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JamesE

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About JamesE

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  • Location
    St. Louis, MO
  • Cars
    '73 Datsun 510
  • Interests
    Time Attack Racing

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  1. Maybe so where you are from, but this car has been in the Midwest all its life and is not rust free. I'll open the filter. It is new and has less than 20 miles on it, but they are cheap enough.
  2. It was an easy fix, but then all of a sudden i'm back to square one. I'll explain. I popped the hood last night and immediately spotted that the electric primary choke/butterfly control was disconnected. Oops. i connected it and took it for a short drive and it was running perfect! With my confidence up I decided to go for a longer drive. After a few miles it started showing some of the old stumble symptoms. Then I went to the gas station and topped of the tank with 5 gallons, and maybe I'm imagining it but it seemed to get even worse still! The previous owner told me he dropped and cleaned the tank but I'm suspicious now that my fuel is dirty and clogging the accelerator pump. But shouldn't my new fuel filter be cleaning the fuel sufficiently?
  3. Thanks for the compliment Banzai but with the Weber I would miss that baby blue intake when I open the hood. I am so close I can taste it! I solved the stumble last night but somehow introduced a new problem. The stumble was solved by blasting carb cleaner through the accelerator pump chamber and accelerator pump nozzle chamber, as well as the nozzle itself. Mike and Rays you were right all along! I didn’t do it sooner because the same was done when the carb was rebuilt not long ago. But the nozzle ID is so fine I suppose it is easily clogged up. I was so excited to drive it to work this morning but just a mile from home I observed a flutter at high load and low rpm. It also feels down on power in general. But the stumble at WOT is completely gone. Something is not right. I’ll look over the linkages and vacuum hoses tonight.
  4. I removed the carb last night and disassembled it a bit. The accelerator pump chamber and nozzle chamber are both very clean. I checked the check balls and they are both 5/32" as specified. I still believe the check ball in the accelerator pump chamber to not making a good seal; but what could be done to improve it? I considered increasing the check ball size to 3/16". I also saw that some carburetors use nylon check balls. I'm wondering if a nylon ball would make a better seal.
  5. JamesE

    Need CARB help!

    Looks a lot like my Hitachi 328. I should know, I've been staring at the damn thing for weeks trying to get it to work properly. You should be able to identify it with the diagrams found here... http://www.carpartsmanual.com/datsun510/Datsun510Index/Engine/Carburetor/tabid/528/Default.aspx
  6. Mike, I think you said something that makes a lot of sense. As I have explained this problem is intermittent. For instance if I go WOT the engine will stumble, but a few seconds later after it idles down I try WOT again and it does not stumble. It could be that in this case the fuel has not leaked out of the accelerator pump chamber yet. If I understand you correctly the accel pump chamber is only primed when the accel plunger rises (throttle backed off). Therefore if there is 30 seconds or so between heavy throttle instances and the BB is not sealing off the chamber perfectly, the intake could be getting incomplete shots. Am I understanding that right? Thanks for sticking with this. I'm looking forward to my next evening in the garage so I can look into this.
  7. I experimented a little more yesterday. I tried disabling the accelerator pump and (no surprise) the condition got worse. I completely agree that the root cause is a lean condition. So is it too little fuel or too much air? In this video below you can see that the accelerator pump is working, and working as well as I would expect. But it seems to me that the air beats the fuel to the chamber. Once the fuel catches up it runs fine. I'm not sure what else I can do to improve the rate at which the accelerator pump delivers fuel. It seems to be working as designed. As a last resort is there any carburetor specialists companies I could sent this to and have them take a look at it?
  8. Is the DCH328 the correct carb for an '73 L16? This is the carb that came with the car and the car is mostly stock so I don't really have any reason to believe it isn't the original carb. My next thought is to check the accelerator pump linkage. I'm going to try to adjust it to work the pump sooner in the throttle travel. The rod (marked as #4 LINK) may have been bent or straitened during dis-assembly.
  9. Thanks for the reply Ray. Good to know I'm working with a DCH328. I'll update the thread. The exploded diagram is very helpful! I'm really surprised that you think the pump shot is weak. I have no point of reference but it looks strong to me. The brass outlet has a very small ID. It is much much smaller than I expected considering the OD of the brass nozzle. The output meets my expectation considering how small the ID is. What should I expect from a proper shot? Faster stream? Thicker stream? Slightly vaporized?
  10. Sorry for the hiatus. I finally had an opportunity to try the most recent suggestions. First things first, my carb does not look the same as the one that Ray posted. He's a photo of mine. It is slightly different. Notice the orientation of the accelerator pump, and the primary jet is different. Is this not a DCH340? My car is Canadian if that is any indication. Second I removed and inspected the accelerator pump action with current and NEW accelerator pump I purchased. Both old and new pump appear to work well to me, but I'm a carb newbie so interested to hear opinions on this. You need to watch the video in HD quality to see the fuel stream. Skip to the 1:00 mark for the best view. Next I inspected the accerator pump and nozzle cavity (sprayer). Everything looked clean. The only surprise was that in the sprayer cavity there was no brass weight as Ray described. The contents are as follows below except the ball bearing. Am I missing something or is this a different design carb? Ball Bearing NOT Shown I put it all back together with the new accelerator pump, warmed it up, and took it for a drive. Behavior is the same. As always the hesitation is intermitent. Hammer the gas and it stumbles as it revs up.. then idle down, and hammer it again but the second time no stumble. Could it be that it doesn't stumble the second time because the accelerator pump isn't shooting a full shot the second time? The consensus seems to be that the engine is not getting enough fuel but I'm curious if it could be the opposite and it is choking on too much fuel. Mike had also suggested checking the timing, idle, and idle mixture. I did all of these things before I started this thread. I have not checked the valve clearance yet. Thanks for the continued support. I'm hoping to get it running great in time for spring!
  11. The new accelerator pump will not be in until tomorrow, so I'll try these suggestions tomorrow. Thanks!
  12. Gotcha. So what is the failure point of the accelerator pump typically? Degraded plunger? My accel pump is virtually new having been included with the rebuild kit, but I don't mind throwing $20 at a different one to see if the behavior changes. Thanks again Mike and all.
  13. I believe this confirms it. Rebuild kit did not come with a new accelerator pump return spring... https://buy.walkerproducts.com/carburetor/components/hitachi/hitachi-15474b-carburetor-components.html Where could I get a return spring?
  14. I was wrong about the above accelerator pump being a "totally different design". I forgot that there are two springs in the system. I read just moments ago at the 510realm a user commented that his return spring was too weak following a rebuilt and this caused intermitent problems. Perhaps this is what I am experiencing because I did the same; replace the accel pump with rebuild but I believe the return spring was reused.
  15. Any luck Len? Your problem sounds quite similar to mine... http://community.ratsun.net/topic/51630-l16-stumbles-at-wot-with-hitachi-dch340-with-video-suggestions-please/
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