Timing basics

sierraspider · Post by **sierraspider** » Wed Oct 22, 2014 7:08 pm

Finally getting my 82 FI close to fully sorted out, but I have a bit of a backfire on hard decel. In reading relevant posts, I'm going back to basics -cam alignment and timing.
Now here's the dumb ? How do I time it. I have light but where do I get power for it (battery is in rear). Do I pinch off advance and what cylinder/wire do I put light on (#4). I put paint on crank pulley and marker during timing belt change so that should part be easy. Also in one of Brad Artique's posts he mentioned timing by ear. (get it close, then listen to how it's running-) Also how accurate are the tachs in these things, my light isn't digital so when setting idle, not sure if I'm close. I have a manual on the way, but wanted to get this done asap, so hence the dumb ?s

aj81spider · Post by **aj81spider** » Wed Oct 22, 2014 7:32 pm

I'm no expert - so in the event of conflict between what others tell you and what I write - believe them. However here's how I did it:

> I took power off the alternator stud. Ground from a convenient screw head in the bay.
> I put the sensor on the front spark plug wire (#1). It doesn't matter if it's 1 or 4, as they both fire at the same crankshaft position.
> When idling (depending on your year) you should have 0-10 degrees of advance. My timing belt cover had 0,5, and 10 degree positions. I just used the 10 degree position.
> Point the light at the crankshaft and adjust from there.

I'm not sure how accurate the tach's are. I set my idle so it looked like about 850 on the tach (hard to tell as the dial doesn't have many gradations - I just made sure it was under 1000) and made sure the engine would stay running.

Good luck. I had never done it before, and it wasn't that difficult.

76was124 · Post by **76was124** » Wed Oct 22, 2014 8:16 pm

For timing light power I use the +terminal on the coil (should be the tab with the red wire, closer to the distributor), and for ground I used the valve cover bolt.

Idle is set by a different procedure, as in with the engine fully up to temperature by setting the idle screw after setting throttle stop and tps, after setting timing.

So first as you are doing, set the timing before setting the idle. Assuming you confirmed the cam pullies are on their marks when the crank pulley is at TDC, then using the timing light set the advance...for me 15 degrees runs better than 10. Basically get the highest idle possible without pinging or backfires when road rested. If I remember correctly, you do need to remove the vacuum hose off the distributor advance and plug the hose when setting the timing.

Then follow the idle adjustment procedure.

sierraspider · Post by **sierraspider** » Wed Oct 22, 2014 9:44 pm

Thanks for the info.

vandor · Post by **vandor** » Wed Oct 22, 2014 9:52 pm

If it's backfiring into the exhaust on deceleration than you likely have an exhaust leak and it's not a timing issue.

toplessexpat · Post by **toplessexpat** » Thu Oct 23, 2014 2:38 am

Agree with Csaba.... But if you do want to play with timing - I use one of these lights....

http://www.tooldiscounter.com/ItemDispl ... &kw=ESP120

.... Just clip it on to the lead from cylinder 1 and off you go. No need to find power, and eases my fear of getting a cable either caught up in something turning or fried by something hot.

majicwrench · Post by **majicwrench** » Thu Oct 23, 2014 3:07 pm

Good advice above. Backfire on decell is not a timing issue.Exhaust leak can cause it, so can other things.
Do unplug your vacuum advance hose.
That bit about "timing by ear" is a classic example of the kind of BS that ends up on the internet. Don't do it.

76was124 · Post by **76was124** » Thu Oct 23, 2014 6:13 pm

Isn't there a difference between the popping on deceleration you can get from an exhaust leak and a true backfire? I always thought that a true backfire occurs from pre-ignition.... So timing too advanced, exhaust valves closed intake still open, and spark, then POW!! Which blows combustion back through the intake, and on FI, potentially bends the AFM flap or blows the air hose off? with Carburetors the true source of the term is apparent.... backward traveling flames!!

sierraspider · Post by **sierraspider** » Thu Oct 23, 2014 6:32 pm

Lots of good posts. Confirmed cam alignment (good). Should have been clearer, it's intermittent popping when I really stand on it then let off or if I go down a steep grade in lower gears not back fire. Having trouble seeing mark on crank pulley so I going to put a dab of white paint on mark.. To be continued

garion · Post by **garion** » Thu Oct 23, 2014 9:09 pm

Just to add to the ways of powering the timing light, I use one of those jump start battery things. No extra wires in the engine bay.

majicwrench · Post by **majicwrench** » Thu Oct 23, 2014 9:20 pm

A little backfiring in exhasut on decell is no big deal.
Is impossible to have timing so advanced it fires while intake open. Engine would not run.

Backfire is due to unburned fuel and unburned O2 ending up in hot exhaust at same time. Anytime you decell that happens to some extent. Pop pop pop is kinda normal. BANG KAPOW KABLOEEEY is not normal and needs to be adressed.

76was124 · Post by **76was124** » Thu Oct 23, 2014 9:43 pm

majicwrench wrote:..... BANG KAPOW KABLOEEEY......

I often wondered how to spell that sound

To continue the clarification http://en.wikipedia.org/wiki/Back-fire

majicwrench · Post by **majicwrench** » Fri Oct 24, 2014 10:53 am

That wiki article is poorly done fiction. You cannot, cannot, have the timing so far advanced that the plug fires with the intake open, the engine would not run!!

76was124 · Post by **76was124** » Fri Oct 24, 2014 6:28 pm

majicwrench wrote:That wiki article is poorly done fiction. You cannot, cannot, have the timing so far advanced that the plug fires with the intake open, the engine would not run!!

Nice thing about the internet....I can always find some one to agree with me even if I am wrong.

I understand what your saying...car wouldn't start AND run... I agree. But I've seen backfires on starting attempts due to incorrect timing.

I know we are taking this thread off track a bit, and seeing all your posts and implied career in your user name, I'll bet I'll be proven wrong but am open to a brain exercise and an education if your willing to continue the discussion.

If you can't blow flames into the intake or carb (which does happen) unless the intake valves are at least partially open during the Kaboom. Doesn't the cause have to be due to pre-ignition if the valves are all working and set correctly to the crank? So then what can cause pre-ignition( Especially with a cold engne)?

riverdadd · Post by **riverdadd** » Thu Nov 06, 2014 9:32 am

I use a small 12 volt battery ( like a motorcycle battery) set on the floor to power my timing light. that way no cords can get caught in the machine. works for me....... my .02

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