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  #1  
Old 01-11-2006, 02:11 PM
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BigRedChief BigRedChief is offline
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Now that I’ve picked up some more diagnostic toys… or tools, I’ve got a new batch of questions regarding the distributor advance and vacuum/emissions system on my jeep. I’m figuring it out, slowly, but I still have questions. I also know this jeep has had some funky fixes done to it over the years.

With my base timing (no vacuum connected to the distributor and engine warm) set to the stock 8 degrees it had a slight off-idle stumble when warm or cold, even after the TFI upgrade. It didn’t like having the EGR hooked up unless it was at idle or floored (I think I know why now –details below) so I disabled it. With the base timing set to ~12 degrees the stumble went away and I could run the EGR with the engine warm, but not cold. I left it disabled for drivability when cold. It picked up a bit of power with the increase in base timing. Hopefully someone can tell me where I’m going right or wrong. Am I covering up some other issue by having my base advance set 4 degrees high? I’ve never heard my engine ping. Then again I have some pretty loud tires.

As far as vacuum, I see 16.5-17 in-Hg vacuum at idle with the transmission in park ~850 RPM. Is this about right? I don’t have a parking brake so I can’t check it in drive without help. This engine was rebuilt about 5000 miles ago, bored .030 over, but I have no details on what compression ratio pistons or cam grind was installed. I assume they are close to stock.



#1 –Connected to manifold vacuum port.

#2 –Connects manifold vacuum to the thermal vacuum switch on the bottom of the air cleaner housing.

#3 –Goes into the firewall. Is this for the heater controls or q-trac? It does not hold vacuum. Should it? The vacuum to #2 is very low. I’m guessing it is because #3 leaks so bad.

#4 –Connected to that large multi-outlet vacuum block that doesn’t look stock. Is it? It goes to my non-functional cruise control and some funky black ball thing on the firewall. What is that thing?

#5 –Hard vacuum line that I assume goes to the transmission.

#6 –EGR line from the EGR CTO that is barely visible through the tangle. I’m not sure if the CTO is functioning correctly. I know it allows vacuum to the EGR valve when the engine is warm. I will have to check it for flow when cold since I haven’t done that yet. It’s a little bit hard to see, but the CTO is on a tee that also feeds one of the heater hoses. Is that a stock ?

#7 –Plugged now. It was connected to the vacuum port of the vacuum valve below (#8).



This vacuum valve was connected #8 to #7 in the picture above. I never questioned it before because I thought it was part of something else. It was buried in the tangle of hoses and mounted low. When #8 is subjected to vacuum 4 in-Hg or higher, #9 is closed. When #8 has less than 4 in-Hg, #9 is open, allowing whatever vacuum is pulling on it to vent to atmosphere. There was a tee off of #9 inline with the EGR line #6. It seems like this would keep the EGR from opening in extreme cases. At idle –high manifold vacuum on #8 –the ported vacuum would be zero, so the EGR would be closed. Under heavy load –low manifold vacuum on #8 –the ported vacuum would be high but since #9 goes to atmosphere it creates a vacuum leak causing the EGR to close. This might explain why, under heavy load, my transmission slammed back and forth between gears. Does anyone recognize this valve? What is it supposed to do or where is it supposed to go?

Did I forget anything??

[ January 11, 2006, 08:13 PM: Message edited by: BigRedChief ]
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  #2  
Old 01-11-2006, 02:27 PM
GWJoe GWJoe is offline
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very thorough. Sorry I can't be any help, I actually hope to learn from the other posts that come after mine.

Thank you for being so thorough with this.

Joe
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Old 01-11-2006, 02:30 PM
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the valve above is part of the EGR. I think it regulates the vacuum felt by the EGR, but I'm not certain.
You don't mention detail on the motor setup, but I don't think you would be able to run 12 static with a carb metered lean for EGR.
If you have an aftermarket cam the advance curve will be way off.
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Old 01-11-2006, 02:34 PM
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That's part of the problem I'm having. I know the motor has been rebuilt, but I have almost zero details on what went into it. The jeep was a gift from a relative. He had the engine rebuilt before he gave it to me. Getting information from him isn't so much like pulling teeth, it's more like fingernails on a blackboard.
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Old 01-11-2006, 02:47 PM
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If the carb is not meant for egr it will run better without it. The richer mixture doesn't need the exhaust gas to cool combustion temps.
If you're not running egr you can simplify things by plugging everything vacuum except vac advance connected to ported vac. Everything else is emissions related; the dual cto controls the egr and air injection, and the other controls vac advance feeding manifold vac when the engine is very hot.
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Old 01-11-2006, 02:48 PM
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The base timing listed on the label of my 87 is 14BTC. I had to back it down just a touch because I had removed the EGR a few months ago to troubleshoot my driveablity issues and it was pinging when I pulled the boat. I agree in general principal to what most have told me here- crank the timing up until it pings and back it off till it stops.
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Old 01-11-2006, 03:00 PM
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BigRed-

That part is known as the "EGR Vacuum Dump Valve". I had one go bad a year or so ago, and went through h-e-l-l finding another one. A member here kindly sold me another one.

From what you are describing above, it is functioning properly. It is bleeding off vacuum when your manifold vac. drops, stopping EGR operation.
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  #8  
Old 01-11-2006, 03:20 PM
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letank letank is offline
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#4 the ball, is your vacuum reservoir.... a buffer for the heater and QT. and feed to the can which a secondary vacuum reservoir for the cruise control

vacuum should be more or less constant for the heater and the QT, otherwise plug everything and trace leaks: at the QT diaphragm and the same for the heater... it should hold some vacuum.

