LT1 Optispark/timing issues

[barno68]

OK, I know this has been brought up before and I have read all the posts... This is a '95 rebuilt (never ran) LT1 with new injectors, opti, coil, wires, sparkplugs, etc. I have tested the injector signals with a noid light, tested the fuel pressure (45psi), tested spark at all plugs- all were good. The engine turns over slowly and the starter has a high pitch whine. I had the starter tested (all fine) and am using a new battery that is fully charged ( 800 cranking amps). The ECM has had the MAF programed out also.

The engine will not start, every once in awhile it will sound like it is catching, but nothing. I have tried starter fluid through the throttle body, nothing. I just finished checking the timing chain alignment and it is good. When putting on the opti (cap is off) I noticed that the rotor is lined up at about 10 deg when #1 is at TDC, not sure if this is the right spot as these distributor caps are a bit hard to trace the routing. It seemed smart to bring this up before putting this thing back together again and coming up with the same result.



I am at my wits end on this, what could be causing the thing not to start?

[MrQuick]

To start diagnostics I would pull the plugs and see if they are wet. Fouled plugs will not burn. Pull them and inspect their condition.

just to verify this is the unit you have right? http://shbox.com/1/opti_back.jpg


Vince

[barno68]

To start diagnostics I would pull the plugs and see if they are wet. Fouled plugs will not burn. Pull them and inspect their condition.

just to verify this is the unit you have right? http://shbox.com/1/opti_back.jpg

Vince

That is the correct opti, but this is where I have some confusion. Mine does not have the TDC markings, but #1 comes up on the opposite side (3 o'clock looking at the cam pin). I aligned the cam gear dot to 6 o'clock and the crank to 12, but by the valve movement and what I have read this is 6 TDC. To get to #1 TDC the dot needs to be at 12 on the cam, I verified this by the valves. I think there is only one dowel pin hole on the cam and if I pull the chain and rotate the cam so the pin lines up at 9 o'clock this just rotates the valve assembly to 6 TDC. Not sure if I am looking at this wrong.

The plugs looked fine when it was last cranked. I went ahead and changed out the injectors to make sure it was getting full. The water pump is still off right now as I want to make sure the timing alignment is correct before putting it back together.

[quikws6]

did you degree your cam when you installed it? I'd also check your grounds.....dumb ? but did you disable the VATS? sounds like an easy fix though...good luck!

[WS6]

The opti can only go on one way so long as you don't force anything on at all. A suggestion I always make for anyone doing an opti swap or change for any reason is to get the opti on, put the crank pulley on, and then start the car. You don't need the water pump on for the engine to run basically. This is just a quick way to ensure you did the opti correctly. First time I did the opti on my 96 formula, the car wouldn't start. I was careful with the opti when putting it on but apparently not careful enough. I simply reinstalled it and the car fired right up.

Anyway, on to your problem. Vince has a good suggestion on checking the plugs. If the plugs aren't wet(or even if they are and the car still doesn't start), lift the fuel rail up and stuff paper towels under all the injectors. Turn the key on and let the fuel pump pressurize the rails. Check the paper towels to see if they are wet. They should be dry. Try to start the car. You only need to keep the key on for a second or two. Check the paper towels, they should be wet. What your doing is checking to see that the injectors are truly good. You've only indicated that you've checked the wiring to the injector. So this will tell you if the injectors are indeed good. You said they are new. Where did you get them? No one makes new factory injectors for these cars. There are only stock rebuilt(ie cleaned) replacements or an upgraded/aftermarket style injector. If injectors sit on a shelf too long, it's not unheard of for them to need cleaning or be bad.

What opti are you using? Is it a new GM unit or a new one from an auto store? I'd never run anything other than an MSD unit or an AC Delco one.


Do you have a multimeter or digital volt meter? On shoebox's website(the site Vince linked to) he has the service manual test procedure listed for checking the opti out. I'd go through it just to be certain.

