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Thread: 1990 jeep backfired, wont start! help!

  1. #1

    Icon317 1990 jeep backfired, wont start! help!

    ok, i know it was the best thing to do,but i have a 4.0 eliminator and i hooked a blaster 2 coil to the stock ignition cap and wires and it worked great for awhile, now ive got a problem with the truck not starting, first i turn the key to run, disconnect the green wire from the gm starter solenoid and touch it to the center bolt(power)engine turns and i have spark, i know the fuel pump comes on and charges the line, but still wont start, im thinking the magnetic pickup in my distributor has gone, causing the backfire, and the the comp would activate the asd relay and id have no spark again until i unplug and replug the ecu/pcm, if anyone has any better ideas im going to go out and hook a wire to my injectors and see if im getting the strobe

  2. #2
    Moderately Senior lunghd's Avatar
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    Having a bit of problem wading thru the paragraph -

    Blaster ignition was up & running ok? - For how long?

    Backfire: was it thru exhaust or throttle body?

    CKS (crankshaft position sensor) on bellhousing check ok?
    LINK: CPS (camshaft position sensor) in "distributor" housing check ok?

    Why are you jumpering the starter at the solenoid? Is the start solenoid ok? (located next to battery, small metal box about the size of a pack of smokes)

    LINK: RENIX SENSOR DIAGNOSTICS
    Last edited by lunghd; 12-12-2010 at 08:36 PM.
    "...the advice given above is somewhat arrogant and in some cases wrong..." . (I'm not an expert... I just play one on the internet.)

    Another Freakin' Jeep Cherokee Website. _____________ Sure you're smart... but do you have what it takes to make "The List"?


    1990 XJ

  3. #3

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    the blaster was working great for months, never had a problem.
    i actually just used female conectors on the ignition module that hold the stock coil.the crankshaft sensor was just replaced to find out the old one was good, so no more replacing without testing, the camshaft sensor in the distributor cap is giving me infinit on my anolo etek meter , (only has 1000 and 10000 settings), and i just found out that my pressure regulator is leeking fuel through the vacume line.the backfire happened twice, through the exhaust i think(alot of black soot came out both times) but the rubber neck going to my cone filter blew a crack in the side so in may have been out the intake, as that rubber wouldnt just tear. i disconnected the vacume line to the regulator and plugged the hole to keep any more gas frome leaking by befor i can relace it.

  4. #4

    Icon317

    ok i actually was testing the cam sensor wrong, which wires do i connect my meter to while starting the vehicle to verify that the sensor is "pulsing"?

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    Registered apstang50's Avatar
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    Have you tried pulling codes to see what if any codes are showing?
    98 Platinum 5.9 Limited, Flowmaster, clear corners, 35% front tint, 5% sunroof tint, reloc IAT sensor, Accel coil, Summit Racing 8mm wires, Mopar front tow hooks, Mopar Performance PCM, K&N FIPK

    90 Mustang LX notch back:cobra intake,70mm TB and spacer,fender mounted CAI, 1 3/4 long tube headers, 2 1/2 off road h-pipe, flowmasters, 3.73s, subframe connecters, e-fan,underdrive pullys, Steeda short through shifter

    thespeedfreaks.net

  6. #6

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    Quote Originally Posted by apstang50 View Post
    Have you tried pulling codes to see what if any codes are showing?
    No stored codes on a 1990.

    You need to resolve your fuel pressure regulator issue. A "rich" mixture can result in a backfire in the exhaust, which is what you said you experienced. If the vacuum line to the regulator is wet, the diaphragm in the regulator is likely ruptured.

    REPLACE your regulator, then see where you are at.

    If it still starts, I generally begin the process with pulling a spark plug, keeping it attached to the plug wire, grounding the plug electrode, and then have a buddy crank the engine while you watch. You are looking for a strong, blue, snapping spark. Yellow/orange/white indicates a weak spark which may not be strong enough to start the engine.

    And I would go back to a stock ignition. It is all the 4.0 needs for most application
    99 XJ Sport, 4.0, A.T. NP242 "Daily Driver"
    Past Jeeps: 49 Willys, 81 Scrambler, 88 Cherokee

  7. #7

    Default 1990 comanche

    two starter solenoids on this one, okay ive read everything on the web about this, i just need to know where to put the leads on my meter to check the camshaft position sensor signal to make sure its pulsing?

