New (used) engine in. Won't stay running.
 

So I just got everything hooked up with my new (used) motor. 136k on it. It fired without an exhaust on it, and now it seems as if it doesn't like my exhaust. NO cats. NO emissions equipment. It will start with a pump of gas, and it will settle into a solid 1000rpm idle almost instantly, and then within 3-5 seconds it shuts off. If I try to give it any gas when it's running it dies instantly. I have spark. I have fuel. I have compression.

Primary Jets are shooting gas into the carb. Fuel level is halfway up the sight glasses. I have everything that should allow for combustion, and it will run, but just at idle. What gives?

-Jim

vacuum leak?

Nope. When it was idling I sprayed carb cleaner around the carb-block interface and all intake manifold block off plates and I didn't notice any difference in idle.

are you getting enough fuel to the carb? plugged fuel filter maybe? does the carb need rebuilt?

If bowl levels are still right after it stalls, it's probably not fuel delivery related, though it could still be a carb issue (like leaking accel pump circuit, fast idle setting, stuck-closed bowl vent etc.) Or it could be ignition rather than carb, like a leading ignitor that is thermalling out under load.

How much of the engine was replaced? Just the keg, or are you using an intake, carb, ignition electricals that came with it? More details of the surgery, please.

My first thought is that damned safety "feature" that will allow the pump to run while cranking, but will not keep it running unless it senses that you have spark on the trailing ignition system.

I suppose an easy way to check this is to see if the float bowls are empty after it stalls.

And hurry up! We've got racing next weekend! :)



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Float bowls are still 1/2 full after the engine stalls.

I am using the dizzy and igniters that were in the engine when I bought it.

I am using the intake and carb from my old blown motor (ran just fine on the old motor). The accelerator pump is leaking, but it did that on the old motor too. I am planning on doing a carb rebuild, but only after I get the engine running and some initial break-in (so to speak...loosen up the seals and whatnot) miles on it.

I am using the cap and rotor from my old blown motor (good condition).

Spraying carb cleaner down the carb when the motor is running causes the engine speed to increase, but only if I'm on the throttle.

I do have tach signal, so my trailing igniter works, however I am not sure that I'm getting trailing spark.

I'll try putting on the igniters from my old dizzy and see if that helps.

I am starting a 2 week road trip for my internship on Sunday driving all over hell and gone in my Impala, so I won't be able to put on my new spindle and race next weekend. I will be in the GR area on the 11th and 12th, so after I'm done with my work for the day I'll probably come out and watch you guys race.

-Jim

Get out there early enough and you're welcome to race mine. :)

We'll see. What time do the races start?

So it turned out that the car was seriously out of time. We fixed the timing issue, and now I am trying to figure out why my choke won't work. I have the cable routed correctly, however when I pull on the choke, it doesn't actuate the choke. Pictures of carb coming soon.

It will run (and run well) if we manually hold the choke.

If it runs only under choke after reaching temperature, then it's mixed too lean.

When you say "actuate,' do you mean the butterfly doesn't move at all when you pull the knob, or that it won't stay pulled out unless you hold it?

Choke linkage is pretty simple; cable to one link to butterfly. Can't see too well in the attached pic, but it looks correct based on the parts you have installed.

I haven't gotten it warmed up to check it. The car ran fine with these exact carb settings (it's the same carb and intake) on my old engine.

The butterfly doesn't move at all when I pull on the choke knob in the car.

If you look at the picture with the red box in it (MS Paint FTW), focus on the interface between the "L" shaped piece in the middle of the box and the part it's touching. When I pull the choke, the "L" shaped piece pulls away from the interface, however the part it's touching is the part that is attached to the choke shaft. The "L" shaped piece, and thus the carb cable, doesn't actuate (turn) the choke shaft.

Another issue: I went through the idle tuning writeup on sterling's website, and now my engine won't stay running at all. I fire it up with the Idle Fuel screw @ 2.5 turns from stopped, and the idle air screw 2 turns from stopped (stopped = bottomed out) and start it. It'll run with the choke, but when I let off the choke, it immediately dies. If I try and give it ANY throttle, it chokes off and dies.

When it would idle, I checked with carb cleaner for vacuum leaks. Sprayed the hell out of everywhere around the intake manifold and carb base, and didn't get any change in engine speed, so I have a system that is devoid of vacuum leaks.

-Jim

What are your Nikki idle air and idle fuel mixture screws set at?

for the choke: the part that has the coil spring in it needs to be put back on the carb, otherwise u'll need to wire/weld the area in the red box.
https://www.rx7club.com/attachment.p...1&d=1307214811

That's what I thought. I zip-tied it for the moment. I'll install that part when I get home from my 2 week work road trip.

Yes, OK, now I can see - your thermo unit is missing. Without the thermostat spring to hold the butterfly lever against the arm, the choke won't close. Rxtasy FTW.

