Vacuum advance

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  • Carbinekid
    230 Tornado
    • May 24, 2020
    • 15

    Vacuum advance

    I purchased a 88 wagoneer a few months ago and have recently been going through everything and I found that the vacuum advance hone has been disconnected from the distributor I drove it home when I purchased it this way I hadn’t realized it when I purchased it. The PO has installed an Edelbrock 4 barrel intake and Edelbrock 4 barrel carb when I hook the line up to we’re the ported vacuum is and rev the engine the engine stalls. It runs fine disconnected and plugged but when hooked up it will stall. Any advice on we’re to start?
    Thanks
  • wiley-moeracing
    350 Buick
    • Feb 15, 2010
    • 1430

    #2
    sounds like the vacuum diaphragm is bad, test it and see if it holds vacuum.

    Comment

    • Brynjminjones
      258 I6
      • Jun 11, 2017
      • 475

      #3
      I had a similar problem recently with my old Ford truck, which has the same ignition system.

      For me, it was the distributor pickup coil that was bad. Every time the vacuum advance rotated it, it didn't like it and the engine would pretty much immediately stall.
      That was with a brand new pickup coil too! Fixed it by replacing with a 40 year old used one.

      I'd try taking the cap off the distributor to inspect the wires to the pickup coil. Even if they're good, check to see if it looks new in there, as some new replacements clearly have problems!

      When I had a vacuum advance that wouldn't hold vacuum, it didn't run great but it wasn't enough to make it stall as it's only a small vacuum line.
      1991 Grand Wagoneer - Hunter Green. All stock. Rebuilt 360, .030" over with Melling MTA-1 cam.

      1998 Cherokee (XJ) 4.0
      1997 Grand Cherokee (ZJ) 4.0
      1974 Ford F100 390

      Comment

      • Ristow
        • Jan 20, 2006
        • 17292

        #4
        it sounds like someone put a Ford application vacuum advance unit on,which does not work. i went thru this years ago. didn't stall but would miss and backfire so bad it would'nt move in gear.
        Originally posted by Hankrod
        Ristows right.................again,


        Originally posted by Fasts79Chief
        ... like the little 'you know what's' that you are.


        Originally posted by Fasts79Chief
        I LOVE how Ristow has stolen my comment about him ... "Quoted" it ... and made himself famous for being an ***hole to people. Hahahahahahahahahha!

        It's like you're unraveling a big cable-knit sweater that someone keeps knitting...and knitting...and knitting...and knitting...

        Comment

        • Brynjminjones
          258 I6
          • Jun 11, 2017
          • 475

          #5
          I just remembered that I took some videos of when our Ford did this. Is this what yours is doing?

          This first video is with the vacuum advance hooked up to ported vacuum. If I held the throttle open for any longer than I did in the video it would have completely died.





          In this second video, I disconnected the vacuum advance and hooked it to a hand vacuum pump instead.
          You'll notice that the engine is operating fine, even with the throttle open. However, as soon as I apply vacuum to the advance unit, it dies almost straight away.

          1991 Grand Wagoneer - Hunter Green. All stock. Rebuilt 360, .030" over with Melling MTA-1 cam.

          1998 Cherokee (XJ) 4.0
          1997 Grand Cherokee (ZJ) 4.0
          1974 Ford F100 390

          Comment

          • Carbinekid
            230 Tornado
            • May 24, 2020
            • 15

            #6
            Brynjminjones, that is exactly what it’s doing I haven’t tried the hand pump but I’m sure it would stall the same as it does hooked up and staying on the gas

            Comment

            • Brynjminjones
              258 I6
              • Jun 11, 2017
              • 475

              #7
              If yours is doing the exact same as mine, definitely look at the distributor pickup coil.
              They're the exact same part number for my Ford truck as on a Wagoneer, and new ones seem to be hit-and-miss.

              See if it either looks new, or if the wires are in poor shape.

