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Old 02-09-2020, 12:15 AM   #1
chrisabes
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Default Kangaroo fuel.

Well, not literally . I have just about finished the rebuild on my '28 Roadster Pickup but am having a difficult time getting the engine to accelerate smoothly. When I depress the accelerator whilst driving, the revs buid up very quickly, making my foot push harder on the accelerator pedal making the revs increase even further. I remove my foot from the accelerator pedal which decreases the RPM. On depressing the pedal again, the cycle is repeated giving the appearance of a kangaroo hopping
I have tried a second carby but am getting the same result. Winding the GAV valve either way doesn't make any significant differance.
Any suggestions would be appreciated. Thanks.
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Old 02-09-2020, 12:39 AM   #2
Tacoma Bob
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Default Re: Kangaroo fuel.

Are you using the foot rest?
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Old 02-09-2020, 01:33 AM   #3
chrisabes
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Default Re: Kangaroo fuel.

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Originally Posted by Tacoma Bob View Post
Are you using the foot rest?
No foot rest. I don't have one in my other model A and haven't felt a need for one. Would prefer to do without.
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Old 02-09-2020, 02:23 AM   #4
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Default Re: Kangaroo fuel.

Watch out for Hector the emu and the wombat with explosives.
https://www.nfsa.gov.au/latest/skipp...ies-remembered
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Old 02-09-2020, 03:57 AM   #5
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Default Re: Kangaroo fuel.

Does it accelerate smoothly when in neutral and operating the throttle by hand?
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Old 02-09-2020, 06:34 AM   #6
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Default Re: Kangaroo fuel.

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Originally Posted by updraught View Post
Watch out for Hector the emu and the wombat with explosives.
https://www.nfsa.gov.au/latest/skipp...ies-remembered
Just as well you didn't ell him about the drop bears!
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Old 02-09-2020, 10:29 AM   #7
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Default Re: Kangaroo fuel.

I don't know what RHD linkage looks like, but it may be a lever upside down.
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Old 02-09-2020, 11:34 AM   #8
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Default Re: Kangaroo fuel.

I'm with Bob in post #2
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Old 02-09-2020, 11:56 AM   #9
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Default Re: Kangaroo fuel.

I think it would be difficult to be smooth and steady without a foot rest, but I have never tried it.
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Old 02-09-2020, 05:36 PM   #10
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Default Re: Kangaroo fuel.

Thanks for the suggestions, may have to resort to fitting a foot rest.
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Old 02-09-2020, 06:05 PM   #11
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Default Re: Kangaroo fuel.

Pox on the foot rest,never used it in 60 years!
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Old 02-09-2020, 06:47 PM   #12
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Default Re: Kangaroo fuel.

So, the power is so great that when you put your foot down you clutch the steering wheel with gritted teath and twisted grin and mash the pedal. Maybe the titanium crankshaft or the moon craters in the driveway. The RHD linkage only has one pivot and is a bugger on bumpy roads.
As above, does it do it with the hand throttle?
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Old 02-09-2020, 10:02 PM   #13
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Default Re: Kangaroo fuel.

Try driving one of the early V8's without a footrest. I drove a 1940 garbage truck (Ford) that had a spoon shaped accelerator peddle, real low gears and would knock me back in the seat on letting the clutch out, bounce forward and floorboard it which jerked me back into the seat, ect, ect. Finally figured out that I needed to have my foot on the footrest and roll it onto the spoon ever so slowly, making for a gradual increase in rpm's that didn't cause me to bounce around like a Super ball. Never was good with it but got better so the boss didn't fire me. I was 15 or so working in a private park picking up trash on the weekends for about 35 cents per hour. (1951)
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Old 02-10-2020, 03:36 AM   #14
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Default Re: Kangaroo fuel.

Quote:
Originally Posted by Dave Slater View Post
Does it accelerate smoothly when in neutral and operating the throttle by hand?
I went for a short drive this pm.using the hand throttle, at low RPM the engine was as before but with an increase in RPM, there was a market improvement.
I will be checking the ignition components next.
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Old 02-10-2020, 03:56 AM   #15
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Default Re: Kangaroo fuel.

Might be running lean, like a lawn mower about to run out of fuel.
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Old 02-10-2020, 06:31 AM   #16
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Default Re: Kangaroo fuel.

Surging sounds electrical. If you think its the lack of a foot rest. Use the hand throttle. How does it run through the gears full throttle? Whats the history on your coil and distributor?

Edit. sorry Chrisabes. I see now you had the same idea two posts up. I just put a flame thrower pertronix coil on my car and I was surprised how it smoothed out my idle and cold running.

Another thing i thought of. The worst my car has ever ran. Back firing like an old movie scene. I had a loose generator connection when the battry ground cable lost contact. Moral of that story check all your connections.

Last edited by mike657894; 02-10-2020 at 06:37 AM.
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Old 02-10-2020, 03:28 PM   #17
Ernie Vitucci
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Default Re: Kangaroo fuel.

Good afternoon...Another possibility might be the exhaust manifold is a bit loose. Check the torque on the bolts and look for exhaust markings on the block. You can also spray something like priming fluid, along the seam of the manifold and see if it changes the speed of the engine...Ernie in Arizona
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Old 02-17-2020, 01:10 PM   #18
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Default Re: Kangaroo fuel.

If it smooths out after idling a while, fuel flow maybe be restricted. Check pipes & fittings. (have seen thread tape partly blocking fuel line produce these symptoms)
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Old 03-04-2020, 04:51 AM   #19
chrisabes
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Default Re: Kangaroo fuel.

A quick update! When using the hand throttle, the vehicle accelerates reasonably smoothley. Once the RPM is increased, the engine stabilises and operates well using the pedal.
As mentioned in an earlier post, I have tried running the engine using three different carbies with no improvement. I have also changed the distributor again no change.
A thought that I have is a lack of exhaust back pressure as the exhaust is non standard. Perhaps this would allow the engine to accelerate quicker resulting in a more sensative throttle?
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Old 03-04-2020, 07:07 AM   #20
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Default Re: Kangaroo fuel.

Quote:
Originally Posted by chrisabes View Post
A quick update! When using the hand throttle, the vehicle accelerates reasonably smoothley. Once the RPM is increased, the engine stabilises and operates well using the pedal.
As mentioned in an earlier post, I have tried running the engine using three different carbies with no improvement. I have also changed the distributor again no change.
A thought that I have is a lack of exhaust back pressure as the exhaust is non standard. Perhaps this would allow the engine to accelerate quicker resulting in a more sensative throttle?
No. A low compression engine runs best with no back pressure.
You can tie a tin can over the end of the exhaust fairly tightly to create back pressure, (will run quieter) and try it.
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