timing off. please confirm my suspicion about timing

[acaciolo]

I found that I had a vacuum leak at my W pipe, so with that sealed up, the idle is rock solid around 850-900.

But, I still have a lack of power at lower rpms.

It was suggested to me that my vacuum solenoid was bad, but I just confirmed that was working. Please verify my (very newbie) conclusion:


Timing at idle (with no more adjustment in the distributor) is at 0.

If i remove the vacuum line to the distributor, timing is still at 0. (warm engine)

when I rev the engine with the vacuum line connected, I feel the solenoid click and I can feel vacuum on the disconnected line

when I rev the engine with the vacuum line connected, the timing jumps quickly to about 15 then more revving pushes it off the chart.

when I rev the engine with the vacuum line disconnected, the timing doesn't jump as quickly (think I am only getting mechanical advance here). more revving pushes it up a little more, but nowhere near as far as when the vacuum is connected.

so my newbie conclusion is that vacuum advance is working since it doesn't advance as much when the line is off and mechanical advance is working since it still advances when the vacuum line is disconnected.

therefore....the only thing that should be causing me to get such a low timing of 0 at idle is a distributor adjustment. and since my adjustment is bottomed out I need to pull the distributor and turn it one notch.

of course, I should verify TDC (not sure what is the best method for that) first.

others who have driven this who own deloreans said it is lacking power at low RPM. Could also be dirty fuel injectors, but I think the timing is obviously off and not caused by the vacuum solenoid as previously suggested.

agree or disagree?

thanks

tony c

[D Knight]

Agree. Your base timing is off


-D Knight-

[DMCMW Dave]

At idle with the vacuum line off zero is wrong (if everything is working it isn't necessary to disconnect the line, but I don't trust anything). Should be about 13 (to the left of zero).

Back where you started, I still bet you are off a tooth.

[NightFlyer]

Yes, sounds like it's off a tooth.

It's possible that the scale moved over time as well.

Bill has a nice write up about how to locate TDC and reset the timing scale:

http://www.dmctoday.com/showthread.php?428-How-to-Locate-TDC-and-Reset-Timing-Scale

Best luck - you'll get it nipped in the butt in no time flat :thumbup:

[DMCMW Dave]

Yes, sounds like it's off a tooth.

It's possible that the scale moved over time as well.

:

The scale can't move 12 degrees off.

[NightFlyer]

At idle with the vacuum line off zero is wrong (if everything is working it isn't necessary to disconnect the line, but I don't trust anything). Should be about 13 (to the left of zero).

Back where you started, I still bet you are off a tooth.

In other words, vacuum shouldn't effect the timing at all at idle, only under open throttle situations.

He's at 0 during this test because his base timing is off.

[NightFlyer]

The scale can't move 12 degrees off.

Good to know - thanks :thumbup:

[David T]

I found that I had a vacuum leak at my W pipe, so with that sealed up, the idle is rock solid around 850-900.

But, I still have a lack of power at lower rpms.

It was suggested to me that my vacuum solenoid was bad, but I just confirmed that was working. Please verify my (very newbie) conclusion:


Timing at idle (with no more adjustment in the distributor) is at 0.

If i remove the vacuum line to the distributor, timing is still at 0. (warm engine)

when I rev the engine with the vacuum line connected, I feel the solenoid click and I can feel vacuum on the disconnected line

when I rev the engine with the vacuum line connected, the timing jumps quickly to about 15 then more revving pushes it off the chart.

when I rev the engine with the vacuum line disconnected, the timing doesn't jump as quickly (think I am only getting mechanical advance here). more revving pushes it up a little more, but nowhere near as far as when the vacuum is connected.

so my newbie conclusion is that vacuum advance is working since it doesn't advance as much when the line is off and mechanical advance is working since it still advances when the vacuum line is disconnected.

therefore....the only thing that should be causing me to get such a low timing of 0 at idle is a distributor adjustment. and since my adjustment is bottomed out I need to pull the distributor and turn it one notch.

of course, I should verify TDC (not sure what is the best method for that) first.

others who have driven this who own deloreans said it is lacking power at low RPM. Could also be dirty fuel injectors, but I think the timing is obviously off and not caused by the vacuum solenoid as previously suggested.

agree or disagree?

thanks

tony c


From your description it sounds like:
Your base timing is still not correct
The vacuum advance is working
The mechanical advance is not working as it should
Firstly I would verify TDC against the timing scale. Next I would pull the distributor and check the parts for the mechanical advance. Once satisfied it will work I would reinstall the distributor setting the base timing to 13 degrees. Lastly I would again verify vacuum and mechanical advance.
It would make sense that you have no power at idle if your timing is still not correct. With the mechanical advance you should get 20 degrees of advance and with the vacuum hooked up another 20 and with both all in you should get 40. With 13 degrees base you would see a total of 20 + 20 + 13 = 53 degrees BTDC

[acaciolo]

certainly seems like I am tooth off.

with vacuum connected;
0 degree at idle

1/4" off the scale above 20 at 2000rpm
1/2" off the scale above 20 at 3500rpm.

I dont' know what those equate to, but my guess is they are about 13 degrees too low since my base it at 0.

gonna pull the dist and move a notch.

[Silverbullet]

Did you change Spark Plug wires?.... You could have got off one hole... seems if you are bottomed out, you could just advance all the wires one hole.

Craig

[acaciolo]

Plug wires have been changed, but I also verified and verified again that they are in the right holes.

The fact that the dist was already adjusted to one extreme leads me to believe that this problem existed before I owned the car.

T

[DMCMW Dave]

Did you change Spark Plug wires?.... You could have got off one hole... seems if you are bottomed out, you could just advance all the wires one hole.

Craig

Uhhh - Not on an odd-fire engine......

[Silverbullet]

Uhhh - Not on an odd-fire engine......

Oh ya... now I remember the Cap.... Sorry, Lots of Chevy experience. It would have to be 2 holes off... man...

Craig