Carburetor Tuning

[FlakeyJake]

I'm getting my money's worth from this forum today. I believe that my carburetor (2150) is not right. I believe it may need to be rejetted as it is, I'm afraid (gulp) a rebuilt from carquest or the likes. I live in Denver and I believe that I need to lean it out some etc.

Where do I go to learn about carburetors? I don't understand how they work, the different circuits etc. I want to understand what needs to be done given a particular symptom rather than someone telling me to "turn the screw to the left".

Does anyone have any books they would recommend on carburetors in general? or more specifically understanding the motorcraft 2150?

TIA

[reddog]

What symptoms make you think you need different jets? What jets are in there now? I have some old holly books that are pretty good with carb theory.
Sorry but I have not seen (or looked) for much on the 2150.

Kerry

[Veepster]

There are some Holley books that are great! they are published by "SA designs" all carbs are the same in theory.....Good Luck!

[FlakeyJake]

Well I just got back from the emissions joint with some very bad news. After replacing about everything I can think of on this thing ( motor, carb, egr, ignition, etc. ), it still fails with high CO.

I need help with what to do next. These were my readings ( more or less )
reading limit result
HC 2+ 4 PASS
CO 62+ 25 FAIL
NOx 2+ 9 PASS

I was thinking that this thing was running rich as when I did the coil/wire/cap upgrade, I remember the plugs being a bit blackened, not overly so, but still black. Today, after the hot spark upgrade for a couple of weeks now and the recent MSD-6A install, I pulled a plug to see what it looked like before heading to the emissions gas chamber. The plug was whitish! And, according to the back of the haynes manual, that means it's too hot, or too lean, too much advance, or manifold vacuum leaks....the opposite of rich.....so I took my chances and went on down, only to be shot down.

Tonite I checked for vacuum leaks by spraying carb cleaner everywhere I could see a vacuum connection -- nothing.

I bought a vacuum gauge as I recall someone's opinion here that it is a good way to set the idle mixture... where do you hook the thing up?

I found a hose coming off the manifold towards the rear of the engine going into what seems to be a air temperature vacuum switch inside the air cleaner. I hooked my vacuum gauge inline to that and there is absolutely nothing on the gauge. If I pull the connector off that, and plug it with fingers, the vacuum gauge hops up to about 15" and up to about 20" with the motor revved. So it looks like that switch is bad for one thing.

Now I'm printing the '89 vacuum diagram (hopefully it's the same as the '88 ) and will check all those hoses ( again ) but I supplicate to the wise tuning gods here in ifsja-land to point me in the right direction.

What do I do now? Help :(

[Dan G]

bnscott,

You replaced the carb right? Let me give you the good news and the bad news. Good news is you probably have a good carb, bad news is it ain't tuned for YOUR engine.

See, a 2150 was also available on a 77 Lincoln Versailles (351W with a 9" disk brake rear which I junked OUCH!) as well as a host of other vehicles.

When these carbs are rebuilt, the rebuilder sets them to an APPROXIMATE setting for most of the motors they apply to.

What this means to you, Get a Haynes manual from PepBoys, the Zone, Strauss, whatever, they've got an excellent procedure (I've been told) for setting the carb. Then dig in. You've got to dial in the carb for your vehicle.

Sorry, that's the bad news.

It could also be your catalytic converter.

[Ernzo]

Hi fellow derverite! MIne failed emmisions as well, twice. I asked to see the referee and made an apoiontment. He looked things over and gave me some VERY good information. Seems GW are a regular in his clinic. I cannot exactly remember the deal on CO, but I know it is a smog equipment deal, the good news is the HC is PASS. Anyway, after seeing him, he told me to call the Emissions clinic, make an apointment and go there for further testing. I did. They were a little surprised to see me, seems not many regular folks use the service, messed up their card game, maybe. Anyway, these are all free to the public services provided by Colorado, or at least they were 3 years ago. The FUrther testing was great, basically I found that I needed a new carb, but the vacume was good, cat was good etc. etc.

There are some very good SMOG sites online as well that really go into detail about the readings and what they all mean.

luck!

