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89 Navistar 7.3 idi----Learner Question

Discussion in '6.9L IH & 7.3L IDI Diesels' started by hrsitton, Jan 11, 2019 at 8:19 PM.

  1. hrsitton

    hrsitton Registered User

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    @Thewespaul

    Those two prongs were checked yesterday. First the connectors were pulled and checked for power with the key in the run position. Both checked at 9 volts+/-. (test setup was sloppy so may have lost some voltage in test)

    Then a hot wire from a battery source (the jump start connections) to each of the spades on top of the IP.

    An internal click was heard on both.

    I just set up to do a flow test out the Schrader. Will come back in and report quantity.

    Edit: I'm back. At least 2/3 cup with the filter return flowing also. That's 10 seconds.
     
  2. hrsitton

    hrsitton Registered User

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    I read somewhere that when the key was in the start position all circuits were deactivated except the starter and FSS.

    So I''m now wondering if there could be an entirely separate circuit for the FSS on start including a separate fuse.

    I'm thinking the key could not turn off the other circuits without turning off the FSS circuit and then turning it back on with the start position.

    Grabbing at straws here perhaps.

    It just seems so strange that one glow plug would be burned completely out with open circuit and the IP not working all while just sitting.
     
  3. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    Do you have a test light or a volt meter? You can hook either up to the fss while cranking to confirm they have power when cranking.
     
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  4. hrsitton

    hrsitton Registered User

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    Have test light. Had it jury rigged with wire to read/test from cab. Will do that again. I don't even know if there is a fuse box like in a pickup. Haven't found one.
     
  5. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    You will have a small fuse box either in the engine bay or under the instrument panel iirc, I dont work on many e series. heres the diagram 2008-02-06_173021_Econoline_fuse_1.jpg 2008-02-06_172944_Econoline_fuse.jpg
     
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  6. hrsitton

    hrsitton Registered User

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    May be getting somewhere.

    Removed both the yellow wire (which also runs to the throttle solenoid) on the dash side of the IP and the red wire on the front.

    With the key on the yellow wire had the same 9.5+ volt it had before. With starter running it dropped to about 6.5 volts.

    The red wire showed the same voltage as the yellow with the key on.

    But on start the voltage went crazy. It would first show a 1 way to the left where an open circuit would show if set to ohms, and then jump to 10 volts and even 14 volts and back down. The 14 volts may be due to the solar panel being connected to the battery with a controller that cuts out at 14.4 volts.

    I went back and checked the wiring again and retested and it went crazy again. Don't know why but that appears to be the problem. Could be a rapidly intermittent short?

    Found the fuse block location on the net.

    Unless you've got another suggestion, it looks like it may be time to make that temporary hot wire jump to the forward IP spade?
     
  7. hrsitton

    hrsitton Registered User

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    We crossed. Thanks for the fuse schematic. Downloaded and saved.

    The fuse block on the Navistar 1600S is up behind the emergency brake structure attachments. That's on the left drivers side. Can't even read what each is for with a flash light. Very inaccessible. So the picture sure helps. Most are circuit breakers. Saw two fuses.
     
  8. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    Try a jumper and see what happens
     
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  9. hrsitton

    hrsitton Registered User

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    Ok. Got a solid jump from the pump wire to the front red/pink connection. The pump only held 3.5+ PSI with the extra current draw. Did not start.

    Reset the jumper to the large jump start cables. Pump held 4+PSI but did not start. The cracked injector connection had been completely opened and screwed back down a turn or so. No fuel. None in IP return line pooling.

    Since the yellow wire did not lose voltage during cranking, it was not jumped.

    When jumping to the front spade from a hot location, there was a surprising, (at least to me), amount of spark when connecting. That made me wonder if there was a short in the coil/solenoid.

    But that would mean there were two problems with the FSS, the current/voltage supply plus the FSS itself, which would seem weird.

    Speaking of weird, the fuel gauge is stuck on full. It always worked very accurately before.

    Looks like the top of the IP has to come off to install a new FSS, if needed?

    What next boss? I can't say how much I appreciate all this help. It's not running yet but it's a lot closer than this morning.

    There's obviously a fuel delivery to the cylinders problem. Would it make sense at this point to pull the FSS and test it out of the truck?

    I've looked for one on the net but haven't found.
     
