Hey guys, I working on my brother's 91 TBI car and I'm having a bit of an issue. I recently cleaned up his engine bay and now the bastard refuses to kick over. I have triple checked everything and it still won't fire. If I have the coil unplugged the car turns over just fine but ofcourse it doesn't start. But....if I plug the coil back in it acts like it wants to kick over but it turns over very hard but won't start and sometimes will backfire out of the throttle body. I've become pretty stumped about this. Does anybody have any ideas as to why this is happening?

 

Just to add all of the spark plug wires are correct, the esc module is fine and the timing is dead on....

 

Anybody? I really need help with this...

 

So what got cleaned? Anything unplugged or removed?

 

Is the dizzy 180* out? That would explain why it spins nicely with the coil unplugged and backfires when it is plugged in. How did you set the timing?

 

I rerouted and shortened the wire going to the starter. I've triple checked it all and everything is as is should be. As far as the timing I never pulled the distributor. I checked where tdc was and set the wires accordingly. I didn't touch any wires associated with timing so this is driving me crazy. I'll post a vid and pics when I get home to show you exactly what it doing

 

If you messed with the spark wires and are now having problems, logic would suggest a couple of leads swapped, one peg around on the cap, something like that.

 

Something is not adding up. Cutting a shortening the starter wires should not affect the cars ability to fire.
Get us some more detail as to what exactly you did so that we have a clearer picture. Which wire(s) did you shorten/reroute(colour, where they connected to). What else may you have touched while doing this job?
To add, you said that you found TDC and set the plug wires from there. This still can mean that you are 180* out, if you found tdc using the piston and not using the rotor. The easiest way to tell(if you did not pull the dizzy) is take the dizzy cap off and check where the rotor is. Then you can set your number one plug wire and follow the firing order.

 

^^^
The backfire thru the tb is a good clue to this.

 

I checked tdc by setting the balancer at zero with the number one piston all the way up in the bore. I restabbed the distributor to point at number one and its still not firing...its not lugging as hard trying to start but its still popping through the TBI and not starting. Is it still off?

 

Like hrspwr said, did you get the instance of no1 tdc on the compression stroke, as opposed to tdc on the exhaust stroke?

Trying to understand what u did - you actually removed all the plug wires during your cleanup?

 

If you brought the balancer up to 0* on the tab (the timing mark on the balancer is at 0* on the tab OR some timing tabs have a larger v cut into them to mark 0*) and then set your number 1, your timing should be there. If you only brought the piston to the top, then it could still be out.
The next thing that I would check is the firing order and plug wires. 1-8-4-3-6-5-7-2. Seems you are very close, but something is still holding you back.

 

You likely installed the distributor 180* out. Meaning it's firing on TDC of the #1 EXHAUST stroke, as opposed to TDC of the #1 COMPRESSION stroke. Remember the engine makes 2 full revolutions for every one at the distributor.

It'll "sneeze" through the intake occasionally but it won't start if you're 180* out.

 

Then how do I make 100% sure its on the compression stroke if everything lines up elsewhere?

 

Two ways. The easier way it to take a look at the balancer and there will be a line (timing line) on it. This needs to be lined up with the timing tab at 0*. The 0* mark will either be a number(most aftermarket tabs have numbers) or on a factory one there will be highs and lows representing the number of degrees before and after TDC. One of the lows will be more than the others. This is 0* or TDC. Line up the balancer mark with 0* and then check your dizzy rotor. It should be pointing to the number 1 piston(driver front). If it is pointing to the firewall, it is 180* out.

The second way is to take off the driver valve cover and make sure that both the number one exhaust and intake valves are closed. To make sure, spin the motor over and you should see the exhaust valve open, then close, then the intake will open, then close. Once the intake valve closes, you are somewhere near BDC, you will then need to bring the number 1 piston TDC and that is you 0* mark. Then check your dizzy rotor.

 

Here's the video I made yesterday, I'll make a few more later today.



One thing I don't understand it that is that we drove this car on to my driveway and I NEVER pulled out the distributor when I redid the harness. So how the hell would it get off time?

 

The first way is exactly how I did it, the number one piston was all the way up and the timing mark was dead center on the zero. Initially the distributor was pointed at the firewall then I removed it, set it to where it was pointing at number one and while it helped the car still isn't firing.

 

I would double check. If the dizzy was not taken out and then when you checked it was 180* out, sounds like it was not set correctly.
Another thing is to make sure that the plug wires are on correctly and the firing order is right. Firing order is above and all odd cylinders are on the driver side and all even cylinders are on the passenger.

 

The only problem with the first method is that you are not accounting for the fact that the crankshaft makes two revolutions per firing of each cylinder. That means that you can have the timing marks lined up and actually have #1 cylinder at TDC between the exhaust and intake strokes.

The second method will work as it takes into account valve motion. But even this can be tricky as the valves will seem to be closed at the overlap point between exh and int. You have to rotate the engine back and forth and look for valve movement. There will be no valve movement with crank rotation if the piston is actually at TDC of the compression stroke.

The easiest way really is to have a helper rotate the engine while you hold a finger over the #1 plug hole and feel for pressure as the the piston comes up on the compression stroke(you can also use a compression gauge for this). When the timing marks line up at the end of this, the piston is in actual firing position. At work I use a remote push button starter switch and a compression gauge when I need to find TDC.

 

Your dist was installed correctly in the first place, of course because it was running and you never pulled it. NOW you've got it 180 out. AND this has nothing to do with your original problem.

 

Well as luck would have it we got the beast running. I followed the "finger in the hole" method and she fired right up. I believe I did have it on TDC for the exhaust and not the compression at first. I just have to fine tune it and we're good to go. I still don't understand as to why it wouldn't fire initially. The videos I put up show exactly what it was doing BEFORE I pulled the distributor.

 

Camaro gods are smiling