[Ernzo]

Check this link

http://www.recarbco.com/technical/index.html#smog

[DjD]

You can go to www.smogsite.com (http://www.smogsite.com) and read all about emissions theory, diagnosis and possible corrective action. They say that, “Too much CO is always from a rich condition. There wasn't enough oxygen to let the burn process finish to get to CO2.”
Since you mention a possible problem with the air cleaner housing temp vac switch, you might just want to make sure that the door in the air cleaner snorkel is opening after the engine is warm to let fresh air in.
The emission numbers you stated are a little confusing. In NJ our standards for a ’90 GW are:
NOx……………1076 ppm (parts/million)
HC………………159 ppm
CO%……………1.42 %
CO2%………….. No standard but is a good measure of engine efficiency and helpful in diagnosis.
O2%…………….. No standard, but could be helpful in diagnosis

Read a post on the board the other day where somebody dumped about 5 or 7 bottles of dry gas in his almost empty tank and passed with no problems. You could always try that.
Good luck!

[DjD]

ernzo, gr8 link! Thanks

[FlakeyJake]

Sorry about the confusing readings. Here is what it says exactly ( from the report ) I'll try to make it stay in a readable table...



An update, while I was looking into the idle mixture scenario I realized that my wonderful mechanic skills had caused a loose connection on my coil wiring job during the msd 6a install. I fixed that and then leaned out the idle mixture to about 7/8 of a turn to the rich from all the way closed. The idle is a bit rougher, but it seems to have more acceleration.

I guess I need to set the idle speed & mixture properly and the timing etc. before I try the test again.

I like the dry gas idea, that's easy to do smile.gif

I now have one question, when I change the idle mixture, how does that affect the normal "run" mode? Does it lean that mode too? Or is that managed by some other mechanism?

Thank you for your patience and wisdom.

[reddog]

The idle adjustment affects the idle and the transition to the main jets but not too much in the "run" mode.
Use straight manifold vacuum for the vacuum gauge. Depending on your Jeep there could be two temp sensors in the air cleaner. One prevents vacuum to the EGR when cold and the other controls the hot air flap in the air cleaner.

I suspect that your problem is not major and I suspect that it in the carb adjustment. Do you know what jets you have in there? Remind me, in Denver you guys do the dyno test correct? I think that since your HC and NO are good and low that you have no major problems going on and will be fine once you find the right adjustment.

Kerry

[FlakeyJake]

reddog:

I don't know how to tell which jets are in the carb -- is it possible without taking it apart?

Yes they do the 4 minute extendo dyno varied speed test.

On the Colorado Air Care website it talks about the 82-91 Grand Wagoneers as being some of the dirties vehicles on the road:




This is why my in my original post, I was asking about rejetting...

[jeepbob]

I would check the jets for size but you have to pull the carb apart. You do not have to pull the carb off the motor to do this just take the top of the carb off. You might also want to check the power valve and/or go to one that opens later. While I don't remember for sure, you may be able to use the ones from Holley and get one that opens at 4.5 to 6.5 inches of mercury (the std measure of vac).
To use your vac gauge hook it up to a port that comes off of manifold vac like the port that goes to the Vac ball that the heater controls run off from. Adj the mixture on both sides until the needle on the gauge remains steady and does not waver. Keep the idle speed down to about 750 so the main metering circut does not kick in.

[Dude]

Check Amazon.com. Look under Holley carbs!!

[FlakeyJake]

Update:

Well, I went ahead and had a new carsound hi-flow cat installed ( could't hurt ) and then adjusted the idle speed and mixture just richer than when it caused a dip in rpm at 600 rpm.

The vacuum at that speed, however, seems to be low, around 10"-12". And the vacuum needle does shake a bit, it doesn't fluctuate by like 3" but maybe 1". I hope this isn't a problem. Could the shaky & low vacuum be due to the 'RV' cam that was istalled at rebuild time?

While in there I checked the fresh air snorkel and lo and behold one of the doors was closed. (and yes, the engine was warm ) I took the vacuum motor off, then opened & closed it a few times, and then put it back on and then it opened the door.

I'll give the smog test another try tomorrow ... cross your fingers...

[FlakeyJake]

Woohoo! I passed.

<blockquote>quote:</font><hr>
Passing numbers:
HC GPM 1.3109
CO GPM 22.6356
NOx GPM 1.8902
<hr></blockquote>

Net changes:

Adjust idle speed & mixture.
change cat ( it was _very_ plugged )
fix loose coil wire.
And.....opened the aircleaner snorkel valves!!!!

Thanks for all your help....now I'm good for 2 years ( I think )