  10. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    This is an odd one. So just to recap, you’ve got power going to the fss via jumper and it makes sparks when it’s connected and an audible sound. You’ve got a steady inlet supply of fuel for the injection pump, but no fuel being returned or injected... it does sound like a faulty fss possibly, try tapping on the top of the injection pump with a mallet, and connect and reconnect the jumper several times to free up the solenoid Incase the plunger is stuck. These fss hardly ever fail, and when they do it’s typically the coil burnt up and it won’t click or spark because it’s an open circuit. You can take the top cover off and test that the fss works, but the armature is very specific in how it interacts with the metering valve. If you install the top cover incorrectly you will have full throttle and no way to shut the engine off without blocking airflow, it can be a little tricky if you’ve never done it before. Does the truck have a tach?
     
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  11. hrsitton

    hrsitton Registered User

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    I found Mel's injector servicing article and will print it out for better review. I will have an air intake cover at hand to immediately cover the intake if the FSS is accessed. The FP is also on a separate switch but not sure how long that would take to kill the engine. I'll figure on being able to do both if needed.

    I think the coil "could" be burnt and shorted out to cause a large spark when jumpered but there would be no click. If there is an arm with play, could there be a click with a stuck plunger?

    There should be a spec "somewhere" on the resistance for the solenoid coil. If the hammer doesn't work it looks like I'll be pulling the top off. With digital camera standing by.

    It's sounding like it's down to a bad FSS or the IP itself. Right?

    No tach on the truck.

    Not sure how the FSS is attached in there. Would simply loosening the cover quite a bit and wiggling it around have any effect on the FSS plunger or does it not know whether the cover is moving?

    Edit: Can the cover just be carefully removed with the inside filled with Seafoam and then replaced? Or are there components attached to the cover?
     
  12. franklin2

    franklin2 Full Access Member

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    The other guys know more about the guts of the IP, but I am wondering/asking them if the IP spinning at a decent rpm would unstick something in there. If you do not find a problem with the fuel shut of solenoid, would it be beneficial to disconnect the glowplugs, and give it a small shot of ether. I wonder if a couple of times doing that would free something up in the IP if it's sticking. And at least you might feel a little better about the whole situation hearing the engine trying to run.
     
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  13. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    It’s either a bad fss or a mechanical issue with the pump so here’s what to expect when you take the top cover off.
    D24A765D-9C1A-4C3F-9A40-DAFE80506674.jpeg
    Here’s underneath the cover, the larger solenoid is the fss, the smaller one is for the cold advance. You can see there is an o ring groove here, make sure to remove your o ring and set it aside while you’re working. You can see there’s no fasteners holding the fss from underneath. FC8DFB00-0AD1-4930-A925-EA72CA03B24B.jpeg
    Here’s the top, you can see the fss is held in from the top on the ground post and fss connector, you can take the nuts off and the fss will fall from underneath. Clean any rust around the plunger and look for any cracks or swelling in the coil case. You can test it with it out of the cover, if it’s good try and locate the metering valve arm, it’s what the arm on the fss acts on. Gingerly move that arm back in forth making sure there’s no stiff spots in its range. Operate the throttle and make sure everything is moving without binding. If you are looking to the back and straight down you will see the plungers move with the engine rotating. Let us know what you find
     
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  14. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    Possibly, if it’s a clogging or sticking issue some higher rpms could sure help, but if it’s a mechanical failure in the pump like a cam ring or flyweights it could really make a mess of the ip. You could even drain the ip from the side inspection cover and fill the pump with atf.
     
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  15. hrsitton

    hrsitton Registered User

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    @franklin2

    Hey, thanks for the suggestion, but hearing it run on either might depress me even farther. I need to save what energy I've left to find the problem.


    @Thewespaul

    Well, I read the article by Wes. I thought it was to be about the innards of the pump but it turned out to be a basic 101 thing. Did say the engine would run away as did you if the cover was not replaced properly but did not go into any detail at all.

    So I'll just be very careful to watch and see how the top comes off and put it back the same.

    But first I'll do some tapping as you suggested and from one picture in the article it does look as if loosening the bolts a little would allow more of a jar to the mechanisms in there.

    As I look at the cover I'm wondering if air could be blown into the return opening to blow out at least part of the diesel in there and fill back with Seafoam. I've had some good luck with that stuff.

    Couldn't hurt and if the plunger is stuck there's a chance it could loosen it up. The top can always be pulled later.
     

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