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Art D · 09-11-2007, 08:57 AM

I have a 31' Sighseer with 8.1L. Recently I topped a very steep interstate overpass in a tight curve in 3rd gear at near full throttle going about 20-30 mph (when I should have gone to 2nd). Anyway aa I went over the top and tried to accelerate, the engine started missing just like it was running out of gas but I had about 1/2 tank. I almost had to pull off the interstate but kept pumping the pedal and it started to run better but took several miles before all the miss was gone. Never had the problem again when I later went up some pretty steep mountains in Colorado. What happened?

Art D · 09-11-2007, 08:57 AM

I have a 31' Sighseer with 8.1L. Recently I topped a very steep interstate overpass in a tight curve in 3rd gear at near full throttle going about 20-30 mph (when I should have gone to 2nd). Anyway aa I went over the top and tried to accelerate, the engine started missing just like it was running out of gas but I had about 1/2 tank. I almost had to pull off the interstate but kept pumping the pedal and it started to run better but took several miles before all the miss was gone. Never had the problem again when I later went up some pretty steep mountains in Colorado. What happened?

offshore · 09-11-2007, 09:00 AM

Can't figure this one...sorry.

PaulC · 09-11-2007, 10:02 AM

Sort of sounds like a fuel pump or fuel filter issue.

Joe Gilbert · 09-11-2007, 01:42 PM

You have not mentioned the outside air temperature. If it was a very hot day it would not be unreasonable to suspect vapor lock. Slow speeds, lots of engine & exhaust heat passing under the RV, 1/2 tank of gas or less. All of these can add to vapor lock if the temperature conditions were high.

No need to pump the pedal. In this age of fuel injection this buys you nothing.

When it is really hot a full fuel tank really helps keep the vapor lock wolfs away from your door.

FrontRangeRVer · 09-11-2007, 01:45 PM

I think Joe has hit the nail with hammer. Vapor lock. We haven't had it happen with our motorhome, but we have it happen all the time with our ATV's at altitude (higher than where we live...)

Redlands Truck and RV · 09-11-2007, 01:50 PM

What year is it? How many miles on it? When was the last time you did a fuel filter?

Oemtech · 09-11-2007, 02:04 PM

Oh boy another $60 fuel filter threat

Tom N · 09-11-2007, 05:03 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Art D:
I almost had to pull off the interstate but kept pumping the pedal and it started to run better but took several miles before all the miss was gone. </div></BLOCKQUOTE>

Pumping the gas pedal will have no effect. You're Workhorse uses shift by wire technology. Your gas pedal does nothing but send a signal to the computer. The computer decides how much fuel is needed. You can not flood a shift by wire vehicle.

max49 · 09-11-2007, 06:01 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Art D:
I have a 31' Sighseer with 8.1L. Recently I topped a very steep interstate overpass in a tight curve in 3rd gear at near full throttle going about 20-30 mph (when I should have gone to 2nd). Anyway aa I went over the top and tried to accelerate, the engine started missing just like it was running out of gas but I had about 1/2 tank. I almost had to pull off the interstate but kept pumping the pedal and it started to run better but took several miles before all the miss was gone. Never had the problem again when I later went up some pretty steep mountains in Colorado. What happened? </div></BLOCKQUOTE>
If you were going up a hill, full throttle, in 3rd gear, 20 to 30 mph, you may have a transmission problem that will make you for get about the engine problem. It should have downshifted itself, floored at 20/ 30 mph.
Mine will go almost 40 in first gear, 60 , in 2nd gear.
I don't know how you could have done that unless you have a tranny problem.

speed racer · 09-12-2007, 06:33 AM

A modern day fuel injected engine will not vapor lock. The fuel pres. reg. continualy recirculates the fuel back to the tank only useing enough to maintain proper fuel pres. I would have fuel pres. checked. I am a retired auto&truck mechanic. 45 years exp.

**Petro** · 09-12-2007, 07:14 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by speed racer:
A modern day fuel injected engine will not vapor lock. The fuel pres. reg. continually recirculates the fuel back to the tank only using enough to maintain proper fuel pres. I would have fuel pres. checked. I am a retired auto&truck mechanic. 45 years exp. </div></BLOCKQUOTE>

speed racer;

You are correct except the fuel pump in some of the earlier W series were known for pump cavitation caused by hot fuel returning to close to the pickup when the tank was 1/2 or less. This problem magnified itself when going up or down hill as the fuel moved to one end or the other. Talk to LeeB as he had the problem and I advised him what to do to solve the problem.

Don

Art D · 09-12-2007, 07:37 AM

Thanks for all the responses. Let me answer your questions and comments in order posted:
1. The first thing that came to my mind is a partially plugged fuel filter and that is first on my list to replace.
2. I will check into how I can test the fuel pump pressure. Any easy way?
3. It was at 10:00 am or so in north Louisiana so not very hot, maybe 80F.
4. Yep, you are right about no good in pumping the pedal. But that's from years of habit since my first auto at 16 was a '51 Chevy.
5. MH year is 2004, 24,000 miles, and original fuel filter.
6. When I said "near full throttle" I actually was just down to the "stop" which if you passed would downshift to second gear. And it does if you go "to the floor".
7. I read once in the Workhorse manual that there are RPM limits you should not exceed in each gear. I have to recheck but I think it is 4000 in 1st, 3000 in 2nd, and 4000 in 3rd. Seems odd but that's what I remember. Oh yes, the tranny is the GM ???85E or something like that.

roy goble · 09-12-2007, 03:55 PM

I have a 2004 LaPalma, back in 2004 when the motorhome had approximatly 2500 miles on it, I was going east up to Eisenhower Tunnel. My engine quit, and I tried to restart and would only try to run. Let it set for about 20 minutes and it started. Had a engine code on but went off before I could get to a dealer. I know that fuel injected engines should not vapor lock, but in all of my years in the car business, I could only believe that it had indeed vapor locked.