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EH surging at cruising speeds after about 1 hour
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Joined: 20/10/2024(UTC) Posts: 2 ![Australia]( "Australia") Location: West Oz
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Hi folks. My brothe-in-law's EH 149 exhibits this cursed problem. He's had the car for about 10 years and was doing it on the drive home back them. The car runs very well otherwise, under load up hill, full throttle acceleration is great. After about an hour it begins to surge at whatever cruising speed you're doing at about half throttle. Floor it and it goes real good, back off and it slow down smooth but hold throttle to cruise at constant speed and it begins to buck. Items recently replaced with new include plugs, points, condenser, leads, coil, dizzy cap. Ign timing set, float level checked, full tank of fuel, new fuel pump, ballast resistor bypassed. Vacuum and mechanical (rpm) advance are working. Sure, it’s either spark or fuel but what exactlyis the cause? Vapourisation was a possibility but because it accelerates up hill perfectly, it ain't that. TIA Freddy Edited by user Sunday, 20 October 2024 6:52:25 PM(UTC)
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Rank: Member
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Joined: 21/12/2018(UTC) Posts: 91 ![Australia]( "Australia") Location: SA Thanks: 22 times
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I would say fuel. But its hard to tell from words on a screen.
Check the fuel pump pressure and flow.
Also check for kinked or crushed fuel lines all the way back to the tank, even with a new fuel pump this could be the problem.
And check the fuel tank is breathing too. Maybe leave the cap off when driving to see what happens. More of a problem on bikes but you never know.
The carb may need attention.
See if the butterflies are moving around, the shafts may have worn at their mountings making them free to jiggle around a litle bit.
Check the cable play, throttle and choke, could also be loose.
Does pulling the choke out fix the surging when driving?
It could also be an air leak. Check the carb is tight on the manifold and also the carb is screwed together tightly. Grab it and give it a wiggle.
Also spray the carb with water when the engine is running and see if the revs change. There could be an air leak in one of the gaskets.
When the car starts surging, switch it off, roll to a stop and check the plugs to see if they are fouling. Black plugs means the fuel/air mix isn't burning properly. It wouldn't hurt to check the fuel level in the float chamber here either.
Checking for looseness in the cables would be my first guess, it sounds like they could be flopping around under half throttle.
Good luck.
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Rank: Newbie
Groups: Registered
Joined: 20/10/2024(UTC) Posts: 2 ![Australia]( "Australia") Location: West Oz
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Great info 202 - THANKS.
Pulling the choke does improve it. I'm not gunna see the car again for many moons so will forward your advice to him to investigate further. He's now away for a month so there won't be an update for a while but I'll ensure there is when it happens. The old EH came with throttle linkage by the way, round the back or the head.
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EH surging at cruising speeds after about 1 hour
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