TBI timing

[VIKING_MECHANIC]

I've been working on this 1989 K1500 with a 5.7 TBI that I'm planing on trading my black K1500 for. The truck has been sitting for about 6 years. After putting a freshly charged battery in it, the engine came into live again. It ran o..k..a..y, but you could tell it definitely needed a tune up and possibly timing adjusted.

My suspicion about the timing being 180 degrees out was correct. With my timing light on it, I could not see the mark on the balancer as it passed the plate on the timing cover. It was no where near the 0 mark, even moving the light up and down on the balancer.

So we take out the distributor, set #1 and reinstalled the dist. When it started, it was about ~10 before TDC so we knew we were getting close. But no matter how we adjusted the dist, we couldn't get it close to 0 - either it would go WAY before TDC, or way after it.

Now here where it gets interesting. We go to get some gas since it was basically empty. Unknown to me at the time, my dumbass friend got E-85. We get back and he puts 5 gallons of it into the tank. It starts, but any throttle it falls on it's face. So.... we mess with the distributor again and this is where I believe I actually set it correctly, as the mark on the balancer was passing at 0 on the cover. But with the E85 in it, it was running like crap.

A few minutes goes by and I ask him what gas he got and he said E85. I was like WTF?? His response: what? I had to explain to him that old(er) vehicles don't like E85. So yesterday we had to do a fluid transplant and I believe I got ahead of myself and messed with the distributor AGAIN.

After a few cranks, all the E85 that was left in it was diluted with fresh gas and it started up and ran great!... Now the mark was about 16 degrees before TDC and it seemed like no matter which way we turned the distributor, it never got close to 0.

I'm about done with it for now as it is really starting to piss me off since I've pulled and installed it about 4 different times over the last two weeks. And yes, we did disconnect the wire for the computer advance to the dist as we were doing this.

Need some help...

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[Dropped88]

2 things come to mind its possible the outer part of the balancer has slipped on outer and itll never show the mark. And does it have a aftermarket ignition module and i have them do weird things with the timing.

But im betting on first cause you said it ran good at about 16 btdc and if it was really that far retarded it would been running really crappy

 

[Dropped88]

You can also put it on TDC by #1 piston and mark the balancer to see it lines with notch on balancer and if not you still have a mark to use for setting timing

 

[smdk2500]

Just a thought did you unplug the tan/black wire when you where trying to set the timing? That can throw off you reading if it is still plugged in.

 

[Schurkey]

An engine WILL NOT run with the distributor 180 out.

Verify true TDC on #1, see if the damper mark aligns with the timing indicator.

I have no idea how you wouldn't be able to turn the distributor to achieve "0" advance.

 

[GoToGuy]

I agree, how could it be 180 out and still run? all you should have gotten is backfires and service malfunction lights.

 

[VIKING_MECHANIC]

Okay...so it may not have been truly 180 off, but it was off enough to run at idle okay-ish, but if given throttle it would fall on its face.

Anyway, after we got off work today, my friend went to work on it some more as I ran some errands. He apparently he has a friend that I guess is a genius with distributors, because I went over and it ran like a champ. We drove it around the block and it was very responsive(other than the throttle cable that felt like glue). I put my foot down and it took off!

We got back and noticed that the wire for the computer advance was unplugged...so we plugged it back in and it fell on its face again. It wouldn't even move 5 feet without dying. So we unplugged it and it ran perfectly. Even drove it around the block again and it was responsive like earlier. We think there may be a short in the wire.

Now we just need to figure out why it's overheating. We saw coolant on at the bottom of the rad support so the radiator or lower hose may be cracked.

 

[PlayingWithTBI]

We got back and noticed that the wire for the computer advance was unplugged...so we plugged it back in and it fell on its face again. It wouldn't even move 5 feet without dying. So we unplugged it and it ran perfectly. Even drove it around the block again and it was responsive like earlier. We think there may be a short in the wire.

Or, your ICM is wigging out. When you disconnect the EST wire, you're bypassing the feedback from the ICM to the computer. May want to trace all of the wires first, then think about replacing it. Here's a typical schematic of the ignition, YMMV

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[VIKING_MECHANIC]

Or, your ICM is wigging out. When you disconnect the EST wire, you're bypassing the feedback from the ICM to the computer. May want to trace all of the wires first, then think about replacing it. Here's a typical schematic of the ignition, YMMV

Well this distributor looks like it's been sitting for a LONG time. It was pretty rust-y when I took off the cap. I didn't really think about the ICM honestly. It's been a while since I've messed with a distributor on a TBI.

But since it runs really good with that wire disconnected, we will just leave it like that for now.

 

[PlayingWithTBI]

But since it runs really good with that wire disconnected, we will just leave it like that for now.

The only issue is you're running with a semi fixed distributor. It will advance some at certain revs (kinda like limp home mode) but won't advance accordingly with MAP and RPM feedback.