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Guest Message by DevFuse
 

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Fuel starvation a carb FIX


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6 replies to this topic

#1 smelly_cat

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Posted 27 November 2006 - 06:34 PM

I had this problem with my 83 GL with the carb running out of gas. AFter changing every filter and pump and rebuilding the carb. It still would run good one day the next it would conk out while I climbed hills or sped up.
Here is what I did and it fixed the problem. I hope this explanation makes sense

I got 2 gas shut off valves.
One went on the top of the fuel filter hose that goes back to the tank.
One went on the gas line that returns gas after the carb float valve fills up

I pretty much closed them almost all the way and now the GL runs fine, all the time. I figure that the gas has to go into the float chamber now due to the increased pressure and the lack of an escape route to the tank.

What does everyone think of this? SC

#2 GeneralDisorder

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Posted 27 November 2006 - 06:37 PM

You increased your fuel pressure (it's the venturi effect of forcing the liquid through a smaller opening), and it's "masking" a sticky float. I would say it's fine, but if you notice really bad mileage then it means that the float isn't capable of shutting soon enough and the fuel level is too high in the chamber. It could also damage the pump eventually as they aren't really meant to be run "dead head" (means without a return to the tank).

GD

#3 smelly_cat

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Posted 30 November 2006 - 06:23 PM

GD, your post was insightful. I agree with you. I don't know why the float still is being a bugger for me. I have rebuilt the the carb and removed the top of the carb 3 times to mess with the float.. poke around .... bending the tab etc. I took the little mesh filter at the float out just because i was mad.

I did start smelling gas last night and opened up othe carb return valve a little to relieve the pressure some. the pump got quieter , I guess due to it has to push gas less hard. I'll be sure to post if I blow up. S/C

I get like 27 mpg in the city and I usually RPM to 3000 between shifts. I figure its running OK and I got the idle on like 1ooo. (I should lower that some) The best I ever got was like 32mpg doing HWY in the 90's
S/C

#4 GeneralDisorder

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Posted 30 November 2006 - 06:30 PM

Yeah - I think that maybe the problem with them is the cheap aftermarket rebuild kits. The float needle and seat assembly seem to be cheap, and I think that is the source of the sticking. It's a really tough problem since you can't really see into the chamber to tell what the cause is, and once you take the top off it's not stuck anymore. I had one that ran so perfect it could have been brand new - and then one day the float would stick. Would run fine for months then stick at the worst possible time. I finally just threw it in the dumpster, and I run Weber's and SPFI on all mine now.

Check out my SPFI write up:

http://home.comcast..../EA81_SPFI.html

GD

#5 smelly_cat

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Posted 30 November 2006 - 06:43 PM

GD, You are way above my repair intellegence. Your FI HTML was very cool. I might be able to change a Carb but converting to FI is too awsome for me. I'm impressed that it can even be done. I am intriqued to get a Carb rebuild kit from Subaru to see it the &&*%$$%%$ float valve will start working with a OEM.

Oh, does my 84 GL have a computer somewhere? I have not found it if it does? I do have a ECU light that comes on after about 15 minutes that maybe from a CPU. SC

#6 bgd73

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Posted 30 November 2006 - 06:56 PM

A swap on the fuel pump with same pressure better volume was a miracle on my 87 DL. Will be doing the same for my 87 gl. I took the carb apart went for factory specs and cleaned it up, and still problems after the usual tune-up. My bro n law was a manager at the local parts store and took time to cross match a fuel pump. Miraculous. It was a larger pump by volume, not pressure.Even with tight exhaust and air plenum filtered oem, it started perfectly at 25 below zero and bellowed like an old holley four barrell when floored.. the strangest part of this upgrade, knowing it was getting crammed with a thing called fuel... the gas mileage sailed into the 40's on the highway and changed the synchros ability to go tall, to really tall geared (more power in other words). The tinkering beyond oem is avoiding the original problem on any carbed engine.More fuel same pressure seems to help old parts. I have found strange anomilies with oem pumps looking and sounding good, but wearing down in non-obvious ways.

I have used a 5-7 lb successfully that was big enough volume to power a v8. The old ea82 took it all flawlessly. :)
2 inch exhaust was a must have- I blew apart the oem setup annually (for 7 years annually! before I figured out what 2 inch saved), just when I thought it was sealed- kaboom!. There goes yet another dainty "lifetime" oem muffler...:grin:
If you try the pump would love to know what it did for you.

#7 GeneralDisorder

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Posted 30 November 2006 - 07:02 PM

Yeah - the CA emissions model had "feedback" carbs. It's got an ECU, and a couple sensors. It uses rapidly switched "duty solenoids" to adjust the high speed and low speed mixture settings of the carb. Look at the "crotch" of your y-pipe. If you have an 02 sensor like the later fuel injected models, then you have a feedback carb. If the "ESC" light is comming on after driving for a bit it means the ECU has detected a fualt somewhere. It's usually either the 02 sensor, or the Coolant Temp Sensor. Both of which are cheap ($20 or so) and could easily be causing you to lose 5 mpg. The ECU is under the dash (black box attached to the steering column), and if you remove the kick panel and drive it till the lamp comes on it will flash the codes in long and short flashes from the front of the ECU. Count the flashes and tell me what you find - I can tell you what the code means.

GD




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