I just towed the LT1 home ..the wife was driving and it just shut off..no ses light.....fuel pump is priming..the motor fires once then dies you know, it goes vroom..die try again...vroom die....any help is appreciated...just turned 90,000....optispark?

 

I don't own a LT1, but IIRC I have read about about similar problems with guys on CZ28.com and it's been Optispark. Don't take it as gospel, others will chime in.

 

Sounds like the oil pressure switch that's supposed to shut the car off of there's no oil pressure; or the fuel pump relay.

Can't very well be anything to do with spark if it cranks right up and then immediately dies.

 

Riley,

First off, nice signature.

Second, RB has a good suggestion. Verify fuel pressure first. However, I had an Opti crap out at about 110,000 miles, and as it got worse and worse, the symptoms were similar. It would fire for about a revolution or two, then puke and backfire.

The question I have is what control system are you using? Presuming you have the OptiSpark, you must have a '92 or later PCM, correct?

If that's correct, and before you get hot-and-heavy into tearing off the water pump and balancer, meter the resistance from terminal to terminal on the Opti cap. You'll have to unplug (and MARK) all the wires, then check resistance on a fairly high scale. When mine finally bit the big one, the worst terminals were about 19K ohms with a regular Fluke DMM. Under the voltage from a 1KV meggar, that went down to about 15 ohms indicated. Obviously, I had a problem.



If you determine that your Opti has pooped the bed. The new cap and rotor kit was about $130.00 (Niehoff DR80K, Standard DR473, Borg/Warner C400, Wells/Conrad DR2026) A complete new Opti (remanufactured) was a $280.00 item at the time, and is maybe a little less now. I had no problems after replacing the cap and rotor and cleaning the SS optical interruptor discs and optical arrays. There are a couple of tricks to opening and servicing the unit, but if you're a little patient you can save a hundred bucks or more.

If you heave no low-resistance from connection to connection, you may have saved a lot of labor. However, Optis seem to have a service life between 75,000 to as much as 130,000 miles, depending on the unfortunate soul behind the wheel.

 

Yeap, mine lasted about 65,000 miles.

I had the symptoms close to what you’re talking about. It was like something broke & no ses light. I couldn't go over 25mph, and it was backfiring the whole way home. Little baby backfires.

The hardest thing with the job is getting an old balancer off. It was an issue with my Vette, cause there’s a bar right there in front. Puller, yea - right.

Good time to do the plug wires, since your there !!!

The Vette guys have all stated varying symptom with failing opti's, so it's sometimes hard to diagnose. Hell I changed my fuel pump, & filter before I accepted it.

BTW: I read awile back, that there was a company that makes a direct fire ignition like the ZR-1 for the LT1. I can't remember!!! It was a little pricey, but anything to get rid of this opti-junk.
Can't even wash the engine without having to take a blow dryer to the opti. awww

Ron

 

ronterry:
BTW: I read awile back, that there was a company that makes a direct fire ignition like the ZR-1 for the LT1. I can't remember!!! It was a little pricey, but anything to get rid of this opti-junk.
Can't even wash the engine without having to take a blow dryer to the opti. awww



ELECTROMOTIVE SDI

 

Sorry for the delay fella's had to get back to work....thanks for the replys.....after thinking about it ALL afternoon...it acts like a carbed car does when its out of gas..its a 1994 vader...I'm thinking fuel delivery....it wont run at all...it fires like it will..then immediatly dies..just like running out of fuel..or trying to start a car right after it dies from running out of gas....Maybe filter...seems to be an awful lot of pressure in the tank when I released the cap...more than usual...Ill check the pressure and get back to ya...I'll avoid the opti option as long as I can

 

Well you can easily verify that it's fuel delivery, by just starting it up and squirting fuel (starting fluid) in it.... if it will stay running as long as you shoot fuel in, but dies when you quit, then you have your answer.

Don't overcomplicate things. It takes 3 ingredients for a motor to run: air/fuel in reasonable proportion, spark at the right time, and compression. Calmly, rationally, and logically evaluate which one is missing. No doubt it will be only one, and the other 2 ingredients are right there waiting, since it was fine until something (probably only one thing) broke. Devise tests that will identify the missing ingredient, then concentrate on finding the culprit.

 

well it is getting fuel....I changed out the fuel filter...now when I try to start the car..it acts like a vehicle that is severly out of time..and no longer tries to start.....what I know about the opti is little but ....shucks! I was so hoping to spend money on my thirdgen this week..I get my block and crank back tomorrow.....thats what makes this post 3rd gen related...if I dont get this fixed I cant put my 3rd gen back together...I cant get at ANYTHING from the top....this will have to wait until Saturday..to do any testing ...keep the opinions and suggestions coming...thanks for the replys guys..Ill keep ya posted..

 

I have no idea if this will help but I had an S/10 2.5 doing the same thing and it was a hall effect prob.. Sounds fuel related being as I've saw LT1's with over 200K miles on them and no timing or other probs.

 

I was hoping for an easy fix....not gonna happen. I went and got a Chiltons for this one....it gives a great flowchart of tests to perform to rule out other ignition parts...I love my 327 carb..1 wire distributor even more now!
a quick question..
#1 talks about a spark tester..st-125 is that your basic probe / clip on a wire type tester?

 

Try spraying ether(starting fluid) down the inlet(throttle body) see if it continues to run,if it does definitely a fuel thing.

