I'll try to keep this as short as possible. A few days ago I was having a bog in the engine. The warmer it got and the more hills I had to climb, the worse it got. All the fuel filters are new and the mech. fuel pump is less than a year old.

I stopped in a shop in Fort Stockton, TX and I do have an electic pump in the tank and it was bad. The pump was replaced and off I went. The engine was running great, lots of power. After about 100 miles I stopped for fuel and checked my mileage, 5.4 mpg YIKES! I couldn't find any leaks, smelled no gasoline smells, the motor oil is clean with no smell of fuel. I thought possibly I had a miscalculated my numbers so off we went.

We stopped in El Paso for the night and I checked everything I could think of. All the gauges read good, all systems nominal. In the morning, we did the I-10 tango for 20 minutes or so and the engine started bogging again but it was different than before so I get off the 10 ASAP and got safe and parked.

I exit the coach and head to the area of the mechanical pump. I find fuel leaking out of part I didn't recognize. It turned out to be a filter/vent the goes to the evap can. It has a single hose running to it. The PO must have cobbled it up since the barb coming off this part was taped up (photo below).



This pic shows the location of this filter. It was screwed to the floor where the red dot is at. The hose that connected to it is circled in yellow.



This leak isn't a gusher, it's is more of a steady drip. Not wanting to take chances with this issue, I called CoachNet and they sent a hook and dragged us in.

The shop is a Ford dealer who works on RVs and was willing to check it out on Monday. Do any of you have an idea of what could cause this? I am going to have the shop check and make sure the lines on the fuel tank were connected correctly and not mixed up. This evap system is the last of the old fuel related lines that have not been replaced so that will be done. I really don't understand this evap system so I'm turning to the pros here on Barthmobile.

BTW, I stopped at BillyT's shop to get some PM work done. New brakes lines and flush, trans and diff service. Super nice folks and did a great job.

Sounds like your 89 is much like my 86.

I believe the function of that vent/filter was to prevent fuel or vapors being released into the air after shutdown. (EPA thing) It is indirectly attached to the top vent on the carburetor. If the fuel in the float bowl evaporated from the engine heat after shutdown, it was supposed to collect in that filter, to be vacuum purged through the charcoal canister filters (the big paint can sized ones) on the next startup.

Problem: sometimes the purge system on the charcoal canister goes haywire and ends up returning the fuel (and charcoal grit!) to the carburetor, leaving a horrendous mess. Mine is no longer connected... it didn't work anyway.

Getting more to the point: if you have fuel coming out of there it is probably coming from the float bowl. This would point to a stuck/leaking float valve, allowing excess fuel to vent overboard and also give you horrendous mileage.

Check the carb float level.

I attached a couple pages of stuff from GM:

Thank you Steve. Your explaination makes perfect sense. When the mechanic was working on my fuel pump, he also replaced the throttle return spring because it was getting very weak. He mentioned the shafts in the carb were rather sloppy and sugested when we got to Lake Havasu City, we might want to think about getting the carb checked out. He also said the power piston wasn't adjusted properly. I wouldn't be a bit surprised if the float valve is acting up too.

I know after seeing inside my fuel tank (I only have one 40 gallon tank)it was in great shape. There was no trash on the fuel pickup filter. I was happy to see how clean it was. I've never seen any garbage in the carb filter so the chassis filter must be doing its job. I run Seafoam real regular as well.

I'm at 95k on the clock. The engine was replaced at 32k under warranty but I doubt GM put a new carb on back then. I figure it is time for a new q-jet. It was rebuilt in March of 2010.

These docs you attached are exactly what I have been looking for, thanks again. Looks like I might have to throw a few more pesos down the hole in the highway for my road boat. I still love the old girl.

Steve, I forgot to mention my Regal is a 1989 but the chassis is a 1985. The orginal owner had a bear of a time getting the engine replaced with all the problems it had. The dealership said the chassis was out of warranty by 1990 but the coach wasn't delivered until late 1989. I have docs showing that Barth got GM to extend the warranty since the coach wasn't actually built up until 1989.

Glad I could help!

For a long time, the fuel tanks and carbs were vented outside, never had any trouble.

Then the EPA decided those vented FUMES(not exhaust!) were too much hydrocarbon for the atmosphere...

