Bad AZz Z28

I have an '89 350 TPI car I bought last fall. After replacing a blown head gasket, I also replaced all the gaskets and bolts on the top end, along with an MSD coil, cap and rotor, some new Summit wires, new spark plugs, and AC/emissions/VATS delete with a Harris chip. The car ran great all summer until it wouldnt start Monday morning.

I have a full tank of gas and good fuel pressure, noid light confirms I'm getting injector pulse. I have a fairly new battery with a battery charger on it throughout this week. I checked coil continuity and it was fine. I checked timing and it was still at the same point we set it at the beginning of the year. I did a quick check of compression on cyl 1 and 3, both came out to 150 and it sounds like it is running smooth when it does in fact run.

If I mess with the timing, I can occasionally catch a spot it will start, but it will only stay running for a few seconds before it dies, regardless of timing or throttle. After 1-3 starts, it wont start again no matter what, even with starting fluid. Spark at the plug seems to be missing when that happens. If i put a spark plug on the coil wire, it always fires though. I put another new cap, rotor and plugs on it but no difference. I put another ignition control module on since it seemed intermittent. Neither has made any difference. Suggestions?

TTOP350

iTrader: (8)

Pickup coil good?

ASE doc

89 is a vats car. Try watching injector pulse as the engine starts and dies and see if the injector pulse isn't dropping off as soon as the engine starts. This would be the VATS module dropping the fuel enable signal. The easiest way to deal with this is to simply install a bypass module that simulates the fuel enable signal to the ECM, eliminating the need for the VATS module. These modules are available on line for about $25. Forget the resistor kits that some sell as "bypass modules" that probably won't help you.

Otherwise, try to figure out why your VATS isn't producing the signal. The problem would either be in the Ign cylinder or in the wiring from there to the VATS module.

Just noticed you have VATS delete on your prom. Check the injector pulse anyway though.

Also, try unplugging the MAF and starting the car. if it starts and runs this way, you have a MAF circuit problem.

Tom 400 CFI

It sounds like you have been pretty thorough, but this last part tells the story for me. There is an ignition problem. Have you ohm'ed the plug wires? That you can get it to "catch" once in a while with fussing with the Dist (timing), makes me wonder about your cap>rotor interface. Button, cap on square, etc.?


It's not the pickup coil; if it were, you's have NO spark (you do from the coil), and you'd have NO injector pulse.

I disagree w/the VATS as the issue, b/c:
1. 2. If it were a VATS issue, (especially in the tumbler or harnes from there down teh column), it wouldn't crank. You haven't said anything about "No crank".

3. You have VATS Delete.


As for a MAF issue, same thing as in #1.; it would start and run on starting fluid.

cIaRmOaCrZo

^ pick up coils can deffinatly be intermittant. been there. watch, i bet money thats what it is, and i havent even started to diag it lol

ASE doc

Good call. I need to learn how to read.

Tom 400 CFI

LOL...me too, at times.

ASE doc

Definitely check out the plug wires. Using a cheapy adjustable spark tester, you can dial it out to 40KV. This will force the spark to either jump the large gap or find ground through whatever hole or leak is taking up the spark now. Cranking the engine in this state should reveal a KV leak. Use a spray bottle to spray water on the wires and around the cap and look for sparks.

Recheck your work in the cap. I'm assuming you're running the stock external coil HEI. Be sure that there is no damage to the rotor that might cause it to ground the secondary ignition to the dist shaft. This is fairly common.

Bad AZz Z28

Guys, thanks for the quick replies. I'm an LT/LS guy, so distributors are a bit foreign sometimes. I did check the pickup coil and wires, both of which turned out fine. But this problem turned out to be a common one from my LT1 days, a bad MSD coil. I've returned too much of their stuff lately for being faulty; I'm definitely sticking to Mallory from now on.

It must have been intermittent when I saw it spark at the coil wire before, because it was finally dead yesterday, and that made it easier to identify. For now I just stuffed one of the 5 stockers I have laying around on it, and it fired right up.

TTOP350

iTrader: (8)

I've been down that road with MSD products myself.

ASE doc

UGH! I hate hearing this as most of my ignition is MSD. It's been great so far, knock on wood. Glad I've got AAA.

Bad AZz Z28

My history with MSD parts have been very up and down. The previous owner of my 4th gen installed and then removed an msd ignition for it. I used an MSD window switch for my first nitrous kit and the adjustable pills for it always failed. Then I bought an MSD opti for $500 that never ran well and the rotor screws kept falling out, even with locktite. Then I had one of their coils fail basically right out of the box.

I tore them a new one in an email, and they replaced my out of warranty opti and coil, and those replacements worked perfect on a bunch of low 10 sec nitrous passes. I sold both and they are working fine on their new vehicles, so I went back to them with this coil, and it only lasted a few thousand miles at most.

I'd say if you have working MSD parts, you're probably okay, but I wouldnt go back for more. Especially for stuff like ignitions, when for the same price you can get a Mallory box that includes a digital display, window switch and multiple timing retard settings without the need for endless add-ons.