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Buttercup · 03-12-2010, 06:08 PM

We had just hit the road for our trip to Death Valley - a 2 week + adventure of touring around and doing some volonteer work for the Natural History Assn when we had to pull over - some things were just not right.

We were taking Airtini - our 345LE w/a 454. The first problem was that there was no power to the MileMarker Overdrive. It is odd because all was working a few weeks ago when we took the rig over to a friends house to adjust the steering box.

But the other funny thing was that the engine was sputtering, mostly when I would get my foor into it and open the secondaries on the carb. it would sputter so badly that it had zero power and felt like the engine was going to die altogether. It was also backfiring somewhere - I could hear it.

So, being only 3 miles from home, we turned around and limped home. I almost couldn't back the poor thing up the driveway (ours is sort of steep near the house) because there just wasn't enough power.

Now, with our trip canceled, I am going to work on this with a friend tomorrow. We are going to replace the usual suspects (fuel filter, air filter, cap, rotor, plugs, etc). I know nothing of these engines and would love to find a source for tuning these up but that information seems almost nonexistent. So, I am going with what I know from my old Volkswagen days.

I am open to all suggestions and sources of information. We sure would like to continue our trip next weekend. So much to see, so little time.

Boondocker · 03-12-2010, 06:17 PM

Missed trips suck. Sorry to hear you ran into trouble. Good luck sorting it out.

3 Dog Nite · 03-12-2010, 06:34 PM

A loss of power that the PO told us about is the fuel pump. He said the electric one in the back had died. The mechanical one on the engine is what got him off the highway to a repair shop. Just something to check if all is good with the usual stuff.

Ricky

guy99 · 03-12-2010, 06:42 PM

I have had similar symptoms which were cured by:

1. New HEI module
2. New coil
3. New (rebuilt) distributor (existing distributor was so worn it was shorting out)

In different instances. IME backfires are usually ignition.

Buttercup · 03-12-2010, 07:07 PM

OK - check fuel pump & ignition systems. That is on the list.

TBRich · 03-12-2010, 07:12 PM

Bummer you had to nix the trip...hope you can get it resolved and get yourselves on the road soooon!

overlander63 · 03-12-2010, 07:16 PM

You have two fuel pumps, one mechanical and one electric. You could have blown a fuse to the electric fuel pump, and the same fuse may power the overdrive unit. It's never that easy at my house, but you may get lucky.

guy99 · 03-12-2010, 07:27 PM

Yeah, but... What about the backfires?

osolow · 03-12-2010, 07:30 PM

My .2 would be ignition as well loss of power sputtering.

Is it happening when you put a load on the engine? or all the time?

check for loose connections at the coil distributor

or possibly bad fuel did you fill the tank up before the problem arose? whats the exhaust smell like?

if you get new plugs and wires cap and rotor bug get a good name brand.

I have noticed here lately that the sets auto zone and Oreillys have been selling here lately are junk and really not that much cheaper then some good OEM or high Performance aftermarket. besides if you give your motor a good spark it should run better and get a bit better mileage

hope this helps

FreshAir · 03-12-2010, 07:31 PM

Tim, almost every time that I have had that same problem with 455s, (and I have had several)....no power on acceleration and sputtering my problem turned out to be a vacuum leak to the vacuum advance on the distributor or just a bad vacuum advance 'module'.
Neil.

osolow · 03-12-2010, 07:43 PM

yeah i would agree with FreshAir on it could be a vacuum problem.

if it a hard place to get to get you a can of brake clean or carb cleaner and spray around all your vacuum line if the motor revs up or smooth es out you found your leak.

Buttercup · 03-12-2010, 09:38 PM

Quote:

Originally Posted by overlander63

You have two fuel pumps, one mechanical and one electric. You could have blown a fuse to the electric fuel pump, and the same fuse may power the overdrive unit. It's never that easy at my house, but you may get lucky.

That is an easy one, I can hear the electric pump running, even over the din of the air compressor. The pump is at least running, cycling in fact. I call it a forwarding pump because that is all it does - forward fuel to the engine. That one runs.

I suspect a plugged filter myself but i am going to try everything....

osolow · 03-12-2010, 10:23 PM

a pump will run and not provide enough pressure and volume of fuel if you think its a fuel issue and you have a pressure tester you might check it.

drag'nwagon · 03-12-2010, 10:54 PM

Tim,

9 times out of ten on big block chevys (especialy if they sit for long periods) it is the rotor and cap. Since you said the fuel pump is humming that is the first thing I would I do (it is also the cheapest). If it were a vac problem you would most likely hear it hissing.

ROBERTSUNRUS · 03-12-2010, 11:14 PM

Quote:

Originally Posted by drag'nwagon

Tim,

9 times out of ten on big block chevys (especialy if they sit for long periods) it is the rotor and cap. Since you said the fuel pump is humming that is the first thing I would I do (it is also the cheapest). If it were a vac problem you would most likely hear it hissing.

Hi, My Mac Tools truck was acting like it was starving for fuel, but in acuality it was just a bad distributor rotor. These are known for grounding under load on any GM engine that has HEI system. Many a good mechanic was fooled by this because of the fuel starvation type symptoms. It's cheap and a good place to start without wasting time and money on fuel system parts.

72 tradewind · 03-13-2010, 03:02 AM

How old is your fuel? Did you add new to old fuel? My suggestion is drain and replace fuel. You can start off with 10 gal or so to be sure. This is an easy fix/test. I am a Auto/Truck technician and can tell you bad /old gas acts just like that.

boondockdad · 03-13-2010, 05:55 AM

Quote:

Originally Posted by drag'nwagon

Tim,

9 times out of ten on big block chevys (especialy if they sit for long periods) it is the rotor and cap. Since you said the fuel pump is humming that is the first thing I would I do (it is also the cheapest). If it were a vac problem you would most likely hear it hissing.

We used to just pop it off, and hose the inside of the cap with WD-40...
sorry to hear your plans cancelled en-route... that's the worst... hope you're down-the-road soon!

ROBERT CROSS · 03-13-2010, 06:12 AM

Agree with Robert...

Would go to the distributor/ign module first. Our 454 Burb exhibited the same
backfire/power symptoms several times in it's 160k. Once carbon tracks in the dist cap, once the ign module.

Your plan is a good one and probably worthwhile if your maint. history justifies it.

Good luck...

richinny · 03-13-2010, 06:44 AM

i'll also join the rotor bandwagon. if the bottom of the rotor looks orange, the advance weights are rusting. hit those with some wd-40 so they don't rust and bind.

wascobob · 03-13-2010, 09:05 AM

B-cup---Good suggestions here about the ingition system---but I would start with the fuel filters first. We have a 290 MH and have had the very same problem twice in the last 30,000 miles.

Both times it turned out to be fuel filters. You should find three filters if your MH has a carburater---one by
the electric fuel pump---one along the fuel line that runs along the frame (usually about half way forward)---and one inside the carb where the fuel line enters the carb.

I have changed the first two filters on our coach but have never needed to change the one in the carb---cured the problem both times!!!

Dist cap, rotor always a good thing to do. If you need ignition wires, be sure to get high quality HIGH TEMP wires only---they will take the heat these monsters create--if routed properly

Hope this helps---Bob