Does this sound like a bad fuel pump?

Discussion in 'Off Topic [BG]' started by jady, Jun 21, 2008.

  1. jady


    Jul 21, 2006
    Modesto, CA
    So I am at my buddies house and I go out to my car to leave. The car cranks but nothing turns over. I just got a new starter a month or so ago and had the battery checked so everything on that end is doing fine but it's like the engine never starts up on its own. After a minute or 2 of cranking it turns over and drives just fine. The next time I try and start it it is the same thing but it never turns over and I have to be towed home.

    I am assuming that it is a fuel problem.

    It is a 95 Jeep Cherokee. Any guys with more auto experience care to chime in.

    I would like to do it myself but if the fuel pump is in the tank then I do not think I have the tools/knowledge to drain the tank and whatnot.
  2. 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.
  3. MoD_Scotty


    Jul 22, 2007
    Thrapston, UK
    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.
  4. J.D.B.


    Mar 11, 2007
    Even if the pump runs it might not be pumping anything. Take it in. Save a whole lot of hassle. Assumptions be damned!
  5. Pump

    Plugs or distributor

    Timing (if Check Engine light comes on)
  6. jady


    Jul 21, 2006
    Modesto, CA
    Cool, thanks.

    It is a 6cyl, I have no idea when the last tune up was. It was before I bought it tho which was 3 years ago. No check engine light.

    I'll check the fuel pump when my buddy cranks it tho.

    Is the fuel pump in the tank?

  7. Yes.
  8. jady


    Jul 21, 2006
    Modesto, CA

    I may have to take it in and pay thru the nose. A week of ramen is in my future :rollno:
  9. Jiggybass


    Nov 15, 2005
    Sudbury, Canada
    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.
  10. MoD_Scotty


    Jul 22, 2007
    Thrapston, UK
    ^^^ 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.
  11. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio!

    Jul 3, 2001
    Chester, Connecticut
    Former Technical Communications Developer, QSC Audio
    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.
  12. Trevorus


    Oct 18, 2002
    Urbana, IL
    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).
  13. 68Goldfish

    68Goldfish Supporting Member

    Nov 4, 2006
    Port Orchard WA
    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. :)
  14. Sounds like a plug problem to me. I had this problem with my motorcycle, changed the plugs and starts right up now.

  15. 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.
  16. 68Goldfish

    68Goldfish Supporting Member

    Nov 4, 2006
    Port Orchard WA
    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?
  17. jady


    Jul 21, 2006
    Modesto, CA

    No, when this happened the 1st time and it finally started it ran like a champ. No smoke, sputtering or anything. I will check and see whether its a fuel or spark issue tommorrow after my gig, it's in the early afternoon so I should have time then.

    Thanks for all the help guys, I'll post more when I check out all your advice :D:D
  18. Ericman197


    Feb 23, 2004
    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 :ninja:
  19. rokkitt


    Jun 7, 2007
    bronx, nyc
    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
  20. jady


    Jul 21, 2006
    Modesto, CA
    Hahaha yea, it actually was towed from a gas station where I had just put $30 in the tank. So I had a good 3 gallons in there :D.

    It is fuel injected so I don't even know how the starter fluid thing would work.