454 Carb Problems

[1987_345]

I bought a really clean 345, but have been plagued by engine performance problems. First we had to replace the rear fuel pump, but before we found out that was the problem, we had also changed out everything from the tank to the carb. It has ran great for the last three trips, but today we left abd got 150 miles down the road before it started giving us problems. No power!! It would only run 40 -55 mph, and eventually got worse. If I could run down the highway with no wind or no hills, it would probably be better, because as long as I only depressed the gas pedal a little it wouldn't startlosing power. Anything more than that and we lose speed and power. I can't even try to run down the problem with all the egr stuff in the way. Has anybody removed all of that from your coach with any pointers? I can't tell if my problem is spark advance, plugs, maybe a power valve, I do know it is getting plenty of fuel to the carb, and when you bump it to neutral and rev it up it does fine. HELP HELP!!

[lsinclair]

From what you describe, it sounds like after the engine reaches operating temperature the problem becomes more acute. That said, I'd check the exhaust system for a restriction (possible cat converter etc). A stuck (down) power valve or secondaries failing to open would be prevalent and consistent throughout all operating temperature ranges. Hope this is of some help, Larry

[thenewkid64]

Check the advance weights in the distributor, if they seize (rust) they need to move freely to allow for advance. If they are seized it is just as simple to install a new distributor. The vehicle will run fine at idle, or no load, but cannot get out of it's own way with any throttle pressure above 20 MPH or so when this happens. At least that was my experience...

[68 TWind]

If the engine idles OK but lacks power I would agree that the cat or muffler may well be blocked. I had the same type thing happen to me several years ago while pulling a U-Haul. No power going up hills, finally got so bad that I had to just idle up hills in 1st gear. Stopping, I heard a strange sound from the tailpipe. Ford trucks then had a screen in the end of the tail pipe. It looked blocked so I got a hammer ( how many times has that fixed things) and a big screw driver and punched the screen out. When I cranked the truck it blew a grocery sack full of rust and stuff out the tailpipe. Made it home with no more problems and drove the truck for 4 more years with no problems.

[1987_345]

I hadn't considered either of those possibilities. While I suspected the spark advance, I hadn't thought of the weights. I don't know about the exhaust. It seems to be ok, but the coach had been setting for about 4 years when I bought it, so anything is possible. How could I check the exhaust other than the obvious?

[ScrapIrony-2]

Similar problems with our 454...I now carry extra fuel filters(the small in-line one at the carb, the larger in-line at the back of the grey water tank, and a spare fuel pump located just forward of the back fuel filter...also, 454's run HOT, and the spark plug wires can be fried...I had racing wires installed. The heat can also affect the starter...has to cool for awhile before it will crank...this is a subject of another forums thread.
mike

[ScrapIrony-2]

OOPS, forgot...if it has been sitting for 4 years, the fuel and fuel lines may be gummed...gasoline WILL turn to jelly or 'varnish' when left on its own for that long...fuel lines are a recommended replacement after that length of time...m

[Honkity Hank]

Originally Posted by 1987_345

I bought a really clean 345, but have been plagued by engine performance problems. First we had to replace the rear fuel pump, but before we found out that was the problem, we had also changed out everything from the tank to the carb.

Okay lets think about this. The engine needs 3 things, fuel, spark and air. You say it starts fine and runs good for a good 2 or 3 hours before losing power. The engine reaches operating temperature well before then so I think we can put temperature related issues near the bottom of the trouble shooting list.

Fuel: I would go back through the fuel delivery lines and make sure the filters are flowing good. The new ethenol fuels are hydroscopic and tend to pick up debris etc from the gas tank. Even though you did this once I think it is worth checking all the filters. Don't miss the in-line filter somewhere between the tank and the carb.

Spark: I can't think of anything that is spark related that fits your description. Changing out the plug wires and installing new plugs might be good maintenence but I don't see how that will fix your problem unless you have a mis-firing engine.

Air: Again this seems unlikely, but check the air cleaner and any ductwork for mice.

Exhaust: The Cat will be full up to temp long before you report the problem so I doubt that is the issue. Remember the engine and system get up to temp very quickly, within a few minutes certainly, and don't take hours.

So I think it is fuel related. Driving along for a while will stir up debris in the tank and that could have collected in the filters, or maybe you have water in the tank and it just takes a while to get into the system. Based on limited information I say check your filters again, replace any flexible lines, and add some sta-bil to the fuel tank.

Report back on what you find out.

[Aerowood]

Had this happen with my dad's old motor home, took awhile to find it but the fuel selector valve was so gummed up that the 454 could not get the volume of fuel flow it needed with power demands

[1987_345]

Even though I had recently changed all the filters when we changed the pumps, you're probably right. It is acting like filter problems. I'm also going to check the weights in the distributor, just because. What about all of the air pumps and egr stuff? Keep it or loose it? Would certainly make things easier if it wasn't in the way. I will report back on the other

[thenewkid64]

Filters are a good thing to check. I am getting ready for the longest trip my MH has had in a few years and I have purchased all the filtrs and will be replacing the frame rail one before I leave...

