ZZ502 died while driving. Need help troubleshooting

[99-LS1-SS]

I was driving down the highway. I had just come off of an onramp where I was in the throttle all the way to merge into traffic. About 2 minutes later the Blazer had one backfire and then the motor shut off. I got it to the side of the road and tried to crank it. The motor turned over just fine but it wouldn't fire up. After a few seconds of turning the motor over it lets out 1 backfire. I had it towed home and I still haven't been able to find out what the problem is.
I have the Aeromotive Stealth intake system and the pump work when the ignition is turned on. The fuel pressure gauge is reading correctly too. I originally thought it might be the coil so I changed it out but it still won't fire up. I think it might be something in the ignition system but, I'm not sure where to start. I pulled the cap off and tried to turn the rotor and it seemed to be ok, meaning I don't think the distributor shaft is broken. Although I'm not sure of anything at this point.
Do you guys have any ideas of what it could be or where would be the best place to start?

[cadillac_al]

Check for spark. It sounds like the module died.

[99-LS1-SS]

Originally Posted by cadillac_al

Check for spark. It sounds like the module died.

I'm pretty disappointed in myself for not thinking of that. I bet that's it. I just went and bought one. I have to run out but, I'll put the new one on when I get back.

Thanks.

[slotard]

I'd start by checking for spark and checking timing.

[cableguy0]

Loss of spark sounds most likely to me. What kind of ignition system do you have?

[99-LS1-SS]

I have the ZZ502 HEI setup. I replaced the ignition module and it still won't start. I turn the key and it turns the motor over fine and after a few second of turning it backfires really loudly. I am very frustrated with this thing. I would love to have a mulligan.

[cableguy0]

Throwing money at it will get expensive in a hurry. Have you verified that it does or doesn't have spark? I assume this engine is carbureted? What kind of Carb have you verified fuel is actually coming out of the carb?

[T and S]

I would pull off the valve covers and check things out while turning the engine over buy hand. Almost sounds like a timing issue, dropped valve etc...

[99-LS1-SS]

Originally Posted by cableguy0

Throwing money at it will get expensive in a hurry. Have you verified that it does or doesn't have spark? I assume this engine is carbureted? What kind of Carb have you verified fuel is actually coming out of the carb?

I have not verified that is has spark yet. I will try to do that tonight. It is carbureted. It's the Holley that comes with the ZZ502 Deluxe package. I can turn the key on and watch the gauge on the regulator (on the inner fender) build pressure. I can look down the barrels and see fuel. I think it is spark or something much more catastrophic.

Originally Posted by T and S

I would pull off the valve covers and check things out while turning the engine over buy hand. Almost sounds like a timing issue, dropped valve etc...

I sure hope that's not the case.

[68gmsee]

Years ago I had a similar symptom on an olds. It turned out to be the cam gear -stripped some teeth.

As mentioned above, first check for spark (if you have a timing light you can clamp it on the spark plug cables to check for a flash). Then check the timing.

[Chevy_mud_truck]

Check to make sure it didn't shear the pin in the drive gear also

[Captainfab]

Are you seeing fuel without moving the throttle?

Originally Posted by 99-LS1-SS

I can turn the key on and watch the gauge on the regulator (on the inner fender) build pressure. I can look down the barrels and see fuel.

[Hollow65]

Originally Posted by Captainfab

Are you seeing fuel without moving the throttle?

Are you thinking too much fuel pressure over powering the needle and seat? like stated earlier pull the valve covers, my 502 ate a valve while driving also.

[Captainfab]

That or a piece of dirt got between the needle and seat?

I'm not saying it couldn't be something serious, but I typically check the easy/simple stuff first....... like fuel and spark

Originally Posted by Hollow65

Are you thinking too much fuel pressure over powering the needle and seat? like stated earlier pull the valve covers, my 502 ate a valve while driving also.

[99-LS1-SS]

Originally Posted by Captainfab

Are you seeing fuel without moving the throttle?

No. I worded that poorly.

Originally Posted by Hollow65

Are you thinking too much fuel pressure over powering the needle and seat? like stated earlier pull the valve covers, my 502 ate a valve while driving also.

