ask41

Recently I decided to get the old RX (79 GS, original owner here, all stock except RB exhaust system) running again after 5 years of inactivity. She's been garaged the whole time. Last time she ran was after changing out the points to electronic ignition from an 82 (?), but she didn't run well, very rough idle and erratic tach. I did't get a chance to troubleshoot before we sold the house and moved.

I reviewed the modifications to the wiring recently and found an error. Fixed the error and started thinking about turning the key...

First I changed the oil, put in a new fuel filter, new battery, pumped out the tank and put in 2 gal. of fresh fuel. Put oil in the rotors and turned the rotors by hand to lube the internals. Pumped fresh gas through the filter to the carb (witnessed fuel there with the line disconnected at the carb.

Alas, no start. Tried starting fluid sprayed in the carb and yes! she runs!! But once the starting fluid is consumed she dies again. Actually runs nice and smooth for maybe 10-15 seconds with starting fluid.

Compression seems fine. This is the original rotary, but only 65k miles and always been taken care of.

So I'm left with the following theories:
1. Fuel pump operates but does not put out sufficient pressure (does this make sense? would this result in no start?)
2. Carb is gummed up somewhere and fuel is not getting to the jets (can this be checked somehow? I've never touched the carb and don't feel up to any tear-down or overhaul)
3. ????

I'm hoping there's an easy fix that I'm overlooking. My next move would be to check the pressure and flow rate on the fuel and see if it's in spec. If not, I'll replace the pump.

Any suggestions or ideas are appreciated!

NCross

iTrader: (18)

Maybe the distributor was put in a tooth off. Restab it a couple times to see if it helps. Next take the air horn off of the carburetor. Remove each air bleed and blow compressed air through them, reinstall one at a time to avoid mixing them up. Blow compressed air through the main fuel inlet.

Fungus Mungus

iTrader: (9)

Since it runs on starting fluid and dies once that's exhausted, seems like turning your attention to the fuel system is a good idea.

You can put a fuel pressure gauge on the fuel line to the carb and see if you're getting ~3psi to the carb.

A carb sitting for 5 years will likely have suspicious fuel in it, jets plugged, etc. Might be a good time to pull it off and rebuild it (or have it rebuilt). But check the pump first. Easy to replace if necessary.

fm

RX7TR7

I just got done reviving a 12a. If you pull the fuel line off the carb and put it in an empty water bottle and turn on the ignition switch it should fill the bottle half way kind of quick. If you get no fuel coming out that's your first problem. Next grab a dentists mirror from the auto parts store. Hook your fuel line back up to the carb and turn the ignition on for a few seconds now using the mirror and a flash light check the sight glass on the sides of the carburetor and see if there's fuel in them. It should be around halfway up on the glass. If there is then look down the carb with a flash light and have some one floor the car once or twice and see if the carb squirts gas out into the primary (smaller) bores. If it does the car should run if not, the jets are clogged and the carb needs to be rebuilt. If the fuel pump is pumping and the fuel bowls are empty the needle and seat are stuck. Whacking the carb on the top and sides with a rubber mallet should free them. If not try disconnecting both fuel lines, then put your thumb over the return fitting in the carb and use a compressor and just blow a little air into the fuel inlet most times that frees up the needle and seat.

DivinDriver

iTrader: (15)

Bringing my 80 back from a multi-year slumber necessitated a carb cleanout and rebuild... it was thoroughly gummed up with residue from evaporated gasoline. Just couldn't flow. The power-valve check ***** were firmly stuck in place, bleeds blocked, etc.

ask41

Pressure checks out, right at 3 psi.

There is no visible fuel in the sight windows. There is fuel at the inlet line, I took out the fuel strainers and made sure they were clean. Fuel is in the strainer area.

So is is possible to get to the needle valves without pulling the carb and tearing it apart? I'd like to free them up and see if fuel can get to the engine.

Sounds like there may be multiple places where small diameter passages can be plugged with gunky gasoline. Looking more like a rebuild is going to be necessary to ensure free flow of fuel to the venturis if I can't get her to run...

NCross

iTrader: (18)

Gently tap the air horn on the banjo bolts with a hammer. It should jiggle them loose unless theyre varnished.

