88305tpiT/A

iTrader: (2)

The timing is not advancing when I look at it with a timing light. this has been a problem with this car since I changed the distributor to and msd pro billet. I am wondering if the leads on the ignition module in the dissy could be switched? What would that do?

When I disconnect the est wire and try to set the timing the mark indicates its at 14+ degrees but when I try to rotate the dissy to bring it down to 6 the mark jumps WAY retarded when I go down past 12. Like its jumping to the previous post or something. Is there any way to adjust the phase of the pickup on this distributor? I looked inside and it looks like the positions of the pickup and trigger star are fixed - no way to adjust.

I also noticed that when I tried to just set the base timing to 14 degrees in the code and leave the base dissy timing there, I started the car and the timing light said it was idling at 4 degrees advanced. That would be coincidentally the amount of timing the computer was trying to add to the base to get to 22. so again I think that the 2 pins on the back of the module in the dissy might be switched????

(cartman voice)_this is really starting to **** me off!

car is an 88 running 6e code, divorced coil, 8 pin module. and I am doing all this with the accel 300+ box disconnected so that shouldent present the problem.

88305tpiT/A

iTrader: (2)

ok so I just had the module tested and its ok. I also looked on MSD's website and the leads from the pickup were switched. so I switched them back.

I started the car with the EST disconnected and was able to set the timing normally to anything I wanted (went from 6 to 14 degrees advanced). the previous behavior of jumping to retarded settings did not happen.

but then when I reconnected the EST wire and started it again, the car almost wouldent start and the timing was around 0 degrees. I am thinking this HAS to be a pickup phasing issue. Is there anything I can do to fix this. Maybe move all the wires over one post?

Grumpy

During crank the timing is just off the module, the EST only goes live over ~400 RPM. If it cranks really slow, then it sounds like your initial timing to too advanced.

If with the EST disconnected the timing advances, that would mean it's connected correctly.

I've never had anything go right with MSD products, BTW.

88305tpiT/A

iTrader: (2)

Grumpy,

Thanks for the help. I grasp what you said about crank timing but I only set the timing with the engine running.

>>>If with the EST disconnected the timing advances, that would
mean it's connected correctly.

Really? I thought that the EST (meaning the computer signal for timing advance) would ADD to the base timing set from the distributor position. At the point I am trying to set timing 800-1000 RPM, the timing should be around 20-22 degrees BTDC. with a base timing of 6 that would mean that the EST wire from the computer needs to signal 14-16 degrees of advance.

Why would the timing advance with EST disconnected? It should retard I am dumb please explain....

88305tpiT/A

iTrader: (2)

And I am beginning to feel the same way about MSD stuff too. Only problem is Accel stuff isnt too much better. Ive had one of their coils and a couple modules go bad on me.

hey this is cool BTW, I feel pretty good drawing you for a reply.

If its not too much to ask I have more questions about the timing circut that you may be able to answer if you dont mind.

First off, you said that the module does timing under 400 RPM which makes sense b/c the main sparc table starts at 400 in the 6e. But the 6e also has tables for "startup spark advance vs. cooling temp" even though it is zeros. Is this table affecting cranking spark?

Second, when and if the module has sole control of spark timing, what is its curve? Is there any variability in the amount of advance the module gives. All my experience suggests that the module adds or subtracts nothing without the EST signal.

Thanks again for the reply. I think after attempting to talk to MSD tech this coming week I will look for a new dissy rather than have them fix mine or sell me another one. Any suggestions?

Grumpy

The distribuutor generates a A/C type signal, so the faster you spin it the more voltage it makes. While they call it a 0 cross detection system, it's not really. So you get a small amount of advance do to that. It also makes the car more driveable in limp home mode.


----/\------

....../\
----/..\----

Ignore the dots as they are just place holders. Maybe this'll help illustrate things.

Grumpy

During cranking at less then 400 RPM, it's all just in the hands of the ignition module.

The built in curve is due to the physics of how an alternator works, spin it faster and you make more voltage, and area under the curve.

The GM dissys are fine. If you're going to spin a V8 much over 6,000 (with a single coil set-up) all you need to do is add a CDI to the existing parts.

88305tpiT/A

iTrader: (2)

cool. Thanks for the enlightenment.

So you are saying that for a higher rpm the "spikes" get bigger and their shape change leads to advance. OK

But I have seen that with my timing light with the engine running and the EST disconnected. it amounts to less than 3 degrees as far as I can see.

What I am seeing is more on the order of 6 to 15 degrees of retard between when I have the EST unplugged to when its plugged in at idle. I guess I could emulate and see if changing the base timing in the code changes this behavior.

GM dissy sounds good to me. At least that way I can hope it will go back to the way it was before I got this MSD unit.

