?

 

A more dangerous and less technical way to test if the fuel pump is working would be to spray starter fluid in the intake, crank and see what happens. I've only done this trick on carburetors though so as a disclaimer, if the Jeep blows up I take no responsibility

 

crazy to ask, but I have to .....

are you sure you have gas in the tank? just asking, it has happened before....


also, do the starter fluid thingy, but you have to hold TB and its members and especially me harmless.....

big al