drifting timing (caution VERY long winded!)

drifting timing (caution VERY long winded!)
Thought this was a interesting article
Mike


This is something for anyone who is converting a vac advanced HEI to ECM controlled timing. I learned this the hard way.
frown.gif


When disabling the rotation of the advance mechanism, care must be taken to ensure that the rotor reluctor phase is not thrown out of whack. In simple, quick terms, the stars have to line up when the rotor is in position on the post contacts.
Do a google search for "rotor reluctor phase" and you'll learn about it better than I can explain it here.

I unknowingly hosed myself when I replaced the original shaft (the rotor mount was loose) with one that I cannibalized from another dizzy. Out of ignorance, I arbitrarily picked a location about in the center of the movement to tack weld the bar secure. The reluctor ended up being about 10* out of phase. It was difficult to start, even though it was timed right. It would cough and backfire. The Jeep would start OK if the bypass wire was disconnected. Then once the engine was @ operating temp, I could shut it of, reset the ECM and restart OK. I spent about a week chasing my tail trying to figure that one out. I guess the computer did a heck of a job compensating for the error, all things considered.
pics are here: http://s76.photobucket.com/albums/j15/bluecjguy/other/hei%20rotor%20phase%20issue/
__________________
www.bsjeepers.com
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'76 CJ7 ; CJ-ified yj tub swap
lotsa home brew items
pics of the project:
http://s76.photobucket.com/albums/j15/bluecjguy/
 
I just had an idea. Does anyone know where to find the fuel pump pressure rates for both the AMC 304 and the AMC 258 i6 / 4.2l ?

My thought is this; converting to a Weber carb you need to use a fuel pressure regulator because the stock AMC 258 i6 / 4.2l fuel pump makes to much pressure for a Weber. Same deal for a Holley 2300 carb. Got to have a fuel pressure regulator because the AMC 258 i6 / 4.2l fuel pump rates at like 9lbs, the Weber and the Holley I've read that they only need 3 to 5 ish lbs.

What about the Motorcraft 2100? Why wouldn't I need to regulate the fuel pressure to it? So, I need to find out what the output pressure is for the stock fuel pump on a 78-81 AMC 304 with a factory MC2100. Because if it's less than that of the stock AMC 258 i6 / 4.2l pump....... I need a fuel pressure regulator.
 
Found it in an old chilton's believe it or not.

Fuel pressures are as follows:

4-134: 2.50-3.75psi @ 1,800 rpm
4-AMC 150 : 4.00-5.00psi @ idle
4-GM 151 : 6.5-8.0psi @ idle
6-225: 3.75psi minimum @ 600 rpm
6-226: 3.50-5.50psi @ 1,800 rpm
6-230: 3.50-5.50psi @ 600 rpm
6-AMC 232 i6 : 3.00-5.00psi @ idle
6-AMC 258 i6 / 4.2l : 3.00-5.00psi @ idle
8-AMC 304 : 4.00-6.00psi @ idle


Well :censored:, just blows that theory right in the you know where doesn't it? It also proves that things I have read on other sites about the fuel pressure from the AMC 258 i6 / 4.2l fuel pump is too high is just :dung:.... Back to the drawing board.
 
Finally, another update. Here's the list;

- I went through and retorqued all of the bolts on the intake/exhaust manifold.

- The better of the MC2100 carbs I have has been "freshened" up, by that I mean went through and cleaned and reinstalled without tearing it apart.

- The gaskets from the manifold to the adapter, adapter to the spacer and spacer to the carburetor have been replaced.

- I double checked to ensure that the carb is secured to the manifold good and tight.

- Every last inch of vacuum hose that I can find has been replaced.

- I added a Mr. Gasket fuel pressure regulator and a cheap-o see threw plastic fuel filter.


Same results, she'll fire right up and sit on high idle, but once it comes down off of high idle it shakes and shutters and dies. I've plugged both the vacuum advance on the distributor and the carb. Same results. I did however keep it running long enough this time to keep one hand over the butterflies of the carb and shoot some carb cleaner around. I think I may have found the culprit of my vacuum leak. The only place that when soaked with carb cleaner effected the way the engine ran was on the base of the carb towards the firewall. Which is leading me to believe that maybe my carb adapter isn't perfectly square/level :wtf:

I guess it looks like I'm tearing the carb back off to take the carb adapter off to see if that's my culprit in all of this...
 
