Jamasaurusrex Posted April 19, 2012 Share Posted April 19, 2012 Had the car for a week now.. 73 240z Electric fuel pump, l28 with mild build and triple carbs, NOW.. Ive been noticing it hesitating, choking in a way, mainly when im taking a corner quickly and getting on it. Few hours ago, I was launching the car at 2k rpm, it spun a little and BAM car literally fell on its face.. it like stalled out, (i was flat out on the accelerator pedal) and after it fell on its face, the rpm came back and all was good. I need help on sourcing this problem.. it seems like a fuel problem but idk, I had a little over a quarter of gas in the tank. Help =( Quote Link to comment Share on other sites More sharing options...
luseboy Posted April 19, 2012 Share Posted April 19, 2012 Problem could simply be not enough gas in the tank. Have you checked the fuel filters/lines, air filters, spark plugs, spark plug wires, distributor, and fuel pump to ensure they are working properly? Any noticeable smoke/abnormal noises/smells when the car falls on its face? If you take it down to the basics, a car needs fuel, air, and spark to run. First check how many of those you're properly getting. The problem may lie elsewhere too, but you'll have to figure that one out. Noticed your from the bay area, what part are you from? I live in marin. Quote Link to comment Share on other sites More sharing options...
Pharaohabq Posted April 19, 2012 Share Posted April 19, 2012 (edited) Sounds like a dirty fuel filter to me, Try swapping that out first and see what it does. it's pretty common for these cars to get some crud in the tank, especially if they sat a while. You start driving, the gas scours some loose, it gets sucked into the fuel lines and clogs the filter. perfomance is reduced anytime you're trying to pull more gas through (such as steeping on the pedal)but it's able to pull enough through to idle and even drive slowly. Start with the filter, then if that fixes it for now, then you may need to drop your tank and get it boiled (any radiator shop should be able to do that) or just buy a bunch of extra filters and replace them every so often. *edit* I supposed it cold also be a hole in your pickup line before the pump allowing it to suck in air bubbles, if you have the same issue AFTER changing the filter, then I'd check that too. Edited April 19, 2012 by Pharaohabq Quote Link to comment Share on other sites More sharing options...
Jamasaurusrex Posted April 19, 2012 Author Share Posted April 19, 2012 Ive checked the spark plugs/wires/distributors and they were fine, i dont fill up over Half a tank because of a leak lol, so eventually im going to have to go over those fuel lines. The previous owner had it for 6 years and put on 15k miles on it so it has been sitting forawhile lol. But ill change the filter first thanks guys. Also @luseboy im from hayward. Quote Link to comment Share on other sites More sharing options...
Lazeum Posted April 20, 2012 Share Posted April 20, 2012 (edited) It could also be the carbs out of tune. How does it feel when you're gentle with the throttle, car reaction at WOT, off idle, during cruising, etc? The idle circuit, progression circuit, accelerator pump, needle valve & float not being ok in your carbs could be one of the reasons. If you can cruise in 4th or 5th gear & accelerate around 4000rpm on highway, your fuel supply is probably ok. In addition to that, if your issues exist in 2nd gear, fuel supply is most likely not your issue. However, if you just got the car, it is always a good idea to go over your fuel lines & fuel filters to replace them. It is a cheap insurance. I would also suggest to fluch your gas tank since it is very easy to do on s30, it would help to get rid of any crud you may have. I usually filter the gas and use it to fill the tank again to be sure I get rid of any foreign material in the tank. Edited April 20, 2012 by Lazeum Quote Link to comment Share on other sites More sharing options...
Racer Z Posted April 20, 2012 Share Posted April 20, 2012 (edited) The 73 had both a mechanical and electric fuel pump from the factory. It does not seem logical, but that's what they did. If the mechanical has failed it could be restricting the fuel flow. You don't need both pumps, so you could bypass the mechanical. But, you will need to add a fuel pressure regulator when you do remove the mechanical and set it to about 4 pounds. You better get that fuel leak fixed before you have a Car-B-Que. The 73 has (had when stock) a charcoal canister and some other EPA forced stuff. If the canister is clogged with crud or full of gas the engine won't run well. There are vacuum and other related lines as part of this EPA system. If any of these lines are damaged it will effect how the car runs. Yes, you can ditch most of it and plug the open ports and it will still run, probably better than ever. edit: Check the legalities in your area before removing this stuff. In some areas it might be illegal. If you have not already found it, there is a return fuel line from the carbs to the tank. There are 5 or more lines that connect to the fuel tank. Your leak is probably one of these lines that rotted away. You need to remove the tank to get to them. Yes, it's a pain in the A$. You will find a drain plug so you can empty the tank before you remove it. Be careful not to damage the main fill tube, it's $100 or better to buy a new one. Edited April 20, 2012 by Racer Z Quote Link to comment Share on other sites More sharing options...
