ZXR_KiD Posted March 19, 2009 Share Posted March 19, 2009 picked up the '78 about 2 weeks ago, needed a fuel pump then ran great. after puting about 5 miles on it total,spread out with quick runs up and down the street (barely getting any temp into it) without any issues. It stopped wanting to accelerate then begin doing nothing but idleing; very rough at that. then shut off completly. ever since then I can fire it and run it for maybe 3 minutes; runs just fine, can rev all the way up without issue. then goes back to rough idle wich will continue for aprox 60 seconds or so then die, after a minute it will fire and idle rough again for a few seconds then die again. then won't do anything for about half hour. then the process is the same. I've checked the fuel pump and filters, have good fuel pressure and flow all the way untill it dies completly*causes fuel pump cutoff* only thing I can figure out is that the EGR was somewhat clogged up *been fixed and still has issue* and perhaps the cat is clogged? anyone have any ideas? Quote Link to comment Share on other sites More sharing options...
neotech84 Posted March 20, 2009 Share Posted March 20, 2009 check coolant and oil. those were my only thoughts Quote Link to comment Share on other sites More sharing options...
rags Posted March 20, 2009 Share Posted March 20, 2009 Are you sure it runs for that long? Are the injectors firing? Have you done the screwdriver to the ear test to check for injector coil firing? Where did you check for fuel pressure and does the FP drop when you open the throttle or does the engine stall if the throttle is cracked? We need more info. Quote Link to comment Share on other sites More sharing options...
EvilC Posted March 20, 2009 Share Posted March 20, 2009 Are you sure it runs for that long? Are the injectors firing? Have you done the screwdriver to the ear test to check for injector coil firing? Where did you check for fuel pressure and does the FP drop when you open the throttle or does the engine stall if the throttle is cracked? We need more info. Joe and I went through a lil saga with the 78 he is restoring. Just give us some more info or even a short video if you could. Fuel or spark has to be your problem and pretty easy to figure out which it is, unless you have both issues Quote Link to comment Share on other sites More sharing options...
VinhZXT Posted March 20, 2009 Share Posted March 20, 2009 I am willing to bet it's fuel. How did you check the FP? Do you have a fuel pressure gauge hooked up? If you don't then you can't really verify the fuel pressure. I've experience with this problem many times before. With the fuel pressure gauge hooked up and at the first start the fuel pressure was fine and then it drops off slowly due to a dirty gas tank and a partial clog at the pickup line/filter in the tank. This will give you the same symptoms as you described. Since you need to drop the S30 tank to inspect the side I suggest you to get a fuel pressure gauge and check that out first. GL. Quote Link to comment Share on other sites More sharing options...
Pyro Posted March 20, 2009 Share Posted March 20, 2009 could also be the ignition module going bad. it is a 4x4x1 black box under the passenger side dash. Quote Link to comment Share on other sites More sharing options...
ZXR_KiD Posted March 20, 2009 Author Share Posted March 20, 2009 I've got a gauge hooked up on the engine side of the filter, also temporarily a 4" section of clear hose into the fuel rail just to visually watch for issues. when I first start it if I act quickly and start driving the car I can make it all the way up then back down my street, if I let it sit and run for a couple it does this issue before it gets back to the house, sp yea it is about 3 min run time when its running normally you can do anything you want with the throttle and it reacts normally, no hesitation or stumbling, altho it does backfire @ 3500 on the way back down if you rev it up to 5500 and let off completly. when it starts its shut down process it will catch a short occaisional burst where it will rev to maybe 2200, but as it goes on longer it gets less and less responsive, but will not stall out if you crack it, just dies on its own at the end of its spat. I havn't checked the injectors yet, the fact that it runs smoothly for the few minutes that it does I didn't think it would be an injector problem Quote Link to comment Share on other sites More sharing options...
