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1989 Ford Aerostar 3.0L EFI Weak Spark

Discussion in 'Aerostar Forum' started by OneHit, March 20, 2009.

^^Searches ExplorerForum.com^^
  1. OneHit

    OneHit New Member

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    1989 Ford Aerostar, 3.0L, V6, EFI, has a distributor and one coil. Started just fine. Was backing out of my space, went 15 ft roughly, slowed down, preparing to shift into drive, engine died. Will crank, fuel pump working. Starting fluid no help. Pulled random spark plug wire, used old plug against engine block, no spark. Replaced coil. Now proper voltage at key-on, continuity skips between gnd into coil and common ground on cranking. No secondary ignition out of dist. Pulled cap, inspected and cleaned pickups and rotor, normal wear present. Slight rust-colored discoloration near cyl6 pickup on inside only. Re-attached cap and wires. No change in situation. Grabbed hold of bare coil hi-tension outlet post and very weak kick...not the huge jolt I was expecting.

    What could be causing this all of a sudden? I was thinking DCM, but would a bad distributor control module allow ANY juice at all to emerge from the coil? What is every single device in this car which can stop it from having a full-strength spark?

    Any help greatly appreciated. This is my daily driver, so time is of the essence.

    Also, does this model take an obd 1 or 2 reader?
     
    Last edited: March 20, 2009
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  3. BrooklynBay

    BrooklynBay Moderator & long time member. Staff Member Moderator Elite Explorer

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    Welcome to this forum! I know that you cleaned the cap & rotor, but it might be a good idea to try a new one to see if you still have this same problem. Compare the resistance of the old coil to the new one. I doubt that they are much different. The ignition module controls the spark timing, and a no start condition usually occurs when it goes bad. You have an EEC-IV system. OTC makes an actual high voltage digital volt meter. I have one of these, and they are quite expensive. It's possible that your old ignition cables are no good.
     
  4. OneHit

    OneHit New Member

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    Thank you, Brooklyn. It's good to be here. The trouble, it turns out, was the distributor control module. The housing had split, and the discharge amplification circuit was exposed to the atmosphere. A stray arc had traveled
    through the casing and tracked along a moisture trail in the insulating gel to the IC in the board. There was a carbon track from this. Replaced the DCM for $1.33 at Pull-A-Part. Got three of them, just in case the first one or two were bad, but now I have two spares in the parts box. Thank you for your assistance, the problem is fixed.

    By the way, I will be stopping by this forum henceforth to answer what questions I may. Thank you all once again....say hello to Glacier991 for me.
     
  5. BrooklynBay

    BrooklynBay Moderator & long time member. Staff Member Moderator Elite Explorer

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    Thanks for the update! The later models of this van rerouted the ignition module to the passenger's side front fender wall to keep it away from the heat of the engine. You could get that wiring harness from a junk yard. Did you use heat sink grease on the back of this part before you installed it? Do you usually have a lot of these vans in your local junk yard? How many miles does your 89 have?
     
  6. OneHit

    OneHit New Member

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    Well, I got three of them just in case they are short-lived. As for the harness, don't fix it if it ain't broke:)I got this car for a dollar, rebuilt the tranny twice, changed the water pump, re-did the brakes, modified the water system, did a bio-diesel conversion and e-85(flexed it out, in other words) and the jet engine is next....lol. It has 485,298 miles on it, but that's not a lot for this engine I don't think....Vulcan V6 cast iron.
    As for heat sink grease, I used Quick Silver CPU thermal paste I have in vats (I'm a computer tech). I benched the module on my Tektronix 2246 4channel Oscilloscope and got nothing past the 2nd loop. The reason I had LITTLE spark instead of no spark at all is that the module is an electronic replacement for the points in an older engine. The voltage drop in the coil primary causes a surge in the secondary which jumps out of the high-tension lead to the distributor. The problem is that this spark is very weak without proper phasing to bounce it back between the stator and the primary to amplify it. The first loop in the DCM initiates a field collapse in the primary coil; That collapse initiates a high-tension buildup in the secondary. The second loop in the DCM refines the output phase of the primary, which slightly draws out the discharge wave in the secondary coil. The third loop is a bounce back amplification circut to constructively interfere with the main discharge and increase its amplitude. Finally, the fourth loop is the re-initialization of the primary current in preparation for the next ignition sequence. Mine went out at the second loop circuit due to the pathway through the insulating gel to atmosphere formed by the separation of the housing, so when the high-tension pulse was forming in the secondary, instead of discharging through the outlet post, it re-built itself in the primary, causing a discharge of ~10kV through the IC and out along the ionization trail initially formed by the first, smaller discharge through the gap. The result is an insta-fried IC, and a partially closed circuit resulting in weak spark.
     
