DRLA jet problems, turbo setup, dies with throttle.

[Thomas Hawley]

so I have been messing with my drla 40 also.

and can't get it to run correctly at all. It's a "turbo prepped"
carb from the guy in italy off ebay.
he said he set it up with 32 vents i think.

i think the idles say 6.5
the airs are 175 and the mains 150?

i am gonna put a picture in here also since I dont know what is what on the
stack of jets....

its for a 1776 with stock heads.


THE PROBLEM

It idles fine. which is expected, but when you give it any gas it dies.
like cuts straight off like no fuel is going to the motor.
then if i let back off the gas it comes back to life like it is normal.
so it seems like it is the IDLE jets.

it also will work if i accelerate very very slowly and will drive fine into the upper rpms. but I cant make it pop when i adjust mixture screws.

i checked the float level and it seems fine, and my fuel pump seems to be working also. and prior to this single carb it was running on duel weber 40s perfectly.


any advice will be appreciated. and any jetting recommendations would be nice also.

[Ohio Tom]

Sounds like you have accelerator pump problem. The diapharm is stiff or your squirter jets are plugged. A simple re-build kit should remedy the problem.

let me get this straight first....

You bought the carb "turbo prepped"?
What does that mean? Did you ask?
The reason I ask is that most Weber or Dellorto carbs used for turbo use have "turbo" emultion tubes. those in the picture don't look like them at all.
2nd for turbo use (with correct emultion tubes) your Main jet should be much bigger as well. (like 180 - 200).

Turbo prepped should also mean that the inlet needle/seat have been changed to 3.0mm (or so).

There are a few other openings that get drilled out and modifed as well.

I gotta question wheather or not they are truley "turbo prepped".

Tell us more about your carb and motor setup...

[Thomas Hawley]

I bought the carb from the Alfa guy off of ebay.
it has the shafts sealed and the rubber gaskets to handle the boost.

not sure if anything else was changed for a turbo setup.

The inlet valve is fine right now, the problem is happening when their is
no boost involved at all.

My motor/carb setup is this.
a 1776 with stock heads a scat c35 cam, cw crank, single centermount
drla 40. compufire on a 009 that is locked.
thats all the basics.
this thing was running great before this carb went on.


what would a rebuild kit be for the accel pump?
could i just take it out and clean it with some air or carb cleaner?

The accell pump was pushed earlier where it was partially open (so it seemed) while driving. I changed that and now it doesnt open until you push the throttle, but it still seems to stick and mess with my idle speed.

also i can see the fuel being shot into the carbs from the squirters.

and it has 32 vents...which seems kinds large


ALSO

just drove it again and it seems to backfire out the exhaust when i WOT
in the upper (above 4k) rpm. after i let off the throttle.
which makes me think its running super rich


thanks for the replie. and let me know if i can give you any more info.
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74 Super- 1776 single drla 40 blow through @ 15psi ! with disc, gauges, wheels, suspension, blah blah.

but needs paint

[Ohio Tom]

OK, correct me if I am wrong. The carb is " turbo prepped" with seals, but you are NOT using for a turbo application at this time.

That said, it still sounds to me like an accelerator pump problem.
Yes, you can take it apart and clean it out. Check the springs (they break) and adjust the linkage for a proper shot volume (a rebuild kit will have instructions on how to do this). Also, pull all the check valves out and inspect them. Take the diaphram out. If it feels hard then it needs replaced. A re-build kit will come with a new diaphram.

After you have the pump sytem working properly, then you can see if you need larger pump squirters or not.

I too bought a side draft Dellorto from that guy several years ago. The carb was fresh off an Alpha and needed rebuilt.
That's OK tho, It allowed me an opportunity to take it apart and understand it.

[Thomas Hawley]

well i have all the turbo stuff on. but dont have it connected to the carb
yet since it has been having these issues without the turbo.

i'll take it apart and see what i can see.

i have an extra weber rebuild kit. could i maybe use that diaphram?




this is what i bought

http://cgi.ebay.com/ebaymotors/DELLORTO-DRLA-40-TU...QQtcZphoto

thanks!
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74 Super- 1776 single drla 40 blow through @ 15psi ! with disc, gauges, wheels, suspension, blah blah.

but needs paint

[Thomas Hawley]

ok. cleaned everything out. have not gotten a rebuilt kit yet.

it seems to be running better, but still has a stumble that is bad enough to kill
the motor unless i get let the throttle completely off.

it also seems that the squirters are shooting less fuel now... .but everything is as it was.
i also have to tighten the nut down to get the accell pump back to its position away from the carb. as in when i let off the throttle it wants to not
let the acell pump go back to its normall position.

it idles very well now, and the carb is much much cleaner.

let me know if you guys have any more ideas, or if i'm headed in the right track.

i'll also put a video on you tube tonight.

and i havent set my timing correctly yet either. im just running a locked one at whatever it was at before, which has to be lower than 24degrees. so i think i am safe.



thanks again guys.
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74 Super- 1776 single drla 40 blow through @ 15psi ! with disc, gauges, wheels, suspension, blah blah.

but needs paint

[mharney]

Your pump diaphragms are shot, most likely. You need to replace them and clean up the linkage and lubricate it. I'd also bet your pump jet o-rings are missing, or damaged, or hardened. You may have some sticking check valves too. You do have the rams and check balls down in the pump circuit I hope.

[Thomas Hawley]

ok. that actually sounds like what i am thinking.

i took out the little jet down in the bottom of the fuel bowl,
i saw the little ball inside it and its all together.

where are the check valves? you have a pic?

i think there might be a hole in the accell pump diaphram, cause it
is random at how much fuel actually comes out of the squirters.

everything seems fine other than this problem, it does seem to lean a little on the top end. but since i have learned so much from this little problem.
i think i can figure out the rest of the jetting.

and are you talking about the "linkage" where it pushes the accell pump, cause that works fine.

also this is a single carb.