My fuel pressure is 5.5 and 6.

[fleetsidelarry]

Originally Posted by 99-LS1-SS

I have the ZZ502 HEI setup. I replaced the ignition module and it still won't start. I turn the key and it turns the motor over fine and after a few second of turning it backfires really loudly...

to me, the backfiring indicates that you most likely do have spark. it still could be fuel (flooding) or ignition. like cableguy0 said, don't just throw parts at it. the sudden shut-off also suggests electrical

always do the easy checks first. no sense pulling valve covers (or other parts) 'til you need to.

I'd bring the engine to TDC #1 (compression stroke, finger on the hole method) and see if the rotor is pointing at the right place on the cap

if that looks okay, pull all the plugs and dry them and spin the motor over to clear the cylinders of any raw gas.

when you're ready to restart, give it a couple of pumps but don't keep pumping if it doesn't fire right up

[Hollow65]

7.5# is optimum fuel pressure. Good luck man

[68post]

I think electrical also. Check the rotor from the bottom to see if it has carbon tracking or a burn-thru, check the coil button in the top of the cap also.

[99-LS1-SS]

Originally Posted by 68post

I think electrical also. Check the rotor from the bottom to see if it has carbon tracking or a burn-thru, check the coil button in the top of the cap also.

There was carbon on the bottom side of the rotor. What does that indicate?

[cableguy0]

Originally Posted by 99-LS1-SS

There was carbon on the bottom side of the rotor. What does that indicate?

Carbon tracking. Basically the rotor is worn out. The cap is likely in the same shape. With the distributor cap off of the distributor crank the engine and make sure the distributor is actually spinning. You need to start at basics and go from there. We can sit here and guess all day but without physically checking things one by one its hard to nail it down. Basically we have to do process of elimination to get you back on the road.

[storm9c1]

Folks already gave good advice. But after you pulled the cap, did you verify that the rotor is spinning and is not loose? I had the exact same thing happen once. Screws broke off on the rotor (very strange), so the rotor was just laying on the metal plate with the plate spinning underneath it when cranking the engine. At first glance, it seemed fine until I could lift the rotor right off! There was also quite a bit of plastic shavings underneath like the screws backed out slowly and then just sheered. After replacing the rotor, I was back on the road. The symptoms were the same. I'd crank it and eventually get a backfire because the rotor was in the right position for one cylinder with each revolution, and that would ignite the built up fuel in one cylinder and then in the exhaust. Good luck. Keep us posted. Try some starting fluid to eliminate fuel delivery.

[toolboxchev]

All engines need 2 things to run, fuel and spark. Then proper amount of fuel, and correct timing.

Get a good book on engine mechanics on diagnosis. We all look for easy fixes at first.

Proper diagnosis, then replace parts with money.

Buddy just spent 500 bucks on a carb for an old 4 wheeler. Did not run correctly after that.

Bought the fuel petcock did not run better.

I actually forced him to ride with me to NAPA to buy a fuel filter. 2 bucks later at that point I was beating him around the track on a 20 year 350 Wolverine, He was on a 2014 700 Grizzly.

I learned something from him. At his expense. The only work I did was the fuel filter.

Shortcuts almost never work. Spray some ether in the carb and see if it runs. I do not think that 2 buck can of ether will hurt while you are picking up a manual on that motor.

[72chevyk10]

how recently had you fueled up? i got a tank of gas that had quite a bit of water in it. truck ran for maybe 5 miles and then had to get towed. opened up the carb and there were between nickel and quarter sized water "pockets" in both fuel bowls (edelbrock carb at time) after i got everything cleaned out it fired up fine. maybe something to check.

[crazy longhorn]

Loads of good info here....just 1 more thought? I have not seen this so much in the chevs, but did see a 460 Ford, shear the roll pin on the dist gear. Maybe pull the dist, & take a look? Longhorn

[99-LS1-SS]

So far, I know part of the problem was the distributor gear. I will find out tomorrow if it trashed the cam gear too. /sigh