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weber stumble at wot


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13 replies to this topic

#1 scubaroo84

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Posted 02 March 2014 - 11:33 PM

I did a search and read some posts but couldn't find exactly what I was looking for. have an 84 gl ea81 with a weber 32/36 dgav that was installed when I got the car. The weber wasn't tuned properly so I tuned it and it ran much better, I thought when I got it that it was awful sluggish when I'd floor it. Come to find out the bottom of the gas pedal was bent and didn't allow for the secondary barrel to open at all. I fixed that and had much better performance, the only thing is, is that upon wot when its warm it sputters and hesitates and wants to bog. I have a vacuum guage and when it hits below 1 inch of vacuum (almost wot) it starts to sputter and when it hits 0" of vacuum it wants to fall on its face. Its done it since I got it back in may but I didn't really pay no mind as I don't often accelerate that heavily. I did make a carb hat and have a cone filter on it which isn't the problem as it did the same thing with the stock weber filter. What could this be? I've done a full tune up on it, it pulls 20" of vacuum at idle and gets me about 23mpg (kind of heavy foot) has a msd blaster 2 coil that was on when I got it. No emmisions equipment and a gutted cat. To me it seems like its lean, is there a fuel strainer in the tank on the fuel sending unit before the pump? I'm wondering if maybe that might be clogged. It has a clear plastic filter under the hood and looks fine. One other thing, the tank vent line that t's with the filter, what should I do with that? Its blocked off right now and when you pull the fuel cap off on a warm day you can hear the pressure release. Just leave it?

Thanks for any help!

#2 bratman2

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Posted 03 March 2014 - 07:40 AM

The secondary filter under the hood should have three hook ups. Incoming fuel, out going to carb and return to gas tank. The primary fuel filter is underneath your Brat. Located underneath the front driver's side of your bed. Replace that filter and make sure you have the right filter under the hood with three hook ups. Seems like a good place to start and see if that eliminates your problem. You may be flooding instead of lean.  



#3 Loyale 2.7 Turbo

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Posted 03 March 2014 - 07:46 AM

Yes I Agree... Flooding instead of Lean; but also seems like the Ignition Timing is not set properly; so I kindly suggest you to check the Timing / move it 'till it develops better performance.

 

Kind Regards.



#4 scubaroo84

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Posted 03 March 2014 - 08:04 AM

Thanks for the replies! Bratman2, its actually a wagon so where would the primary filter on that be? Im assuming in a different location as the fuel lines run inside the cabin. It does have a 3 nipple filter under the hood.

Loyale2.7turbo, I read on here that with a weber you can adjust timing to about 12* base which I did. The PO had it at 15*. I had adjusted it to stock 8* but it didnt have the get up and go like it does at 12. I will retard to 8* and see what it does. This isnt my DD anymore so it may be a few days till I get to it due to weather and its not top priority.

#5 spazomatic

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Posted 03 March 2014 - 09:12 AM

Its just the nature of the beast, being an oversized mechanical secondary carb on a little motor. The metering needs to take place at your foot. I dont care how its tuned...throw it wide open before its ready, and it will fall on its face. It is technically a lean condition; air moves much faster than fuel does.
The only way i figure to alleviate this, is if an accelerator pump circuit were present on the secondary side.

#6 Loyale 2.7 Turbo

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Posted 03 March 2014 - 09:35 AM

... Loyale2.7turbo, I read on here that with a weber you can adjust timing to about 12* ...

 

On the EA82 engines, you can advance the timing further than stock specs when they has a Weber carb; in fact seems like they like the advanced timing when they has a Weber. I went as far as 22º despite that the Stock timing should be at 8º, but I run my "BumbleBeast" @ 20º; now talking about the EA81 engine you have, I bet that at 8º the timing will be somehow "Retarded" for the Weber... So, I kindly suggest you to try advancing the timing, instead of retarding it; try it at 18º or around that and give us feedback.

 

Also, I only run a single outlet fuel filter on my "BumbleBeast" and the return line isn't hooked; in order to avoid fuel starvation during high acceleration moments, in example: Passing another car on the Highway or going uphill loaded.

