’68 Scout 800 – 266V8 – SURGING !?!

Discussion in 'General IH Tech' started by Sweli, Jun 26, 2015.


  1. Sweli

    Sweli Farmall Cub

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    Any help is appreciated.

    Background:
    Bought this in running condition last August. Ran, but not great.
    2150 Motorcraft carb with venturi meant for a 350/360, worn points, and spark wires out of order.
    Repairs last fall:
    Ignition (+) wire to a 42a relay on the firewall, that pulls a 10ga wire from the battery to feed three fused circuits.
    Fuses to coil and choke, to fuel pump, to radio.
    Pertronix Ignition (pointless replacement), with slightly hotter coil (30k instead of OEM 20k)
    Electric fuel pump and regulator. Cheap Mr. Gasket red pump and reg. (bites me later).
    Rebuilt Carb with a kit
    New cap, rotor, plugs(NGK XR5 3332) , wires.
    (other stuff, but does not pertain to the issue).
    The truck ran fine all 500+miles in the fall and winter, and early spring.

    In April, it started “surging”. This happened right at start up after sitting in my work lot 4hrs.
    It is enough of a surge, that you cannot drive it. It shakes the drivetrane going down the road.
    It does it from idle all through the revs.
    Then suddenly stopped after 10mins. And ran fine for two more days.
    I chased this random issue for a couple weeks until it became more permanent.
    Repairs last 6 weeks: - (and issue randomness comes back)
    Fuel Filters before pump and carb replaced.
    Fuel Regulator – found as the truck hit bumps, the pressure would go up and down from 2 to 7psi. Replaced it with a Mallory unit with wet gage.
    Carburetor – replaced the Motorcraft 2150 with a rebuilt 2100 with correct venturi and jets.
    Seemed to run fine for a few days, then issue started coming back
    While it was running without surge, I sprayed all around the intake manifold with carb cleaner looking for a leak, but could not find one.
    Compression check – 120-130 on all cylinders.
    Pulled the valve covers to check for a cracked/broken valve spring, none.
    Started to measure rocker throw. Most in Odd bank were the same before I lost oil in the lifters and had to stop.
    Distributor – found it full of crud, small amount of bushing slop, with incorrect centrifugal springs. – replaced with a rebuilt one.
    Seemed to run fine for a few days, then left me stranded when the cheap fuel pump died
    Fuel Pump – new Carter4070 with sintered filter in front of it.
    Ran fine for last two days and 25miles, now the issue is back when I went to start it this morning.
    Timing is set, and good.
    From what I read, Pertronix pointless systems either work or don’t, they are not intermittent??
    Fuel system is totally replaced.
    It has new poly tanks (one has really old gas in it so I keep the vavle on the drivers tank only.)
    Has good spark
    If it was a bad lifter, I’d hear it.
    If it had a worn cam, it wouldn’t be intermittent, right??
    Stuck valve?? But you would hear it too??
    Debris in drivers tank being used – but fuel pressure is steady, and surging is every second. Carb bowl and system would have enough fuel to keep running many seconds.

    I'll try and post a decent video showing it, tonight.

    I am stuck and frustrated.
     
  2. Sweli

    Sweli Farmall Cub

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    Intermittent 42a relay I am using to drive the ignition and pump?? - going to check
    VAC leak, but where? I sprayed everywhere I could on top of the intake manifold.
    Could it be on the underside where I cannot get spray?
     
  3. kevingweq

    kevingweq Y-Block King

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    The next bit of diagnosing should be checking manifold vacuum with a decent gauge , do a little research on what to do and how to interpret the readings
    also a compression test just to get an idea of general health of motor
     
  4. Sweli

    Sweli Farmall Cub

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    Compression was 120-130 acrossed the cyl.
    When not surging, VAC is OK. I'll get an actual number and post. Also if surging again, I'll get swing of VAC.

    thx
     
  5. Sweli

    Sweli Farmall Cub

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    Just bizzare that my kids and I ran around for over an hour last night and it ran great.
    Parked it in the garage.
    Come out the next morning and it surges from the start.
    ??
     
  6. Bob BMW

    Bob BMW Binder Driver

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    Seems like you have tried about everything but something you wrote prompted my suggestion.

