Eric Garside Posted July 12, 2011 Report Share Posted July 12, 2011 1978 620 pickup with L18 and weber 32/36. My truck was running great up until yesterday morning on my way to work. I commute 35 miles to work and have been making this trip daily in the Datsun for about four months now. The truck ran fine when I left my house yesterday morning, I stopped at my usual gas station and fueled up with 87 octane (same as I always run). When I pulled off the interstate and pressed in the clutch at the first stop light the truck died, it started back up as soon as I turned the key and without hesitation but if I didn’t feather the throttle it wouldn’t stay running. Last night I checked a few things to try and figure it out. I pulled the choke out a little to keep it running and checked the timing, it’s the same as its always been. Its getting spark to all cylinders, the plugs aren’t fouled, all necessary vacuum lines are there and attached, and the carb appears to functioning properly (linkage and fuel wise). The only recent changes made to the truck were a stereo installation on the 4th (truck ran fine all last week) and fueling up yesterday morning. The fuel filter looks to be in pretty good shape but I think this has something to do with fuel delivery… The truck runs decent at speed with only mild hesitation if you push the throttle to the floor. I think it might be the carb or bad gas?...?... Any suggestions or help would be greatly appreciated. Thanks, Eric Quote Link to comment
dryheat Posted July 12, 2011 Report Share Posted July 12, 2011 Had the same thing happen on my old wagon. Remove the air screw on the side nearest the valve cover and flush it out with some parts/carb cleaner ... worked great for me. Quote Link to comment
Eric Garside Posted July 12, 2011 Author Report Share Posted July 12, 2011 That's sounds strange, did you ever figure out what the cause was? Anyone else have any ideas? Quote Link to comment
banzai510(hainz) Posted July 12, 2011 Report Share Posted July 12, 2011 idle jet may be plugged. thats the usual simtom of a plugged idle jet but truck runs fine Quote Link to comment
Eric Garside Posted July 12, 2011 Author Report Share Posted July 12, 2011 I will give this a try on my lunch break and let you know the results. Quote Link to comment
Eric Garside Posted July 12, 2011 Author Report Share Posted July 12, 2011 I pulled the idle air jet out and sprayed copious amounts of carb clean trough the top hole and the bottom... Idle slightly improved but not fixed. The truck does not idle down when shifting gears (it will stay up at 3500-ish after I push in the clutch). Any other ideas?... Do I need to fully rebuild my carb?? Thanks, Eric Quote Link to comment
banzai510(hainz) Posted July 12, 2011 Report Share Posted July 12, 2011 if idle is UP? ck the choke 12volt wire didnt fall off and choke plate is still closed. If dont idle but works and drivers above then idle jet id plugged. so now you say you have 2 different proplems. Quote Link to comment
Eric Garside Posted July 12, 2011 Author Report Share Posted July 12, 2011 if idle is UP? ck the choke 12volt wire didnt fall off and choke plate is still closed. If dont idle but works and drivers above then idle jet id plugged. so now you say you have 2 different proplems. Did you start drinking already ;) lol I have a manual choke and it is open. Im saying that it wont idle properly and after I sprayed the idle jet out with carb clean the engine doesnt idle down immediatly after the clutch is pushed in. Its like the engine hesitates to slow down after the load is taken off... Hopefully that makes sense Quote Link to comment
ggzilla Posted July 12, 2011 Report Share Posted July 12, 2011 The symptoms in your original post match dirt/water in the carburetor. When you cleaned out the one air jet, it got better. Now clean out the rest. Remove the carb top and clean out both air jets and both main jets and the idle port. I use a turkey baster to remove the cruddy gas from the bowl. Quote Link to comment
Eric Garside Posted July 12, 2011 Author Report Share Posted July 12, 2011 Thats what I was originally thinking.... I just drove the 35 miles home and by the time I got here the engine/carb was unresponsive low-mid throttle and only seemed to want to run from mid-hi.... Im headed outside right now to tear into the carb, I will let you guys know what I find. Quote Link to comment
Eric Garside Posted July 13, 2011 Author Report Share Posted July 13, 2011 Carb fully dismantled and cleaned, new fuel filter, iso-heat in the tank, and still no improvement.... What are the odds of a mechanical fuel pump going out? It sputters when I feather the throttle and will only run if I hold it at 3/4 throttle or further... It seems like its getting too much fuel or not enough and I dont think its too much because I cant smell gas or see anything like that. Need help fast, gotta drive this beast to work in the morning. Thanks, Eric Quote Link to comment
ggzilla Posted July 13, 2011 Report Share Posted July 13, 2011 What are the odds of a mechanical fuel pump going out? Test it, it takes only a few minutes. Caution: don't let the gasoline spill! 1. Volume test: disconnect line from carb, put in quart/liter container. Start engine and run at 1,000 rpm for one minute (use a stopwatch). 450 cc or more should be pumped If this pumps less than 450 ccs, try without the fuel filter. 2. Pressure test: Use a tee line to tap your vacuum/pressure gauge into the fuel line near the carb. Pressure with engine running should be between 3.0 and 3.8 is normal at all engine speeds. Quote Link to comment