Jamasaurusrex Posted April 20, 2012 Author Share Posted April 20, 2012 (edited) It could also be the carbs out of tune. How does it feel when you're gentle with the throttle, car reaction at WOT, off idle, during cruising, etc? The idle circuit, progression circuit, accelerator pump, needle valve & float not being ok in your carbs could be one of the reasons. If you can cruise in 4th or 5th gear & accelerate around 4000rpm on highway, your fuel supply is probably ok. In addition to that, if your issues exist in 2nd gear, fuel supply is most likely not your issue. However, if you just got the car, it is always a good idea to go over your fuel lines & fuel filters to replace them. It is a cheap insurance. I would also suggest to fluch your gas tank since it is very easy to do on s30, it would help to get rid of any crud you may have. I usually filter the gas and use it to fill the tank again to be sure I get rid of any foreign material in the tank. Its really difficult to be gentle with the throttle 1st and 2nd gear. The car will stutter at WOT sometimes in the lower rpms, off idle it feels like its gunna die around 2k, but it idles fine at 1k. Around 4k rpms in 4th and 5th it moves pretty smooth though. So this would equate to the carbs being out of sync? Edited April 20, 2012 by Jamasaurusrex Quote Link to comment Share on other sites More sharing options...
Lazeum Posted April 20, 2012 Share Posted April 20, 2012 (edited) Sync for Weber are for idle & light cruising only. Synchronisation is about controlling throttle plate position while they're almost closed. If engine is quite responsive with no loss of power in 4th & 5th, I believe fuel supply is ok. Your issue is most likely on idle jets. It's confusing but idle jets control the progression from idle & main circuit, not idle. It could also be the progression ports on your carbs. If they are the new DCOE style (DCOE 151), other members have reported erratic results without drilling an extra hole. Main circuit can also be not very well tuned but it won't allow you to have a smooth operating engine but once you start to bring them back to where they should be, you'd clearly feel the difference. Go in the FAQ area, there's a thread about Weber, you'll learn a lot. Edited April 21, 2012 by Lazeum Quote Link to comment Share on other sites More sharing options...
Racer Z Posted April 20, 2012 Share Posted April 20, 2012 Carb sync (out of sync) is most noticeable at an idle, as the RPM pick up things change and mask the bad sync. A full tune-up includes carb sync as well as points gap and ignition timing. How many of the previous suggestions have explored? They're all good suggestions. Seeing as how you just bought the car, don't assume anything is good and can be ignored, no matter what the seller may have said. To chime in with a previously noted suggestion, my 73 acted like it ran out of gas once. I knew it was getting low so I dumped 5 gallons in it and it continued to act like it was running out of gas. It seemed OK in the straights and starved on the curves. (this is my track car and I was on a track) We later isolated the problem to a cracked pick-up in the tank. The pick-up cannot be changed so we made our own pick-up. The fuel starvation issue went away. Is this the problem with your car? I can't say for sure. But you can test it by using an alternative fuel supply. Don't drive during this test but if the symptoms change or don't change you will know which way to look. Ignition problems can cause strange symptoms. Coils and condensers can overheat and fail at high RPM's. (been there, done that) Points can float at higher RPM's. This does not mean the points are bad. The distributor bearings can fail and let the points open whenever as the shaft bounces around. (been there, done that) If somebody put the wrong points cam in the car you will have high RPM issues. (been there, done that) Timing advance (mechanical and vacuum) can go bad. I just went through that on my Ford. The vacuum advance failed and I had to get towed home. Turns out the mechanical advance needed to be serviced and the points were ready to fail. Truck runs better than ever now that I sorted that out. A loose wire can cause tremendous problems and be a mofo to find. (been there, done that) I don't want to overwhelm you with possibilities. But for us to help you we need to know what you checked and what you found. Start with the easy, simple, and inexpensive things first. Quote Link to comment Share on other sites More sharing options...
