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Thread: Runs, but not well

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    Senior Member FlyingCat's Avatar
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    Runs, but not well

    Now that I got my 1980 Spitfire (1500 Federal, no overdrive) running, I want it to run a whole lot better than it is. It's hard to start (at least, the first time), and it seems to be cutting out when I take it around the block. It also doesn't seem to have a whole lot of power, though I haven't gotten it out of the neighborhood yet. The shop that put my exhaust on says it needs to be tuned. And they may be right, but I don't want to pay somebody else to do it. I mean, isn't that the whole point of a project car... to do it yourself? It has new everything on it -- Weber carb, new wires, plugs, filters, oil, cooling. It doesn't seem to be leaking anything, but I question whether the seals on the engine are as good as they should be. I haven't touched any of the factory settings on the carb. Any ideas where I should start?
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    Re: Runs, but not well

    To start, check for vacuum leaks in the manifold, intake and exhaust. Spray carb cleaner around the areas the manifolds join and lessen for the engine to speed up.
    Last edited by trrdster2000; 05-30-2019 at 07:27 PM.


    '37 MG TA, '49 Triumph Roadster, '70 TR6, 2000 Jaguar XK8, '78 Spit6

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    Re: Runs, but not well

    Glad you got it going--- I remember how much effort you put into it. My trouble shooting is better on a tr3. Anyways, check the obvious like firing order, dwell, valve adjustment, and timing. I like to pull the plugs often on a fresh start to see what they look like, and with Triumphs the problem is often running rich often because the choke is stuck, but again you cannot correctly set a carb until the other stuff is addressed. I would add also in my experience if the motor is popping the problem is often in the ignition cutting out and coming back blowing up the unburn fuel, and if the motor is doggy it is fuel delivery—but not a hard fast rule. You will get it; I would pick up 3 sets plugs to keep after fouling problems and some new points, rotor and cap.

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    Re: Runs, but not well

    When checking the ignition timing, also check that the centrifugal advance is working as expected. Hook up a timing light, shine it on the mark, and watch what happens as you slowly rev the engine up and let it back down. The mark should move smoothly with rpm (up to some maximum, which I don't know offhand). If it jumps around at any speed, or doesn't move, you need to get the distributor serviced.

    I would also run a compression check, just to make sure there isn't a problem there.

    A stock 1500 is no barn burner anyway; always seemed short on power to me.
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

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    Re: Runs, but not well

    To show my ignorance, I'm not truly sure what compression is, and I don't know how one checks such a thing.

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    Great Pumpkin NutmegCT's Avatar
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    Re: Runs, but not well

    I was going to point you to several YouTube videos on how to do a compression test ... but each one I found was preceded by four or five ads running from 30 seconds to 90 seconds. Yeesh.

    Basically, you want to see if the pressure created by the upstroke on the piston inside the cylinders is approximately equal for all the cylinders.

    There are different ways to do a test. The gist is: Disconnect ignition wire from distributor. (You'll want to crank the engine, not start it.) Then remove all spark plugs, screw a compression tester hose into a plug hole, crank the engine, and read the compression number on the tester. Do this on all cylinders, to see if they're all about equal. You want to have each number be the same, or +/- 10% different from the others. Example of a good test: 120 psi, 125 psi, 120 psi, 118 psi. Example of a bad test: 120 psi, 60 psi, 70 psi, 118 psi.

    Here's a general overview:

    https://www.dummies.com/home-garden/...r-compression/

    Also a good idea to hold the gas pedal to the floor (put a brick on it) so there's free flow of air in manifold.

    Tom M.
    Edit: you're looking to see if each cylinder is "tight" and develops maximum power each time its fuel/air is sparked, or if it has pressure losses due to cracked head, sticking piston rings, stuck valves, etc.
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    Re: Runs, but not well

    The nice thing about the kind that screw in: you don't need a helper or a starter switch. Just screw the gauge in, then lean over and turn the switch to the 'start' position (after making sure the transmission is out of gear and the ignition is disabled). The gauge has a valve in it, so it will hold the reading until you get back to the gauge. There should be a pin or button that you press to release the pressure before doing the next test.