Along come sealed gas tanks and caps, fuel vent lines the length of the vehicle, carbon filters, check valves, purge valves, AIR injection pumps (2!) EGR, temperature vacuum valves, etc. Along came engines that ran worse, were less reliable and covered with belts, hoses, pumps and brackets. Hassle to work on...

This is my GM rant because we are left with these aging factory cobble jobs. (Remember by 1980 most GM cars and light trucks had fuel injection... not till 1990 in heavy trucks, how come?) I have considered retrofitting a throttle body injection system but it looks like major work for little return. Maybe someday...

If you live in a state that allows it, I suggest removing most of that garbage since most of it isn't working, never did work well, gets in the way, and can actually cause damage (IE charcoal grit in carb, seized bearings, throwing belts, etc.) Michigan had smog testing for some years. I never had trouble getting any of my vehicles passed even after the stuff was gone, since they ran right!

There are pdf files with the 1986 GM service manual on this site. (Ads, Documentation, etc...) There is a chapter on the Quadrajet in there. Might be useful.

On the Barthmobile CD there is a 97 Chevy Motorhome manual with good stuff on fuel systems.

Good luck!

The Q jet float is a Nitrophyl foam that slowly loses its buoyancy as modern fuels attack the outside coating. Over a period of years, a higher fuel level in the bowl can result. I like to replace them with brass if I can find one.

I would not advise removal of SMOG equipment if there is any thought of selling the vehicle later. Unfortunately, many states are now following California and in some cases Federal mandates, that part of the SMOG check is a visual to insure that ALL SMOG equipment is present and operable. If the equipment isn't there, you will not e able to pass the testing and will not be able to register the vehicle.

If equipment is removed, make sure it is stored and could be replaced if the vehicle is sold.

I have never agreed with this concept but this is reality. Many States just have a "sniff test" so it would be easier to pass without "A.I.R. pumps and other associated stuff attached. Many States exempt vehicles over 25 years from SMOG testing, BUT not California. Here any vehicle 1976 or newer will be tested.

Cleaning up or improving vehicle emissions is one BIG political and technical football and we the public are caught in the middle!

For the record, I am a BIG advocate of fuel injection even the earlier throttle body injection systems are far better than carburetors, Fuel economy will be better and drive-ability greatly improved.

FWIW

Ed, some of the SMOG equipment is already gone. The AIR pump belt was bypassed when I got the coach. It was tight to turn so I removed it and the air tubes off the exhaust manifold. I saved everything I took off however.

I've been doing tons of reading up on Q-jets. I do believe that folks who hate them just don't understand them. The last time I touched one would have been around 1980 on my old '71 Catalina and it was quite a bit different than what is on this 454, at least the electric choke. I guess I'll have to get some education.

Bill H, I will take your advise on the float. Once I get to Lake Havasu City I'm going to replace this carb or at least give it a major overhaul (by a pro). The Q-jet isn't the only carb to have that float issue for sure.

I really would love to have FI but I don't care for the aftermarket solutions. This topic will come up in the future when the engine needs to get replaced. Since the engine has 60k miles on it, this shouldn't come up for a few more miles *knocking on wood*. The engine has been running great the last 10k miles I put on it.

The shop didn't have much time on Monday to look at it because they were working a half day. They think the added pressure of the new rear pump is more than the old carb could handle. They will attack the problem on Wednesday.

All this makes me love my OBDII vehicle even more. I have an ELM327 bluetooth adapter on my 2002 Jeep Liberty. It connects to my smartphone or Asus Infinity tablet with the Torque app. The adapter is too slow for hardcore diags but for basic troubleshooting, it shines. A few years back I asked about installing an OBDII engine in the Barth, something I still dream about. Maybe some day.

Thank you all for your input and merry Christmas to you all. I'll follow up with the solution to this once we find it.

After wasting several days waiting for service, CoachNet got us towed to Las Cruces, NM. We landed at Bogart's Auto & RV Service. It took them about 2 hours to come up with a solution.

First off they found another hose leaking in the area of the curbside leaf spring. I didn't even know that line was there. They tested the pressure coming out of the tank pump which was 12 psi. The mechanic put a pressure regulator on and dialed it down 3 psi.

We took a 30 mile test drive which was uphill most of the way. She runs like a champ. I believe all the flexible fuel line is now offically replaced. I have access to the regulator if it needs more but they told me only if needed, 3 psi is plenty and more is not better.

The vapor canister didn't puke into the carb so I got lucky there. We have a 60 mile drive in the morning to Demming so that will be the final test.