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!988 Jeep Cherokee MPI fuel pressure problem. New everything on/in the fuel system. Can only make it run with a jumper wire from the fuel pump to the battery. Any ideas?

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Have you checked the fuel pump relay. If you haven't locate the relay and jump out pins 30 and 87 (there should be a diagram on the relay or if you look at the bottom of it, the pins should be numbered, jump out the corresponding sockets in the relay housing). If the fuel pump turns on when you do that you've verified the power feed is good and the wires to the fuel pump are good. Now with a digital multimeter check that there is battery + on pin 85 or 86. If that checks out, when cranking make sure there is a good ground on the opposite pin (if pin 85 had + on it, pin 86 should have a ground). If all that checks out you can suspect the relay is faulty.

Posted on Aug 26, 2010

Testimonial: "thanks for the info. still don't know which relay is the fuel pump "


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My 1995 Jeep Cherokee won't stay running after it warms up could it be fuel pump everything else test fine

Sounds like. MAP sensor or cam sensor. You didn't say if Chechen engine light is on. No light on check throttle. body and TPS . it may be loose.

Aug 12, 2015 | 1995 Jeep Cherokee

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Fuel pressure 1998 jeep grand cherokee 4.0 L V6

You should have a test port on the Fuel Supply rail, use a tool from a local auto parts "Tool Loaner program" where you can borrow tools for free,w/a deposit of course,then follow the steps provided;

MPI Fuel System Pressure Test

The MPI fuel system used in vehicles equipped with a 4.OL engine employs a vacuum balanced pressure regulator. Fuel pressure should be approximately 55-69 kPa (8-10 psi) lower with the vacuum line attached to the regulator than with the vacuum line disconnected. System fuel should be 214 kPa (31 psi) with the vacuum line connected to the regulator and 269 kPa (39 psi) with the vacuum line disconnected. CAUTION: Some fuel may be discharged when connecting fuel gauge to fuel rail.
  1. Connect a 0-414 kPa (0-60 psi) fuel pressure gauge to test port pressure fitting on fuel rail (Fig. 7).
  2. Remove vacuum line from pressure regulator.
  3. Start the vehicle.
  4. Note gauge reading. With vacuum line disconnected, fuel pressure should be approximately 269 kPa (39 psi).
  5. Connect vacuum line to pressure regulator. Note gauge reading. Fuel pressure should be approximately 214 kPa (31 psi).
  6. If fuel pressure is not approximately 55-69 kPa (8-10 psi) higher with vacuum line removed from regulator, inspect pressure regulator vacuum line for leaks, kinks or blockage. CAUTION: Fuel pressure will rise to as much as 655 kPa (95 psi) when the fuel return tine is pinched shut, shut engine down immediately after pinching oft fuel return line.
  7. If fuel pressure is low, momentarily pinch shut the hose section of the fuel return line. If fuel pressure remains low, inspect the fuel supply line, fuel filter, and fuel rail inlet for blockage. If fuel pressure rises replace fuel pressure regulator.
  8. If fuel pressure is above specifications, inspect the fuel return line for kinks and blockage.

Capacity Test

  1. Remove the cap from the pressure test port in the fuel rail.
  2. Connect a 0-414 kPa (0-60 psi) fuel pressure gauge to the pressure fitting on the fuel rail (Fig. 7).
  3. Start the vehicle. Pressure should be approxi- mately 214 kPa (31 psi) with the vacuum hose connected to the pressure regulator and 269 kPa (39 psi) with the vacuum hose removed from the pressure regulator.
  4. If the pressure is not to specification, check the following before replacing the fuel pressure regulator:
  • 4a - Inspect the fuel supply and return lines/hoses for kinks or restricting bends
  • 4b - Check the fuel pump flow rate. A good fuel pump will deliver at least 1 liter of fuel per minute with the fuel return line pinched off. If the fuel pump does not pump adequately, then inspect the fuel system for a plugged fuel filter or fuel pump inlet filter (sock). Fuel pump flow rate can be done by connecting one end of an old A/C gauge hose to the fuel test port on the fuel rail and inserting the other end of the hose into a container of at least 1 liter capacity. Run the fuel pump by installing a jumper wire into diagnostic connector terminals D1-5 and D1-6. Be sure to pinch off the fuel return line or most of the fuel will be returned to the fuel tank.

