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So, I've got the 12a running pretty good. float levels good in rebuilt carb, new fuel pump/filter, wires, cap, rotor, condensers, plugs, oil and filter, timing set, carb adjustments still iffy, idles a little fast but ok other times. The main problem now is that while driving it seems to run pretty good, smooth to 4 or 5000 rpm(at least). but then after awhile it'll lose power, runs terribly, won't idle, quits completely. then if just shut it off and let it sit for a couple minutes it usually runs ok for a while, but then runs weird again, can smell lots of hydrocarbons from the exhaust, float levels look good, it seems like the carb adjustment screws don't have much effect on anything (sometimes?) not sure at this point what the problem is, but I think this might be the reason it was parked for 10 years in the first place. not sure how to trace the problem since it only does it while driving.
that makes sense, New filter, haven't dropped tank, it's half full now, what would be the easiest way to check it? run the fuel supply to a hose and see if it eventually stops flowing? seem like the motion of the moving car would be needed to stir up the crud if I did that.
The SA has an EGR Valve located just above the Thermal Rector that could be deteriorated and allowing too much exhaust gas to be reintroduced into the engine. This would account for a loss of power and intermittently when driving, then after it cools down the valve has reset and back to normal. If you remove the hoses and cover plate on the EGR, you'll find a metal disk with a carbon filter element on one side. Be sure there aren't any tears or damage to the valve elements and give it a good cleaning. Also, check the integrity of the hoses supplying fresh air to it, looking for cracks and such - as these will be huge vacuum leaks to your intake.
Long duck, are you talking about the device on the back of the engine? (with the pipe connected to the cat) or the passenger side of the engine above the therm reactor? seems like I'm getting a lot of exhaust gases in the engine compartment, but don't hear/see an obvious leak
It could also be ignition issues. When the ignitors heat up they shows signs of failure resulting in poor/missing spark, running rich do to that etc. Let it sit, they cool off and things are fine. It will get worse and worse over time (months usually) and cause you all kinds of grief trying to debug the issue. Once you are sure there are no fuel issues or vacuum leaks and it persists this would be my next guess. The FSM has a tester you can make to test the ignitors but they may only fail when heated up. Basic transistor failure modes apply.
tg, it's a 79 with points, I didn't think it had igniters, and It doesn't really need to cool down, 2-3 minutes shut off and it will run ok (for a while). when I had an 84 I had a lot of igniter problems, but either they worked or didn't, not much in between. I went through a bunch of them with that car. I was hoping i wouldn't have that problem with the 79.
pulled EGR and disassembled it, no noticeable problems there, ran my endoscope camera into the tank, but couldn't see much, then the camera quit working, and I was correct in that my car does NOT have igniters, so it's not that. it seems like it might be electrical because of the intermittent nature of the problem, but the gas tank theory makes sense too, so I guess I need to drain/pull the tank next (ugh)...I suppose I can drain it at the carb and that will show whether it clogs eventually, so may not need to drop the tank. I also have another carb that I need to test anyway, so I may swap it out to see if that makes any difference, after that I'm outta ideas
Classic plugged tank syndrome. My 80 did this too. Esp when tank was 1/2 or less full, would run a few minutes fine, then stall out. Your note of long-term storage is a usual preface to this problem. Last person never correctly pickled the car. Remaining fuel leaves air pocket. Heat cycles create moisture above fuel level, rusting up tank. Loose material off walls then slough off into fuel when its resurrected...yadda-yadda... plugged output.
Sits a while, gunk in tank drifts away from outlet till next start up. Rinse. Repeat. Fuel filter 'may' show some debris, but depends what is floating around in the tank.
79 has NO tank drain. Syphoning is part option. Better: remove level float cover (buy a gasket first!!) behind driver rear wheel, behind the plastic panel against the tank, drain out from there. Be gentle with your fuel float. Is Unobtainium.
