RotorPoke

OK, This has been driving me crazy for about 2 weeks now and yes, I've spent countless hours searching the forum and reading every related post. I will proceed by telling you guys exactly what I've done and checked and what the symptoms are:
(and yes, I have the FSM and have read it/used it extensively)

'85 GS 12-A w/ 148,000mi, all stock. The car was exhibiting symptoms of a vacuum leak (hard starting and inconsistent idle). It would hold the normal 750rpm idle occasionally but then would want to die if i didn't hold the choke out slightly or give it a little gas w/ the throttle (much harder starting in very cold weather). The hard starting was getting worse and worse so I decided to just dive into the carb since it had never been rebuilt and I figured it was about time/overdue.

Took the carb apart according to the FSM and cleaned all jets/air bleeds/ and all other parts. I ended up finding 2 vacuum leaks...the accelerator pump diaphragm looked like cheese cloth and the No. 2 choke diaphragm was bad too. Replaced the accel. pump with a new one from the rebuild kit but cannot find a source for a new No. 2 choke diaphragm (sealed metal pot on front of carb)...more on that to come.

Replaced the needles and seats with new ones from the kit. Checked and adjusted float levels precisely according to FSM/rebuild kit specs and performed the tests on the richer solenoid and air vent solenoid...both function. Fuel level in sight glass is staying right in the middle as it should.

Reassembled everything back to stock conditions and did not use the new provided carb spacer to intake mani. or throttle body to carb spacer gaskets as these block small ports in the spacer and throttle body and are not needed anyway since the carb insulator has molded on gaskets. Yes, the air horn to main body gasket is installed properly (not upside down).

So I put the carb back on the car assuming I have found the vacuum leaks and cleaned everything thoroughly and expecting it to run like new...it doesn't. Cannot get it to hold an idle below about 1,300 rpm (idle mix set at 3 turns out and won't hold idle if I adjust the speed below about 1,300). Since I cannot find a new No. 2 choke diaphragm, i simply take it off and plug the ACV directly into the vacuum port where it and the choke diaphragm originally went...so no leak there.

Everything I've read points me to a vacuum leak if I have hard starting, and a rough, bouncing idle...so i decide to do the rat's nest removal tutorial for the sake of simplicity and hoping to find another vacuum leak in that mess.

Followed the tutorial to a "T" and made my own block off plates w/ custom gaskets and sealant...no leaks there. Capped the 1/2" hole on the back of the intake mani, both ports on the shutter valve, the small forward port on the passenger's side where the ACV/No. 2 choke diaphragm went, and the two rear most ports on the carb spacer as per the tutorial's direction. Routed the hoses as shown...front most port on spacer to AC solenoid/cruise control, second port to vacuum advances on distributor, third to bottom of PCV valve, and the fourth (actually on throttle body, not spacer) to the top of the PCV valve. Tee'd the big hose out of bottom of PCV valve to oil tube vent and air vent on carb by fuel return line. Top of AC solenoid to throttle opener.

Started the car up again w/ fingers crossed...but same problem. I've sprayed carb cleaner around every spot I can think of (no noticeable change in engine sound). I've vacuum tested the brake booster and vacuum advance pots on the distributer...all that is good.

I can see fuel coming out of both primary ports in the venturis but it appears to be coming out kind of unevenly/surging/pulsing out but I have no frame of reference on how it should look as it comes out. So at this point I'm completely stumped and decide to check out some other possible problems. I put on a new fuel filter (which was pretty dirty) and performed the FSM test light procedure on both ignitors...tested good. I installed a cheap ($17) Mr. Gasket fuel pressure gauge on the fuel supply line between the firewall and carb steel lines...it's only reading between 1.5 and 1.8 psi. I know the stock spec says the fuel pressure should be between 2.8 and 3.5 psi...could this be the problem? Weak or intermittent fuel pump?

I also hooked up my timing light to the L1 lead and the leading timing mark (yellow) is showing some advance (yellow mark is about 1/4" counter clockwise from the indicator pin), which is about what it should be considering I'm idling at 1,500 cuz it won't run below that...at least according to the advance curves in the FSM). I also then hooked the light up to the T1 lead and the marks did not move at all...it's as if the trailing is firing at the same time as the leading. This can't be normal...can it? Shouldn't I see the red/orange mark move closer to the indicator pin when i switch the light to the trailing lead, even w/ building in some advance from the engine running at 1,500rpm?