May 19, 2014 | 1996 Jeep Grand Cherokee

1 Answer

Which is the fuel pump fuse?

what country, ? and what engine option? ????????????
the pump may not have 12v power until cranked, is engine dead/?
post the systoms so we can understand the context ....
or just curious. has the drawings.

here, ill look for you. USA, and take wild guess on engine.
ok, the toy has a test port conn.
key on, check pressure after.....doing....
Using a jumper wire, short both terminals of the fuel pump check connector. The check connector is located near the air cleaner. Connect the terminals labeled FP and +B.

reasons for pump failure.
  1. If the fuel pump failed to function, it may indicate a faulty pump, but before removing the fuel pump, check the following items within the pump system:
    1. All fusible links
    2. All fuses (EFI-15amp and IGN-10.0amp) "names"
    3. H- fuse (AM2 30A)
    4. EFI main relay
    5. Fuel pump
    6. Circuit opening relay
    7. All wiring connections and grounds related.

i just check pressure cranking, (rubbers meets rode, logic)
if fail, to have 12v at pump i work backwards.
if 12v at pump, then pump is dead if pump is dead.
simple logic, here, and 100% effective.....!

toy spec on pressure is.
The fuel pressure should read 38-44 psi (265-304 kPa).
and running. with MPI engine the pressure will drop 10psi
due to vacuum reg. rules.......etc....

Nov 30, 2013 | 1991 Toyota Corolla

1 Answer

Where is the fuel filter for 4.0 v6 cherokee located

  • Disconnect the negative battery cable and then remove the fuel tank cap to release fuel tank pressure. Remove the fuel pump relay from the PDC. Start the engine and allow it to run until it stops. Select any injector and unplug its connector.

  • 2

    Connect a jumper wire from an injector terminal to the positive battery terminal. Then, connect the other jumper wire to the other battery terminal. Briefly touch the end to the negative battery terminal.

  • 3

    Locate the fuel filter/pressure regulator near the front of the fuel tank, mounted to the body above the rear axle. Disconnect the fuel supply, fuel return and fuel pressure lines. Remove the mounting bolts and then the fuel filter/pressure regulator.

  • 4

    Attach the new fuel filter/pressure regulator to the body and tighten the bolts to 30 in-lbs. Reconnect the fuel supply, fuel return and fuel pressure lines. Reconnect the negative battery cable. Start the engine of your Jeep and check for leaks

  • good luck hope this helps

    Dec 04, 2010 | 2003 Jeep Grand Cherokee

    2 Answers

    No power to fuel pump 1990 eagle talon tsi awd turbo 5 speed. checked all fuses and ecu for damage and all seems fine, new fuel pump so i know thats the the problem the mpi/mfi relay is not clicking when...

    I hope this helps? Are you missing anything else? Engine cranking you have spark at the plugs and fuel injector pulse? Any applicable trouble codes? Battery has a full charge? See load side of mfi relay, that line with arrow head, with key on, good voltage at upper wire? If so, if you use a jumper wire between proper wire colors, the pump should run.

    Jul 03, 2017 | 1990 Eagle Talon

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    1995 Jeep Cherokee Country straight 6 cyl 4.0L: I

    First of all, the fuel pump is generally located in the fuel tank, not always though. Yours probably is, in did not research it. The fuel electric fuel pump turns on only when the ignition key switch is turned to the start position and then left on. A series of one or two relays along with a pressure monitor in the fuel rail delivery system may or not cycle it on and off depending on design. Enough of that. I suggest that you remove the spark plugs to see if they are oil/heavy cabon deposits.If so, professional attention is reguired. One more thing you could try is replacing the spark plug wires. the may be old/worn out/damage. This would give the engine spark a stronger spark,if worn and also replace the spark plugs.

    Jul 30, 2009 | 1995 Jeep Cherokee

    1 Answer

    93 ZJ 4.0L has intermittent fuel-pressure drop when starting

    You have a good theory but haven't finished testing so you can verify it...check actual fuel delivery when in no-start...also probe the pump wire on the pump side of the harness and see if you are in fact not getting power to the pump all the time. (also in no-start). Don't test after it gets started, or testing will tell you what you already know...It runs fine once started...tests will then tell you it's fine (you know it's not) Problem itself could be anything from a bad connection somewhere to a balky pump.

    Jul 06, 2009 | Jeep Grand Cherokee Cars & Trucks

    1 Answer

    Electric fuel pump on 1990 cherokee, 4.0 liter won't turn on.

    A delay in fuel pump may be due to either a "lazy" relay or an insufficient ground (fender, firewall, or pump itself) It could also be a poor connection at ignition switch. However I took a look at the wiring diagram I have and it seems that there are several items connected to the power supply for the pump, which I see no real reason for even being on that circut at all. Have you tried a code check?
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    I know I have not "cured your problem, but I hope I've given you enough to go on to begin testing.

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    1 Answer

    No fuel

    as far as I know, there is no secret stuff. but as I said, you have to check power going into and out of all components you changed and do what I said above before just plugging in a ton of new stuff 'till you happen to find the problem.PS if you do find power at the pump, perhaps it's defective?

    Jan 15, 2009 | 1996 Jeep Cherokee Country

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