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Chrysler blown maxi (flf) fuse - Update- Help appreciated

Discussion in 'Repairs, Maintenance, Help' started by MarkT, Jul 6, 2017.

  1. MarkT

    MarkT Member

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    I posted a week or so ago on my 1996 Chrysler New Yorker, 3.5 w/ 86 k miles. I was pulling out a parking lot one night and car stalled. Car blew the 'B' maxi fuse in the under hood power distribution center. Fuse is for the starter relay, fuel pump relay. With appreciation to tomguy for the wiring diagrams i checked all the wires for the fuel pump.

    I traced and checked all the wires and ground for the fuel pump. Found nothing. I swapped the relays since they are all the same part number. Didn't help. I checked every wire and ground for the car i could find. Can't find anything anywhere shorted, touching, burned, corroded, oxidized or anything else. Looked at wiring for the injectors, oxygen sensors, abs and everything i could see. I removed the wires from the starter and cleaned them. Took the power distribution center out and checked everything on the underside and it looks like new.

    Basically the car will run for a few seconds and blow the fuse. Along with much back pain i put in a new fuel pump that is identical to the original. I figured the pump had gone bad. Started the car with the new pump, ran a few seconds and blew the fuse. I disconnected the electrical connector from the pump and put in a new fuse with the connector to the fuel pump off. Started and ran a few seconds and blew the fuse.

    Now I'm really stumped. Help is appreciated since with my back i can only work on it for so much time each day. Battery is 1 1/2 years old. I can hook everything up and not start the car and the fuse will hold. I can turn the key to activate everything but not start the car and the fuse holds. Start the car and in a few seconds it takes out the fuse.
     
  2. ImperialCrown

    Level III Supporter

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    Need to go back to diagnostics. I'm confused about which fuse is blowing.
    My diagram shows fuse 'A' for the fuel pump motor (A141), starter motor solenoid (T40) and Ignition switch (A81).
    Fuse 'B' for the ASD/Generator field circuit (A142) and PCM/TCM power feeds (A14).
    Lets draw up a plan of attack before you go back in with your tools.
    lh600267.gif lh600307.gif
    I find it more comfortable to raise the car up a few inches to work under the hood with a sore back. Sometimes a hot shower and stretching exercises before a physical workout makes my old-man bones more limber. Get as comfortable as you possibly can. Deep breaths.
    I know that it's hard to concentrate on the work in front of you when you are in pain.
     
  3. MarkT

    MarkT Member

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    I appreciate your help and don't mean to be a pest and pain. This fuse had me confused. Long story short. I was originally told this fuse 'B' was for the power train control module. The cover list it as 'engine contlr ' 20 amp. I was sent wiring diagrams for a 1994 New Yorker/LHS. Mine is a 1996. That 'B' fuse was listed fuel pump relay, starter relay. I looked at it in detail today. All the relays match, none of the fuse descriptions match. I have it oriented the correct way.

    I got a diagram for a 1997 model. The relays are all labeled the same. The fuses are all labeled different and match the cover from my box under the hood. I will attempt to attach the diagram. Page 8W-10-4, page 22 of 374 shows the 'B' fuse coming out of the Power Distribution Center to s116. (Splice 116). Page 8-W-10-7, page 25 of 374 shows the fuse running in the Automatic Shutdown Relay and out of that into the Power Train Control Module. The engine contlr. label now makes sense.

    I just realized the 1994 model had OBD-I. My 1996 and the 1997 model have OBD-II. I can't the file to attach. Said it's too large. I will attempt to attach the two pages like i originally wanted.
     
  4. MarkT

    MarkT Member

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    Hi again ImperialCrown,

    Your wiring diagram for the "b" fuse on coming in is the same as what i have. Coming out the ones i have show it going to the transmission controls and another detailed page to the generator and on. It is a PDF file and won't let me convert to Microsoft and won't let me attach the individual pages. I can sent the entire file, 374 pages and tag the necessary pages if you have a separate email account or i can post mine and reply to that.

    I certainly appreciate the help because my 58 year old back is in very bad shape and it limits my time. I'm trying to concentrate directly on the problem and not go on a wild goose chase. Thank you.
     
