Gigantor Posted July 11, 2011 Share Posted July 11, 2011 I have a 1970 240z with an L28 (N42 block/head with flattop pistons)and the original SU carbs. I also have added an electric fuel pump which is suppose to pump at around 5-6 psi. Ever since completing the swap I have been unable to drive any farther than 9-10 miles without having to pull over and stop. The engine begins to "bog" out almost as if it is not getting fuel. I can delay this by keeping at low rpm. However I'm sure it is not vapor lock because almost immediatly after stopping I can restart the car and go another 8-9 miles. I have the timing set to 10' from TDC (I plan on trying to retard it tomorrow, see if that makes a difference) , and the points at .0020. I have replaced the condensor, points, rotor, resistor, and coil. I am really fed up with this issue. Does anyone have any other ideas as to what else I should check? The car runs FLAWLESSLY for those first 9 miles. Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 11, 2011 Share Posted July 11, 2011 Fuel pressure does what when this happens? Quote Link to comment Share on other sites More sharing options...
ezzzzzzz Posted July 11, 2011 Share Posted July 11, 2011 Did you do the L28 conversion? Did the car ever run proper? Why did you add the electric pump? Where is the pump installed? How are you powering it? I run an electric pump (RX-7 4psi) at the stock rear location and use a regulator to drop it to 2.5psi at the fuel rail without any issues (as do a lot of other people). Like Tony pointed out, what about pressure at the fuel rail? You could install a gauge and run the engine at 2500 sitting in the driveway and monitor the pressure. Alternately, you could install an electric sensor in the fuel line and place an 'electric' gauge in the cabin to monitor. There's also a mechanical gauge that uses a pressure sensor connected by oil or glycol. To state the obvious, NEVER run fuel directly to a gauge installed in the cabin! Burning to death is one of my greatest fears. Quote Link to comment Share on other sites More sharing options...
Gigantor Posted July 11, 2011 Author Share Posted July 11, 2011 I did the swap, the car has never ran perfectly since then. I added the electric pump as sort of a "while im at it" thing, so for no real particular reason other than I could. It is being run at the stock rear location. I do not have a regulator, so could the 5-6 psi be to much for the carbs? I plan on installing a fuel pressure guage today to answer Tony D's question. Quote Link to comment Share on other sites More sharing options...
ezzzzzzz Posted July 11, 2011 Share Posted July 11, 2011 Assuming that it actually puts out 5-6 psi then it could cause flooding. You'd know that because there would be raw fuel pouring out of the air cleaner as the fuel bowls overfilled. We're to assume you swapped the SU's off the L24 and that engine ran fine? The pressure gauge will be telling. Quote Link to comment Share on other sites More sharing options...
ezzzzzzz Posted July 11, 2011 Share Posted July 11, 2011 You should check into the Northern Va Z club. Good and knowledgable folks. Quote Link to comment Share on other sites More sharing options...
beermanpete Posted July 12, 2011 Share Posted July 12, 2011 I think your first hunch is correct, it sounds like you have a fuel flow problem. Perhaps you have a fuel hose pinched or squeezed that is limiting the fuel flow. Check the fuel flow rate. It should be able to deliver at least 2 gallons per minute (per factory manual). Check directly at the fuel inlet to the carbs. Quote Link to comment Share on other sites More sharing options...
jasper Posted July 12, 2011 Share Posted July 12, 2011 Drive the car till the problem occurs. While running remove the fuel cap. If you hear a sucking rush of air into the tank, you have a tank venting problem. This was not unheard of with 60's vented fuel caps being replaced with emissions non vented fuel caps. Quote Link to comment Share on other sites More sharing options...
19762802+2 Posted July 12, 2011 Share Posted July 12, 2011 (edited) I was having this same issue, I put some SU's on my L28 with a 5-6 psi pump and after some trouble shooting I figured out that my pump was pushing too much PSI and filling up one carb more then the other or it would cause it to Overflow with fuel, while this happened the motor wouldn't rev and sounded like a Lawnmower. (This was also due to me cutting off the return line restrictor hole, which I thought wasn't necessary.) After I put on a 2.5-3 PSI electric pump and fixed the return line so that it held some back pressure, my car has been running fine after that. Edited July 12, 2011 by 19762802+2 Quote Link to comment Share on other sites More sharing options...