    Since you are only looking for the comparison between cylinders, the gauge doesn't need to be strictly accurate (and most of them aren't, in my experience). I picked up one of these
    https://www.harborfreight.com/compre...ression+tester
    last summer (mostly because it had the 18mm adapter to fit the tractor I was working on), and it seems to be a reasonable kit for the price. No idea how long it will last, but it did what I needed.

    On an older car with electronic ignition (your Spitfire may or may not still have the factory electronic ignition, an aftermarket electronic ignition, or have been converted back to points), I think it's best to disconnect the low tension side of the coil rather than the high tension wire (as the link Tom gave suggests). The Pertronix aftermarket electronic ignitions in particular are sensitive to being left on for a long time with the engine not running; but the coil and points will get hot even with points. Then you don't need to worry about the high tension wires, as there won't be any spark.

    Obviously you have to reconnect after you're done, along with reinstalling the spark plugs, putting the plug wires back on and anything else you changed.
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

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    Re: Runs, but not well

    IMHO it is best to set the valves before doing a compression check. Get a manual on Spitfire and it will have simple way to set the valves. Regardless, I always pull the plugs out so I can turn the engine easily over by hand.

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    Re: Runs, but not well

    Great link. I just bought a timing light. Now it looks like I need a compression guage. Thanks!

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    Re: Runs, but not well

    My car has points. This all seems like it's not very hard to do... once I know what I'm doing. You've been a lot of help. I have a whole list of things to check. Thanks!

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    Re: Runs, but not well

    I'm making a list, and setting the valves is now on it. Looks like I got my spare time filled for the next few weeks. Thanks!

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    Re: Runs, but not well

    It's all pretty easy, and gets easier with repetition. The downside is when the compression test tells you something you didn't want to know!
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

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    Re: Runs, but not well

    Before I can check the compression, I need to get the car to where it will idle without dying. That's not asking too much. I'm thinking it could be the coil, the rotor, the points, or the wires to the sparking plugs. My guess is it's all four.

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    Re: Runs, but not well

    The engine is not running when doing a compression test..
    DRIVE 'EM IF YOU GOT 'EM

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    Re: Runs, but not well

    You have to check and probably set the valve lash first before you do any other stuff; it is easy to do. You do it with the engine cold. Read up on it and ask questions if it is not clear. You basically just need to have the valve closed that you are setting and then putting a feeler gauge between the valve stem top and the rocker so there is some room for the engine to expand when it warms up, and IIRC spitfires were .010 cold.

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    Re: Runs, but not well

    If it doesn't have compression, it's not going to idle right.
    Running under load actually puts more stress on the ignition, because its harder for the spark to jump when cylinder pressure is higher. Not impossible for it to be an ignition problem, but less likely IMO.

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    Re: Runs, but not well

    Turning back the clock....

    Last month I believe I sent you a marked up schematic showing how to change the coil wiring to eliminate the ballast resistor and properly power your 3 Ohm coil. Did you make those wiring changes yet? If you did not and the ballast resistor is still in the coil's low tension circuit you may have a very weak spark at the plugs. Let us know if you have updated the ignition wiring and/or if I need to send the marked up schematic again.
    Doug L.
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    Re: Runs, but not well

    I've already set the valves. For the most part, they were fine (my engine has less than 40K original miles on it... that's what happens when your car sits in a garage for 25 years). The timing is way off, though. Numbers three and four sparking plugs were fairly well toasted when I checked them, so they've all been replaced. But I can't get it to idle anywhere near specs. And I'm pretty sure my ballast resistor shouldn't be smoking. I'm thinking I need to replace the rotor and points, at a minimum. Heck, I've had to replace everything else so far.

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    Re: Runs, but not well

    I just got a compression tester, so that's my marching orders for today. We'll see what we see, then go from there.

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    Re: Runs, but not well

    I've got so much stuff it's hard to tell what is what. So if you could, send them again. I have a ballast resistor on my car right now, but I'm pretty sure it shouldn't be smoking. I'm also probably going to replace the coil... just in case. I've replaced everything else as it is. But, yeah. It runs, but really... REALLY poorly. I drive it about a mile and it just dies. After it sits a few minutes, it'll start back up (which tells me something is overheating). As well, it will not idle without dying. So right now, I'm not driving it further than I want to walk home. I know that could be the dwell, or the points or rotor could be bad, so I'm probably going to replace both of those. It could also be the coil... or so I've been told by me knowledgeable FLAP. Today, though, I'm checking the compression!

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