454 in tight quarters gets hot....gas don’t flow when it turns to vapor....some even seize a piston

I concur. I had the same thing happen on a trip 20 years ago in our first 345. Ignition coil.

1987 325 MH died on the road....help!
 

Whew! Thanks for the great responses. I usually get an email when I get responses to posts but received nothing on this.

Great stuff and all note worthy.

I have replaced the original gas tank as the original had rusted out. I went around the bend to insist the fuel system be tested and verified and they assured me they had. The sticky fuel cap seemed like a very simplistic solution but they said fuel pressure and delivery is good. The 454 runs and idles very well.

On a previous repair job for the same issue, I insisted we rebuild the ignition system and had the distributor and coil replaced. New plugs and wires. Less that 20 hours of travel on that fix. That does not mean that there may not still be a problem there. It is of my biggest suspicion.

I am leaning more toward a wiring issue and a failure somewhere in the system that happens randomly. Some dodgy wiring has been done behind the dashboard and I suspect this may be a cause. The issue arose after a 3 hour drive outbound without issue and the happened as I was almost home after 2.5 hours. Last week it happened 30 minutes outbound.

I have addressed many of the issues that have been noted in these posts:

Replaced rusty gas tank and verified fuel pressure. I love the idea of moving the tank up front tho, brilliant!

Particulate from rust in tank fouled the carburetor so that has been replaced.

I am currently having them trance the continuity of the wires related to the ignition system.

I am greatly heartened by the posts from y'all saying you have had similar hard to diagnose problems, for this I don't feel so alone. Without a reference for names the post on not being in love with this mechanic makes very good sense. As well the heart of this house on wheels beat the powerhouse of a truck, using classic, simplistic technology. I am trying to treat it in this manner.

Will post future developments, many, many thanks to my Airstream comrades. Your devotion, knowledge base and passion is irreplaceable.
Cheers to you all !

I too am leaning towards the coil. By and large the coil in cap is a good design but it has its weaknesses. The biggest problem is heat causing the breakdown of the epoxy filled coil. And with the majority of replacement parts being made in China these days, quality is suspect. First of all insist on genuine Delco Remy parts for your ignition system.
There are also kits that remove the epoxy coil from the distributor cap and replace it with an oil filled coil mounted remotely. Something a competent mechanic can do easily

After your detailed list of what you have done, I am very curious to hear what the cause of your problem turns out to be. When I do preventative maintenance, I keep the known working part in my carry on Parts bin, just in case new didn't turn out to be reliable.

I would replace the coil, the fuel pump, and the crankshaft position sensor, or camshaft position sensor if it has one.

You might investigate the possibility of replacing the old distributor with a more modern electronic unit......solves lots of issues.

I bought an MSD brand coil when ours failed, no problems since.

MH died on road
 

I have a 1988 325 I had similar problem unit would stall out, my solution was to replace the electric fuel pump. We tested it and found faulty. I was in Rochester NY. We replaced it and went to auto wreckers and found a sediment bowl from and old olds installed it.New gas in line filters. Drove all the to Calgary Alberta Canada with no problem.

I had a P30 chassis MH years ago and had the same problem. Short answer, the vapor recovery system was plugged and wouldn't vent the tank. After a while the pump would pull a vacuum on the tank and starve the delivery.


Removing/loosening the gas cap was a quick fix to get home.


The giveaway of the problem was after being parked for a few minutes, I heard a GONG noise. It was the tank re-expanding after being sucked in.

when you go through the wiring, you may want to take a good look at the fusible link(s) on top of the engine. This picture is a 1979, but I know my 1992 has 1 as well.

You have lots of good suggestions here. Here's a really cheap fix. Wrap your fuel line in aluminum foil and reroute it if it's too close to either the intake and/or exhaust manifolds. This will help prevent a fuel lock. Second, those older GM motors had mechanical fuel pumps that relied on their pumping action coming from a rod that rides up & down on an oval lobe that is machined at the front of the crank shift. The lobe and rod wore out quickly in the big bore motors causing them to starve for fuel and the motor bucks due to irregular fuel supply. The trick is to remove the fuel pump, remove the rod then put the fuel pump back in place. Install a new electric fuel pump and route the fuel lines as needed. Good luck!

I believe that the lobe is on the camshaft........just saying.....you don’t need anymore mid-information, Regards, Bob

my 345 has died over the years . first it was a failed coil /easy to replace sits on top of the block in terrible heat -not expensive. secodn was a short on the electrical lines to the midship fuel pump just a worn wire shorting on the frame and of course worked until you hit just the right bump... also a cheap fix. depends on where you are .tough to find good mechanical help so best to begin learning .

Probably not applicable but . . .
 

I had an '87 El Camino that experienced the same issues, turned out to be clogged CAT. After 20 years they get pretty dirty. FWIW.

I reread your original post, you referred to your ground strap hot/ loose ect .
My 345 had many various and vague ellectrical problems, starter, dash gauges ect that I went looking for bad earth points.
My 345 had been untampered with, so original ? It relied on the battery earth strap that ending on the chasis then one web strap from there to drivers side off motor. I added another short 200 amp earth strap from that chasis point across onto the Bell Housing bolt.
My tail lights came up brighter, rear fuel pump sounded louder, starter now worked on a hot motor restart , dash also, all down to an original design weakness. As they get older crud builds up between things! Like us all :-)
I read a 2003 forum fixing a 454 backfire issue caused by a bad earth.
I always go for the fundamental's befor I go part swapping.

Rus

Maybe mentioned above. I did not read all comments. Sounds to me like your catalytic converter is bad and needs replacing.

You could buy an awful lot of parts before you catch the right one. So I would suggest finding a really good diagnostician to give you an opinion. Or maybe your bus just doesn't want to come home!

Plugged CAT converter.
BINGO....remove it and drive.
Take out a pre CAT O2 sensor & drive, hole saw it and drive all methods I have used to diagnose.

Also mentioned the 'sock' filter in the fuel tank can also cause intermittent loss of power.

Bob
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Warm negative terminal? Check the chassis ground cable. Sometimes alternator bracket to frame or engine to frame.