  5. ImperialCrown

    Level III Supporter

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    The 1997 LH 3.5L wiring should be a better match.
    It is here:
    http://oskin.ru/pub/chrysler-dodge/manuals/Service Manuals/1997_LH_NewYorker_Concorde_Intrepid_Vision_LHS/ELH_8W.PDF

    Begin at p. 8W-10-7 where the Rd/Wt wire (A14) goes to ASD, PCM and TCM as you have noted.
    After the car starts and runs, the ASD then carries the power from fuse 'B' across the relay contacts to the DGn/Or wire (A142).

    Scroll to p. 8W-70-5. These are the wiring and components fed by DGn/Or (A142). This includes the:
    1) Generator field (+).
    2) four oxygen sensor heaters (+).
    3) PCM (eng cntrlr). Connector 1; pin #6
    4) six fuel injectors (+).
    5) Ignition coil pack (+).

    Since the fuse is OK in the key 'run' position, but blows shortly after starting the car (when the ASD contacts close), then I would take a close look at everything after the ASD relay. The DGn/Or wire (A142) and everything that it feeds.
    Something on A142 is shorted or drawing excessive current.
     
  6. Tomguy

    Level 2 Supporter

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    The O2 sensors would be the likely culprit I'd think - as soon as the PCM turns the heaters on, they blow... The sensors are not used for startup but are initialized shortly thereafter. The coils & injectors would be used for startup.

    Measure resistance across the heater circuit of the O2 sensors, check for dead shorts.

    Sorry, I think we assumed (incorrectly obviously) that you had the right circuit using the diagram, that turned out to be the wrong one for your car! If I had time I would have double-checked the diagrams myself. That's what happens when you're too busy working on your own project car.
     
  7. MarkT

    MarkT Member

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    I appreciate all the information. I need to find time this week to get back at the car. I never did the test to measure resistance across the heater circuit for the 02 sensors nor do i know how. I have a Chilton book on that car, hope it's in there.

    I'll try that first when i figure out how to save some wear and tear on my back and hopefully don't have to do a lot of wire tracing.

    I should have realized the earlier manual wasn't for my car. This car has me aggravated and i didn't bother to think things through.
     
  8. Tomguy

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    Pin 1, BK (Black) is ground for the heating element
    Pin 2, DG/OR (Dark Green / Orange) is the heating element power
    Pin 3, BK/LB (Black / Light Blue) is the ground for the sensor
    Pin 4, DK/DG (Black / Dark Green) or TN/WT (Tan / White) or LG/WT (Light Green / White) is the sensor signal (resistance)

    Check for shorts from pin 1 to 2, 1 to 4, and 2 to 3, 2 to 4.

    Colors pulled from the guide ImperialCrown linked, page 84 & 85 (8W-30-8 and 8W-30-9)
     
  9. MarkT

    MarkT Member

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    I greatly appreciate the help from you two guys. Sorry for the barrage of stupid questions but i never did this test before.

    1. Is the reading taken on the actual pins and not the slots for the wiring going into the actual sensor? My guess is the pins themselves.
    2. Doe's it matter the order of the leads from the multi meter? Doe's the read (+) and black (-) need to go in a specific order? My question is (although probably stupid) for example when measuring 1 to 2 or 2 to 4 would the red need to go to 1 and black to 2 or doe's that matter either way and this is just completing s circuit? My guess is it doesn't matter but i know for household, AC on an outlet for example red would go to positive and black to negative to test. Thank you.
     
  10. Tomguy

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    The heater circuit has a fixed resistance, and the sensor circuit has a variable resistance. Neither are diodes so that means polarity does not matter. You would want to measure the sensors themselves, it's possible it's a wiring issue - but much less likely - and you want to check the sensors themselves first.
     
  11. MarkT

    MarkT Member

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    I again appreciate the help. I only had a Chilton book on this car. It said the 3.3l and 3.5l have two heated oxygen sensors on the exhaust manifolds and made no mention of the two after the catalytic convertors so that had me confused along with the fact my electrical is fair, at best and with electrical i need to stop and really think everything over first.

    When i did a visual looking for touching wires i just put a jack under the car. For those two downstream sensors i need to get the car up off the ground and with the aid of Aleve i hope to start that tomorrow evening. I looked at the one upper sensor last night and on the back of the sensor connecter itself with the whites and black wire there are raised numbers 1 to 4 on the connector so that should help.
     