How slowly is this engine turning over? Does it pick up speed as you hold the key or are you praying the starter is spinning fast enough for the car to start? Good or not, the engine must turn at a fast enough speed to start or else it won't overcome the pressures in the combustion chamber as the fuel mixture is ignited. How do you have the starter wired?

I'm assuming you have no codes present through all this? Who programmed out the MAF?

If you have a multimeter, check the resistance on the engine temp sensor that's in the water pump. That's the sensor for the PCM. If it reads that it is -40* outside, it's bad and could be causing these problems.

I have more but check this stuff out first and let us know. Also, do you have a scan tool or program available to you?

[barno68]

did you degree your cam when you installed it? I'd also check your grounds.....dumb ? but did you disable the VATS? sounds like an easy fix though...good luck!

VATS was disabled when the PCM was programed. Not sure what you mean by degreeing the cam...

[barno68]

I appreciate all the replies, and some of the suggestions I have not tried yet. But, I do not want to put the crank pully back on until I get the timing alignment figured out. As is I think I need to pull the timing cover again. Looking at both the shoebox photo and those in the Haynes manual, when the sprocket alignment dots are closest to each other, the dowel pin should be at 3 o'clock. Mine is only at that position when the cam is at 12 and the crank sprocket is at 12. I can rotate the cam back to this position, but there is no valve movement which tells me that #1 is at TDC, not #6...

[67goatman455]

okay, cam gear dot at 6 o'clock, and crank gear dot at 12 o'clock. you need to verify that you have those lined up correctly first, and that your not a tooth off. Now when looking at the OPTI where the cam dowel pin will fit into, there are 3 narrow slots. One slot will look different than the other 2 (pointed out in the diagram posted earlier) http://shbox.com/1/opti_back.jpg

You have to be dead certain that the dowel pin went into the correct slot, and not into one of the circular depressions. When installed correctly the mounting points on the opti will sit completely flush with the front cover. If there is a gap then you most likely dont have it installed correctly. With new o-rings on the opti, I usually have to use more force than i would like to for it to slip into the cam.

one last thing is that you dont need to pay attention to where the opti is oriented, the timing is not manually adjustable at all in any way, as long as you have your timing chain installed correctly, and the opti is lined up correctly, then everything is set up fine.

Im just trying to lay it out completely just incase you might have overlooked something.

[barno68]

Goatman- appreciate it, sometimes you need to go back and look at things again. I pulled the timing cover to check the gears again and verify the cam sprocket part number and noticed that I had it lined up for #6 TDC and it looked good. Still not sure on the valve movement as I have the covers back on. Need to pick another timing cover gasket before I can do much more. However, I cannot see how the timing could be off- these things are pretty idiot proof... I will get it back together and try working through some of the items WS6 suggested.

[SRT-68]

I am not a GM guy, but do these engines have adjustable rockers? If the intake rockers are loose it will never start. If they are too tight you should get a pop out of the intake. Also if it is a "dead head" injection system with no return you may be injecting air. I have had this issue with the new hemis. bleeding the rail works.

[barno68]

The engine is back together, but still will not start. It is turning over faster and sounds better on the starter, however is still seems a bit slow considering the high CCA battery and 2ga wires. I may order a new starter and see what happens, it could also just be the new engine. I started to pull the fuel rails to check the injector status but ran out of time as I have to leave town for most of this week. Try again next weekend. Thanks for the tips.

[67goatman455]

SRT-68 has a good thought.....how did you adjust the rockers?

[WS6]

no need to buy a new starter yet. If the motor is turning over and it doesn't kick back, then it's not the starter. By kick back I mean the engine goes to start but the compression and explosion inside the cylinder overcomes the starter and pushes back against it. It doesn't sound like you're even getting to that point. So you're still not getting fuel, air, and spark at the proper time. One or more may be missing or they may simply be getting there at the wrong time. Don't start throwing parts at the engine. Go through it step by step eliminating the possibilities first.

