No spark issue and needing help!

[87R10GMC]

It's running! I feel like a moron. The issue the 2 wire plug from the coil to the module. 1 of the pins was pushed back just enough that it wouldn't connect. Thanks for all the help. I may not be out of the woods yet with this truck but now I can at least push forward. Thanks again

 

[HotRodPC]

It's running! I feel like a moron. The issue the 2 wire plug from the coil to the module. 1 of the pins was pushed back just enough that it wouldn't connect. Thanks for all the help. I may not be out of the woods yet with this truck but now I can at least push forward. Thanks again

Thanks for the update. Always nice to know the cure. Come on back when you need more help, tips or tricks.

 

[87R10GMC]

I've got it all back together and am about to set the timing. It is running a little rough which I expected with pulling the distributor multiples times and the swap in general. I believe I need to set it at 0 degrees and the ECM takes over from there? I'm not home currently and was wondering where the timing wire disconnect is on an 87? I was thinking drivers side firewall? Thanks for your help HRPC

 

[wagonman]

To test for continuity you need a Volt ohm meter, Hobo freight sells a cheapy that works. When I worked on these rigs at the dealer 9/10 it was the module next was the pickup coil. Once you get a V/O meter you can test the integrity of the wiring. 8 volts is low to the coil on cranking. I would also look at battery / cable grounds ect. Also google voltage drop test. Once familiar with it it will be a favorite diag tool for you.

 

[HotRodPC]

At this point he has it running he's just wanting to set the base timing. Don't get me to lying Cody. It's been so long now since I've worked on the TBI smaller HEI, I could be wrong on which plug to unplug and what the base timing is to be set at, but I'm fairly certain it's not 0.

Does it have a underhood emissions sticker? That might give the base timing spec. Someone jump in here and help him out.

 

[89Suburban]

There is a plug on the brown wire with a black stripe that needs to be unplugged, located near the brake booster area of the TBI wire harness. That controls the ignition advance signal from the ECM. Set timing to 0* then reconnect that wire.

 

[HotRodPC]

So there you go. I was wrong about the base timing being 0.

 

[87R10GMC]

Well the truck was running rough when I first found the wiring issue and got it running. Now that I've adjusted timing to 0 with the timing wire unplugged (and plugged back in) it doesn't seem to want to run at all. I found TDC compression stroke and verified the rotor was pointing at number 1. Firing order is correct and running clockwise. There is a ground that I found at the back of the passenger head that comes out of the harness not connected. It's not the strap from body to block. This truck ran fine before so I'm not sure what's up. Where should I start? Fuel pressure?

 

[87R10GMC]

Alright guys. I've got it running pretty good. It idles good and is responsive. I ended up setting the distributor by feel and sound. The timing mark on the harmonic balancer is almost at 1 o'clock and pretty far from the timing tab. Im assuming somethimg is wrong with the tab location as I was confident in setting the timing to this point

 

[HotRodPC]

In most cases like this, it's the Harmonic Balancer has spun in the rubber and needs replaced. Timing tab isn't a moving part so it doesn't wear out. However, you do need to confirm that you have the correct timing tab for your balancer since there is 2 different ones for SBC. Mine was off like that on my 454. I could never time it by light cuz it was so far out. So I looked at the timing mark in relation to the keyway then compared that to a KNOWN good balancer and it had slipped almost 1/4 turn. Replaced the balancer and was able to time the engine using a light again.

 

[74 Shortbed]

Do it "RIGHT", use a piston stop rotate one way to the stop and mark dampner, rotate the opposite direction to the stop and mark dampner, divide the distance in half and that is "exact" TDC... The only way to do it with the heads on..

 

[87R10GMC]

In most cases like this, it's the Harmonic Balancer has spun in the rubber and needs replaced. Timing tab isn't a moving part so it doesn't wear out. However, you do need to confirm that you have the correct timing tab for your balancer since there is 2 different ones for SBC. Mine was off like that on my 454. I could never time it by light cuz it was so far out. So I looked at the timing mark in relation to the keyway then compared that to a KNOWN good balancer and it had slipped almost 1/4 turn. Replaced the balancer and was able to time the engine using a light again.

Balancer looks good. This motor is a little older than the truck. I had no idea there were multiple locations for the tab. I think you're correct on it being the wrong one. The truck is an 87. From my research the timing tab should be more towards the top which is where it's at with my timing light. Hoping for a test drive later today! Thanks a million for all the help and input from everyone!

 

[74 Shortbed]

Balancer looks good. This motor is a little older than the truck. I had no idea there were multiple locations for the tab. I think you're correct on it being the wrong one. The truck is an 87. From my research the timing tab should be more towards the top which is where it's at with my timing light. Hoping for a test drive later today! Thanks a million for all the help and input from everyone!

You'll never know if the outer ring moved or not unless you mark it, I've seen brand new ones moved within a couple hundred miles, I always put two center punch marks one on the ring and one on the hub across from one another and every time I check timing I look at the dots to see if the ring moved. The tab goes where the line on the balancer is from the factory at TDC, you can put the tab anywhere you want but you'll have to put a new line on the balancer and that will be your new TDC mark..

 

[87R10GMC]

Good info. Thanks 74. I looked and I will say that the timing chain cover from the original motor has the built in tab and it is in a different location than the older style. This probably explains while I was pretty far off on the tab.

 

[74 Shortbed]

Yes, if it's a different cover with the tab in a different spot then it will be way off, the only RIGHT way to check this is to find absolute TDC, with the heads on the piston stop method is the accurate way to do it.