    You said the Scout has new poly tanks but one has really old gas and you don't use it and the other tank has debris in it. Just to eliminate the possibility, why don't you take both tanks out and thoroughly clean them? That is something you need to do anyway and it just could be causing the surging problem. While the tanks are out you should also blow compressed air backward through all your fuel lines while switching the tank selector valve to both positions to unclog them. You may even want to disconnect the fuel lines at the valve so you work with shorter lines. The lines themselves could be the source of rust flakes too.

    Good luck.
     
  7. Sweli

    Sweli Farmall Cub

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    Thanks for the reply Bob!
    Previous owner had the poly tanks installed. At that time they also installed new plastic fuel lines. I say 'plastic', because it is a shiny black material I am unfamiliar with. I have never shifted the valve.

    Drivers side has had a hundred gallons through it since I owned it. No debris that I know of. I was just throwing the idea out there.
    I pulled the fuel filler neck out and brazed a 1/4" stainless tube into the size wall of the steel elbow. The 1/4 tube runs 6" into the poly tank filler neck and angles upward. The outside of the tube runs upward and does a loop downward with a marine one way breather valve on it. I did that in September last year and ran afterward without issue.

    Passenger tank is poly, but has stale gas in it. Same funny plastic fuel line up and over driveline to the switcher valve.

    To rule out the breather valve on drivers tank I will start it again and if surging, remove the gas cap.
    To rule out bad gas from the other tank, I will dead end the fuel hose from it and direct plumb the drivers tank to my filter and pump.

    thx again.
     
  8. Bob BMW

    Bob BMW Binder Driver

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    Gas cap is a good idea! You might also consider blowing out the fuel line from the carburetor end while you are messing with the lines.

    Another thought. Hopefully the person that installed the 'plastic' fuel lines used the correct type. I have read that today's fuel with ethanol will dissolve certain types of rubber and plastic.

    Yes, I am leaning toward not enough fuel being delivered which will cause surging and dying. You can have OK pressure but at the same time very limited flow volume. That is unless you are measuring pressure at the same time the surging is happening.
     
  9. Sweli

    Sweli Farmall Cub

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    Granted, it's an old truck, that has not has the right maintenance in the last 20yrs. So a gummed up and worn dizzy was probably not it, but needed done. Slightly oversized carb, def not it, but needed done.
    But it is really funy that I find the cheap regulator I put on in the fall acting squirrely, but when I replace it it happens to run OK for a day, then surge again. Then later the cheap fuel pump dies. Replace it and it acts fine for another two days, then surges.

    The Mallory regulator has a wet guage on it. When it was surging this morning, the guage was steady at 3.5psi.
    That is what makes me think it is more motor, carb, intake related, then upstream.

    Still dumbfounded!
     
  10. TheScoutMaster

    TheScoutMaster High Wheeler

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    Do you have the thermal emissions vac valves on the heater lines or manifold? Could be cracked... I would plug all vac driven acc (emissions, dizzy, brakes, etc.) and see if it continues.
     
    Last edited: Jun 26, 2015
  11. Sweli

    Sweli Farmall Cub

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    Thx for replying!
    Only VAC line is from carb fitting to VAC advance on dizzy.
    Crankcase breather from the valley pan, goes through a heavy duty, steel, gravity ball PVC valve then into the rear of the intake manifold.

    No emissions, no power brakes.
     
  12. TheScoutMaster

    TheScoutMaster High Wheeler

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    Pull the fuel line running into the pump and plug. Run a section of hose from the pump to a coffee can with fresh gas in it. Does it still surge?
     
  13. Sweli

    Sweli Farmall Cub

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    Last fall the truck took 15min to get 5gal in the saddle tank. The fuel would spill back as air tried to escape.
    Here is the fuel filler neck I fabbed up that worked well. I brazed in a stainless line with the tip of it at the highest point of the tank. It allowed use of a marine no spill breather to allow air in and out of the tank.
    The clear tubing (green in the drawing) said CPE on the box, which is suppose to have good oil and solvent resistance. If it wasn't and is leaching, think it could actually cause this??
    Fuel Tank Filler Neck.jpg
     
  14. TheScoutMaster

    TheScoutMaster High Wheeler

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    To verify and eliminate the tank I would pull the fuel line, plug and run a section of line to a gas can filled with fresh gas. If the surging stops the problem is in the lines running to the tank or the tank itself and is introducing a lean condition into the carb...
     