Eric Garside Posted July 13, 2011 Author Report Share Posted July 13, 2011 Tried that... I got roughly a pint glass in a minute, which to me seemed like more than enough fuel. Im thinking it doesnt have to do with fuel delivery but maybe something in the carb? could the diaphragm be responsible? I checked the spark again and all wires have a nice bright white spark... I feel like im running out of options here. Anymore suggestions?? Quote Link to comment
ggzilla Posted July 13, 2011 Report Share Posted July 13, 2011 if I didn’t feather the throttle it wouldn’t stay running I pulled the choke out a little to keep it running If it idles OK with the choke on, it suggests it is a fuel problem. Air leak probably because the choke richens it back up. Maybe a hose fell off, or cracked? The hesitation on accelleration also indicates it is lean. But if you have points distributor, I'd check the dwell, cause that's fast and easy. Quote Link to comment
Eric Garside Posted July 13, 2011 Author Report Share Posted July 13, 2011 Quote if I didn’t feather the throttle it wouldn’t stay running Quote I pulled the choke out a little to keep it running If it idles OK with the choke on, it suggests it is a fuel problem. Air leak probably because the choke richens it back up. Maybe a hose fell off, or cracked? The hesitation on accelleration also indicates it is lean. But if you have points distributor, I'd check the dwell, cause that's fast and easy. These were symptoms at first. Now it has gotten worse and I cant even keep it running below ~3800 rpm... I agree it feels like a fuel problem but I cant seem to figure out what that is or where to look. I only have one hose going to the carb and that is the vacuum advance and I think I have an electronic dizzy. I will post pictures as soon as I can. Thanks again for all the help. Quote Link to comment
Eric Garside Posted July 13, 2011 Author Report Share Posted July 13, 2011 Pictures as promised...... The float bowl doesnt have very much fuel in it and the floats have some weird corrosion looking marks on them. Quote Link to comment
HRH Posted July 13, 2011 Report Share Posted July 13, 2011 Hey, someone else from the Inland Northwest! I work at Post Falls NAPA if you need any help. Live in Spokane though. How does your filter look? Do you have a clear one in between the pump and the carb? That would help to figure out if the fuel pump is throwing gasket material towards it. You'd probably notice this in the carb also. I'd say it's likely some little piece of crap is still stuck in your jets. You got both idles out and cleaned, right? Did it spray through all three holes on the jets? Quote Link to comment
Eric Garside Posted July 13, 2011 Author Report Share Posted July 13, 2011 Ill have to stop by and say hello sometime. I live in CDA and work in downtown spokane. I am in the process of rebuilding the whole carb right now. I took it apart and cleaned it yesterday but it didnt help (I sprayed any and every hole I could find). I think the little thing in between the floats with the spring on it was the culprit... I hope anyway because the little rubber diaphragm under the 3 screws was pretty tore up. What is this part and its function(s)? Thanks!! P.S. The photobucket app for droid I just downloaded is epic for uploading pictures and posting them to the site, works extremely fast!!! Quote Link to comment
ggzilla Posted July 13, 2011 Report Share Posted July 13, 2011 The thing in between the floats is the power valve plunger. Is is operated by vacuum, so if it's broke, you have an air leak. Quote Link to comment
Eric Garside Posted July 13, 2011 Author Report Share Posted July 13, 2011 Sweet, hopefully I found the problem. I did create another problem though, I broke a piece of the float pin holder... Anyone know how well JB Weld will hold up in this environment? Quote Link to comment
ggzilla Posted July 14, 2011 Report Share Posted July 14, 2011 JBWeld might work OK. I use it in my Hitachi carburetor to hold the air cleaner stud that stripped out. Quote Link to comment
mike Posted July 14, 2011 Report Share Posted July 14, 2011 Hey man, I just saw this... Outside the fuel bowl JB weld would work fine, but if its constantly exposed to gas it gets soft and wont work. I should have an extra top piece to a weber (I dont remember if that is the one with the oval top or the standard square top... Is the aircleaner base cut to fit around it?) Also the floats are good unless there is scale (shouldnt be, they were all clean, just stained). Do you know of anybody in town that sells a complete weber kit? Lighthouse wants $45 and their kit and it doesnt include the power valve... Quote Link to comment
Eric Garside Posted July 14, 2011 Author Report Share Posted July 14, 2011 If you had an extra top that would be awesome! I will post a picture of the carb. I bought one from motion this morning and it had the power valve, accelerator pump, and many other components... I paid 46 after tax. Hopefully the jb lasts until I can find a new top. It's the mount for the float pin so it shouldn't be submerged but it will come in contact with fuel. I pm'd you awhile back. Quote Link to comment
ggzilla Posted July 14, 2011 Report Share Posted July 14, 2011 Is yours a standard DGV carburetor? Quote Link to comment
Eric Garside Posted July 14, 2011 Author Report Share Posted July 14, 2011 How do u check? Quote Link to comment
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