 

Maybe you can try to close the return and see if that changes your engine's acceleration behaviour.

 

Kind Regards.



#7 Subaru_dude

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Posted 03 March 2014 - 09:36 AM

I have the same problem with the fuel pressure building in the tank. I have the same 3 nipple filter, but there's no place for the hose coming off the third nipple to go either. Doesn't have a charcoal canister anymore and I didn't remove it so I have no idea if that has something to do with it or not. Word of advice, if you ever start losing power on the interstate, pull over and let the car sit a while and then pull the gas cap off. Sometimes it will build so much pressure it will cause it to run way too rich.

 

Edit: Also, I've got my weber set to 8 deg and yes it has the stumble at WOT but it's getting GREAT mileage and it very rarely diesels on shutdown. When it does diesel I have a feeling it has to do with all the pressure built up in the fuel system, but really I don't know.


Edited by Subaru_dude, 03 March 2014 - 09:44 AM.


#8 Loyale 2.7 Turbo

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Posted 03 March 2014 - 09:44 AM

Believe me, I run my "BumbleBeast" without the Return line Hooked, nor the Fuel Tank's vent line hooked; both are Hangin' down, next the Brake Booster and that completely avoids high pressure build up on the tank, also avoid fuel starvation; and you must know that I have been runnin' my subie like this since 2006 without issues.

 

In fact, at first I tried to connect both lines and the results were as you described: Gas tank pressure build up and fuel starvation; so again: I kindly suggest to try running a straight fuel line from a single outlet fuel filter to the Weber carb, and let both tank's lines (Return and vent) unhooked.

 

Then let us know the Results... it is easy and worth try.

 

Kind Regards.



#9 ferox

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Posted 03 March 2014 - 01:50 PM

So, I kindly suggest you to try advancing the timing, instead of retarding it; try it at 18º or around that and give us feedback.

 

An ea81 will not tolerate 18 degrees.  10-12 degrees seems to be the sweet spot for a Webered ea81.



#10 bratman2

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Posted 03 March 2014 - 05:21 PM

I think mine is 10 but have not checked it in years!



#11 Subaru_dude

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Posted 03 March 2014 - 07:12 PM

So, I kindly suggest you to try advancing the timing, instead of retarding it; try it at 18º or around that and give us feedback.

 

An ea81 will not tolerate 18 degrees.  10-12 degrees seems to be the sweet spot for a Webered ea81.

Mine tolerated 20 degrees for about 8,000 miles then I put it back to 8 after reading that it's not good for an EA81. We'll see how it effects it long term later on down the road.



#12 scubaroo84

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Posted 03 March 2014 - 07:22 PM

Thanks for the responses. Firstly whenever I open it wot im driving and already have it open more than half throttle. I will look into the return and vent line and see how it does. Ive never had any problem with losing power it actually accelerates decent enough on the highway but nothing like the HO 4.3 in my van. The weather cleared up so I will go outside and tinker with it. Ill report back later.

#13 scubaroo84

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Posted 03 March 2014 - 09:44 PM

So here is what I did, first I wanted to be 100% sure it was actually opening all the way when I floor it. I took the carb hat off and pushed the pedal to the floor, the secondary only opened about half way, after some adjustments I got it to open completely. Uncapped the vent line and checked timing 12* still. Took it for a very short drive down my road and got it up to 40mph and floored, at wot it didnt sputter but it didnt run perfect either let off to about 3/4 throttle and it would sputter back most of the way out of the secondary and it ran great and got up pretty quick. I did notice since it has a gutted cat and a few exhaust leaks that under wot after I let off it smells extremely rich so im thinking that when the secondary opens its getting too much fuel. Im not sure if the PO who put the carb on got it specifically for an ea81 or threw one on that was for a different application and maybe has bigger jets in it. Ive read on here of people with lifted ea81's with a weber getting close to 30mpg, the best ive ever gotten was 26mpg and mine is stock height and tires.

#14 bratman2

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Posted 04 March 2014 - 08:10 AM

I average around 29-30 mpg but I do live in the country. That makes a big difference. Sounds like your close to getting it right.






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