I wonder if an electric pump from mech pump to carb could solve anything? Sounds like over kill, but who knows

Perhaps the answer is a high pressure fuel pump (fuel injection type) at the tank selector valve to a regulator set at 4 psig just in front of the carburetor. Eliminate the mechanical pump. A 60 psi line should raise the vapor pressure quite a bit plus a rerouted line keeping it in the coolest areas.

You're gonna get all the bugs worked out of Nose and be ready to burn up some highway once everything is opened back up

As GM received complaints on vapor lock starting in the 70's, they began a series of changes. Started with a long suction line from tank to engine pump with metal line from pump to carb. Then rear inline pumps. Ended with higher pressure intank pumps, fuel return lines and fuel injection etc.

Check in our archives. There are several GM bulletins relating to this topic.

When I got the 86, it had intank pumps, and a fuel pressure regulator in the line to the engine pump. At the pump a return line to the tank and a line to the carb. I never had vapor lock problems but it was obvious the carb and line from the engine pump were pretty hot.

Personally, I believe the recirculating system is the final solution. Without that, most of the time the fuel line is a dead end. The fuel just sits there waiting for the carb to use it. Having a higher pressure will inhibit boiling some but the real problem is that the only fuel that actually flows through the line is the small amount that goes into the carb. The fuel gets hotter and hotter as it makes its journey forward to the engine. It runs down the frame, down along the side near the exhausts and hot air from rad, then to the fuel pump, (which is attached to the engine block and runs at engine temp) then follows a metal line to the carb to preheat some more along the way. It is wonder it ever works.

If I were faced with one like Duane's, I would keep the inline rear pump. As he considered, run that pressure line forward, up high and to the rear of the engine. At that point install the 4 psi regulator, but use one that has a third port for a return line. A short 4psi feed line to the carb, then run a new return line to the tank. (Tie it into an existing vent to dump back into tank, etc)



As long as the rear pump is rated more than 4 psi there would be constant flow through the pressure line, regulator and return line. (It shouldn't take that much pressure, maybe 10 psi or so) The fuel stays nice and cool. It never sits still getting cooked in the hellhole engine pump area. You will not miss the engine pump. (The 454HO replacement engine that I installed did not even have a place for an engine pump to be installed!)

I believe this would cure almost every case.

Steve, good point having the electric fuel pump doing the recirculation. Presently the mechanical pump has the recirc line and when the engine RPM slows down, it probably does not recirculate much if any fuel. Fast slow downs from speed are a prime cause for locks. Shutting a hot engine off and doing a restart after a short time is another problem area, allowing the electric pump to recirculate fuel right from start up would probably prevent lock at this point also.

Think this system at least warrants a cost analysis gonna check it out!

As I remember you have 2 tanks and a wye valve. Pick one tank as primary and the other as reserve, the reserve is 1/2 full at start of all trips with stops under X miles. Secondary tank will be the running tank so excess flow goes to primary. Figure 10mpg and some greater bypass flow, watch the gauge, when destination with no stop is >60? miles use the primary tank. It will warm but be in use. If you're approaching traffic switch to the other tank which will provide cooler fuel and overflow to the other tank.
Thermocouple wire is not very expensive and you could drill a hole in the filler necks run the wires to the tanks near midpoint so you could monitor. All so much cheaper than buying a new coach and possibly new home! My hand held won't let me use images so picture a very large but slightly emphatic grin!

Still debating the vapor lock issue!!

Nose of course decided to throw another problem my way!

Thought the water system should be checked before the Minnesnowta GTG, fill up the tank turned on the water pump, got the heater tank filled, left the pump on over night. yesterday I noticed there was a drip drivers side about mid-coach. Found a leak in the cold water fitting connected to the kitchen sink, a plastic fitting, tightened it and it broke, got a new brass fitting flared the plastic tube, seems to be holding but there might still be a leak let it dry and check it again.

Nose is not done with me yet, need some advise here, the grey water holding tank connected to the kitchen sink has a crack and is leaking. Thought maybe an aluminum sheet backing coated with a good sealant and placed over the crack might patch it. Anyone have another suggestion?? What would be a good sealant? Assume that the tank is polyethalene so no solvent will seal it.

PC-7 epoxy. Clean the area with acetone, roughen the area with say a Dremel mini grinder. Mix the epoxy well and rub firmly onto the area followed with the remainder applied to form a heavy coating. In 48 hrs. it will be stronger than new.

Ditto on the epoxy. I would use a layer of fiberglass cloth over the patch area as well.

JB weld, sanded the area around the crack, cut a piece of thin and very flexible aluminum about an inch and a half wide, coated the inside with JB about .125 thick, put a thin coat on the tank and stuck the big mess together.

Not smart enough to wear plastic gloves so fighting JB weld fingers, might have to just let it wear off!

There was someone in there trying to fix that crack prior to me, Sanded off a thin coat of what I assume is epoxy, if they had used a backing and made it thicker as as you guys suggested the new repair would not have been needed!! Did not check here prior to going at, we shall see!!

I hope the aluminum works as well as the fiberglass backing suggested.

Now back to the vapor lock problem!!!!

I hope the JB WELD shields the aluminum since grey not black probably not a big deal but pay attention to the cleansers use a liquids dumped.

The JB should be the seal, the aluminum just to help it not crack like it did, at least that was my thought, bonded on two sides. I did not know cleansers damaged stuff, learn everyday!!!

Nose's generator has gone amuck, consensus was a loose valve seat by local engine repair guys. The thing will not run smooth, pops and misses, will not get up to speed.

Did a compression test today, about 80 psi on both cylinders but slow bleed down. Told this is low compression but both about the same so confusing?????

Spark plugs both are super black, full of carbon, but the gap is open.

I hope it is the carburetor, just to much fuel. Can not find a rebuild kit that contains the parts I need...dropped the float spring and can not find it or a decent replacement. might have to buy a whole carburetor, but unable to find that exact model, probably have to get proxy and interchange parts.

With popping, missing, and low revs I am wondering of the ignition system is marginal...

If plugs are black, there is fuel (maybe too much) but misfires will load up with fuel too. Be sure your points are clean, plugs and magnetos OK. I have had numerous magneto failures over the years, many were heat soak partial failures and intermittent too.

Hope you can find the float spring.

Steve, I took the carb out and rechecked it, put the whole mess back together, nothing not even a pop!! Checked for spark...None!!!

So this is funny to me, two cylinders, flat engine horizontally opposed for those who like. One set of points, no distributor and a coil that has two outlets, this thing must fire both sides at the same time, making the electrical system run as single cylinder!! Am I crazy!!??

Have yet to check but, bad coil, capacitors, fuse or a short somewhere. Only used one plug to check for spark if the other was shorted and both fire together it might take all the coil power.

Professor does it again Thanks Steve!!! Might be more problems too. It is Nose bound to be!

Yes there is gas up the ying-yang!! I did find a similar carb online that may have the spring!!

Here is a link to a diagram https://www.bing.com/images/se...RM=IRPRST&ajaxhist=0