Any ideas on this post?

Well, until you can run it long enough to get it up to operating temperature, your idle settings really can't get refined. When the carb's on choke, it's not using just the idle circuit to control the mix.

If you cant put the thermo unit back on, try wiring the choke butterfly to the choke arm, so you can keep the car choked long enough to get it warm. Then you can sort the base idle out.

There's a sequence of circuits the carb uses as you advance the throttle off of idle - - idle, then transition, then mains, and the accel pump plays into covering that transition if the throttle opens rapidly.

But IMHE troubleshooting any of that on-car requires getting the engine up to operational temp.

When you had the carb off, did you meddle with your throttle initial opening at all? & are the secondaries tight closed at idle?

I had a vacuum leak on the hose off the back of the lower intake mani. i don't know exactly what it is off hand b/c at the time mine was plugged from removing my emissions long ago. The bottom of the hose that sits right above the header was cracked but the carb cleaner spray did not show a single sign of motor speed change. The only way I found the cracked hose was to take it off and visually inspect it via advice from the board here after checking a bunch of other things it could of been to no avail. Bottom line is I no longer trust the carb cleaner spray to tell me if theres a vacuum leak 100%. I used an entire can too.

That's the imfamous "mystery leak;" on SA's it's the brake booster hose that goes in that fashion.

My understanding is that on FB's that the hose that works the shutter valve that tends to burn, crack, and leak.

I did not change any of the settings when the carb was off of the car. That's why it was so strange when I put it on, that it would idle for ~5 seconds w/o any throttle, then shut off.

I did screw down both the idle fuel and idle speed screws and set them to Sterling's recommendations.

I have gotten the engine warm (now that I've zip-tied the choke actuator), and that hasn't helped keep it running.

I eliminated Anti-Afterburn Valve #2, so that hose is gone.

Jim, start by simply increasing the idle speed until you can get it to idle. Once you reach that point, then start tuning the idle mixture (just get it to where it runs smoothest). If that results in an increase in engine speed, then reduce the idle speed accordingle, then move back to the mixture screw again incase that has changed. keep repeating until you feel it is tuned finely enough.

Then check the timing.

P.S. Races usually start around 11am

So I've had the last 1.5 weeks to contemplate whats been going on with my engine. I put the plugs out of my old engine into my new engine. It flooded out once while I was trying to get it to start, and the plugs are quite black and carboned up. I'm going to pick up a new set of plugs and see if they help the issues.

Usually if it will start, but not stay running, then it isn't your ignition system. Starting the car is the hardest thing it has to do, sort of. But then again, new plugs certainly can't hurt.

You need to live closer... :)

I have actually been bombing around the GR area for the past week or so for work. I've been exhausted and not getting to my hotels until ~10pm after dinner and whatnot.

If you are in town this weekend, and have time to kill, give me a call...

I worked 9:45-9:45 on Saturday (including the drive back to Ann Arbor). I dont' have your number...

-Jim

Another question: I pushed in the clutch pedal. Hydraulics all actuated correctly. Clutch did not disengage. Bad clutch? (Same throwout bearing, etc. from old motor)

-Jim

I'll PM you my #

Hm, did you actually see the slave cylinder move the fork thingy? Not sure what that means off the top of my head. Jeff20b could tell you...

So I had a minute to fart around with my FB yesterday. I put in fresh BR8EQ14's, turned the idle speed screw out 3.5 turns from fully seated, the idle mixture screw ~2 turns, gave her two pumps of the pedal and she fired right off. The tach was at about 4k rpm with the choke pulled, and so I let her warm up. She still won't stay running, and when I try and give her a bit of gas, I can hear air being ingested into the motor, but she won't increase RPM's.

I can get the RPM's to increase with a tiny bit of throttle, but that's the only way. This is really bothering me.

Does anyone have suggestions for initial idle mixture and idle speed settings?

Thanks

-Jim

From Sterlings website:

* Step 1. Adjust the Deceleration Dashpot and the AC Idle Compensation Valve so that they are not interfering with the primary throttle operation.
* Step 2, Open the primary valves to get the engine running on the main circuit by turning the PTS in. (81½-85 & SMW modified Nikkis only.)
* Step 3. Set the IFA to 1½ turns out from closed. (Never bear down on this screw to tighten!)
* Step 4. Set the Idle Air screw to 1¼ turns out from closed on a stock Nikki, or ¼ turns from closed on an SMW modified Nikki. (...if you have one on your carburetor.)
* Step 5, Start the engine, reduce the engine RPM using the IAA / PTS screw, and let it warm up.
* Step 6, Turn the IAA screw in on pre - 81½ Nikkis, or the PTS out on post - 81½ Nikkis, until the engine almost shuts off. (This will lower the engine RPM.)
* Step 7. Turn the IFA in, in ¼ turn increments, waiting 2 seconds after each change, until the engine starts to skip. (This will raise the engine RPM.)
* Step 8. Repeat steps 6 & 7 until the desired idle speed is achieved. (Usually this is between 750 & 850 RPM.)
* Step 9. Back the IFA out less than ¼ turn to ensure that the idle is not too lean. (This may require readjusting the Idle Speed screw first.)
* Step 10. Readjust the Deceleration Dashpot and the AC Idle Compensation Valve.

