tropicalfrost Posted May 7, 2019 Share Posted May 7, 2019 Hi everyone. My car is having a strange problem, strange because I think I've already repaired the parts that could be causing it. It's an 83 BRAT w manual transmission. After driving about an hour on local roads, or 6ish miles on the highway, the car starts jerking and quickly losing speed as if it's not getting enough gas. Pressing firmly on the gas pedal makes it worse. Slowing down immediately calms it somewhat, but it will still jerk and sometimes stall. On local roads it will do this if I press "too hard" or quickly on the pedal- not flooring it or accelerating fast, just what's needed to speed up a little for an incline, through a yellow light, or if traffic speeds up suddenly- if it's not totally gradual and featherlike it jerks, loses speed, and stalls. Shutting the car off then back on usually resets it enough to cruise at like 25 again, but once this starts it keeps happening til the next day when the car is *fully* cool- a few hours break isn't enough. Does this sound familiar to anyone? I've had the carb rebuilt at a carb place, fuel pump and filters replaced a few months ago somewhere else. However, I've needed to go back to the carb place a few times because they didn't fully fix it on the first, second, or third go. They swore they had, til my mechanic who doesn't work on carbs told me to point out a fuel injector he could see malfunctioning. It seemed fine when we took it on a test drive after that, but it wasn't long enough of a drive I guess. Carb place suggested it could be the fuel pump. I'm skeptical since the injector thing, but I'm not knowledgeable enough to rule anything out. (I keep going back to this shop bc I'd rather not go to a whole new shop for work I've supposedly just had done!) I've tried searching online for more info on these symptoms or parts failing but haven't really figured out much from it. Has anyone had this problem before, or could suggest which carb/non-carb parts could be causing it? Thanks so much for any help pointing me in the right direction! Quote Link to comment Share on other sites More sharing options...
naru2 Posted May 7, 2019 Share Posted May 7, 2019 It is not such a strange problem.I`ve dealt w/similar cases several times. The strainer in the tank becomes plugged after a bit of driving. After stopping,the dirt drops off and the car runs better for a while. You can prove to yourself it is a fuel supply issue by observing the fuel level sight glass on the carb. Fuel will likely be in the middle where it is supposed to be after starting (but before driving) in the morning. Observe it again after the sputter.Fuel will be much too low. Driving w/a fuel pressure gauge attached is an even easier method. Problem could be the pump or strainer.Probably the strainer.from your "reset" description. Worth checking voltage and grounding of the pump though. Quote Link to comment Share on other sites More sharing options...
DaveT Posted May 7, 2019 Share Posted May 7, 2019 Does sound like fuel starvation, or accelerator pump not working. Quote Link to comment Share on other sites More sharing options...
silverhelme Posted May 7, 2019 Share Posted May 7, 2019 Is it temperature sensitive or does it happen all the time? Quote Link to comment Share on other sites More sharing options...
DaveAP Posted May 7, 2019 Share Posted May 7, 2019 I'm guessing fuel pump Quote Link to comment Share on other sites More sharing options...
FerGloyale Posted May 7, 2019 Share Posted May 7, 2019 Failing coil and or bad spark plugs plugs. Quote Link to comment Share on other sites More sharing options...
Dee2 Posted May 7, 2019 Share Posted May 7, 2019 Definitely sounds like a fuel problem. Since you've done the carb, filter and pump, looking further back at the tank seems to be a reasonable idea. Check the manuals on how to resolve the strainer problem. If that doesn't help then go back to the carb/injector issue. Quote Link to comment Share on other sites More sharing options...
FerGloyale Posted May 8, 2019 Share Posted May 8, 2019 Change the spark plugs Quote Link to comment Share on other sites More sharing options...
naru2 Posted May 8, 2019 Share Posted May 8, 2019 (edited) 26 minutes ago, FerGloyale said: Change the spark plugs Look at the sight glass first. Easier,cheaper,more likely given this " Shutting the car off then back on usually resets it" Bad plugs would be more consistent.An overheated coil is possible,but,does not explain the "reset". That said,looking at the plugs is always a good idea. Edited May 8, 2019 by naru2 Quote Link to comment Share on other sites More sharing options...
