I just purchased my 84 barth in LA and drive her home to boise, ID. before I left for my journey, I filled up both gas tanks. She was running so nice and so powerful! I switched to the next tank for about 5 minutes and it stated to bog down and die..

I quickly switched back to the "good" tank and it slowly started to get better. The problem never went away completely. It cruises just fine, but when you get on it, in the higher rpms it bogs and loses all power. I found a local mechanic that said he'll drain and clean both tanks/replace fuel filter for $200, but before I do that I want some input from you guys to see if you thunk this is the problem..

Thank you!!

Start easy, filters. Should be one in each line,and one at the carb intake. Now on to what I've debated with everyone for 7 years. If you lift the throttle for a while, such as down hill or at a light, then take off and go good for maybe 10 or 12 seconds, then it cuts out, sputters, and eventually cuts in nice and smooth, that's vapor lock and it was a serious condition that GM ignored for many years, bandaging it when they could but mostly saying it's not a problem. This isn't my opinion, it's from a very good long time tech that argued this with GM back in those days and finally won the argument because they had to come up with a different fuel system. I still fight with this, but I'm winning.
Oops, got rambling there. Your problem is surely fuel related, but I wouldn't do a bunch of money spending till I knew more.

Danny might be right about the vapor lock issue, but it wouldn't get better switching tanks. Vapor lock is due to the fuel getting too hot in the line or the carb and vaporizing causing a lack of liquid fuel flow or, more often, a complete shut down.

I'm with Danny on changing your filters as a start. I wouldn't spend the money draining tanks until you look at the filters carefully for what kind of contamination. If they are paper, cut them open and analyze.

You might also have water in the fuel. Throw some dry gas or fuel conditioner in both tanks. Unless the filters are plugging up immediately, just keep changing them out until they run clear.

As a matter of course, why not throw new plugs, cap, air cleaner and wires at it to eliminate future problems with the little things?

It has been a year since I got my Barth. When I picked it up it ran a bit rough (sat for 2 years). Got it fueled up and got some Seafoam in the tank and ran a tank of fuel through it. The idles smoothed out but I had a similar situation. When the 4 barrels opened on the quadra-jet, it bogged big time. If I kept my foot on it, the engine would stall. Just back off enough and it would stay running and even pull up a hill. I drove from Lake Havasu City to Scottsdale like this with no problems. It ran fine, just don't open 4 barrels. Got about 7 mpg on the round trip.

I had the carb rebuilt by Chuck's Carb & Fuel Injection in Lake Havasu City AZ (yep thats a plug). He checked it out and nailed the exact problem. There are 2 brass tubes for the secondaries in the carb that often fall out. They press-fit in and heat, time and vibration can make them drop out. 3 hours and $350 later, Chuck had the 454 humming. 3000 miles later she still runs like a top.

Do like Danny Z said, do the easy stuff first. I'm just sharing what mine Barth took to get running proper. Love Seafoam for all my ICE toys.

Thanks for all the good info! So the filter at the carb intake, is that the same filter as the in line filters? I was already planing in doing plugs, wires, cap etc...if this doesn't solve the problem I'll go the carb rebuild route.

The filter at the carb is where the fuel line connects to the carb. It's a small cylinder that does the final filtering, and is very fine.
Re the different tanks and vapor lock, if the vapor lock is occuring back in the line due to the exhaust running within a fraction of an inch of the line, not a problem according to GM, but a very real problem in the real world, the rear tank will experience VL, and the side one won't, because it enters the switchover valve downstream of the heat source.

I have an inline filter about mid-ship near the entry door (might be different on yours). On my carb, I unscrew the fitting on the steel fuel line, then there is a larger filter nut. Take that off and the filter fits into this nut. There is a spring inside the filter housing on the carb that keeps the filter pushed into the nut.

Be VERY careful to not over torque or crossthread that filter nut. I got chewed out by my carb guy for having the nut way to tight. He also said the filter I put in had a check valve to was way too heavy. It is supposed to keep the fuel from syphoning out of the float bowls but if it is too heavy it can cause fuel stavation. He said since the pump is mechanical and old the check valve filters can cause problems. He suggested going with an electric pump with a return line when the mech pump goes out. That way you can adjust the fuel pressure to overcome the check valve and with the return line, have less problems with vaporlock.

I should mention I'm not an expert mechanic. This is what I have learned or been told up to this point so take what I say with that in mind. Some of the pros here should be responding soon and I'll see how well I've been paying attention.

ADDED: Here is an exploded view http://dyeager535.topcities.com/CCCqjetdiagram.html
The fuel nut is #370

Ok. Sounds easy enough to change the filters. As fast as the carb filter goes, I looked online for the replacement pay online as my local autozone says they don't carry it..it says there is a long filter it a short filter. Which one should I get?

I took mine out first and just took it to the auto parts shop to match it up. I have fun ordering parts. My Barth is a 1989 but the chassis is a 1985. The original owner had lots of problems with the 454 and it was replaced under warranty in 1991 so the odometer is off by 32k.

Because of all that, I take in old part to make sure everything matches up.

How does it run with the gas cap off the "bad" tank?

How many hoses are there on the fuel selector valve? Does it have a good connection and a good ground? Do the hoses and clamps look good on it?

Do the tanks have an electric fuel pump?

A fuel pressure gauge will tell you a lot.

quote:

Originally posted by Brandon:
Ok. Sounds easy enough to change the filters. As fast as the carb filter goes, I looked online for the replacement pay online as my local autozone says they don't carry it..it says there is a long filter it a short filter. Which one should I get?

Probably short, but if the filter is good for one tank, it is probably good for the other. Be sure to use a flare nut wrench. 9/16, I think. An open end can cause trouble.

In the mid '80's, Chevy Engineering & some coach builders did a study of the vapor lock issue.
Here's what they had to say:

http://f1.grp.yahoofs.com/v1/U...ock%20Fix%201984.pdf

Chevy P32 Vaporlock Issues - (742 KB) ~ P32 vapor lock

So..i cruised around all last night on the "bad" tank of gas with very little/no problems. It bogged down a few times and when I take off its very slow to respond to the throttle and kind of bogs diwn as well. It is very cold here in boise, ID so I'm thinking maybe that's why its not VL on me. When I was driving on my trip home (900 miles) something was DEFINITELY wrong with the fuel delivery.

I am still going to replace the filters and do a full tuneup. Another thing I noticed when I was looking around its that it recommends min 89 grade fuel. I was using 87 the entire trip. Don't know if that would mater at all?

I don't feel well versed enough in DIY to rig up an electrical fuel pump and gauges and such. So if my tuneup didn't sort the issue it I'll take it to a mechanic to do that work.

quote:

so I'm thinking maybe that's why its not VL on me

What's VL?

One possibility is you were sloshing water from the bad tank into the fuel line. If it is now a block of ice (water freezes before fuel) then the water can't get in the line. This is a remote possibility only.

VL=vapor lock..sorry