Weber 38/38 DGAS question

Alright guys I'v got the I6 258, 4.0 high head output, upgraded cam and bored .30 over. Nothing special just thought I would fill ya in. My Weber 38/38 has been running OK but far from great. With constant tinkering I can get it to perform. Until last week! Now it starts and Idles just fine but when I get on the throttle it starts spitting and spurting like I'm either flooding the bowel or starving it out. I DO NOT have a pressure regulator on it and I did just try the easy fix of a new fuel filter. And well it runs worse... Any help would be appreciated so I just don't end up throwing money on a new fuel pump or larger jets or a pressure regulator when that's not the problem. Also I'm going to post some pics when I get a chance as to find out if I actually adjusting the correct screws. My guess from reading the manual and Redline's web site is I need the regulator and larger jets...... THANKS IN ADVANCE RJ

 

What ignition system you running by chance?

 

An 81 CJ digital ignition box with 8 mm wires, new solenoid and newer distributor. I'm drawing blanks on the brands.

 

Factory equipment for an '81 CJ is Motorcraft Duraspark.

If it cruises ok, then you don't need larger jets. What do your spark plugs look like after a highway cruise? That will give you an idea of the overall mixture (main jets).

If the carb responds poorly to a sudden change in throttle position, that means the low-vacuum enrichment (power system and accelerator pump) is not working. Unfortunately I have no idea how a Holley-Weber works. Each carb manufacturer has their own way of doing things, but the principles involved are fairly standard. If you have a link to a manual, I can take a look when I have a few minutes.

 

Here are some pictures of the plugs. Remember that I'm idling ok and under throttle is when it's cutting out. Also I checked my 1 and only vacuum and it's got vacuum to the advance. Also I put the timing light on it today and it seemed fine until I dropped it and broke the bulb nelson haha. Anyway this was an all of a sudden thing. Drove fine (a little rich maybe) then 100 yards out the parking lot when I got on it, it went to ****!!!

Plug 1

Plug 2-5 all basically looked like this

And plug 6

 

Ok, you need to get up to full operating temperature and go for a drive on the freeway. Then park and look at the plugs before you drive again. You want to sample the appearance at constant throttle.

Plug 1 is way way rich. Plug 6 looks rich. The others look kindof ok. That's strange because the end-most cylinders on an inline engine should run leanest of all. The wet threads are suspicous unless you have a leaky valve cover.

No documentation for the Weber? If it were mine, I'd lift the top off of the carburetor and look. But I'm not sure what that entails with a Weber.

 

I did lift as much as I could on the Weber before interrupting gaskets and to me it looks like I'm running rich and a bit wet. I will try and take it for a highway drive tomorrow but I honestly don't think I can get to 55 with the way it's running unless I take 60+ seconds to get up to speed, but I'll try...... Also the pictures of the plugs are after sitting for 24 hours with an hour of constant attempts at tuning the day before.
Here is the link to Redline's tuning guide http://www.redlineweber.com/html/Tech/38_dgas_tunning.htm
I don't if this will help but they don't seem to have a lot of info to help a guy out.

Thanks Timgr for the help. RJ

 

Mmm. Assuming it's the carburetor that is the problem, I would take the carb off and see how much I could easily disassemble. But I have a fair amount of experience with carburetors, and have successfully dis- and reassembled a lot of them. I might buy the rebuild kit before I start, just to have the extra parts on hand.

Just about everywhere you look says you should be running a fuel pressure regulator at about 2.5 psi. That's something you might consider.

Here is a exploded diagram of the carburetor - http://www.carburetion.com/diags/38DGASDiaginfo.asp - looks pretty conventional, except for the separation of the barrels into primary and secondary.

There are several YouTube videos that show you how to take one of these apart and rebuild it. Sorry, I don't have time to watch videos. But you could watch them and maybe that will give you enough confidence to look inside this carburetor.

Good luck!

 

I have one of those carbs on my 85 CJ7 with a stock 258 with to GM HEI ignition. The carb is simple to rebuild and easy to change jets while the carb is on the engine. However, it is the most finicky carb I have ever tinkered with. All my research indicates a fuel pressure regulator is required unless you use a low-pressure electric fuel pump. I am currently using an adjustable fuel pump regulator from Holley and installed a schrader valve so I could easily attach a fuel pressure gauge for testing.

