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Old 08-05-2012, 04:56 PM   #1
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Vapor Lock?

I have a 2003 Holiday Rambler w22 with an 8.1L GM engine. I am driving through Oklahoma in 95-100 degree weather with the AC on. Suddenly, pushing on the gas pedal no longer gives power. When I slow down to pull over, the engine stalls. I put it in park, wait 30sec and the engine starts back up with no problem. This has happened twice in the last 100 miles. We are not yet completely broken down but, if possible, I'm trying to identify the issue before it gets worse.

I am thinking vapor lock, but, wanted to reach out to see if anyone has any ideas. I'm really hoping it's not the fuel pump..

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Old 08-05-2012, 05:43 PM   #2
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Your fuel pump should be in the tank with a fuel return line which should pretty much eliminate vapor lock. I've had that happen on my Chevy 1 ton work vans, more than once and it was fuel pump on all 3 these trucks had over 1000,000 miles on them. Good luck. I hope you don't need a fuel pump, they are not cheep
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Old 08-05-2012, 08:04 PM   #3
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Welcome to irv2 jdc4x4.
You may need a heat shield near your fuel line or return line to tank. Check lines near your exhaust pipes.
Something else if its raining could get water into your air intake horn that will put engine into a safe mode with 1/2 the power.
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Old 08-05-2012, 09:37 PM   #4
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We've had MPI (fuel injected) boats that love to have this problem. However, their pumps are not in the tank and their fuel systems do not recirculate.

I am, however, having the issue with a generator.

If I had a modern 8.1L, I'd see if it's setting any codes (check engine). If not setting any codes, I'd probably get a OBD-II scanner that can show me real time data. (Note, if you use an Android phone, you can do this for under $30 total... )

If vapor locked, you'd measure near zero fuel pressure.

Last way to check - and this is more dangerous: Find the schrader valve on your fuel rail. Let it stop, depress the valve. If vapor locked you'll get air. If not, you'll get fuel. Note spewing high pressure fuel on hot motors is dangerous, so the standard disclaimer of - have a mechanic do it is in order...

To gather more evidence without all of the difficulty above:
1) Switch to running your coach AC off the genset.
2) Drive in the morning or in the evening after the sun is down. Pavement temperatures right now are crazy, easily over 120 degrees.
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