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Old 06-21-2010, 01:32 PM   #1
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1990 33' Land Yacht
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Water separator / fuel filter for gas motor home

I have been chasing an intermittent loss of power and miss in my 1990 Airstream LY, equipped with the Chevrolet 7.4L TBI engine.

I have narrowed the problem down to the poor quality ethanol/gas being sold nowadays as a result of federal stupidity (but that is another subject for another soapbox -- please don't get me started!).

When I bought the MH in 2006, real gas was readily available, and I was satisfied with the MHs performance.

Now I am not!

Here is my question, aside from using Stabil Blue, will a fuel filter/water separator help me regain some measure of performance?

I know that diesel engines all have water separator/fuel filters -- anybody out there have one installed on their gas rig?

If so, did it work?

What brand?

Thanks in advance.
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33' 1990 Airstream Land Yacht: Edelbrock, Banks, Gear Vendors, MSD, Taylor wires, Super Steer bell cranks, Bilsteins, Roadmaster sway bar, Safe Steer, Pressure Pro, Crossfire, Bigfoot levelers, Rickson 7.5" rims & 245/70 R19.5 Bridgestones on steer axle.
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Old 06-21-2010, 02:18 PM   #2
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Quote:
Originally Posted by Taxman View Post
I have been chasing an intermittent loss of power and miss in my 1990 Airstream LY, equipped with the Chevrolet 7.4L TBI engine... I have narrowed the problem down to the poor quality ethanol/gas being sold nowadays ...
For various reasons, I do not think a water separator will cure your engine's ills. The addition of one, though, will certainly will not hurt anything.

FWIW, my 7.4L recently gave me very similar trouble & I had drawn a similar conclusion. You can read the tale of what appears to be a successful repair at this link.

Tom
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Old 06-21-2010, 02:55 PM   #3
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Fuel Pressure????

AS MH's are notorious for losing fuel pressure -

Install and check the fuel pressure going into the carb (or FI system) prior to going any further....

There should be an "intermediate" fuel pump on your system (I think).

The primary electric fuel pump (and maybe the secondary) are controlloed by an oil pressure contact switch on the curb side of the engine....

Do a search on your problems here on the forums - balky fuel systems have been covered many, many times before.
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Old 06-21-2010, 04:57 PM   #4
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I have the same engine and it runs OK on the political gas.

I have a water separator in my boat but don't need one in the RV.

Sounds more like a fuel filter problem the engine should run fine on 87 octane if everything else is in good order like plug wires and such.
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Old 06-22-2010, 08:32 AM   #5
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Tom,

Thank you for responding -- I'll certainly check out that possibility.

Safe travels,

FRank
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33' 1990 Airstream Land Yacht: Edelbrock, Banks, Gear Vendors, MSD, Taylor wires, Super Steer bell cranks, Bilsteins, Roadmaster sway bar, Safe Steer, Pressure Pro, Crossfire, Bigfoot levelers, Rickson 7.5" rims & 245/70 R19.5 Bridgestones on steer axle.
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Old 06-22-2010, 08:35 AM   #6
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Dennis,

Thank you for your suggestions -- all have been previously checked, to no avail.

I really believe that since I have do not drive my MH every few weeks, that the gas goes bad and causes the misfire problem.

Safe travels,

FRank
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33' 1990 Airstream Land Yacht: Edelbrock, Banks, Gear Vendors, MSD, Taylor wires, Super Steer bell cranks, Bilsteins, Roadmaster sway bar, Safe Steer, Pressure Pro, Crossfire, Bigfoot levelers, Rickson 7.5" rims & 245/70 R19.5 Bridgestones on steer axle.
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Old 06-22-2010, 08:40 AM   #7
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Garry,

Thanks.

As I mentioned, I have checked and double checked every possibility -- gonna try Stabil-Blue and fresh premium gas, after I change the fuel filter.

I got the idea for a water separator/fuel filter from a marine site -- the theory that boat engines are run infrequently fits the pattern of my MH usage.