That being said, If I had it to do over again, I would go with the Ford conversion. There is a guy on ebay that builds and tunes them especially for Jeeps.

I just noticed a Holley pressure regulator is for sale by a member.

http://www.earlycj5.net/forums/showthread.php?110304-Holley-12-804-Fuel-Pressure-Regulator-1-4-psi

 

Well unfortunately I've been working long hours and out of town the last week and a half. But I did pick up a fuel pressure regulator and hopefully by the end of the weekend I will have good news thanks for the help guys!

 

That didn't work

 

Well I got a little time to wrench tonight. Unfortunately my old girl left me stranded in the middle of a busy road with 5pm traffic. I got the fuel pressure regulator installed and set to 2.5 psi. She ran okay as long as I was under a 1/4 throttle. After that a whole lot of miss firing and back firing. Then let's just say it did nothing. I'm guessing my fuel pump went out on top of my carb problems. After she came to a dead stop the fuel filter was only half full and no matter how hard I cranked it over I couldn't get it to fire. Beside putting a pressure gauge in, is there anyway to test that fuel pump????

 

You can run from a gas can bungie-corded on the cowl, and a siphon/gravity feed to the fuel filter. Been done many times. Take one hood hinge loose and block up the back of the hood to clear the hose.

 

Well I'm running out of ideas guys. My fuel pump did basically go out I'm guessing. The other day when I took it out to try and get it up to temp (to recheck the plugs) after about 10 min she died and would not restart. i did notice that the fuel filter was basically empty. After a tow from my truck home and a days rest it fired right up fuel filter filled back up so I started driving around the block and it did it again. so new fuel pump ordered and I'm waiting. I also did the gas can trick to check to see if the carb would act up and it did. So I torn it off and step by step took it apart while looking for damage, torn gaskets, etc. To my limited carb rebuilding trained eyes I didn't see anything wrong.... Soooo here's where I need your help.... i'm going to post a pic heavy thread here in a min if you guys could take look and pass anything on you see!!!!! Thanks in advance!!!!!!

sincerely
damn it runing out of warm weather RJ

 

Maybe a little sloppy, but not broken. That's the booster venturi that spans the main venturi. The side you are pointing at doesn't do anything more than support the BV across the span. BVs are swappable, but don't take them out. Don't take the screws in the butterflies out either.

Looks ok - looks pretty darn clean.

I'd get a rebuild kit and put it together carefully and by the instructions, with new gaskets and other soft parts. As you disassemble, regard the exploded diagram that comes with the carb kit, and make sure you have any little pieces like check balls and weights. Take it apart over a tub so if anything falls out, you'll catch it. I'd get a couple of cans of good spray carb cleaner and clean everything I could. Spray down into the little passages with the red wand that comes with the carb cleaner. (I like Berryman's carb cleaner, but I bought a couple of cans of Advanced Auto generic on sale, and it seems fine).

 

agree. Wear glasses. Berryman's in the eyes burns like no other, garden hose water feels good... Oh, damhik... Younger days, looking in carb of motorcycle, spraying....

 

Very good looking CJ5 for sale!!!! Just doesn't run 3k miles on a full rebuild.
Okay new fuel pump installed. New fuel filter installed. New fuel pressure regulator installed. Carburetor rebuild kit done with no extra or missing parts. But hey it did start and run pretty clean for 2 min and now it won't do anything... I'm getting fuel it just wont turn over anymore. FOR THE LOVE OF JEEP beat me on the head with a bat. thanks for the opportunity to vent.

 

Step back, relax. My neighbor put a Weber on his '83 Jeep to replace his BBD. His son tweaked it a bit to get it to run better and yes, a pressure regulator was needed.
I would guess that most of us have had a moment of frustration working on a Jeep. In my case it was usually someting simple I overlooked and it was fairly obvious the next day.

 

That's what I'm doing. I put the battery on the charger and will try again after work. Can anyone tell me what size jets they're running???