1. #1
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    Where is the fuel pump relay?

    Where is the fuel pump realy on a 1989 jeep cherokee 4.0L inline six

  2. #2
    MudderChuck's Avatar
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    Re: Where is the fuel pump relay?

    Supposed to be second from the front. But on my 88 it is in a different location, so it is likely there are some variables.

    What is your problem? It is likely I've seen it before. I've been screwing around with XJ's since 1987 .

    I've looked at two different drawings of the relay layout, one says the fuel pump relay is second from the front, one says it is third from the front. My guess is it depends on whether you have A/C or not and an A/C clutch relay in there also (three relay configuration and four relay configuration).
    Last edited by MudderChuck; 07-09-2013 at 01:30 PM.
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    Re: Where is the fuel pump relay?

    Hey chuck ? My '92 has a second relay for the fuel pump ballast resistor that is mounted on a bracket outside the PDC. Does an AMC have one too ? My dad had an '89 and I haven't had my hands on it in years , don't remember.

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    Re: Where is the fuel pump relay?

    There are 3 or 4 relays in a block (row) about where the PDC goes in later years. The fuel pump relay supplies power to the ballast resistor after the motor starts (good CPS signal) and also primes the fuel rail (for a few seconds) when the key is turned to run on the way to start.. The starter relay bypasses the ballast resistor during cranking and the O2 heater relay bypasses the ballast resistor at WOT (wide open throttle).

    A good quick test for fuel pump function is to jump the Orange and Black wire on the starter relay (usually marked BAL on the relay face) to one of the red wires on the main power lug on the starter relay and see what happens. If the fuel pump doesn't run, you have an open wire, a bad ground at the fuel pump or a bad or sticky pump.

    I have an 88 and a 96 XJ, both Limited models (export).

    A sticky pump sounds funny, but I've had mine stick, whacked on the side of the fuel tank a few times with a rubber hammer and had it work fine for years afterwards.

    Last edited by MudderChuck; 07-09-2013 at 02:01 PM.
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    Awesome, the problem is is that the car won't start. The starter goes and the engine rotates but it's not actually starting. It could be a number of things that causes that but the fact that I don't hear the fuel pump kick in when the key is turned to run, tells me it the pump or an electrical issue leading to the pump. And I don't want to change anything out till I know for sure what it is haha

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    Re: Where is the fuel pump relay?

    The noise of the fuel pump priming the fuel rail when the key is turned to run is kind of subtle. I'd check for spark while cranking the engine over. If you have spark, look at the front of the starter relay, a hard to read molded in word will say BAL. Orange and bLack wire at the starter relay, this wire is a straight shot back to the fuel pump, but the wire does go through around 5-6 connectors before it gets to the fuel pump. Next step is to check for power at the fuel pump connector and to test the ground.

    While you are cranking the engine (starter relay is activated) the power for the fuel pump bypasses the fuel pump relay anyway, it get power from the starter relay, so the fuel pump relay is unlikely to be your problem.
    Last edited by MudderChuck; 07-09-2013 at 02:28 PM.
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    Re: Where is the fuel pump relay?

    I got to get some shuteye, I work swing shift, I'll be back in 5-6 hours. Good hunting.
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    Then what is the purpose in a fuel pump relay -_- pluss when I went outside just now and unplugged the fuel pump relay and plugged it back in the car started haha. So I'm thinking fuel pump relay or Devine intervention

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    And thanks!

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    Re: Where is the fuel pump relay?

    The fuel pump relay routes current for the fuel pump through the ballast resistor, which actually lowers the voltage to the fuel pump. The current to the fuel pump is supposed to go through the ballast resistor after the engine is running. Though there is a second or two of overlap during starting when the fuel pump relay is closed and the balölast resistor bypass from the starter relay are both working.

    Those relays rarely go bad, I do keep a couple of spares just for testing though, anything is possible.
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    Re: Where is the fuel pump relay?

    Great ! Talk about lucking out ! Glad it's running , but wondering , could it be possible that there is a lazy relay or the ballast is over heating and causing the relay to back up if current flow becomes restricted ? Might be worth swapping out ballast resistor ? Never had that happen to my '92 , but just wondering if has ever happened to you ? What do you think MudderChuck ?

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    Re: Where is the fuel pump relay?

