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Old 05-30-2017, 08:22 AM   #1
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1979 24' Airstream Excella 24
Hereford , Herefordshire
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More help please! Fuel pump question

We have a 1979 240 Excella Motorhome with the original 454 engine. We recently had our inline fuel pump replaced, the one that is bolted to the chassis half way between the fuel tank and the engine. It seems that this electric one is the only one that is working! However since it's been replaced we are experiencing a fault whereby the engine "misfires" under load, by that I mean any sudden acceleration or whilst going up hill. Could it be that the fuel pump that has been replaced isn't giving the correct amount of fuel at the correct pressure? My question therefore is what specification fuel pump do I need? Any help would be greatly appreciated, thanks to all you awesome people in advance.
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Old 05-30-2017, 08:32 AM   #2
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1974 20' Argosy 20
Richmond , Kentucky
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I would suggest installing a Carter P4070 electric pump as the pusher pump (or ensure your pump has the same characteristics) and replace the failed mechanical pump with a new one. The Carter fuel pump will ensure a steady supply of fuel to the mechanical pump and the mechanical pump will ensure the carburetor gets enough fuel at the correct pressure.

Brad
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Old 05-30-2017, 08:41 AM   #3
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1984 34.5' Airstream 345
Franklin Park , Illinois
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I'm going to assume you meant sudden DEceleration
My personal guess is carburetor problems
Do you know, if you have a mechanical fuel pump bolted to the engine?
My 1984 345 has the same 454 in it
I thought my engine was starving for fuel, when I accelerate it would bog down, under 3/4 acceleration it would work just fine.
I installed electric fuel pump back by the tank when I bought my Motorhome a few years ago
it didn't have electric pump back there
Also I have install a fuel pressure gauge at the carburetor it runs about 4 to 5 PSI on the fuel gauge, The electric pump I installed seems to have helped. But I still have the bog down problem under full acceleration but again I suspect mine is a carburetor problem it just seems like it's running very lean under full acceleration just like fuel starvation
Sorry I couldn't be of more help and I'll be following this post as I'm having almost the same problem
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Old 05-30-2017, 10:23 AM   #4
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1975 20' Argosy 20
Chestfield , Kent
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Quote:
Originally Posted by bkahler View Post
I would suggest installing a Carter P4070 electric pump as the pusher pump (or ensure your pump has the same characteristics) and replace the failed mechanical pump with a new one. The Carter fuel pump will ensure a steady supply of fuel to the mechanical pump and the mechanical pump will ensure the carburetor gets enough fuel at the correct pressure.

Brad
I have the Carter P4070, and had the mechanical pump removed. The electric pump really helps as, if you turn on the ignition and wait for 3-5secs, it primes the carburetor and so starting is much easier (especially when it is hot and fuel lines vapor lock). But you really need a low pressure, 4-8psi pump (different from an EFI pump), if not you will recirculating large amounts of fuel around the bypass/return line.

The only downside I have found to using the Carter was when the battery went flat; I felt the engine ran uneven until the battery was back up to charge so seriously considering adding a Carter mechanical pump back in series.

I do have a spare Carter P4070, that I carry in case of failure, that I would happily loan you if you want to give it a try?
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Old 05-30-2017, 11:21 AM   #5
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Oxford , Oxfordshire
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My coach also bogged down on occasion. It's a different set up, with the TBI, but I had the throttle body rebuilt and replaced pretty much everything hanging off the engine/iac valve, pcv valve, tps, injectors, sensors, coil, distributor,leads etc etc. Never had a problem since.


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Old 05-30-2017, 11:52 AM   #6
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1984 27' Airstream 270
Scotia , New York
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I went through numerous fuel supply problems when I went from a carb to TBI http://theouterlimits.ws/projects/ai...ressureProblem
Some of them that may be part of a carb only problem are as follows:
1) Check your real tank fuel level, one of my problems way a fuel guage that read 1/2 tank when empty. Every time I accelerated or hit a corner, the fuel pump would suck air and I would start stalling.
2) Check for water in the fuel, check the pickup screen for being clogged and check the fuel filters for clogs. When I pulled my tank there was 2 hand fulls of loose rust particles in the tank.
3) Make sure your electric pump can pull air as well as fuel, since the tank pickup tube is higher than the pump, it needs to be able to suck the gas up 2 feet before it gets into the pump. When some electric pumps run dry, they wont work. Also be sure there are no leaks between the tank & pump which will pull air faster than fuel.
4) Check your carb float. I had a brass one in my old Argosy, it got pin holes in it and it sunk, flooding the engine, (with similar effects of lack of fuel)
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Old 05-30-2017, 05:17 PM   #7
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1987 34.5' Airstream 345
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Hey,
Before you go buying stuff, and taking things apart, you may have a slug of bad fuel. Water in the fuel will give you that problem. Throw about 6 bottles of heat in the tank. Run some octane boast too. Is your electric pump working. I have this 325 with 5K miles on it . The rear electric pump was frozen up. Put a new Holley electric one on, fired the unit up, still nothing. Taped the new fuel pump with a wrench, boom, it stats up. Go figure. You ll hear it running kind of a buzzing noise.
You could also have carbon deposits on the valves. That will act like a burnt valve and cough sometimes. Spark plug wires will do that too. It s always missing, but under a load it becomes real pronounced. DJ
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Old 07-18-2017, 01:19 PM   #8
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1979 24' Airstream Excella 24
Hereford , Herefordshire
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What a relief, bought a Carter P4070 Fuel Pump and fitted it today, replaced a garage fitted pump (i discovered that it was a Headi 1216 12v, totally wrong pump, only delivering 60ltr per hour! And it was poorly fitted, inlet pipe was being crushed by tie wraps). Drove my Silver Machine up the hill out of the city, and she was cruising at 60mph with lots more in the tank, no loss of acceleration...what a relief, I now have my baby back! Thanks guys for all the advice and help!
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Old 07-18-2017, 01:44 PM   #9
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1975 20' Argosy 20
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Great news Chris, just in time for another festival this weekend?
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Old 07-18-2017, 02:03 PM   #10
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1979 24' Airstream Excella 24
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Great news Chris, just in time for another festival this weekend?


Lol the fuel pump issue didn't stop us from attending our music festivals, went to one in Trowbridge last weekend, off to Upton on Severn Blues Festival this weekend, it just mad me nervous going up ANY incline!
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Old 07-18-2017, 02:32 PM   #11
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Gosh, reading all these threads on fuel pumps, carburetors, spark plug wires, coils and such makes me work up a real appetite. How do you guys have time to camp?

Cheers
Tony
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Old 07-18-2017, 02:46 PM   #12
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1979 24' Airstream Excella 24
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Originally Posted by Isuzusweet View Post
Gosh, reading all these threads on fuel pumps, carburetors, spark plug wires, coils and such makes me work up a real appetite. How do you guys have time to camp?



Cheers

Tony


Lol like I said, it's a labour of love!
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Old 07-18-2017, 03:45 PM   #13
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1974 20' Argosy 20
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Originally Posted by Isuzusweet View Post
Gosh, reading all these threads on fuel pumps, carburetors, spark plug wires, coils and such makes me work up a real appetite. How do you guys have time to camp?

Cheers
Tony
Ahh....the diesel troll strikes again....
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