RX7TR7

If you have an air compressor you can take your blow gun and put it in the rubber hose that goes to the carb. Then disconnect the rubber hose on the return line and plug it with a bolt so the air pressure can't leave the carb. Now shoot the blow gun a few times it should knock the floats back down. I've done that on a lot of cars if tapping the carb doesn't free them up. If that doesn't solve it, its time for a tear down and honestly it seemed like a daunting task to me too. But it was shockingly simple just put things back exactly how they were take lots of cell phone pictures, and don't bend your floats at all. Be beyond careful with them.

DivinDriver

iTrader: (15)

It is possible to pull only the top cover from the carb without doing a full tear down or removal. Couple tricky bits involving the choke linkage but if you are careful and think things through it's not too bad. This will get you access to the floats, needles, and seats.

High probability that you'll have to change the gasket, though, as it's most likely gonna come apart if it's been on there for years. So ordering a rebuild kit would be step one anyway.

Then you'll look at it and say, 'Well, I got new needles in the same kit, and they're right here...'

If it's so sticky inside that the needles won't flow gas, the rest of the carb is probably pretty gummed up too.

ask41

Spent a while going over the possibility of removing the air horn and conclusion is it looks to be possible to take it off without removing many of the attachments.

I don't believe I need to remove the fuel inlets, disconnecting the fuel supply and return hoses should be enough.

The back of the carb is where it gets tricky, as you said. There are several linkages and springs that appear to have some flexibility to them, and I'm wondering if you think I have to disconnect all these from the air horn before it will come off?

I found a good description of the carb parts and disassembly here - http://www.scribd.com/doc/77761205/M...nual-1979-1985
but it wants me to take all these attachments off, assuming the entire carb is removed from the manifold and is on a bench.

ask41

Just to follow up, I put air pressure on the fuel inlet with the outlet plugged. Rapped the carb body with a rubber mallet...no success, still no fuel in the sight windows.

DivinDriver

iTrader: (15)

I suspect the Viton tips on your needles have turned to goo.. or else the tiny screens that sit on top of the needle seats (not the round ones under the banjo bolts) are crapped up.

The rear linkage... IIRC, you need to undo the choke cable, and there's a c-clip that holds the choke linkage in place. Also a tiny cotter pin. It's been some years since I did this...

The carburetor manual on Sgt Fox's website is very valuable reference material.

ask41

I found some serious motivation yesterday and removed the entire carb. Not as hard as I was thinking, even managed to get the 4th nut off without losing much blood. Made some notes and took some pics so I hope she goes together OK.

Two things that will come up on reassembly:
1. the bimetal spring was under tension when I took off the assembly. Does it need to be under tension when it goes back on? Or just replace as is??
2. I had to loosen the upper locknut on the throttle cable to get the lower locknut to turn. I imagine this will need to go back on in the same location as it was? Is there an adjustment procedure for the position of the throttle cable?

Once I got the air horn off, I was able to remove and inspect the air bleeds and jets...all but one that is. The rear bleeds were clean and clear. The front bleeds were harder to remove and some were plugged. I removed and cleaned those that could be removed. One - the primary slow air bleed & slow jet (item 63 on Mazda carb manual) - could not be removed, in fact I broke off half of the top of the bleed in the process. So, a screwdriver is useless. It is plugged, and needs to be unplugged and/or removed/replaced. How to unplug? Solvent? Fine wire? Other???

I may try some heat on it today and see if it comes loose. I don't want to damage it, since I have not seen replacement parts online for these bleeds. I figure it will be OK if I can get it unplugged even if I can't remove it.

I pulled the primary and secondary jets - accessible through the fuel bowls - all were clean and clear.

The floats were clean and the needle valves clean also. The tips were a bit gooey but OK after cleaning. I removed one of the needle seats (part 26 on the Mazda manual) and the small screen was ok, soaked in solvent anyway to make sure. The other one was stuck and did not come out. I'll try again, and these are available in rebuild kits if I damage it. I'd like to see that screen and make sure it's clear.