I stated earlier in the thread that I followed Sterling's suggestions, to no avail.

Note for myself for the next time that I work on my FB:

Check the vacuum advance lines going to the dizzy. Make sure that the single line coming off of the carb base plate is plugged into one of the two rearward-most nipples, so that the dizzy isn't receiving a vacuum signal at idle. The vacuum advance will be working if the dizzy is seeing vacuum signal at idle.

I've always used the nipple farthest forward (assuming no emissions and Nikki carb). That one only sees vacuum during acceleration, when you want the vac advance to work.

The stock location will show vacuum at idle, so if you've removed emissions then that vacuum will go straight to the dizzy and mess with your idle settings. Plus, once you start to accelerate, you lose the vac advance right when you need it most.

When setting up a carb for the first time, I would leave it disconnected until everything is working, just to avoid having any potential interference with your tuning.

I assume cap the one port before you try and start the engine to eliminate the vacuum leak that will create?

Oops. Sorry! :blush:

So did you find it to be the vacuum line?

Car is out at my parents house, so I don't have a lot of time to work on it. I'll work on it some this weekend and let you guys know.

Throw it on a trailer and drag it over this weekend. You can race my car, and we'll work on yours. Should be a good half dozen rotorheads hanging around my place this weekend...

This is a viable option. I'll do some logistics work tonight and let you know Mark. Thanks for the invite!

No problem! The wife is taking the kids camping this weekend, so I've got the place to myself starting Friday afternoon. Got two empty bedrooms now for company to use. :)

This fresh motor does have good compression, right? You're symptoms sound an awful lot like blown seals. Doesn't hurt to check...

Yes, it does have compression. It would fire and idle just fine, and then I fucked with the idle speed and mixture settings...

So, out of curiosity: there is an electrical connection on the passenger side of the carb. I unhooked that (because that was the only thing still connected to that sub-harness) and removed the whole harness. This won't have any affect on the way the motor is running, will it?

Thanks

-Jim

Motor just locked solid on me. No clue what happened. I'm going to pull the starter and see if that's just stuck, but it looks like time for a new motor again.

I have one lined up about 20 minutes from my parents house for $60 from a guy who used to race a GT-3 RX-7 in SCCA competition, so hopefully this one is a bit better.

Sorry to hear that Jim. Good luck...

Thanks Mark. The motor has oil in it, and the starter has been pulled, and the motor is still locked up. I'm going to go and pick up the new motor this weekend.

If you tear it down, let me know what you find. I might have a good rotor and a useable housing. Maybe we've got enough parts to put together another motor. :)

You've got about a month until the Lansing event (August 6th/7th)

It's that weekend? I have a wedding to go to in Chicago...

So I picked up my "used" motor off of CL last night. It turns out that the nephew of the guy whom I purchased it from had rebuilt it (under his supervision) from the best parts of 6 engines that they tore down.

The guy I purchased it from raced an IT7 for years before switching to a GT3 RX-7. He also gave me a Panhard Bar and a couple of reinforced front lower control arms set up for Heim Joints.

He has a pair of MSD 6a's that I'm thinking about picking up from him in a couple of weeks, and he also has two sets of 4x110 aluminum racing wheels off of his GT3 RX-7 that (if I can find the CL ad) I'd be willing to pick up and ship for someone if they wanted them (I have no $$ for them and no use for them).

I'll put up pics in a bit.

So I now have my clutch and flywheel installed. I was looking at my intake manifold, and noticed a port that would be normally be covered by the intake manifold. JoeNoble and Chris Muise said that it's the ACV port. I remember Jeff20b saying that he uses Kwik Steel to fill it in. I'll do a search. Picture below.

http://i265.photobucket.com/albums/i...7/IMG_3904.jpg

It also looks like this is a channeled manifold. The primaries and secondaries have channels linking them. Is this one of those high-flow-70's-manifolds that people look for? Pics below.

http://i265.photobucket.com/albums/i...7/IMG_3905.jpg
http://i265.photobucket.com/albums/i...7/IMG_3906.jpg
http://i265.photobucket.com/albums/i...7/IMG_3907.jpg

Any other suggestions? I'm going to rotate the tires on my Impala and start draining fluids from my seized motor.

Thanks

-Jim