[barno68]

SRT-68 has a good thought.....how did you adjust the rockers?

per the manual, there is not a lot of ways to screw up the valve adjustment. Actually I went a little light this time and only tightened 2/3 turn past when the pushrod quite turning (manual calls for 1 turn).

[barno68]

no need to buy a new starter yet. If the motor is turning over and it doesn't kick back, then it's not the starter. By kick back I mean the engine goes to start but the compression and explosion inside the cylinder overcomes the starter and pushes back against it. It doesn't sound like you're even getting to that point. So you're still not getting fuel, air, and spark at the proper time. One or more may be missing or they may simply be getting there at the wrong time. Don't start throwing parts at the engine. Go through it step by step eliminating the possibilities first.

I would lean toward the "getting there at the wrong time" thought. I have gone through the steps multiple times with the same result. The only thing I did not try was pulling the rail with injectors attached, which is a great suggestion. When I get back I will pick up a noid light again and go through the process again and see if anything has changed. Also plan to buy a scan tool and check/reset the codes, although I am not sure what this will show on a non-running engine...

Is there any way to figure out if the timing sequence is correct for these engines without them running?

Thanks.

[birdsandbowties]

i feel your pain, we had a really clean 94 z28 with the dredded opti in it , the car ran so well and a/c was cold very cold !! and all of a sudden it quit running, i put a new opti in it , checked all the injectors,changed the computer and about 400.00 worth of little sensors,, even had a few buddies come over with the snap on scanners and still no luck, it would not fire,,,,,,period, even after i put the msd unit on it, what a waste !! so since i had the parts business at the time i just stripped the car and crushed it , i can only give one part of adivice to ya,,,,,, dump the opti and put a normal rear distributor in it , then it will run, the cost of machining the intake is cheaper than a few sensors :(

[quikws6]

This is a reply that is straight from a well known engine builder. "You need to degree the camshaft when you install it to ensure that it is ground properly. We don't perform 100% in house QC on cams for fun - they need to be checked if the customer doesn't want to degree them, and wants the camshaft installed on a specific centerline...(dot to dot,advanced,retarded)... That isn't to say it won't run if the camshaft/timingset/etc. tolerances stack up and it isn't where you think it is, but it is worth consideration." Plenty of info out there on the procedure.

Also, If you haven't seen the ls1 computer conversion people are doing over on ls1tech you may want to look into it. Hope that helps, good luck!

[SRT-68]

Even if the cam was off 8-10 deg it would still show some signs of life. If it is turning over at a fair rate then the starter is fine. What feeds power to this ignition system? How is it grounded? Are the block and body both grounded? Have you bled the fuel rails? From what I have read here this thing should be running. There is something very simple that is being overlooked. I am not trying to insult you, just trying to get you back to the basics.

[HectorM52]

You need three things go get the engine to run.

Air
Spark
Fuel

Hopefully you're getting air. Is the throttle opening?

Spark - are you getting it? Pull the wire between the coil and opti from the opti side (you do have this wire installed, right?) Have a buddy turn the motor over, put the end of the wire near something grounded. Is it sparking?? If so, at least you've confirmed you're getting spark.

Fuel - pull the four bolts that hold the rail to the intake. Pull off one injector pigtail. Put an old gatorade bottle or something under this injector. Now get you a couple test lead wires. Put one on the positive terminal of the batter, one on the negative. Put them on the injector pins. Have your buddy turn the key to "on" but not start. This should prime the fuel pump. This should confirm at least you're getting fuel.



Personally, I think the opti gets a bad reputation. Have personally never had an issue with one. Though I agree the unvented design was silly.

Run through the "simple" steps and confirm the basics.

[paul67]

If the plugs get to wet it will kill them, have you a ground from battery to frame frame to engine battery to engine,watch a hot rod boyds program once and it was a voltage fault to a sensor.