DaveT Posted May 8, 2019 Share Posted May 8, 2019 T in a fuel pressure gauge. Quote Link to comment Share on other sites More sharing options...
tropicalfrost Posted May 8, 2019 Author Share Posted May 8, 2019 Thanks so much everyone for all the responses! This is really helpful. Here are the answers to a couple questions and a new observation. -The spark plugs and ignition coil are new. I wondered if it could be something around the distributor but the symptoms don't seem consistent with that. -I first thought the jerking and sputtering was getting worse when it heated up, but now I think it gets worse the lower the fuel level. Tank was at about 1/3 the other day when I posted this. I completely filled it today: on the way to the gas station it was starting to sputter within the 5 minutes it took to drive there, especially going up inclines. After filling its now driving much more smoothly on local roads. Havent tried the highway, but this all seems consistent with something clogging around the gas tank. I wont be able to check the fuel pump for a few days but what would be the repair or test for a clog around the strainer? Could it be done without removing the whole tank? Would switching out the filters be relevant? I looked in the Haynes manual and dont see the strainer mentioned in this gas tank diagram. Is it called something else here? Quote Link to comment Share on other sites More sharing options...
subnz Posted May 9, 2019 Share Posted May 9, 2019 (edited) If its not a fuel issue then, after investigating the obvious - fuel filters /gauzes fuel pump / pressure etc. Then agree it could be a hi tension leads (ignition) issue. These can break down under load and performance becomes progressively worse when these get warmer / engine approaching running temperature. (when failing) Have had two different vehicles that have done this ie failing leads / coil (not Subarus) Another thing to consider is carburetor icing. Is the diaphragm operated flap on the air cleaner intake working correctly? ie to pick up warm air when required to prevent icing. Was the vacuum line reconnected /air temp sensor? If it has a manual summer / winter flap lever on air cleaner intake, try setting it to winter position. This is what my 87 Brumby (Brat) has. That diverts air intake off engine - warmer air to prevent icing. Icing Symptoms: jerking, surging, loss of power, getting worse as more throttle applied, coming to a stop - another type of fuel starvation. This could explain the momentary improvement after stopping with the heat in engine bay melting icing Edited May 13, 2019 by subnz wasted space on page extra content. Quote Link to comment Share on other sites More sharing options...
Steptoe Posted May 9, 2019 Share Posted May 9, 2019 the strainer is just a given thing on most makes and models and is not really a "service item" such as other parts mentioned in the service schedule. An item that is in schedule PCV valve yet rarely gets any attention or replacement. As such is likely never replaced on life of most cars, so just as likely not available. I punched mine out as a 15 year old and just became more vigilant replacing fuel filters and not using dodgy fuel containers for supply. No more problems. Moral of the story is ok to remove or pierce the intank pick up nylon gauze sock for better fuel flow. I also had crud build up inside metal fuel line cause cold start running problems. I think it is why previous owner sold it. I resolved it Quote Link to comment Share on other sites More sharing options...
naru2 Posted May 9, 2019 Share Posted May 9, 2019 (edited) The strainer is not shown in the diagram because it was never a replaceable part on EA81s. If the strainer plugged while your car was still on warranty,the dealer gave you a new tank. Only car I can think of that the strainer is not relatively easy to replace.A design flaw for sure. I guess they did not expect these cars to last so long. Pump manufacturers usually specify mandatory filter and strainer changes along w/tank washing for warranty coverage I would pull the drain plug and see what comes off the bottom of the tank. Diagnosis of a plugged strainer is a little difficult because of its possibly intermittent nature. Low fuel pressure combined w/a new pump/filter w/good voltage is a BIG clue. Fairly quick reset of fuel pressure after stopping the engine is an even bigger clue. An improvement in pressure and flow rate when allowing the pump to feed from a gas can is pretty definitive too. Your pump pressure should always be 1.35-2,06 psi and it should flow 28 litres/hour I think a lot of the EA81s suffer partially clogged strainers.My own 84 turbo will not meet the flow rate requirement even w/a new pump. You might be able to puncture the strainer w/a stiff wire,not sure.A radiator shop will be able to help. I`ve seen EA81s w/filters added between the tank and the pump presumably for similar reasons. Edited May 9, 2019 by naru2 Quote Link to comment Share on other sites More sharing options...
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