RBob

iTrader: (1)

Someplace, somewhere, I recall the MSD ref+ (DRP) signal as being inverted from the standard GM ref+ signal. Wish I could remember where I saw that. Anyway, if I wasn't dreaming about seeing that. . . it will cause exactly what you are seeing. The GM ECM uses the failling edge of the DRP as the initial timing position of the distributor.

By inverting the DRP signal the ECM will 'see' the initial timing setting earlier. As Grumpy mentioned a standard small cap GM distributor and module is hard to beat.

RBob.

88305tpiT/A

iTrader: (2)

You know, I remember on the MSD website seeing a trouble shooting page that said you should use the polarity of pickup leads that gives the most retarded timing.

I think thats what I did a year or two ago when I tried to tackle this problem and settled on having the leads reversed to the module.

But either way I still think there is a phasing problem because both polarity configurations have problems with timing consistency.

Im thinkin GM -- BTW where would I get one cheap?

Grumpy

Cap and rotor from your local Delco Parts Dealer, and the actual Distributor from a junkyard. The small caps, allow for using a coil of your choice. I put a lot miles on a Crane CDI, and coil set up without a hint of any problems.

3.8TransAM

you know, can anyone chime in on this one any further?

After a spate of distributors dumping on me the past yr or so(6 including my own and friends cars, all gm distribs too on tpi cars)(multiple nuked pickup coils, one reluctor and one magnet set) I broke down and dropped the $$$ on a nice MSD one for my car.

I havent started it yet(or even tried to) will I run into mystery timing issues on my new 383 now? Have to get complete new guts for my dissie(GM) or find another one in the yard.

later
Jeremy

RBob

iTrader: (1)

Sure. Yes.

RBob.

88305tpiT/A

iTrader: (2)

here is a link to the thread I started on the MSD tech site.
http://www.msdignition.com/forums/in...ST&f=5&t=3033&

I will see what I can dig up for y'all.

{edit}
I searched this board a few times for people running this distributor and didnt bring up many people that had problems. I think I might be more the exception than the rule.

88305tpiT/A

iTrader: (2)

Ok update.

The guy at MSD seems really helpful and he even sent me a new module for free without seeing a recipt (cool guy). But the problem is still that the timing seems to jump around with the EST disconnected. With the EST connected the timing seems more normal so I am going to mess with the main spark table to see if it truly is giving the correct amount of timing.

I think I will buy a timing tape to put on the damper so I can tell what I'M really getting here.

RBob

iTrader: (1)

The timing jump you are seeing as the RPM's increase is correct (msdtech posted the same in that thread). With the EST disconnected and the engine RPM < 1200 the timing should hold rock steady. As the engine RPM is increased, somewhere around 1400-1700 RPM there should be a sudden jump in SA. Typically around 12 degrees more.

Then with the RPM falling the SA should go back to the base timing.

RBob.

88305tpiT/A

iTrader: (2)

yes that is what I am seeing now but before the "switch" would happen at a much lower rpm making setting the base timing very difficult.

88305tpiT/A

iTrader: (2)

I also seem to have solved my high rpm spark problem. I set the base timing ( and distributor timing) to 14BTDC in the code and I can get the full 45 degrees of timing when free reving in park. I guess when you run the ARAP its better if you set the base timing high so that the computer doesnt have to advance the phase of the pickup much.

RBob

iTrader: (1)

Interesting. I believe this goes back to where you felt there was a phasing problem. I concur with that assessment. The GM distributors do not show this anomaly. Nor do they need the base timing advanced so far in order to properly fire at 45° BTDC.

RBob.

chickenhawk

Sorry to resurrect this one from the dead but I just want to say thanks for posting your results as I have run into the same problem... ( surging when setting the dist. timing to 6 deg, commanded timming incorrect)

My changes were slightly different as was my distributor ( still have yet to determine who in the hec makes it but my best lead to date tells me its a Procomp)

I set mine to 10 deg btdc ( base timming in chip as well as the dist.) Now the car starts perfect and the SA is correct.

I actually had my stock distributor in the car, which worked flawlessly before replacing it with this one. I only purchased this one because the price was right and I thought I might gain a little more performance.

If I had to do it over again, I would pass as there was no difference other than the headache I encountered trying to get this one to work.

I still have yet to determine if i can get a replacement pick-up coil for it. ( I recieved correspondance from Procomp and they think its thiers so i will place an order for a spare pick-up coil on Monday and find out indeed if it matches)

The only reason I even wasted my time on getting this one to work was that I was stuck with it as the person that sold it to me gave me the proverbial middle finger regarding a refund

Sorry for rambling.... Thanks again for the post, it was definitely helpful.

88305tpiT/A

iTrader: (2)

Thats what this board is all about!

Very Glad I could help.