Before you tear it off look really close to make sure nothing is hitting anything, keeping it from sealing.
 
Old Dog said:
Before you tear it off look really close to make sure nothing is hitting anything, keeping it from sealing.
Click to expand...


Got in there with a flashlight, I can't find any reason that it shouldn't seal up tight :confused:
 
Cheepjeep85 said:
maybe the plate is warped, i know that the mr gasket adapter isn't very high quality because thats what i'm running, but no leaks
Click to expand...


It isn't the Mr Gasket adapter, it's a solid hunk of machined aluminum I bought from a guy who sells the MC2100 conversion kits on ebay ehrmannmp. That doesn't mean it couldn't be warpped though :bang:
 
If the leak was that large and that accessable you would have found it when you sprayed it with carb cleaner.
 
If the plate IS warped, that's a pretty easy fix. You can drawfile it flat again, using a dead-dry mill file, taking care to clean the file VERY often to prevent it from "pinning".

Same goes for the intake and bottom of the carburetor. You can nearly always make stuff flat.
 
Okay, so I ordered a replacement adapter plate from Summit made by Transmission dapt. Got the new adapter installed, along with new gaskets and a good K&N fuel filter. Pumped the gas a couple times, turned the key, she fired right up. As a matter of fact she sat right there and idled pretty well for a good 15 minutes.

So I thought hell, I should take her for a spin. Jumped in and took off down the road. Got to the first stop sign and when I downshifted to second to stop, it stalled. I think it's just cold, no big deal. Well, after I'm sure it's good and warm every time I left off the gas it tries to die. I can't tell if it's flooding itself or what. I grabbed my wifes phone and took a video, it's kind of crappy, but maybe you can get an idea.

th_0228001348.png

I really had to crank the idle adjustment all the way up to 1000 RPMs to keep it running, but the idle is still fluctuating up and down. The only two things I haven't replaced are the distributor, or the summit ignition box, any idea's?
 
It's now sat and cooled off for a couple of hours. I just went back out to the garage, fired it up and it sat there and idled, a little rough, but it idled. "Goose" the engine, and it will die. That's got to be in the carb, power valve, begger jets, something.

I also checked manifold vacuum pressure, dead on 20lb/hg. I'm so freaking confused... :confused:
 
Did we already ask you about your EGR? I don't remember.
 
Are you using a filter with a bypass?
 
Ok. Let's eliminate some things. First, did this engine ever run well in your presence? Did you ever start it with the YF in place? Did it run decently (albeit a little weakly) with the YF? No... I won't suggest swapping the intake manifold back.

Find every vacuum line coming out of the carburetor & intake manifold. Go pick up a pack of vacuum hose plugs from NAPA & plug EVERY vacuum port on the whole motor. There should be... well, there should be about three, if you don't count the PCV (which we'll leave in place). Start it (it should start fine without the vacuum advance on the distributor) and warm it up well. If you like, drive it to the corner & back. When you get back, give it a listen - does it seem to idle normally now?

If not, toy with the idle mixture screws first. Get it to 1/4 turn out from "too lean" if you can. A tach may help, a vacuum gauge may help. If the idle speed rises while you back out the mixture screws, adjust it back down again.

If that gets you a double handful of noplace in a hurry, get a can of starter fluid & spray everywhere you think a vacuum leak might possibly be... including the brake booster if you have one.

I'm betting, though, that it DOES idle normally now, with all the vacuum lines plugged. I'm betting you have a temperature-controlled vacuum valve that's turning on when it warms up & directing vacuum to someplace problematic. If in fact it does idle normally with everything plugged, put ONE circuit back where it belongs while it's running. Run? Put another circuit back. Rinse. Repeat. One by one, bring the vacuum stuff back online WHILE IT RUNS until you find one vacuum line that brings it all down when you plug it in. THAT one connects to whatever your problem was/is.

Could just be a bum carburetor, though - one that only really wants to idle when the choke's on. If so, we'll fix THAT, too. You said you swapped the 1.08 jets out of it? What happens if you put 'em back in again? I've heard before that those are the ones you WANT... but they shouldn't affect the idle, only normal cruising mixture.
 
