Hi everyone, this is my first post, but have used the site for lots of info and advice. I bought a 1988 regency woh a 454 in the spring and spent the summer getting it ready for a military move from Alaska to upstate New York. Long story short it ran great from Alaska all the way to Arizona. Now we’re losing all power when the engine heats up and eventually dying. I’m assuming this is Vapor lock as it didn’t start until we hit the heat of the desert. The mechanic replace all the filters today, but that didn’t fix it. I could use some advice on what else to look at. I know it’s a fuel delivery issue, just don’t know what else to look at. The shop is taking about replacing the carb, but I’m not convinced. Thanks in advance.

Electric fuel pump is a good $100 answer to vapor lock. Not as cheap as Reynolds wrap on the lines but more effective. The electric pump near the tank will push to and through the regular pump. I am planning on putting them on my boat engines with a switch so the bowls will be full at startup. I would also switch on when fire walling the throttles, a bad time for fuel starvation.
Just to invite descention, I have been known to add 1 to 3% diesel to reduce knock and vapor lock.

Tim, I believe it was Rusty that told me if I wanted to get a new engine add diesel...hey I think on my way to Mary Rays GTG I got VP also and I have electric fuel pump, it was a 95F degree day. More on this trip later.

There may be several issues at play here. The problem may be altitude sickness. One of the major drawbacks of a carburetor is that it responds to volume, not mass, of air flowing through it.

A gallon of air at 5000 ft weighs 20% less than a gallon of air at sea level. That's 20% less oxygen, 20% less power. Warm the air from 70 degrees to 95 degrees, it expands and you lose another 5% or so. Bottom line: there is only about 75% power available at best. Airplanes deal with this all the time.

Airplanes can adjust the mixture leaner to match the air charge. (Still less power but not burning rich) The Qjet delivers the same amount of fuel it would it sea level, so there is an over rich mixture for even less power...

I live at about 1000 ft. The first time I drove my 454 to Denver it was really weak at 5000 and down to 45 mph at 7000. For various reasons, I later decided to install a fuel injection system on the 454. Fuel injection systems use "mass air sensors" to adjust fuel delivery to match air density, like all new cars now. The next time I drove it west, it ran well albeit a bit weak all the way to 7000 ft.

This may be the heart of your problem. Also, the thin hot air cools the radiator less as it flows through, more throttle is needed (esp on hills) to help offset loss of power, and things get hotter.

I suspect your coach still has the mechanical fuel pump on the lower right side front location. An absurd location, nested behind the radiator and the lower rad hose, running at and in 200 degree air. Then we run fuel into this percolator and up a fuel line on the front of the engine to the carb, all downstream the radiator air. It is a wonder it doesn't boil all the time.

So, what to do?

Other than rejet the carb until lower altitudes (a PITA) you are stuck with the carb rich mixture.

Anything you can do to feed the engine cooler denser air will help. Make sure the air filter horn is not blocked. An outside cold air feed pipe to the air filter can help. Lower altitudes, drive at night...

Be sure radiator is clean inside and out. Aux electric radiator fans may help.

Meanwhile, back to the fuel. An electric pump at the tank end, pushing fuel under pressure through the hot zone can help. With the appropriate pump at the correct pressure, I would (did!) bypass the engine pump entirely, keeping the feed line higher and behind the engine.

The fuel injection system has a recirculating system which keeps surplus fresh fuel flowing right to the injectors. The was my final cure.

good luck

Steve,
I actually saw the posts of your conversion and was considering it before we left Alaska but didn’t have the time. I completely agree that the altitude could make a difference, I’m actually an aircraft mechanic. Believe it or not, I found a fix that is temporary but seemed to work, wooden clothes pins. You put 2 on the flex line from the frame to the mechanical pump and it creates a higher pressure and continuous fuel flow to the carb. I just tested it and it worked. Not perfect but should get us out of the desert. We are also going to drive at night until we reach cooler climates. Once we’re home and have some time, I plan to dig much deeper into the fuel system on the old girl and get her top notch again. Who knows, maybe even do a TBI, or fuel injection.

Cool! Great idea with the hose clamps. You are obviously on the right track!

There are some nice newer fuel injection conversions available now. You will not regret, esp at higher altitudes, or as the airplane guys say: at "high density altitude"

(That always bothered me, at high altitude the density is less... so a "high density" altitude would be at lower elevation! Maybe "high altitude" density instead?)

good luck

quote:

Originally posted by Duane88:
Tim, I believe it was Rusty that told me if I wanted to get a new engine add diesel...hey I think on my way to Mary Rays GTG I got VP also and I have electric fuel pump, it was a 95F degree day. More on this trip later.

Never add diesel to gaso.

I fought vapor lock for all 14 years I had the Euro. The clothespins helped, the electronic fuel pump helped, the heat shield I fabbed between the exhaust and the fuel line helped, but nothing ever cured it completely. Cool air and slower speeds were the 2 things that helped the most. One thing that was a constant - it always happened after I lifted the pedal, either to slow down or at a light etc. The engine would always accelerate for about ten seconds or so, then die for anything from a sputter to several seconds, depending on how long I had lifted. This made me think the vaporization was in the line, and the engine was burning off the gas in the carb and maybe a little from the line before the vaporized gas got there and wouldn't ignite. Most of the time I had enough speed up so the engine would re-fire once the vapor was pushed through and I was getting liquid again. I learned to live with it but it sure scared a lot of first-time passengers!

Converting our Euro with the 350 ci engine here is our solution: move the fuel line and vapor line off the frame at the transmission by splicing a new 3/8" line to the underside of the floor and run it up to the top of the bell housing; then run a braided fuel line along the intake to the carb fuel inlet with a 90 degree elbow; make sure the carburetor has the high temp spacer under it; remove the crossover heat riser that fed the old style automatic choke and replace with the newer electric choke. This requires removal of the intake and installation of an aftermarket intake that blocks the passage to the manifold as well as removing the riser valve in the exhaust pipe. Measuring with a hand held temp gauge showed the carb and lines were below 100 degrees and no evidence of any performance issues.

Even with an electric fuel pump on a hot day if I stop for fuel, often when I restart and try to accelerate after , I get a stall or chug for a bit until enough fuel is used to cool the hot spots, most of the time it does not quit entirely. Same happens for a quick slow down in heavy traffic.

Duane is the electric pump close to the tank or near the engine?

quote:

Originally posted by ccctimtation:
Duane is the electric pump close to the tank or near the engine?

Tim, it is right in front of the 6 way valve used for tank switching at the back of the chassis. I seem to only have real problems when its hot out. Went almost 6 hundred miles in 70 degrees, all was fine.

Bessie, The Barth do a search on here I think Kevin posted the Chevrolet solutions to Vapor Lock in P30's someone else also posted the same report. Try this link

http://truckroadservice.com/ba...vy_P32_vaporlock.pdf

Hmmm... Not so sure why the only time we have vapor lock is when you stop for gas she just doesn't want to start real well. Even thru Arizona, NM and Texas last summer with temps in the 115-125 range. You did say that the carb. fuel filter was replaced right?

Hey Benebob, I had a bit of an over heat on this trip, turned out the water pump/alternator belt was slipping without a squeal. Just a thought before you buy another fan assembly. I want to save you money for more craft beer!!!