Label set a timing of 5 but use 12.... vacuum read about 19 at sea level... how high is chandler... about 1200 feet... so you could be a bit low... but the cam being unknown.... you will have to live w it. Is the reading steady,,,,

test your cto to make sure they are doing what they are supposed to do... no egr w cold engine.... or that the manifold vacuum is diverted to carb ported vacuum when warm

imagine the cto as a ball bearing moving up when the engine is warm. so the middle port goes to the controlled device... the upper port is the one connected w cold engine and the bottom connected w warm engine....

I had some cto go bad... all ports connected... so a mix of manifold vacuum and ported vacuum for the distributor....

[ January 11, 2006, 09:23 PM: Message edited by: letank ]
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  #9  
Old 01-12-2006, 05:47 AM
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BigRedChief BigRedChief is offline
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Okay, I performed one more test this morning. The EGR CTO does function. It holds vacuum when cold and allows vacuum when the engine is warm. I don't know what temperature it switches at, but it apparently does switch.

Walt/Anyone: How do I tell if I have a carb meant for EGR or not? Aside from having an overly rich mixture, is there some number or other defining feature I should look for? I thought my carb was the stock one, it is a Motorcraft 2bbl, all the 2100 parts from the rebuild kit fit and it does have a port on the left front like the 1979 vacuum diagram shows for an EGR port. Could someone have re-jetted the carburetor, effectively making an EGR carburetor into a non-EGR carburetor? Are there numbers on the jets that I could check to see if they have been changed out for richer jets? I'd get in and look, but since I'm asking...

letank: I'm trying to understand what you've written there. Let me know if I have this right...

I can understand the ball on the firewall being a vacuum reservoir, but it is only hooked up to the cruise control.

Does the line that goes through the firewall (#3 in the picture) control both the q-track and heater controls?

The vacuum reading I get at idle is not rock-steady. It wanders back and forth relatively slowly between 16.5 and 17 in-Hg.

Both CTO's seem to be functioning. I'm not sure if their switching temperatures are correct, but they do switch, so I'm going on the assumption that they are doing so at the correct temperature.
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  #10  
Old 01-12-2006, 09:49 AM
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nograin nograin is offline
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That's a decent vacuum reading at idle for a stockish cam. A more radical cam would be lower and slightly less steady. Odds are good you have a close to stock cam.

EGR is supposed to come into play when engine is warm and at part throttle or cruise. It should not come into play at wide open throttle.

Your '79 emmissions is different than the later set ups. Same concepts, different and more complicated execution. For example, vacuum dump was eliminated around '84. (No really, the new system has more hoses and CTOs).

Therefore the initial timing etc. may be a little different for your Wag than say mine or any other year. Engine compartment label is the best reference if it is still there. Some place there is '79 vac diagram on the web. If you need I may have saved a copy - e-mail me.

IIRC, there is some info on CTOs and delay valves in the tech library at www.ifsja.org

Also, if you missed it, there is a post on searching this site. Do a search for search. I think you'll find it helpful now and in the future.

FWIW. On my wag, there are 2 vacuum reseviors. One is the coffee can like thing on the driver side fender and the other is the black ball on the firewall. The black ball is the main one. Without it the heater controls and 4wd switch don't work. Well what I mean to say is if there is a leak they won't work. If the ball is bypassed, they'll work only when the engine vac is high enough. However the quadratracs vac controls may have been hooked up differently than the selectracs. Some one else can fill you in on that.
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Old 01-12-2006, 10:36 AM
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TexasJ10 TexasJ10 is offline
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I know that people here have had trouble with Customefis in relation to the delivery of FI systems, but his web site has a really good explanation of how the emissions systems work on these rigs. The article is designed to be used to connect the emissions systems following the conversion to FI, but his explanation of how each system works will help you get yours working right.

Emissions Explanation by CustomEFIS
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  #12  
Old 01-12-2006, 10:39 AM
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BigRedChief BigRedChief is offline
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Good to know about the vacuum reading. I found the vacuum leaks that were in the #3 line. That line is the main vacuum line to the E-drive switch in the glove box. The E-drive switch was leaking, so I rebuilt it, put a small spacer in to get more spring pressure on the sealing faces and used a little bit of non-hardening permatex gasket sealer on the sealing surfaces. The switch holds vacuum really well now, but the E-drive actuator on the BW 1339 won't hold vacuum at all. Can I get that off/out without performing major surgery? If so I'll probably convert it to manual.

Lookie what I found:

According to my title the jeep is a 1979, but the hood sticker shows a vastly different vacuum diagram than what I downloaded for a 1979 FSJ. I had such a hard time seeing it I haven't looked at it in a while. A good, zoomed in picture reveals a lot.

I've got the search thing down (googlin'), but finding the specific information I'm looking for is nearly impossible.
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  #13  
Old 01-12-2006, 03:14 PM
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Good luck with the vacuum systems! Depending on who worked on it, it may have little resemblance to stock... I know mine did not when I got it!
If it looks like a stock carb, it must be. I don't think any rejeting kits are available, but don't take that for gospel.
Maybe a bad power valve would make it very rich? They do go bad and make a rich condition. But if you rebuilt it you would have replaced the valve.
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Old 01-13-2006, 01:34 AM
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Sent you the '79 diagram I had collected off the web. Functionally the same as what yours shows except yours also has the vapor lines to the charcoal cannister hookups.

Your e-sticker doesn't say, but I suspect that the 8 degrees @ 600 is under the following conditions: Vac to dist. removed and plugged. Transmission in drive. If the CTO is working, the first shouldn't matter, you'll get zero vacuum at idle. The second as you point out, is a little dangerous. Do it N, and if you can't get the idle down to 600, then set it say 2 degrees more (10) at 800. Adjust the mix. Then Reset the throttle speed.

Probably should start a new post on the BW vacuum switches.
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