I had to replace the Frame rail filter ever 1000 miles right after I bought it, but now it get changed every 10K... Very fine sediment form the tank kept clogging it.

Once it was clogged, it was clogged. That is what rules out the fuel filter for me, that 2 hr run time.. You could also have a mechanical fuel pump issue.

I eliminated many of my motor related issues right after I bought mine. I simply blew the motor up and replaced it and all the accessories... Not the recommended way to go about it, but it has been a good runner ever since...

[Honkity Hank]

Originally Posted by 1987_345

Even though I had recently changed all the filters when we changed the pumps, you're probably right. It is acting like filter problems. I'm also going to check the weights in the distributor, just because. What about all of the air pumps and egr stuff? Keep it or loose it? Would certainly make things easier if it wasn't in the way. I will report back on the other

The secondary air injector pump works with the Catalytic converter, if you still have the cat I would keep the pump. If the cat is gone and you don't have to pass smog inspections then the pump can go along with the plumbing that makes it work right. I really do not think these have anything to do with your issue though.

As a side note I had similar but not identical symptoms that were solved when I replaced the in-line fuel filter on the frame rail. Mine was so clogged you could not blow through it, how it ran at all I don't know but it would start and idle, go for about a mile and then basically stall out and barely idle. This happened a year ago when ethanol made its way into all the gas here in GA. I think the ethanol was last straw in a already compromised fuel filter's life.

[ScrapIrony-2]

My MH would run for an hour or two, then start crapping out when I put stress on the engine, and would finally quit...back pressure on the fuel filter would eventually resolve(about 1 hour sit time), but the problem wasn't solved till I replaced the inline(behind the gray water tank) filter...cheap test, but I'd still replace the small one by the carb...buy two or three of each, as the fuel is probably contaminated...if you don't have a full tank, an old spark plug will make a good plug while replacing the filter(s).
m

[Chuckles]

Two things cropped up on my beast after the engine ran for about an hour or so.

The fuel filter in the carb was blocked with 'Lacewings' - To us they are a very fine Moth; hardly seen, but has the tendency to find its way almost every where, especially if their hiding place has not been disturbed for some time.

The other was a loss of power due to the secondary needles. Mine were worn badly but that did not stop them working well some times, but another time just causing the engine to "die" when using the gas pedal, not hard, but just when pulling away from a junction etc. Out of interest have you smelt unburnt fuel just as you pull away or accelerate? That was the signal to me, that made me look and eventually rebuild the carb.

Hope this helps - someone.

[Astrodokk]

Sounds like the fuel filters.
But the main reason I'm piping in is that if you do remove all the smog stuff, please don't get rid of it...store it all away for the future. When I bought my MH it didn't have any smog stuff and I had to install it in California. It was a pain (and expensive) to find. Sure wish the PO had saved all that stuff. Even if you don't think you'll ever sell it, still keep the components.

[1987_345]

I think I will remove all the stuff, but like you said keep it. I have been to busy to completly fix my engine problems, but I figured I would start at the tank and work foward. So far I have replaced the fuel line and the filter up to the fuel push pump. Those items were ok, so I continue foward. More to come.....

[guy99]

The PO of my 1984 310 had horrible problems with no power on hills. He even put on a Banks which is nice but didn't correct the problem.

The problem turned out to be a contaminated fuel tank, it seems that crude in the tank was limited the amount of fuel that could be pumped. He had the tank removed, cleaned out and sealed, problem solved.

[1987_345]

I finally got some time to work on the problems i had been having. From the drivers seat it so seems like fuel so I started at the tank. I replaced all of the flexable fuel lines and blew out the solid lines, replacing both in line fuel filters at the same time. No luck. Got out on the road at she wouldn't run but maybe 35 mph. Idles fine, but at some point during accelerating it falls on its face and won't come back to life unless you back almost completley off the gas. Next I hooked up a portable 6 gallon fuel tank in the rear passenger side storage compartment to the rear lift pump thus eliminating any problems withe the main gas tank. Nothing. Still only about 35 mph so I guess the tank is ok. Next I took off the new lift pump I had installed 2 months ago and tested it. It was pumping ok it seems. At least enough to power my 454 anyway. I then made sure that the wires that power the pump were hat and the hot one was. Who knows, I think I will take a colser look at the carb next. I did notice that the lift pump hot wire would not energize unless you actually started the engine. It would not energize by merely turning the key to the "on" position. Any thoughts?

[guy99]

Originally Posted by 1987_345

.... I did notice that the lift pump hot wire would not energize unless you actually started the engine. It would not energize by merely turning the key to the "on" position. Any thoughts?

I think there is an oil pressure switch in the circuit so that the pump shuts off if there is no oil pressure.

Too bad it wasn't the tank

I have had ignition problems which looked like fuel starvation problems. Once it was an intermittent failure in the ignition module, another time it was the coil.