Gigantor Posted July 15, 2011 Author Share Posted July 15, 2011 Replaced the fuel pump with a cheap Autozone one putting out 2-3.5 psi, and it no longer "bogs" out. Thank you all for your help! Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 16, 2011 Share Posted July 16, 2011 Thing is, at the top end, you should have 5-7 psi! It's how the small needle and seat combination keeps the small SU Fuel level steady during extended high power pulls. If you can't pull 6500 in 2nd, then pull to 104mph in 3rd, shift to fourth all the way to redline your fuel pump isn't keeping up! Bucking, surging, outright detonation.... It's a terrible thing! Quote Link to comment Share on other sites More sharing options...
ozconnection Posted July 16, 2011 Share Posted July 16, 2011 Thing is, at the top end, you should have 5-7 psi! It's how the small needle and seat combination keeps the small SU Fuel level steady during extended high power pulls. If you can't pull 6500 in 2nd, then pull to 104mph in 3rd, shift to fourth all the way to redline your fuel pump isn't keeping up! Bucking, surging, outright detonation.... It's a terrible thing! Yeah, try this stunt and you'll be explaining yourself to Mr Policeman...... "it's a terrible thing!" LOL Chuck it on a dyno, gets the results without a world of hurt for you or your engine. Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 16, 2011 Share Posted July 16, 2011 You should have seen the 330 parts at the Odaiba Island Swap Meet...wow! My tests are done on 3rd Street merging with the CR60 Westbound every morning going to work...when in town! Third is pretty easy, and with the new tranny it was an "Ooops! 5200 in 4th? Better slow down, eh?" Quote Link to comment Share on other sites More sharing options...
ozconnection Posted July 18, 2011 Share Posted July 18, 2011 You should have seen the 330 parts at the Odaiba Island Swap Meet...wow! My tests are done on 3rd Street merging with the CR60 Westbound every morning going to work...when in town! Third is pretty easy, and with the new tranny it was an "Ooops! 5200 in 4th? Better slow down, eh?" What sort of stuff did you see? Did you happen to have taken any pictures? Aaaaaaarrrrrrggggggghhhhhhh, I gotta get over there and check it out, one day Thanks Tony Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 18, 2011 Share Posted July 18, 2011 Actually I met up with a bloke named Jacob from Australia, and he tagged along with me and Mr. Okamura to the Toyota Megaweb. He had a nice 'Japan Car Guide' which gave directions on how to find everything that is anything in Japan (in ENGLISH!) plus Japanese for your occasional Taxi ride. Stuff? Fresh bumpers, grilles, lights, interior parts, all sorts of crap. There were 20 vendors who cancelled due to predicted rain. I can't imagine what it would have been like had they all been there! I spent money. Okamura said I was crazy... Looks like I land at Kingsford Smythe Airport for another Banzai Run to Eraring on the 26th... At least my Vodaphone stays active! I'll ring you if I get the time, have another engineer tagging along and we may have to rideshare. Don't know his disposition quite yet, first job in the field together. Quote Link to comment Share on other sites More sharing options...
ozconnection Posted July 19, 2011 Share Posted July 19, 2011 Actually I met up with a bloke named Jacob from Australia, and he tagged along with me and Mr. Okamura to the Toyota Megaweb. He had a nice 'Japan Car Guide' which gave directions on how to find everything that is anything in Japan (in ENGLISH!) plus Japanese for your occasional Taxi ride. Stuff? Fresh bumpers, grilles, lights, interior parts, all sorts of crap. There were 20 vendors who cancelled due to predicted rain. I can't imagine what it would have been like had they all been there! I spent money. Okamura said I was crazy... Looks like I land at Kingsford Smythe Airport for another Banzai Run to Eraring on the 26th... At least my Vodaphone stays active! I'll ring you if I get the time, have another engineer tagging along and we may have to rideshare. Don't know his disposition quite yet, first job in the field together. Yes call if you can by all means..... Did something special catch your eye Tony? Wanna share? Couple of stock L series camshafts perhaps? Long live the Vodaphone! Sorry to go so far off topic, blame him but Quote Link to comment Share on other sites More sharing options...
kolonelklink87 Posted July 20, 2011 Share Posted July 20, 2011 You should have seen the 330 parts at the Odaiba Island Swap Meet...wow! I couldn't figure out the policy on 330's when I was there... I went to the JCCA meet in tokyo this year and saw just one 330 in boring paint and stock trim... I was wondering where all the cedrics were... (mind you there was heaps of 60's models) Quote Link to comment Share on other sites More sharing options...
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