              If you don't have a hand vacuum pump, another thing you could try to help with diagnosis is connecting the vacuum advance directly to manifold vacuum instead of ported.

              When I did this, the truck would crank and try to fire. As it tried to fire it would build enough vacuum to operate the vacuum advance, and immediately stop firing. Vacuum would then go down and it would try to fire again, over and over!
              Ultimately it wouldn't run at all like that.
              1991 Grand Wagoneer - Hunter Green. All stock. Rebuilt 360, .030" over with Melling MTA-1 cam.

              1998 Cherokee (XJ) 4.0
              1997 Grand Cherokee (ZJ) 4.0
              1974 Ford F100 390

              Comment

              • Carbinekid
                230 Tornado
                • May 24, 2020
                • 15

                #8
                So I had a chance to look at this yesterday evening I have an 89 gw that is the parts car due to rust it starts and runs great I’ve driven it around the neighborhood point is it runs good I looked at the current distributor and it looks like it could have replacement parts in it so I swapped distributors between the 89 and the 88 started the 88 up and hooked up the vacuum advance to the ported vacuum and it stalled out. Could it be something with the vacuum or timing off ? It revs up and runs fine without it hooked up I believe the distributor was working fine before I swapped it the other engine appeared to be running fine with it hooked up.

                Comment

                • wiley-moeracing
                  350 Buick
                  • Feb 15, 2010
                  • 1430

                  #9
                  I believe they are correct, check the replacement diaphragm, it may be the wrong one and is pulling in the wrong direction when vacuum is applied?

                  Comment

                  • tgreese
                    • May 29, 2003
                    • 11682

                    #10
                    The last rebuilt AMC Motorcraft distributor I bought had a clearly rebuilt vacuum diaphragm. The builder pried open the can and replaced the diaphragm. This does no provide much hope that these diaphragms are available by themselves on the aftermarket.

                    If you need a diaphragm, suggest you buy a reman distributor and take what new parts you want from it. The seller will probably accept the new distributor as a core even missing some parts. Probably cheaper than some rare NOS AMC part you might find on eBay.
                    Tim Reese
                    Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS, hubcaps.
                    Browless and proud: '82 J20 360/T18/NP208/3.73, Destination ATs, 7600 GVWR
                    Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
                    GTI without the badges: '95 VW Golf Sport 2000cc 2D
                    ECO Green: '15 FCA Jeep Cherokee KL Trailhawk

                    Comment

                    • Crankyolman
                      350 Buick
                      • Sep 27, 2017
                      • 891

                      #11
                      Originally posted by Carbinekid
                      So I had a chance to look at this yesterday evening I have an 89 gw that is the parts car due to rust it starts and runs great I’ve driven it around the neighborhood point is it runs good I looked at the current distributor and it looks like it could have replacement parts in it so I swapped distributors between the 89 and the 88 started the 88 up and hooked up the vacuum advance to the ported vacuum and it stalled out. Could it be something with the vacuum or timing off ? It revs up and runs fine without it hooked up I believe the distributor was working fine before I swapped it the other engine appeared to be running fine with it hooked up.
                      Does the distributor you took out of the 88 work when installed in the 89?


                      Are you sure the 89 ran well with the vacuum hooked up?
                      '72 J4500

                      Comment

                      • Carbinekid
                        230 Tornado
                        • May 24, 2020
                        • 15

                        #12
                        Good question in regards to trying it out on the 89 but i’m unable to do so I started tearing the truck apart a week prior to my original post I wish i had as far as the 89 running I believe it ran great with it hooked up it started and idled fine as well as revved up I was able to drive the 89 around a little bit and it seemed to run good but the same distributor on the 88 just stalls out as soon as I hook up to the ported vacuum could it possibly be pulling to much vacuum from the carburetor I believe I mentioned it’s an aftermarket Edelbrock 4106 on the 88

                        Comment

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