  7. BrooklynBay

    BrooklynBay Moderator & long time member. Staff Member Moderator Elite Explorer

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    The module is more like an amplifier in comparison to a contactor (point ignition). The actual pick up works on the Hall Effect principle just like ABS sensors. Do you have any scope pictures of these phases? How did you make the E85, and biodiesel conversions with an ordinary gasoline engine? What do you mean by modifying the water system? Is this water injection?
     
  8. OneHit

    OneHit New Member

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    Close...while the circuits in the module do act as a solid-state amp, the points act as an electromagnetic amp. Using the Hall Effect to sense where the rotor is in its rotation, the ECU determines when to initiate the collapse of the primary coil current, to begin collecting the charge in the secondary coil. The circuitry in the DCM bounces the current back and forth through the primary to stack the potential difference in the secondary to ground. Like dipping a candle in hot wax, then in cold water, then in hot wax to build layers and increase the weight of the candle. The second loop (or circuit) in the DCM uses a series of small solid tantalum capacitors to delay and refine the return wave. The points in an older vehicle also amplify the discharge via the Hall effect, they just do it without the tiny junk that breaks/explodes easily:)
    [​IMG]
    The details of using bio-diesel in a gas engine are <a href="http://www.journeytoforever.org/biodiesel_make2.html#gas">here</a>
    E-85 stuff is <b href="http://www.metacafe.com/fplayer/754542/how_to_install_an_e85_conversion_kit.swf">here</b>

    I modified the water system out of necessity, rather than any true desire to do so. While changing the thermostat, a rusty bolt broke off at the outlet, despite a week-long soak in WD-40 and Bust-loose. The solution, aside from putting the van on a lift and disengaging the sub-frame to lift the body high enough to fit a drill under the hood, was J.B. Weld. The Outlet hose was cut in half, two outlets from O'reily were Blue RTV'ed to either side of a new thermostat, followed by some nuts and bolts. So now a section of the outlet hose has two water outlet bodies which hold the thermostat.

    I could post some photos, but I do not use sites like photobucket and whatnot....they are not reliable.
     
  9. OneHit

    OneHit New Member

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    Huh. How do I enable html?
     
  10. BrooklynBay

    BrooklynBay Moderator & long time member. Staff Member Moderator Elite Explorer

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    Nice graphics! So now you have an external thermostat? Does it work just as well as one which has the thermostat making contact with the engine block or is the temperature range slightly off since coolant will cool down a little as it travels through the rubber hose?
     
  11. BrooklynBay

    BrooklynBay Moderator & long time member. Staff Member Moderator Elite Explorer

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    What are you trying to do? Non Elite members can't upload to the site if that's what you're referring to. Were you trying to embed the link?
     
  12. BrooklynBay

    BrooklynBay Moderator & long time member. Staff Member Moderator Elite Explorer

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    The links in post # 7 don't work. Could you provide updated links?
     
  13. K80

    K80 Active Member

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    Ah. Here it is....It had been so long, I'd forgotten my login info! Anyway, for the record, OneHit is I. Now that I have my stuff back, I'll post as K80. Is there a chance I can take ownership of the posts in this thread? OneHit is more my gaming moniker :)

    I'm trying to make a link that appears as the word "here", and when you click on it it opens a new tab on x page....You know, href! lol


    As for a clickable link, this will have to do for now:
    http://www.journeytoforever.org/biodiesel_make2.html#gas
    http://www.metacafe.com/fplayer/754542/how_to_install_an_e85_conversion_kit.swf

    The site went down completely this morning....what happened?
     
  14. BrooklynBay

    BrooklynBay Moderator & long time member. Staff Member Moderator Elite Explorer

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    It went down a little while ago again. I don't know what happened earlier. According to the rules of the forum, I will have to close the newer account since you can't have two active accounts at the same time.
     






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