    My first guess was he had a connector making flaky contact someplace or a ground making flaky contact. Usually when the ballast resistor starts to go, it will starve the fuel pump of current (low fuel pressure) or even more common the motor will start off of the starter relay (fuel pump power bypass), then the motor will quit as soon as (or a few seconds after) the key is returned to the run position after the motor starts.

    Could be his fuel pump power bypass wire from the starter relay has an open circuit and he is getting enough fuel for a start from the prime or when the fuel pump relay closes- Just a wild arsed guess.

    If you get a bad ground someplace no telling how the current will flow, backwards through another sub system, your guess is as good as mine, whatever the path of least resistance is..

    Jumping the ballast resistor for a test is common practice, the ballast resistor is really unnecessary, but it does have to work as long as it is in there. They say the only real function the ballast resistor has it to cut down on pump noise. My 87 never had one and worked fine, my 88 does and I had to replace the ballast resistor once. My 88 would starve for fuel at interstate speeds when the ballast resistor was slowly failing..
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    Re: Where is the fuel pump relay?

    Quote Originally Posted by MudderChuck View Post
    My first guess was he had a connector making flaky contact someplace or a ground making flaky contact. Usually when the ballast resistor starts to go, it will starve the fuel pump of current (low fuel pressure) or even more common the motor will start off of the starter relay (fuel pump power bypass), then the motor will quit as soon as (or a few seconds after) the key is returned to the run position after the motor starts.

    Could be his fuel pump power bypass wire from the starter relay has an open circuit and he is getting enough fuel for a start from the prime or when the fuel pump relay closes- Just a wild arsed guess.

    If you get a bad ground someplace no telling how the current will flow, backwards through another sub system, your guess is as good as mine, whatever the path of least resistance is..

    Jumping the ballast resistor for a test is common practice, the ballast resistor is really unnecessary, but it does have to work as long as it is in there. They say the only real function the ballast resistor has it to cut down on pump noise. My 87 never had one and worked fine, my 88 does and I had to replace the ballast resistor once. My 88 would starve for fuel at interstate speeds when the ballast resistor was slowly failing..
    Well , there it is . Back to basics . Hope Tristan owns a computer compliant 10 mega ohm impedance VOM to start checking grounds and voltage drop as its back to basics . Somewhere on the sheet metal of that XJ is corrosion that is wreaking havoc and inviting gremlins to party on with his electrical system . Join the crowd as we all battle electrical glitches and enjoy less than proper performance from our mighty four wheelers . Not so mighty when we step on the gas and it misses or just lags along and the gas gauge goes down faster than the speedo goes up.
    Very poetic , but in reality , time to get dirty . Time to disassemble connections starting from the battery , take measurements and clean all the way to the negative and o2 and PCM grounds.
    With have to reach under and clean that ground connection at the sending unit even though it mainly serves to make connection for the gas gauge. But yeah , sounds like some engine harness insulation by the power distribution center is brittle . A good cleaning of the ballast connectors too as they are always over exposed and corrosion just infests them . PBS blaster makes a product that is supposed to be good for this , wonder if that will help him ? At least he knows not to fall into the "parts changing trap " without proper diagnosing first . That a boy !
    We'll make a fine four wheeler of him yet ! I remember , " bless me father for I have sinned , this is my first four wheel drive ..." Lol. We all learn that jeeps are just not maintenance free or they would be made of vinyl . I would say he should start by inspection of wiring too and move on to cleaning connections . With any luck , that may do the trick . If not , time to give the VOM a workout . Just don't rest on anything hot or pull on the leads so it falls on hot or moving parts . We lose more meters that way ! I abused the hell out of my high school radio shack meter
    i learned from then . COMPUTER SAFE is the ticket . He will have his hands full , this will no doubt start a thread of a few megs . Well , let me not put you to sleep , I know what splits are . They consume life. Ok , Tristan ? Whatever questions you may have , I think you got some time under the hood but what ever you may need to ask , I'll do my best as MudderChuck Has been working hard and we got to take it easy on the man. Stay tuned and as EricTheCarGuy says , stay dirty .
    P.S. - my brother always wears gloves when he works on his car , he's a guitarist to and yells at me when I don't . Can you say , dexterity ? Hate gloves . Greg
    Last edited by greg92jeepxj; 07-10-2013 at 08:40 PM.

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