Lazeum Posted April 21, 2012 Share Posted April 21, 2012 I agree with Racer Z's comments. That's the way to go! Quote Link to comment Share on other sites More sharing options...
Jamasaurusrex Posted April 22, 2012 Author Share Posted April 22, 2012 (edited) alright after some time, the carbs are dcoe 152 45's. there are 2 hoses that start at the gas tank that i need to replace forsure. other than that not sure. car feels better, pulls smooth after 3k rpm in all the gears. but first gear before 3k rpm when i go WOT is when it chokes. sometimes. Edited April 22, 2012 by Jamasaurusrex Quote Link to comment Share on other sites More sharing options...
Racer Z Posted April 23, 2012 Share Posted April 23, 2012 45's are big carbs and don't do well on the street. 40's are a better choice for street driving. The 45's will cause it to stumble at low RPM because there is not enough air flow through the big venturi's . Those 45's are worth more than a set of 40's. You could possibly sell them, buy some 40's and have a few extra dollars to spend on the car. No, I'm not in the market for a set of DCOE 45's. Quote Link to comment Share on other sites More sharing options...
Tony D Posted April 23, 2012 Share Posted April 23, 2012 Its really difficult to be gentle with the throttle 1st and 2nd gear. The car will stutter at WOT sometimes in the lower rpms, off idle it feels like its gunna die around 2k, but it idles fine at 1k. Around 4k rpms in 4th and 5th it moves pretty smooth though. So this would equate to the carbs being out of sync? This sounds like an issue transitioning to the mains circuit. You may need a different accelerator pump jet, a bigger idle jet, bigger main jet... When you put the car in first gear and just crack the throttle and feather the clutch to get the car moving, does it stumble at 2k? That test takes accel pump out of the picture. If you are idling fine, and can smoothly accelerate at 4000 in 4 th or 5 th, then likely your main is the right size. My bet is something clogged in the accel system, or an idle jet not large enough to feed the transition ports from 2000 to when the main jet starts tipping in at 3000. Quote Link to comment Share on other sites More sharing options...
Tony D Posted April 23, 2012 Share Posted April 23, 2012 My 46 DCOEs ran fine on a bone stock L28, tuned properly they are most definitely "not" too big! You say "chokes" below 3k when you go WOT. Check your acceleration pump stroke, delivery volume, and shot duration. In Japan now they are selling accel pump nozzles with multiple spray holes to better mix the accel shot than the old single spray setup. Also remember, if you don't have a lightened flywheel, this will make a big "bog" off the line. The airspeed needs to catch up with the engine... At low Roma if you are over-choked (too big) you will have this low speed bog as well. What chokes are in the bores? 30, 32, 34, 36, 40??? It isn't a Smsll Blovk Chevy, BTW. Going WOT before 3000 in anything but 1st gear is really poor driving technique. Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted April 23, 2012 Share Posted April 23, 2012 (edited) Maybe the positive terminal of the battery is momentarily contacting the body during launches or a corner. Edited April 23, 2012 by HowlerMonkey Quote Link to comment Share on other sites More sharing options...
GOTHALOSISM Posted April 23, 2012 Share Posted April 23, 2012 ^^ thats what I was going to say, make sure your battery is tied down correctly. Quote Link to comment Share on other sites More sharing options...
Leon Posted April 23, 2012 Share Posted April 23, 2012 You should be able to floor it in high gear, at low rpm (by low I mean loooow, i.e. 1200rpm) and have the car lug but not bog. If your main is too lean, the engine will die. There is plenty of air-flow to get enough fuel, your carbs are just not set up right. I 'll also second Tony's statement about the pump shot, you're either too lean or too rich. I suggest installing a wideband O2 sensor and gauge so you can understand what's truly going on. To EVERYONE using Weber DCOE's, join the Sidedraft Central Yahoo Group and at the very least read Keith Franck's "White Paper" on tuning Weber sidedrafts. Keith is a retired LBNL engineer who has been reverse-engineering the Weber DCOE for the last decade or so. Read the files, links and threads to catch yourself up. He's developed new idle-jets and e-tubes that perform far better than Weber's own. There is no good reason for a triple-Weber'd Z to not have EFI-like tractability with the performance to boot. Quote Link to comment Share on other sites More sharing options...
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