Help! E4ME Dwell problem

[beige81]

Greetings,
If some one can point me in the right direction it would be greatly appreciated! The previous owner didn't take very good care of this car and I'm trying to get everything back the way it should be. I'm now at the point of trying to get the carb adjusted and am having a problem with the dwell. No matter what I do I can't get it to move from "10" on the scale. If you rev the engine it looks like it tries to move but no more than a couple of degrees. It is running lean but there are no vacuum leaks and no codes when I check the ECM(has been replaced twice-no difference). I did rebuild the carb and put all the settings where they are supposed to be with the proper tools. I can cover the carb throat and get a slight increase in idle speed but no change with the dwell either. The O2 sensor has been changed.
I have searched all of the threads that I can find and seem to be missing something. I purchased Corvette 1966-1982 Shop manual and all it has is the cross-fire info, AIM has nothing so any help would be awesome! If I can provide any other info please let me know.
Thank you again!!
Keith

 

[6880 Mike]

I'm confused. Dwell is a timing setting; a lean condition would be carburetor. Is the computer storing error codes?

 

[Barry08]

Greetings,<br>
If some one can point me in the right direction it would be greatly appreciated! The previous owner didn't take very good care of this car and I'm trying to get everything back the way it should be. I'm now at the point of trying to get the carb adjusted and am having a problem with the dwell. No matter what I do I can't get it to move from "10" on the scale. If you rev the engine it looks like it tries to move but no more than a couple of degrees. It is running lean but there are no vacuum leaks and no codes when I check the ECM(has been replaced twice-no difference). I did rebuild the carb and put all the settings where they are supposed to be with the proper tools. I can cover the carb throat and get a slight increase in idle speed but no change with the dwell either. The O2 sensor has been changed.<br>
I have searched all of the threads that I can find and seem to be missing something. I purchased Corvette 1966-1982 Shop manual and all it has is the cross-fire info, AIM has nothing so any help would be awesome! If I can provide any other info please let me know.<br>
Thank you again!!<br>
Keith

<br>
<br>

If memory serves me correct... dwell meter should be set for 6 cylinder.

 

[Peer81]

Yes you have to look at the 6 cyl. scale and when the L81 is warmed up. But I think you already know that.
First when you have rebuild the carb did you remove the idle tubes (with collar)? Under the idle tubes there could be some dirt that is blocking or slowing down the fuel.
How much did you turn the idle screws out? 3 1/3 run? Try it again with 5 of 5 1/2 runs out. Even for a standard engine the idle screw openings are to small. I opened mine up to '79 specs.

What I would do. First buy yourself a 81 GM Shop Manual AND the Cliff Ruggles carb book.
Good luck!

Greetings Peter

 

[LT4man]

Rochester E4ME, E4MC and E4MED Service Manual

Rochester Quadrajet E4ME, E4MC and E4MED Service Manual

137 pages: Covers all computer-controlled Quadrajet models. Includes step-by-step overhaul procedures, diagrams, adjustments and theory of operation. Fast, secure e-book download.

Cost is $9.95.

Should have all the information you are looking for!

The 6 cylinder scale on the dwell meter is used. Optimum dwell reading should be 30 degrees at idle. Dwell between 25 and 35 degrees is acceptable.

As far as covering up the throat of the carburetor and having the idle speed increase slightly: This definitely points to a small vacuum leak. I would always spray carb spray along the intake manifold gaskets, the carb base, the carb itself and anywhere else vacuum is present (vacuum hoses and connections). Any change in the idle speed would expose the leak.

 

[LannyL81]

I agree to the above: if covering-up the carb throat does anything other than cause the engine to die....air has found another path...there is a leak.
First suggestion - remove the vacuum line at the back of the intake manifold and cap-off the intake manifold. This will eliminate all the headlight vacuum lines.
Second - check the line coming out of the back of the carb that goes to the MAP sensor. The hard plastic line sure gets brittle over time.

To check the carb mixture control solenoid dwell - connect the positive or red dwell meter lead to the green connector located on the passenger side front of engine, connect the black or gnd lead to a good gnd on the block. Set or read the 6 cylinder scale.

If the dwell is not moving, and with the engine running put a small plastic straw or something similar down the hole in the carb so that it touches the mixture needles....if the "straw" does not move up and down then neither is the mixture control solenoid.

You say the engine is running lean which would mean the needles are pulled down into the primary jets and staying there.

If you need further help....it is here....just ask.

 

[beige81]

update

First, thank you very much for the few replies that I recieved. Each one was a little different and provided a piece of the puzzle. The biggest problem was the vacuum leaks that were looking straight at me. Replaced both headlight relays and had the carb base plate rebushed for the vacuum leaks. Since they were available I replaced the map sensor and the tps.
Everything adjusted and worked like it is supposed to. Now just waiting on some dry weather!
Thanks again!!
Keith

 

[LT4man]

Thanks for the update. You would not believe how many folks fix their issue and we never hear back.

I still have the vacuum gauge I bought when I first when into business over forty (40) years ago. I feel a vacuum gauge should be the first tool used by a mechanic when facing any type of engine problem. Tells you so much information immediately.

Please be sure to SAVE the WAVE!

 

[LannyL81]

First, thank you very much for the few replies that I recieved. Each one was a little different and provided a piece of the puzzle. The biggest problem was the vacuum leaks that were looking straight at me. Replaced both headlight relays and had the carb base plate rebushed for the vacuum leaks. Since they were available I replaced the map sensor and the tps.
Everything adjusted and worked like it is supposed to. Now just waiting on some dry weather!
Thanks again!!
Keith

Great that you got it fixed...but a bit confused with your post above; you say you replaced the tps and the map sensor. Just wanted to know for sure that it was the tps that you replaced. The tps is internal to the E4ME carb; so you removed the carb air horn? Did you replaced the tps pluger seals or the tps itself?

Just curious.

 

[beige81]

Lanny,
Yes I removed the air horn and replaced the tps itself and the seals. Just a general overhaul of the carb. Read every thread I could find and got the manuals.
Keith