  12. Muther

    Muther Well-Known Member

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    I strongly recommend a GOOD chiropractor. If you find a good one, they can wonders for all sorts of pain. I see a chirp every other month or so. They are almost always on all insurance plans.
     
  13. MarkT

    MarkT Member

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    Working on the car tonight. Got the sensor connectors apart and identified. The bottom ones were next to impossible to get at. I'm trying to get resistance (ohm) readings on the oxygen sensors. The top connectors are little round prongs that are impossible to get the leads in. The bottom are pins that are difficult to get the leads to stay on. Any tricks to getting accurate readings. The two meters i have aren't the best and I'm in tight conditions. Ideas (other then burning the ca) greatly appreciated
    .
     
  14. Tomguy

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    Unfold 2 paper clips (so you have long wires essentially). Wind them around your terminals for your multimeter or put them in the clamps depending on your terminal type. Use electrical tape to help hold them in, and insulate the ends. This will allow you to get into those female connectors on the sensor plug.
     
  15. MarkT

    MarkT Member

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    Finally took resistance readings today of the 4 oxygen sensors, connectors on the sensor side as follows:

    Upstream Left (White wires 1 & 2) Upstream Right (White wires 1 & 2) Downstream Left (White wires 3 & 4) Downstream Right (White wires 3 & 4)
    1-2 7.0 Ohms 1-2 6.7 Ohms 1-2 No reading 1-2 No reading
    1-4 No reading 1-4 No reading 1-4 No reading 1-4 No reading
    2-3 No reading 2-3 No reading 2-3 No reading 2-3 No reading
    2-4 No reading 2-4 No reading 2-4 No reading 2-4 No reading
    3-4 No reading 3-4 No reading 3-4 6.4 Ohms 3-4 6.7 Ohms

    Again I'm not an expert on electrical. I looked in the Chilton book and it said resistance across the white wires (power and ground) for the sensor should be 4-7 ohms. If I'm reading these numbers correctly (not completely certain) this tells me the sensors are not the problem? Input and information will be greatly appreciated at this point.
     
  16. ImperialCrown

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    It looks like the O2 heaters are all between 6Ω to 7Ω and are OK. Keep looking.
    What does the DG/Or (A142) wire read to ground for ohms with everything plugged in? If it is very low (which would blow a fuse), try unplugging the loads one-by-one while watching the ohms until it jumps up significantly. That one you just unplugged may be your issue.
     
  17. MarkT

    MarkT Member

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    I appreciate the reply but... i don't fully understand. Sorry to ask for detail. I don't understand ground to ohms for everything plugged in. Where would i take a reading for this? When you say unplugging the loads I'm not really sure either? What is on the wire is the coil pack, oxygen sensors, fuel injectors, generator, PCM. I'm guessing you mean disconnecting the individual connectors? Sorry for the questions and being held by the hand but my electrical knowledge is fair at best.
     
  18. Tomguy

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    You put your multimeter's negative terminal on the ground, IE: A bare metal spot on the car chassis nearby. You put the positive terminal on the wire(s) in the circuit you are testing. This lets you see if anything shorts to ground or has low resistance to ground.
     
  19. MarkT

    MarkT Member

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    I very much appreciate the information and I'm sorry for the constant questions. I am not an electrical expert but I'm learning. I just need to see if i will be doing this right. When you say positive I'm figuring that would be the DG/Or wire to the component? As an example the battery will be hooked up with a fuse in and i would read say for a fuel injector the DG/Or wire on the connector to the injector or on the coil pack the DG/Or wire on the connector to the coil pack with the connector apart? Basically the supply side and not the component itself? Sorry for the constant questions. When i get this figured out i will send you guys payment for all the advice.
     
  20. ImperialCrown

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    Yes the DG/Or is the supply side on the A142 line. You want to measure ohms with no power in the circuit. Ign off and/or the ASD relay pulled out.
    This will measure the total circuit resistance to ground. If the resistance is close to zero, this would be a short to ground and probably what is blowing the fuse.
    As you unplug the injectors, generator field, ignition coil, (loads), etc, on the A142 line, your total resistance should gradually increase.
     

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