Safe travels,

FRank
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33' 1990 Airstream Land Yacht: Edelbrock, Banks, Gear Vendors, MSD, Taylor wires, Super Steer bell cranks, Bilsteins, Roadmaster sway bar, Safe Steer, Pressure Pro, Crossfire, Bigfoot levelers, Rickson 7.5" rims & 245/70 R19.5 Bridgestones on steer axle.
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Old 06-22-2010, 08:41 AM   #8
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Garry,

PS What kind of water separator do you have in your boat?
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Old 06-22-2010, 10:14 AM   #9
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Quote:
Originally Posted by Taxman View Post
Dennis,
Thank you for your suggestions -- all have been previously checked, to no avail.
Frank:

I still think you have a fuel pressure problem -

What I failed to type in my previous post was a recommendation to install a fuel pressure meter just upstream of your carb/throttle body/FI take point.

The slightly older 345's and 325's are famous for one or more electric fuel pumps failing (or partially failing) and causing a vapor lock condition.

A fuel pressure meter is relatively cheap and easy to install - as is a supplementary electric fuel pump located close to the fuel tank.
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Old 06-22-2010, 11:28 AM   #10
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Have you tried manually draining your gas tank to remove any water that might be in it? Water is heavier than gasoline and therefore would stay at the lowest point in the tank. This is also the point the contents of the tank are drawn out into the fuel lines. You might also try checking for possible points of moisture entry into the tank. Just a thought.
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Old 06-22-2010, 12:21 PM   #11
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while a water issue is always possible, and perhaps DRAINING the fuel tank 1 time is a sensible idea...

and stale gas might be an issue sometimes in some settings (stall gas is a VERY over used excuse for issues...)

but then the question becomes for LONG TERM inactivity is a FULL TANK or empty tank better...

i dunno and neither does ne1 else.
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87mh is spot ON, on this issue.

and WAY before universal reformulated gasoline,

a/s moho owners were dealing with the mystery and many faces of vapor lock.

IF you haven't fully evaluated the fuel pump/s and pressure and gas line RUNS (for heat exposure) ...

vapor lock is STILL the most likely problem.
_________

you've not described WHAT exactly is happening or HOW the bad fuel conclusion was reached...

so we've got nuthing to go on in the armchair mechanics corner...

but PREMIUM fuel isn't gonna solve any problems in these relatively low compression engines.

cheers
2air'
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Old 06-25-2010, 04:57 PM   #12
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My fuel separator looks just like a standard screw on oil filter and I change it out once per year.
I think I bought it at Boaters World very easy to install and replacement filters are not expensive.
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Old 06-25-2010, 05:17 PM   #13
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Etoh (ethanol) in gas is huge problem for boaters. I was having terrible problem with my Mariner 150 until I started adding Startron to the fuel. It is an enzyme product that is keeps the Etoh from separating from the gasoline. Etoh is a much bigger problem in tanks that are vented to the outside (like boat tanks) and yours may not be vented. Etoh is very hygroscopic and the longer fuel sits the more chance of absorbing water from the atmosphere. The Startron prevents this. They are also just started making an Etoh formulation of a product called Sea Foam. I have used it for years to dry gas and clean fuel systems in small engines and 4-wheelers with great success. The new formula is supposed to do the same with fuels containing Etoh.
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Old 06-25-2010, 06:57 PM   #14
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Quote:
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Etoh (ethanol) in gas is huge problem for boaters. I was having terrible problem with my Mariner 150 until I started adding Startron to the fuel. It is an enzyme product that is keeps the Etoh from separating from the gasoline. Etoh is a much bigger problem in tanks that are vented to the outside (like boat tanks) and yours may not be vented. Etoh is very hygroscopic and the longer fuel sits the more chance of absorbing water from the atmosphere. The Startron prevents this. They are also just started making an Etoh formulation of a product called Sea Foam. I have used it for years to dry gas and clean fuel systems in small engines and 4-wheelers with great success. The new formula is supposed to do the same with fuels containing Etoh.
As I was reading down this thread, my thoughts turned to motorcycles and the problems I have been having with missing, power loss and poor fuel mileage. (My trucks and van are all diesel).

My shop is upstairs from a big marine service shop, and they also recommended Startron. They use tons of the stuff in their customer's boats. The stuff performs EXACTLY as they say. Better mileage, smoother running....a noticeable difference for sure. I buy it by the case now!
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