2 straps hold the tank. You do NOT want to be man-handling it with much gas sloshing about! becomes very unwieldy once loose. NOTE!- various connecting hoses (there are 3-4 of them) on the rear/top; note where they each attach!!! Photos are your friend
Good time to replace ancient fuel hose lengths here too...
Tank will need to be professional power cleaned. usually a good rad shop can dunk-and-clean it for you. Then you need to RESEAL the tank walls. POR15 makes a specific gas tank seal kit that you mix, pour in and slosh around to seal up the insides. sounds hap-hazard, but it works! Ask me how I know
tg, it's a 79 with points, I didn't think it had igniters, and It doesn't really need to cool down, 2-3 minutes shut off and it will run ok (for a while). when I had an 84 I had a lot of igniter problems, but either they worked or didn't, not much in between. I went through a bunch of them with that car. I was hoping i wouldn't have that problem with the 79.
Blew right past the title where its says, right there, 79. Probably fuel issues then. Good plan to drain at the carb, let it pump and see if it slows or stops. If it does, drop the tank. If it doesn't look at the carb more closely.
now I don't know, drained fuel from the engine compartment fuel line using a clear hose so I could see what was happening, fuel flow was slow, but consistent without any bogging down of the pump,(I know it's only supposed to be about 4 psi, but not sure what that would look like)bounced the rear bumper up and down a bunch to simulate driving and stir anything up. at one point a piece of *something* (pink) floated through the line, I tried to filter it out, but not sure where it went, but I know the something like that could definitely mess with the carb and plug something up. but other than that it was pretty uneventful, not sure if it;s worth dropping the tank, and I have NO idea where the "thing" came from as it showed up after the filter/pump stage, I also noticed the rear float chamber was a little low so swapping the carb will probably be the next step, going over now to finish draining the tank and take another look in there with the endoscope
OK now I think I know what's going on, when my mechanic had the car he replaced the fuel filter(even though the one on there was brand new?) but this one is clear so it reveals a lot. I can't upload the video, but it shows that the fuel is dribbling into the filter, there is a ton of crud in the filter after less than 50 miles, and the filter is in line AFTER the pump, not before where is should be, I knew that it was like that, but he said he fixed that. so the pump may be clogged with that stuff too as well as the pick up in the tank. So, new filter, pull and clean tank, coat inside, make sure pump is clear and working properly, put back together in the proper order, and I may have something.
pulled the tank, it's in pretty good shape otherwise, sending unit removed easily(screws were loose!) but what about vent on the top of the tank? it's held in place by a rubber gasket. it doesn't seem to be too tight of a seal. but do I remove the entire vent or just remove the hose before I have it cleaned ( I finally found a place that will do it at a reasonable price) I'd like to replace that gasket, but haven't ever seen it for sale anywhere, or will the POR seal that up?
the guy that referred me to the radiator shop said that after he cleans it he coats it with kerosene to seal the rust. does that sound appropriate? does kerosene act as an etching solution? or should I just use the prep and skip the kerosene before using POR?
Kerosene? as a sealant? Chemistry not my strong suit but AFAIK Kero is a SOLVENT. Might be good as a cleaning agent, but as a sealant?? That is a head-scratcher. The POR IS a sealant, and a bulletproof one. The kit includes a cleaner AND a metal-prep solution to maximize bonding. The POR Prep actually converts the rust and neutralizes it. So its gone. After all the work you are going thru here I would be hesitant to monkey with it.
Seals: Have heard the gasket for the tank gauge is now NLA, so you might have to make one...or a t least add sealant to the existing one if it is reusable.
Top vent: anything removable/rubber should come off as the cleaning process may damage it. Give the rubber vent cover a good hose-down with WD40 or silicone to make it as soft and pliable as you ca for remove/install so's not to damage old rubber. None of these components are available from Mazda anymore, am guessing.
I used a pressure washer on the inside of the last tank I did to get the varnish out of the tank. It would not budge otherwise. Came out great though. I'll post some pictures a little later. How pliable is the goo on the tank?
03-29-21, 10:26 PM