TDHofstetter said:
Ok. Let's eliminate some things. First, did this engine ever run well in your presence? Did you ever start it with the YF in place? Did it run decently (albeit a little weakly) with the YF? No... I won't suggest swapping the intake manifold back.
Click to expand...

Yes, I bought the CJ right about 4 years ago to the date. It ran well, it just needed a new Dura-spark module. I left the CJ with my dad for all of 2006 and into 2007 while I was stationed overseas. He drove it to work about once a week. After I came back I drove the CJ to work all summer long in 2007 and 2008. It wasn't until this time last year that I decided to start really tinkering with the engine.


TDHofstetter said:
Find every vacuum line coming out of the carburetor & intake manifold. Go pick up a pack of vacuum hose plugs from NAPA & plug EVERY vacuum port on the whole motor. There should be... well, there should be about three, if you don't count the PCV (which we'll leave in place). Start it (it should start fine without the vacuum advance on the distributor) and warm it up well. If you like, drive it to the corner & back. When you get back, give it a listen - does it seem to idle normally now?

If not, toy with the idle mixture screws first. Get it to 1/4 turn out from "too lean" if you can. A tach may help, a vacuum gauge may help. If the idle speed rises while you back out the mixture screws, adjust it back down again.
If that gets you a double handful of noplace in a hurry, get a can of starter fluid & spray everywhere you think a vacuum leak might possibly be... including the brake booster if you have one.

I'm betting, though, that it DOES idle normally now, with all the vacuum lines plugged. I'm betting you have a temperature-controlled vacuum valve that's turning on when it warms up & directing vacuum to someplace problematic. If in fact it does idle normally with everything plugged, put ONE circuit back where it belongs while it's running. Run? Put another circuit back. Rinse. Repeat. One by one, bring the vacuum stuff back online WHILE IT RUNS until you find one vacuum line that brings it all down when you plug it in. THAT one connects to whatever your problem was/is.
Click to expand...


The only vacuum lines/systems left on the engine are for the PCV valve, the power brake booster, the vacuum advance from the dizzy to the carb, and one small vacuum line to the base of the carb for the choke pull off valve. The rest are plugged, including the CTO (coolant temperature override) switch which is still installed on the block. I did cap those off with vacuum caps and a little dab of RTV. I've even capped off the non used ports on the charcoal canister, and the vapor return line to the gas tank, which I'm not using because of the fuel pressure regulator.

I have sprayed carb cleaner all over the place, that is what lead me to replacing the carb adapter plate. I can go through and cap all of the vacuum lines, see if that gets me anywhere.


TDHofstetter said:
Could just be a bum carburetor, though - one that only really wants to idle when the choke's on. If so, we'll fix THAT, too. You said you swapped the 1.08 jets out of it? What happens if you put 'em back in again? I've heard before that those are the ones you WANT... but they shouldn't affect the idle, only normal cruising mixture.
Click to expand...


The 1.08 is the venturi size of the Motorcraft carburetor. I currently have the smallest size (46) set of jets that I have in the carb. I have already tried backing down the idle mixture screws to about 1 1/2 turns out, with no real noticable results. Now when I go back out to the garage, I can really smell gas. I thought it smelled really rich earlier, but I wasn't positive, now three hours later when I walked back out to the garage, it really smells like gas. I'm wondering if the choke is stuck open, flooding the carb? It doesn't explain the wandering idle, but it would explain the flooding.

Speaking of bum carbs, I'm almost fed up with tinkering with this freaking Motorcraft carb. Everyone has said it's a great carb and other people have had good success with them, but I'm on the edge of throwing both of them that I have in the garbage and just ordering a Holley.

Thanks a lot TD, keep the ideas coming, I appreciate it a ton :chug:
 
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The choke being OPEN won't flood the carburetor - the choke being stuck CLOSED will. It'll make it run like greasy chit, too, after the engine's warm. Let's look at that good & hard. Electric choke?

If that doesn't do it, do plug off the distributor vacuum line & at least put your thumb over the brake booster line (after the motor's warmed up). Ya ain't goin' anyplace right now, no need for power brakes. :) I think we can leave the choke pulloff in place; if starting fluid didn't leak in there, it ain't leakin'.

Those Motorcraft 2100-series carburetors really ARE very good carbs for these engines. We'll track down this bug & kill it & you'll be just WICKED pleased for having done the swap. :)
 
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