  15. Sweli

    Sweli Farmall Cub

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    Tried to get a video of it, but it does not really show the extent of it.
    At Idle right here it is actually fluctuating 300 rpm up and down.
    It was like this for 8-10mins while I checked a few things, then it leveled itself out. I drove it for 10mins with no issues again.

     
    Last edited: Jun 26, 2015
  16. Sweli

    Sweli Farmall Cub

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    I didn't have too much time tonight.
    • While it was at idle and higher, while surging, the wet gauge on the regulator never moved.
    • I believe the hose from the saddle tank valve back to the tanks is newer black nylon that gets heat shrunk onto the fittings?
    • Removed the gas cap while it was surging it had no effect.
    • I verified the relay supplying power to the fuel pump and ignition wasn't fluctuating. I bypassed it hot from the battery with no change.
    • The surging stopped before I pulled out my VAC gauge. But with it leveled out, I was getting +/-16inches HG at 700rpm idle. At 1200 RPM it bumped up to 17 inches HG. It was fairly constant, with just the smallest bit of movement that was less then 1/4inch HG.
    I bumped up the timing from 5deg after TDC to 0deg.
    Actually want it to surge when I try and start it tomorrow, so I can have a gas can with fresh gas in it ready to try to pull from.
     
    Last edited: Jun 27, 2015
  17. Bob BMW

    Bob BMW Binder Driver

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    I watched your video and thought back to your descriptions of the times your Scout ran OK for awhile after you made changes to the carb and fuel supply system. I think the gas can test to eliminate lines and tank will be good information. I am sure you realize this test doesn't eliminate all the fuel system. If it still surges while drawing gas from the can, you then need to look at the remaining lines and filters between the pump, regulator and the carb. Now some points to consider.

    I couldn't really read the number on the pressure gauge but you had mentioned 3.5 psi. I had always thought around 7 psi was a better number. I wouldn't think either of those pressure numbers would affect idle surging though. Is there any possibility you could move the regulator/gauge right to where the fuel enters the carb?

    I am guessing you miss typed when you wrote you bumped the timing from 5 deg AFTER TDC to 0 deg. I am not sure about International V8's but all the other motors I am familiar with run much better with the timing set 5 to 7 deg BEFORE TDC. Even 0 deg can make them run kind of lazy/sluggish but I am not sure about surging.

    To complicate things for you. You could disconnect the fuel line at the carb and run this line into a another empty can and run only your electric pump to see if the fuel flow is good. You should have plenty of flow and not a trickle. Motor should not be running for this test. I would disconnect the hot wire from the distributor. Why? The instructions that came with my Pertronix distributor say not to apply power to it for longer than 30 seconds without the motor running or the distributor could be damaged.

    I am sure I don't need to tell you but I will anyway. Be really careful with these tests and open cans of gas. Even a small spark can cause a fire. All of this should be outside to get ventilation.

    Again, good luck.
     
  18. Sweli

    Sweli Farmall Cub

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    Gas tanks are 5 to 10 year old Poly tanks, put in by previous owner.
    I have only been running on drivers side tank, as the passenger side smelled like bad gas and old varnish.
    Pulled the passenger tank and cleaned it out. Silver soldered a new copper and brass pick up tube. Drilled out the other 1/4 NPT and move to my marine one way - breather valve to that side.
    Installed a 2 inch 90 degree rubber filler tube.
    Rannu 5 sixteenths hard line all the way to a filter in front of the fuel pump.

    Truck ran great for one day, 10 miles. Went out to drive it today and as soon as I started it it began to surge.
     
  19. Sweli

    Sweli Farmall Cub

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    Started reading up on any issues with Pertronix pointless ignitions.
    Many articles said any resistance from battery to dizzy of more than 1 ohm can cause issues.
    I was at 1.7ohm.
    New and on the negative battery cable to the block which cleaned up anchor points in dielectric grease. Clean up the clamp points for the dizzy as well.
    Now at 0.9 ohms.
    No change still surging
     
  20. Sweli

    Sweli Farmall Cub

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    Swapped out the 40kv coil for the old 20kv coil and ballest resister.
    No change, still surging.
     

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