SO...next steps...
Try to remove or at least unplug the plugged air bleed
Try to remove the stuck needle seat

And maybe - disassemble entirely and clean the exterior thoroughly. A lot more work and risk of damage/lost/broken parts. ???

Any other ideas/thoughts/suggestions? Other things to check/clean before reassembly and reinstallation??

Happy Thanksgiving to all!!

ask41

Finally got the plugged air bleed open by allowing solvent to sit in the top opening and working (carefully) with a fine copper wire...finally the pluggage broke free.

I've also done some major cleaning on the outside to remove years of grunge. It's actually looking pretty good now, and I'm thinking it may be time to reinstall it.

However..I DON"T want to do this again so before I reinstall I'm going to think long and hard about any other things to check/clean/verify function before reinstalling.

I'm open to suggestions to those who have been down this road before!

Cookboy

iTrader: (10)

The simple answer is spray carb cleaner with the straw through every little orifice you can find and make sure it's blowing out somewhere. Fishing line helps sometimes.

Banzai

iTrader: (13)

Its always good to see original owners here looking to get their cars back on the road again. Sounds like you're getting there. Don't get too discouraged and keep an open mind. These kinds of things go hand and hand with classic car ownership. Shortcuts and easy fixes rarely work. Normally, its more like a series of dominoe's that need attending, but worth it in the end.

Things you've never done before can be daunting but a lot of times you'll find its easier than you first thought. Plus, more you do and learn, the easier it all becomes to keep the car maintained. Having experienced a problem, you know where to look and what it probablly needs. From your description, I believe your problem is the carb. Sometimes, posting pictures can aid in diagnosis.

ask41

I finished the re-build (partial rebuild only - I didn't remove the throttle boddy from the main body, only the air horn) and reassembled the carb over the weekend.

I replaced the fuel pump with a stock Mazda pump. I was getting 1/5th the flow (only 200 cc/min) and under 3 psig pressure. New pump tested out and worked like a charm.

Installed the re-built carb yesterday, but after it was on, I realized I didn't install the choke/bi-metal housing correctly so had to re-do that. Found out it the bi-metal housing can be removed and replaced without pulling the entire carb.

Today, she started and kept running! Choke functioning as it should. Well, running a little rough but not so bad. I think it needs mixture and idle speed adjustment. Need to get warmed up to normal temp. to adjust idle and mixture. If it doesn't smooth out I'll be back on asking for advice

Checked the timing since the new distributor and elec. ignition was not finalized before she went into hibernation. Leading timing set OK. Trailing plugs are not firing at all (no timing light trigger when the pickup is put on the trailing plug wire). I have a spare igniter, so I'll try swapping it out and see if that's the problem. Other suggestions?? Trailing coil?? Possible bad wiring connection??

This has been an enlightening, enriching experience. It seemed incredibly daunting at first, but I kept going, and found several areas of the carb that were problem sources. How long they were there I don't know, but I feel good to know that I found plugged jets and got them cleaned.

Thanks for the words of encouragement to all...

NCross

iTrader: (18)

Test for 12v at the coil and before and after the ignitor. Does your tach work? Your testing on the front rotor? Also test resistance of your coils. 1.22-1.48 ohms.

RX7TR7

If you want just flip the coils. Put the conecctions from the trailing on the leading and the leading on the trailing. The you'll know if its a coil or ignitor. Also check for 12 volts at the coil. I recently gutted my bad ignitor and made jumpers and installed a gm he I module because ignitors are expensive new and I didn't have the cash. So far it works well.

ask41

Yes tach works fine. I'm going to post a couple videos as soon as I can figure out how. Maybe if someone with good ears hears what I'm hearing they may have an idea of what to check.

As the videos will show, initial startup and idle is good, with the choke on. But as things warm up it gets worse and after a few minutes it won't keep idling without a foot on the gas.

I'll try switching coils, and post the outcome.

ask41

OK, just got in from the garage, and had my daughter keep the engine running to keep it from dying.

I may have had 1 bad igniter, I switched them around, then put in a spare igniter that I had. The trailing plugs fire when the engine cranks (timing light flashes...), but they do not always operate during normal running so I believe the coils and igniters are OK. This car is a '79 California version.