-i ordered a rebuild kit off ebay. so we'll see if that makes it all better.

advice still appreciated and love getting it.

i'll try and add some pics to my gallery tonight and give you guys an idea of my bug, i'm normally on stf. but you guys have been more of a help.


thanks again!
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74 Super- 1776 single drla 40 blow through @ 15psi ! with disc, gauges, wheels, suspension, blah blah.

but needs paint

[Thomas Hawley]

so i replaced the pump diaphram, and now it works.... sometimes

i have to let it idle for a few seconds then it seems to be perfect.
i rev at WOT and it doesnt die or anything, it is nearly perfect.

then if i give it any gas again it will die, but it will idle fine.

i dont think this is a fuel pump problem cause i can turn my fuel pump off and it makes no difference.

so i think that something is getting partially clogged that is trying to fill the accel pumps ? what could that be?

thanks guys. its almost done. no videos cause its all icy here. but i'll have some later.
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74 Super- 1776 single drla 40 blow through @ 15psi ! with disc, gauges, wheels, suspension, blah blah.

but needs paint

[Thomas Hawley]

so bump.... its doing the same things.
i have my holley blue pump in also as of now.


vids to be put up tonight. hopefully.


i cant drive my car, so any help would be very appreciated.


http://www.youtube.com/v/o5C-JVSNmoo
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74 Super- 1776 single drla 40 blow through @ 15psi ! with disc, gauges, wheels, suspension, blah blah.

but needs paint

[mharney]

Thomas, when you installed the pump diaphragm, was there a spring between it and the carb body inside? It just looks like you're not getting much pump shot.

But flooring it should not cause it to die completely. The main circuit oughta come in anyway. There should be a hell of a lag without the pump shot, but it should still get going afterwards.

If you can tool it down the road try this:

Get the car in second gear or so, and use your brake to keep from going too fast.. SLOWLY hit the gas pedal (such that it would take about 10 seconds from off to full throttle) and see if there is a point where the engine wants to die. RPMs in the 2000-3000 range the whole time would be good. If it still wants to die, there is more going on than accelerator pump. Might be floats way out of adjustment, fuel delivery problems, problems related to the aux vents, something like that.

[Thomas Hawley]

yes the spring is there.

it gives it shot, but the size seems to not be enough gas.

i'll check what you said tonight.
i'm pretty sure the floats are at the right height.
5mm closed and 13 mm open.


thanks for the help! i'll let ya know
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74 Super- 1776 single drla 40 blow through @ 15psi ! with disc, gauges, wheels, suspension, blah blah.

but needs paint

[Thomas Hawley]

i'll also make a video tonight of the inside of the carb while pushing the throttle, so you guys can see anything that i might be missing.
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74 Super- 1776 single drla 40 blow through @ 15psi ! with disc, gauges, wheels, suspension, blah blah.

but needs paint

[mharney]

You can test the volume of the shot too.. coming out of the pump jets, you need a container that you can shoot it into and then measure. I don't remember what the amount is, but I am sure someone here knows.

The accelerator pump circuit has a few critical parts.

One is the ball and ram under the screw in the top of the body. Those have to be there, and have to seal properly.. Another is the o-rings and springs that are on the acclerator pump jet assembly. Without those you might get leaks that cause the fuel NOT to come out the jet. The last is that your pump check valve in the bottom of the bowl needs to be o-ringed and work properly. With all these things in check, it should be a pretty good shot of fuel.

[Thomas Hawley]

ok i dont know what you mean by the ball and ram in the top of the carb.

but i will do everything else.

thanks!!
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74 Super- 1776 single drla 40 blow through @ 15psi ! with disc, gauges, wheels, suspension, blah blah.

but needs paint

[mharney]

Look at a Dellorto diagram. when you pull the cover on a DRLA, there are two brass screws toward the edge of the carb just inside of where the acclerator pump jets are. Unscrew those and look down in there.. there should be brass rectangular rods that go in there, and under those are little steel balls. Those have to be there and working. If they are not there, or not sealing, the fuel will drop down there and you'll push mostly air through the jets. You'd probably have to pull it off and tip it over to check for the parts.. they should just fall right out.

[Thomas Hawley]

yea those are there.


when i had the top of the carb off and moved the throttle it
give a shot through the squirters at the top, but also it seemed to shoot
fuel within the bowl of the carb, like it was being blocked by something and shooting it against the floats from the bottom of them.

is this normal?
i have a pic of where i am talking about.

thanks again guys, will get that pic up asap.
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74 Super- 1776 single drla 40 blow through @ 15psi ! with disc, gauges, wheels, suspension, blah blah.

but needs paint

[Billyisgr8]

My 1584 singleport pull trough turbo started at 165 main, and it ran just like you are describing. We'll I'm at a 215 main now and every time I upped the main, the car became smoother and faster every trip down the track. Try a richer main.

Having spare jets around would be helpful.

Kevin

[Thomas Hawley]

hmm interesting.

i dont think it would have to do with the main, since i can hold the throttle partially open and will slowly accellarate all the way to 5k rpm.

but maybe? i dunno.

i'll try and get some new jets asap.

thats the inside of the carb.
see in the bowl there is a
.
...
the two in the middle are brass, and the one at the top. by itself.
squirts gas out into the bowl when i give it throttle with the carb top off.

is that normal?

thanks guys
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74 Super- 1776 single drla 40 blow through @ 15psi ! with disc, gauges, wheels, suspension, blah blah.

but needs paint

[Paul Wilson]