Engine flooding at higher elevations

[BHChieftain]

My 1990 Westy has an orig engine, rebuilt. Starts easily with no throttle input at sea level, but when I get to 5000-6000 feet it has a real hard time starting. I often need to floor it and have it crank for quite awhile before it will catch. Last camping trip I flooded the engine and had to sit around for about 4hrs before it would start.

When I go camping, I do spend a lot of time at very low RPM crawling along dirt roads-- I'm wondering if this is part of the problem.

Any tips to improve starting at higher elevation? I was thinking after low RPM driving maybe putting it in neutral and revving it for a while before shutting it down but not sure if that would help.

Thanks,
Chief

[0to60in6min]

check (or have someone) the timing. - how old is the fuel pressure regulator?

[DanHoug]

check your O2 sensor... the Digifant system has no baro sensor to adjust to altitude so the mixture compensation is done with a functioning O2 sensor. if it is NOT functioning, the mixture may be richening at higher altitudes, fouling plugs and possibly causing hard starts.
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'87 Westy & '89 Westy both 2.1 4spd

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[BHChieftain]

I was suspecting the O2 sensor... I'll get that checked out. Thanks!

In the meantime, do you think revving the engine for a bit before shutting down would help anything (I'm not at altitude so I can't test it...)?

Chief

[E1]

If it's loaded up, I'd rev it clean.

Onboard with O2 sensor thoughts here.
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1984 Westfailure/2.1 Digijet/5.43 Ring & Pinion/Peloquin/D-rated BFG KO2s
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[Wildthings]

The O2 sensor should not affect starting as it doesn't come on board for a while after startup. You might be seeing a leaky injector or have the AFM set to the rich side.

To get it to start in a pinch, you could pull one of the larger vacuum hoses off the plenum to create a lean condition.

[DanHoug]

[tencentlife]

I'd try a fuel pressure test, but then I always start there.
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[BHChieftain]

Hi,
I have not been on the forums for awhile-- just thought I'd close out this thread. Turns out I had a bad temperature sensor. Easy fix.
Chief