I kept it running long enough to get the choke to shut off. It was pretty smooth at 2000 rpm with foot on the gas pedal, but with no foot on the gas pedal it would slowly die. I screwed the mixture screw all the way in - no effect. Screwed it out at least 5 full turns and no effect. Doesn't seem right to me... Screwing in the idle screw (top, large screw) did run the rpm's down.

It was dark, and I noticed the rear header pipe glowing red, while the front header pipe was not glowing...pic below...is this unusual or potentially bad? I've read this is due to retarded timing...but why only the rear header? There is no way the front and rear rotors can have different timing, right? It suggests to me the front isn't getting fuel?

Another question - the 79 plugs are different from the 80-85...I assume I should switch to the 80-85 plugs since I've switched to the 81 electronic distributor...can anyone confirm?

ask41

If at first you don't succeed....

After looking down the venturis and seeing no fuel coming from the front idle jet, I decided to tear down the carb again. I can say this, it's faster and easier the second time!

Found the primary idle nozzle plugged - the one that extends to the centerline of the venturi (when looking from the top). I also found the secondary nozzle plugged on the front venturi, so it was well worth the effort to do the teardown. I decided to change the accelerator pump while I had it apart...it was pretty gunked up. Sprayed carb cleaner everywhere I could and reinstalled the carb.

Let me tell you when she started and idled with only a minor misfire here and there, I felt it was all worthwhile... When the choke shut off, I adjusted the idle and mixture and she smoothed out really nice. Timing was set for L and T, right on the marks.

Driving was smooth...revved nicely, idle got smoother. There was a minor hesitation when accellerating hard, but I didn't push it past 4k on the tach.

Summary - new fuel pump, new fuel filter, carb rebuild (twice). Previously had changed oil and filter, new dist cap and rotor, new plugs and wires.

Any opinions on running a can of seafoam through the gas tank?

Opinions on the best plugs? Do I go with the 3 electrode or 4 electrode plugs? Currently it's the BR7ET's with 3 electrodes.

ask41

Update...
After tiring of changing fuel filter every 50 miles or so, I pulled the tank, took it to a radiator shop and had it cleaned and coated inside. They also painted the outside. $225 but well worth it. I've not had a problem at all (and don't anticipate having one) in several hundred miles. No hesitation, she pulls right up to redline (and beyond...) with not a hiccup.
Remaining to dos:
New tires! may go with 185-13 for now, on stock rims, since 205/60 is nowhere to be found. Ideal would be step up to 15" with 195s or 205s.
Water pump inner gasket...there is a very small leak that appears to be coming from the inner gasket. Outer gasket is fine.
Hatch struts - just ordered the Strong arm struts on amazon...$15 each.
Exterior - need some very minor body work and paint touch up. The years took a toll under the bra and when I pulled if off recently the paint is dull and needs buffing/clear coat. rear bumper where my ex--girlfriend put rested her ski boot on it to buckle it way back in 1981...the scratches need to go! Minor rust spots on the fender wells where I installed mudflaps way back in 1982 (seemed like a good idea at the time) A small dent in the driver side door from a shopping cart collision from 1987. Repaint of windshield trim (faded and worn through in a couple spots...not terrible but I'd rather have it look uniform)
New leading coil?
After these are done I'll re-evaluate again...
Thanks to everyone for all the encouragement and guidance, my 7 has truly been reincarnated and I believe it runs as good as ever.

7aull

iTrader: (2)

Sweet! nice resurrection - and by the original owner? even better. Hope it makes you feel the same age as you were when you bought the car. Mine does. Thanks for updating your Thread.

Water pump - beware when you pull the main pump body off the block there is ONE mount point which also requires a washer/gasket around that bolt point, to allow the body to flush-up correctly to the front iron. You will see it when you pull it off, one of the upper ones…

Fender rust: If your "minor rust" at mudguards turns out to be just that, (minor) it will be a first (if we are talking the rear fenders) - notorious rust point. Remove the tail lights, get a flashlight in there and brace yourself. Sorry. Been there. POR15 is your friend…

Keep your GF away from the car…

Stu
80GS
Alaska

TheRX7Project

iTrader: (3)

Awesome. I like this thread. Great to hear another one is on the road.