I'm out of ideas and this thing is driving me crazy!!! Sorry for the long post but I wanted to give you guys any and all information I could...
Can anyone think of anything else that could be wrong? Vacuum leaks that I can't find (really, there shouldn't be any...triple checked everything)? What's up with the low fuel pressure? would that cause this much trouble at idle, even with the float bowls showing the proper level? How bout the trailing ignition issue? What would cause that? I've read that the fuel pump cuts out w/ the trailing ignition, but like I said, I've tested the ignitors as good according to the FSM light test.

Please, any suggestions or ideas would be greatly appreciated...I can't understand how taking the carb off and rebuilding it meticulously...and finding and fixing 2 vacuum leaks would cause this sort of poor idle/power surging issues...it's worse than before even after fixing the vacuum leaks. The thing runs pretty good with the choke out (albeit with what sounds like a minor ignition misfire that was always there before the rebuild) but starts sputtering and hunting as soon as it releases...It was doing this after I put the carb back on and before I removed the rats nest, so I don't think it was anything I did when removing the emissions. Also, even after warming up, I have to pump the gas pedal a few times to get it to start...what else could possibly be causing this? BTW the No. 1 dual diaphragm for the choke is good...left the altitude compensator on and the vacuum diaphragm for the secondaries is also still good...idle mix screw/needle is in good shape.

I'm going to go check the compression on both rotors but only have a conventional compression tester...what is the best way to use this to see the compression on every face? Do I need to turn the engine over by hand or bump it with the starter?

I'm out of ideas and about to stick some dynamite under the hood or roll it off a cliff (maybe both)...PLEASE HELP!

Kentetsu

The fuel spray in the primary barrels should be very strong. If there is a sign of dribbling, or anything other than a very impressive spray of fuel, then you likely still have something clogging your jets. Is there any possibility that you accidentally put the secondary jets in the primary position? This happens quite often. If you do need to pull the jets out, there is a very simple way to do it without disassembling the carb again. Just run a search for "jets wooden toothpick" and you will find the info.

The fuel pressure gauge you got is most likely crap. They have such large variances in "accuracy" that you can't really tell what you are really running. However, since you are having issues at idle, I doubt that you have any issues with the pump. Especially since the fuel levels are correct in the sight windows.

I didn't really understand what you were saying about the carb spacer that you did not use, so I can't help you there.

Leading and trailing ignition firing at same time: This would make me want to go over the routing of all of the ignition cables and wires to make sure that they are correct. During all of the work that you have been doing, something may have gotten itself swapped around. I did this myself last year, and had a hell of a time figuring out what happened simply because I was so sure that I could never mess something like that up. lol.

If this car was sitting in my driveway right now, the first thing I would do is dump a can of Seafoam into the gas tank. I prefer to do this with only about 1/8 tank of gas. Then, just keep it running for 15 minutes or so to clean the carbon out of the apex seals and restore any possible lost compression.

If anything else comes to mind, I'll post back again. Very nice first post, by the way. Good luck with your troubleshooting.

.

RotorPoke

I'm sure all of the plug wires are routed correctly. So I still have no idea about the trailing timing thing. All I was trying to say about the carb spacer gaskets is that i didn't use the ones that came with the rebuild kit cuz I've read they are unnecessary and can block the holes in the throttle body/carb spacer/intake mani.

I didn't think it would be the fuel pump either, especially at idle since the bowls are staying filled to the proper level...and I did suspect that cheap gauge wouldn't give me an accurate resolution at such low pressures...so I might actually have the correct pressure but the gauge just reads low.

I guess I'll take this bitch off again and double check the jets...I was very careful to keep everything separate during the rebuild so I don't see how I could have accidentally swapped the primaries for secondaries...maybe there is still a clog somewhere...we'll see. Any other input on the timing thing or info on how to accurately see the compression on every rotor face?

74RX4

iTrader: (10)

Remove the cables from distributer to coils. Remove 1 trailing plug. Turn the engine over with the starter. There should be regular pulses of gas/air coming from the plug hole. Try the same procedure on the other trailing plug. This will let you judge the general condition of your seals. If you get similar regular pulses from both rotors you know that the seals are in place and probably not sticking.

rotordogg

iTrader: (4)

Was this problem ever fixed? What was the outcome?