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    Quote Originally Posted by lonthompson View Post
    two starter solenoids on this one, okay ive read everything on the web about this, i just need to know where to put the leads on my meter to check the camshaft position sensor signal to make sure its pulsing?
    You stated above that you have spark, this means the cam sensor and crank sensor are working. Like suggested, I would start with the fuel pressure regulator.
    98' ZJ 5.9 Limited (mine)
    98' ZJ 4.0 2wd (wife's)

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    Your backfiring and no start could be the result of jumped timing, either valve timing or spark timing could do it.
    98' ZJ 5.9 Limited (mine)
    98' ZJ 4.0 2wd (wife's)

  10. #10

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    ok the fuel pressure regulator is capped off at the vacumm fitting, im gonna try now, in the beginning though i thought the cam sensor was ok because the injectors were dumping fuel , but im not sure if that was because they were being told to stay open or?maybe the cam sensor going out made them stay open until the computer killed the asd giving me my no spark, then i unplugged/replugged the pcm and "magic" spark again, but now i believ my injectors are not pumping at all and they seem to have power

  11. #11
    Moderately Senior lunghd's Avatar
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    lonthompson: Capping the vacuum line did not repair the ruptured diaphragm. Take lakerXJ's advice. You have to eliminate known issues before moving on to "maybes". Regulator function on the RENIX system is controlled by vacuum so bad diaphragm or no vacuum will both interfere w/ fuel flow. (And if that leak finds it's way outside the vacuum lines you might wanna have a bag of marshmallows on hand to roast until the fire trucks show up.)

    Quote Originally Posted by lakerXJ View Post
    No stored codes on a 1990.

    You need to resolve your fuel pressure regulator issue. A "rich" mixture can result in a backfire in the exhaust, which is what you said you experienced. If the vacuum line to the regulator is wet, the diaphragm in the regulator is likely ruptured.

    REPLACE your regulator, then see where you are at.


    If it still starts, I generally begin the process with pulling a spark plug, keeping it attached to the plug wire, grounding the plug electrode, and then have a buddy crank the engine while you watch. You are looking for a strong, blue, snapping spark. Yellow/orange/white indicates a weak spark which may not be strong enough to start the engine.

    And I would go back to a stock ignition. It is all the 4.0 needs for most application


    You asked where to attach meter leads to test camshaft position sensor... link to test procedure is in my first post above.
    Last edited by lunghd; 12-12-2010 at 07:56 PM.
    "...the advice given above is somewhat arrogant and in some cases wrong..." . (I'm not an expert... I just play one on the internet.)

    Another Freakin' Jeep Cherokee Website. _____________ Sure you're smart... but do you have what it takes to make "The List"?


    1990 XJ

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    Test for injector pulse: Unplug injectors one at a time and test with a noid light for pulse while turning over (you can use a bulb with two wires for this). One wire is power+ (5 volt I think) the other pulses ground-

    test cam sensor: One wire is power+ in one is pulsed signal out. Probe the wires without disconnecting. I don't have a diagram do a search online or probe till you get it right.
    98' ZJ 5.9 Limited (mine)
    98' ZJ 4.0 2wd (wife's)

  13. #13
    Moderately Senior lunghd's Avatar
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    Default Please separate yer thoughts!

    Lon: we can help ya better if you break down those 50 word sentences with some spaces and punctuation. I missed something ya posted & only found it just now by trying to break the post down myself. (Are you using a smartphone to post?)

    You "unplugged/replugged the pcm and "magic" spark again" ?? Are you talking about the ECU? This is a 1990 XJ, right? If I'm reading you right - you unplugged the ECU harness from beneath the dash and spark returned after you reconnected it?
    "...the advice given above is somewhat arrogant and in some cases wrong..." . (I'm not an expert... I just play one on the internet.)

    Another Freakin' Jeep Cherokee Website. _____________ Sure you're smart... but do you have what it takes to make "The List"?


    1990 XJ

  14. #14

    Default

    ok, sorry. i did unplug the ecu and then plug it back it. but now im not sure if maybe i didnt have spark because i didnt have the key in the run position or because the asd relay had shut it off, but now that i have spark, still no start, pressure regulator is busted though, gotta go find 50 bones

  15. #15

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    im going to check the injector pulse and the sensor pulse both in the morning. its supposed to freeze balls tonight. thanks, i guess that the worst that could happen is that i have to pull the timing chain cover. it is twenty now and never really cracked it open except for valve cover or oilpan.

  16. #16

    Icon314

    and the link for the testing procedure works, but the last step of the procedure is a little vague as to where to have your leads when the needle should flux back and forth.but i think i can probe it out till i get it, but ill check injectors too

  17. #17

    Default ok!

    okay i am getting a signal to my computer from the sensor, but it only fluctuates to 2 volts and 0, so my question is, can i swap a h.o. distributor from a 1993 4.0 in and splice the three wires?

  18. #18

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    and i am getting the 5 volts to the cam
    sensor

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    without a working regulator, it won't have enough fuel to run. The reg keeps the required pressure for the injectors to work. Right now fuel feeds your fuel rail, and goes back to the tank via the return line. The reg. will make the fuel rail pressurized. See if it will start with starting fluid or wd40 in the throttle body.
    98' ZJ 5.9 Limited (mine)
    98' ZJ 4.0 2wd (wife's)

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