 

Vader its a 94...now do i check the terminals with a regular ohm meter, on the high side? And I do this with the car cranking ? (i would assume with just the ignition on as moving parts might hurt my body parts) Duh! but I had to ask...Remember this is just a hobby for me not a profession...even though its becoming a full time job lately....
Regular fluke dmm??? What is that? diagnostic multimeter? All I have is an ohm meter..will that do it?

 

That is exactly what my father would have said had he not passed in january...thanks for helping me get things back into perspective.
Thanks for always responding to my sometimes silly questions RB you are very much apreciated! And the rest of ya to!

 

Thanks for the suggestion...but the car wont even fire now...I will get it to my garage and run all these tests this weekend....I use my dads garage...since I dont have one

 

Just tried the filter.....no luck...I think you are right Ron...Thanks for the help...and I will also change wires and plugs.....funny just last saturday I had it at the track running 2.3 2.4 60' at 78-79 mph 1/8 how quick things can change...

 

Yea, I paid about what Vader stated, around 280 or so. The dealer wanted 700 hahahahaha...

Just remember they sale them in two pieces under two part numbers for the base & cap. <- At least at Checker Auto.
I should know, I thought I was getting a steal till I went to pick it up. It was only the cap! I knew It was to good to be true.

The Helms flow chart was off the scale with testing high res this-low res that. Forget-a-bout-it!!!

One more thing, I'm serious - If you haven’t changed your water pump in those miles, do it now. If your pump goes bad in 10,000 miles you can kiss that new opti goodbye!!!
Oh je$$$$, do your radiator hoses also You just can't risk dumping antifreeze on that opti.

BTW: Even if it turned out to be something else, rest assure - there’s those that had, and those that will fail. It's opti-science



Ron

 

so what year did they start the vented opti-spark...I thought 94...but I'm getting mixed signals...as to 95-97

 

I think it was '94, but it only had the little holes on the bottom of the base.
I think the 95-96(Again-Vette knowledge) had the vent tube or what ever.
The 95-96 also had a different cam key, so a little harder to just retro fit.

I sealed my cap to the base with RTV, to help. Don't seal the holes, cause the moisture has to go somewhere.

If I remember right, I got a '94 base, and a 95-96? cap (Like the pic that Vader has). I only remember seeing the little vent tube on the bottom. I just left it open.

Ron

 

yep the 94 had the 93 opti ....unvented POS...after i finish my 89, I will upgrade that...I found a guy on our local GM board that has one(unvented) he will sell me cheap...I call him today..thanks for the help..

and moderators thanks for letting this post run..I really needed some help with this...the LT1 is a strange beast if you ask me ....but it sure kicks butt!

 

Rliey,

DMM = Digital MultiMeter. Just your basic meter. Check from terminal to terminal on the highest resistance scale you have. There should be no reading from any terminal to any other (infinite resistance). The common problem is a breakdown of the epoxy insulation around the internal bussing. Sparks go everywhere except where they should.

Check the resistance with the engine off (and preferrably, cool).

That cap in the photo is from a '94, and is force ventilated. If you don't have the vacuum line and vent line, I can get you a diagram of the connections and parts reqired. The vented Optis were introduced in '94 on the 'B' cars, and in '95 on the 'F' and 'Y' cars. That seems a little backward, but I guess it was a "trickle UP" theory instead of the customary opposite.

As for leaving the thread open, you never said that the LT1 wasn't in a ThirdGen. There are quite a few ThirdGens with LT1s in them.

I'm not surprized that you're back to the ignition. After reading your symptoms, I was fairly certain, having been there myself.

Once you get the Opti checked out and remove it, you'll need some instructions. There is good information at this page:

OptiSpark Disection

 

Ok Ron I just picked this one up on ebay....sounds like the same set-up as yours..I didnt want to spend the $$$ on a new one . I'll do that when when I upgrade to the newer style. That will come with the LT4 hotcam and header Mods...hope this works out for me!
http://cgi.ebay.com/ebaymotors/ws/eB...410254059&rd=1

 

ok here is an update...after weeks of downtime on the LT1...I took the old opti apart...the rotor was in about 5 pcs and the dist. was a rusty torn up mess....the ebay part wasnt much better...I bought a new dist. and cap and rotor.(remanufactured)..the install went very well...wires all checked and double checked..the darn car wont start...turning it over, I get what sounds like improper firing order,,and bad timing..backfires out the intake, plenium......Im stumped! When I saw the condittion of the exploded rotor, I thought I had it solved....what else could have happened at the same time the rotor fragmented? any help is very much needed.. Thanks.

 

To me it sounds like a fuel pump. My moms Buick did the same thing.

Have you actually put a fuel pressure gauge on it? My moms Buick was getting fuel but the pressure was only about 3 psi. It would start and immediately die. I replaced the filter first and with the fuel lines disconnected from the filter I would turn the key on and the pump was pumping fuel. Just no pressure!

 

Thanks for the reply. That is my next step..Seems kinda odd that the rotor would fragment at the same time the fuel pump quit working..I do hear it prime, but I havent checked the pressure yet. I'll check it out.
Thanks again.

 

Reset your timing before you go doing any large repairs!

 

There is no timing adjustment with an Opti. You take what the PCM gives you, and reprogram if you don't like it.

Did you clean the interruptor disc on the Opti? Did you test the low- and high-resolution optical arrays? It sounds like the PCM isn't getting the correct low-res signal to start base timing. Another possibility is that the Opti was indexed incorrectly when you installed it. It is possible to install it in THREE different positions, but only ONE of them is correctly timed. There are three indentations on the drive coupling on the rear of the Opti distributor, and it is possible to force the camshaft drive pin in any of them. The correct indentation has an elongated slot that engages the camshaft drive pin.