rags Posted March 20, 2009 Share Posted March 20, 2009 What is the pressure reading after it develops the problem and won't start? If you have pressure and can hear the injectors firing while trying to start it, do the plugs get wet? If they do check for spark. If they don't you are back to fuel. All this is dependent on having good fuel pressure. Quote Link to comment Share on other sites More sharing options...
islanddozer Posted March 20, 2009 Share Posted March 20, 2009 Did you test after fuel pressure regulator ? How about the fuel pick-up in the tank ? definately fuel flow problem Quote Link to comment Share on other sites More sharing options...
theghosttanker Posted March 23, 2009 Share Posted March 23, 2009 Believe it or not, a bad ignition coil can cause this problem. I spent many hours figuring out this problem on my car. The coil would get warm and quit, then after it cooled down the car would run again. Quote Link to comment Share on other sites More sharing options...
evildky Posted March 23, 2009 Share Posted March 23, 2009 hey curt, when it stops running, check the plugs, if they are wet the car is flooding, might have a bad CHTS, causing the car to run rich when cold it's not as big of an issue but ince warmed up fuel fowls the plugs, this also explains the exhaust backfire Quote Link to comment Share on other sites More sharing options...
ZXR_KiD Posted March 25, 2009 Author Share Posted March 25, 2009 sorry I hadn't posted back in a couple days, computer issues. I've just discovered today that my fuel pressure gauge is flawed so it could yet be a fuel issue (needle sticks in the position of what ever it was reading untill you disconnect it, fails to indicate pressure drops, guess thats what I get for buyin a cheapie) I've tried the coil and chts to no avail so I think we can call it down to fuel for sure, unless someone else has another idea. even went as far as dropping the exhaust to check for a clog in the pipeing (never know on junkyard cars) but wasn't the case. I guess when the weather dries up I'll check the tank and pickup on another note with the exhaust off it sounds like it may have a mild cam installed... seems to have more lope than I recall out of the stock '79 Quote Link to comment Share on other sites More sharing options...
Spooler Posted March 26, 2009 Share Posted March 26, 2009 If you have a lope you have a big vaccum leak.... Check the boots coming from the airflow meter for cracks and the intake gasket for leaks. Spray the intake gasket with carb cleaner. The vaccum leak is after the AFM. If the plugs are fouled that is not the issue. Quote Link to comment Share on other sites More sharing options...
ZXR_KiD Posted March 26, 2009 Author Share Posted March 26, 2009 checked EVERY vaccume hose I could find and have no apparent leaks. but after letting the tank sit with a bottle of SeaFoam over night I now have the ability to start it and run it for 30 min without even a stumble or mis fire. once the pipes cool off again I'll hang the exhaust back up and try driving it.... keep your fingers crossed for me Quote Link to comment Share on other sites More sharing options...
sweetleaf Posted March 26, 2009 Share Posted March 26, 2009 You should really drop the tank and clean it out. The seafoam may dislodge the crap but it'll end up in the rest of your fuel system. Quote Link to comment Share on other sites More sharing options...
evildky Posted March 27, 2009 Share Posted March 27, 2009 seafoam=snake oil Quote Link to comment Share on other sites More sharing options...
Pyro Posted March 27, 2009 Share Posted March 27, 2009 have you read post #6??? Quote Link to comment Share on other sites More sharing options...
ZXR_KiD Posted March 28, 2009 Author Share Posted March 28, 2009 yea I read # 6, everything checked out. I dropped the tank this afternoon and drained the seafoam ooze out of it, (Its all purdy lookin inside now) and put it back together and she runs just fine, if not better than the 280ZXR ever did *even with a hot cam and full exhaust* my little test run today entailed a surprise ignition of both rears from a throttle punch from 5-10mph *WITHOUT CLUTCH DUMPING* and shocked the crap out of me and my passenger. (COULD very well be paired with REALLY old crappy/dry rotting tires currently on the car) in all honesty I think she's pretty much good to go. MAY even be brave and bring her out to the Auto-X this weekend (if I get my good tires mounted before then) Quote Link to comment Share on other sites More sharing options...
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