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The Silver Buick's 1969 Firebird OHC six project.

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  • Thanks for the tip on the carpet paint, it is certainly a route I'm willing to go. It's only on the passenger side there, so even if it doesn't come out quite right it'll be out of my field of vision 90% of the time.

    The highlights of today are, I heard the engine run, a couple of times, but it certainly wasn't smooth sailing. Long post warning.

    Started the day pretty good. Hooked the battery up and no smoke, sparks or pops. Headlights, tail lights and dome light worked, figured I'd check the stock systems first. Then tried the key. Found my trigger wire to my relay didn't power with the key. Not a big deal, found the needed power source. Then had the megasquirt and fuel pump relay power reverse. No problem, swapped plugs moving on. Things were looking good at this point. The system powered up, the megasquirt was reading the sensors, the engine cranked when pressing the start button. Though it seems the neutral safety switch is out of adjustment as it won't crank in park, but will in neutral. Won't crank in any of the gears so it somewhat works. Problem for later. Then it started to go down hill from there....

    Started working on checking the fuel system and first the lift pump wouldn't prime, so I threw 7 gallons of fresh fuel in the tank (probably needed fresh fuel anyways) and used the shop vac to blow air into the filler neck and the lift pump promptly started leaking at both ends..... After tightening up the fittings, the filter, breaking at least one hose clamp, I tossed the pump and got a new one that had the fitting built in and a new filter. Only bathed in a gallon of gas in the process *blah*. Had a minor leak at the fuel rail and ended up moving the fuel pressure gauge to the regulator. By now it was mid-afternoon so I figured I'd skip filling the cooling system with water because I'd have to promptly drain it, and proceeded right to start up

    Started the car up a couple times for ten or so seconds at a time and topped off the transmission fluid as well as ran it through the gears (speedo works now! Didn't when I got the car), and while doing this had no problems. The engine started reasonably well and shut off when I turned the key off like it should until......... it didn't...... The big difference between when it was working fine and when it didn't was I rev'ed it up high enough to get the alternator charging, and when I turned the key off the alternator was feeding the system, but cut off from the battery because I had the charging wire on the wrong side of my master relay and then bad things started to happen. The engine didn't shut off, but didn't sound right either, and I hit the power switch to the megasquirt to kill the engine but it was too late, the damage was done. When I key'ed back on the megasquirt did not power up. I checked and the fuse was good, it had power on the wire going into it, but nothing. Took a sniff at it and it smelled burnt =/


    Dragged it into the house and opened it up and yup, a few cooked parts, some obvious and some not so obvious. Using the obvious visual cue's was easy for the damaged parts, but I hooked it back up to the JimStim and started testing the power circuit to find the two bad diodes. Started testing and replacing parts until I had power at the processor pins, and turned out just to be the two diodes.

    Here is an obvious exploded capacitor


    And an obvious burnt out power trace. (the copper color, it's not copper and doesn't conduct)


    So I started troubleshooting. The exploded capacitor is essentially the first part that is installed when building a megasquirt and is part of the power circuit. So I started there. Fortunately I have some spare parts (not that any of them are exotic, but I was able to get it going again today). I replaced these four parts. The capacitor on the top right may not be bad, but I didn't trust the way it looked compared to the good ones. The bottom two diodes were toast, no conductivity in either direction.


    New capacitors installed.


    A jumper wire installed in place of the cooked trace. (it doesn't look pretty, but will work and is hidden in a case!)


    So I went back out and took a video after the fact =D The phone picks up the fuel pump sound more than you can actually hear it in person.
    Last edited by TheSilverBuick; February 9th, 2014, 08:48 PM.
    Escaped on a technicality.

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    • so...you gave the MS too much voltage? or did it get reverse polarity? or is it still a mystery?

      Anyways, looks like a lot of progress for one day. Running is good!
      My fabulous web page

      "If it don't go, chrome it!" --Stroker McGurk

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      • Rock-n-roll, bout that time to give her a bath.

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        • It shouldn't be too much voltage as the input voltage is designed for the standard automotive range. I'm thinking some thing along the lines of a high amp draw through the megasquirt when the relay was shut off disconnecting the positive side of the battery from the system, though the 10 amp fuse didn't blow, so I'm now looking at a lower rated fuse

          I've since moved the alternator charging wire to the same side of the master relay as the battery so it shouldn't be able to create a run on condition again when the relay is shut off.

          And Thanks!
          Escaped on a technicality.

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          • Another thing that just crossed my mind as a mini-victory is the transmission shifts into reverse and drive. Torques over both directions and I ran the speedo up to about 10-15mph (it's not accurate). Couldn't tell if it shifted or not, but definitely had wheel movement.
            Escaped on a technicality.

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            • This is caused by load dump.. when the alternator loses connection to the battery the alternator output voltage surges - can be >70V - the tantulum input cap shorted out - it rated for like 50V at best. Once it shorted the input current spiked and fried the track - the input fuse to the MS should never be more than 1 Amp. Better check the input transorb and the 5 volt reg. (or just change them) - they may be working now but possibly a failure waiting to happen.

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              • and fast burn fuse.. loose the automotive type spade and get a fast burn fuse

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                • It ran, that's a good day.

                  You continue to inspire me Randal, thanks for the long and detailed posts.
                  I'm still learning

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                  • It's generally a good idea to wire the alternator output directly to the battery....
                    My fabulous web page

                    "If it don't go, chrome it!" --Stroker McGurk

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                    • Originally posted by squirrel View Post
                      It's generally a good idea to wire the alternator output directly to the battery....
                      I know that now =P I guess my thought process was "it didn't matter which side of the relay the alternator charged too because it wouldn't be charging when the car was off anyways" Ooops.... Forgot about the possibility of the alternator causing a run on condition, I know better now!


                      Thanks for the background info Marc That helps me understand the root cause better. I'll be watching closely for funkyness in the MS logs and such. I ohm'd and diode tested each component of the power circuit against a known good one and the two diode's were the only two that didn't match the other MegaSquirt. The MOV1 (5v regulator?) part ohm'd identical to a known good one. Well I didn't check the blown up capacitor or the other one I replaced. I'll change out the MS power fuse to the smallest one I can find. I'm glad that I was able to bring it back to life and the processor wasn't toast.


                      Welcome Bob
                      Escaped on a technicality.

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                      • Cool! Sounds like it runs nice.

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                        • Nice work Randal , you should be proud of yourself . As for all this MS talk , I'm still out in left field but I'm still trying to learn .

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                          • It'll be a happy day when the S-10 gets to that point. Maybe I can get Russell to come over and make a vid when I gt that far - I have no clue.

                            As stated - GOOD for YOU! Sounds excellent and all the dials and gages move.

                            Dan

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                            • I know this might be a stupid question. but while at parts store I see 12 types of j/b weld..what one are use using??

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                              • I only know of two types and they each come in two sizes

                                Regular JB Weld, then JB-Kwik Weld. The Kwik weld cures a lot faster (and comes out much darker) but isn't rated for as high of temperatures. Regular JB weld takes a good while to fully cure (especially in the cold). 90% of the time I use the Kwik weld just because of the cure time. It gets tacky enough to support its own weight much quicker. I'll let it sit five minutes or so before applying, where as the regular weld I might let sit for a half hour or more before it'll hold a shape.

                                On the EFI bungs, I try and get it to flow through fairly slowly and keep adding some until it builds up around the top. Then after a day (even the kwik weld) I'll take the die grinder to it inside the ports and blend it in.
                                Escaped on a technicality.

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