margohochstetle

i have a 95 lt1. it quit running while i was looking for a parking space. will crank but won't start. checked the cam/crank sensors and they're ok. computer didn't read out any codes. someone said it could be the opti spark control. had a lot of oil around it. could this cause it to malfunction and just quit? it back fires after 3-4 cranks. mechanic has checked all wiring, hoses, etc.... wants to make sure it could be this before tearing into the motor. please help.

jloshotz

Where are the "cam/crank" sensors on the LT1? Curious what you may have actually checked...

moparman

Has the fuel pressure been checked?

CamaroBoy96Z28

Crank no start...fuel pressure is a definite check. My car ran on a slowly dying fuel pump for months until I swapped it for a Walboro 255LPH. A sudden electrical issue could happen, but its hard to say what the issue is. Either way, check the basics. If you have spark then opti should be fine.

I don't remember but I think that 95 doesn't have CPS. 96-97 timing cover is different from 93-95 I believe for this reason.

mrmint69

The mechanic must have checked the fuel pressure since its one of the first things to do and a large percentage of the time, the culprit! Scary your talking about tearing into the motor so quick also.

Injuneer

You only have a cam position sensor, and its an optical pickup in the Optispark distributor. There is no crank position sensor on a 95 LT1. The CKP sensor was added in 1996, and is only used to monitor misfires. It won't shut the engine down.

Failure of the optical cam position sensor will set one or two codes (DTC 16/DTC 36). DTC 16 for the low resolution pulse signal from the sensor will cause the PCM to shut down the fuel system, and the engine will not start. But DTC 16 does not turn on the SES light.

How did you scan it for codes? You can't flash the codes on the SES light by shorting the ALDL connector pins on a 95, and many people see the 16-pin connector on the 95 and assume it's OBD-II, which it isn't.

margohochstetle

i replaced the fuel pump first but that wasn't it.

margohochstetle

all i know is he hooked it up to the computer and it was to old of a model. so he borrowed another one for 95 and older and said it still didn't read a code. i wanna know if i'm getting jerked around here by him

shoebox

That's going to be pretty hard without being an eye witness to the events. Lots of people have issues trying to scan a 95. The right cable and scanner work. The wrong combination doesn't.

Injuneer

Did the scanner "connect"?..... that would be the question to ask. If it didn't connect, it wouldn't show codes or anything else.

SCNGENNFTHGEN

Wow back to the LT1 issues again!!! Any help folks is greatly appreciated as usual. My 90 Silverado, with the 94 LT1. I have given it to my little brother, because I couldn't afford to keep 2 of them going...lol! I was driving it for a couple weeks, he's been driving it almost since I gave it to him. He's been upgrading it since. It's got the latest MSD opti with the late style timing cover. I parked it one night, came out in the morning and it's cranking, but will not start. I have good fuel pressure, spark (6AL msd box), just had boost labs clean my injectors. The icm tested, checks good. New bosch plugs. I'm stumped, because I can't imagine an MSD opti which cost him $500 bucks didn't last a year??? Any ideas?

Injuneer

The MSD distributor is nothing special, no better than the OEM part, and maybe a bit worse. Did anyone loc-tite the rotor screws before installing the unit? They fall out just like every other brand. Has anyone played with the MSD's "timing" screw? Since there is no "0" reference, it's possible it's "off".

Did you verify spark at both the coil wire, and at a few plugs? When the engine cranks, does the timing sound off, with backfiring?

By "late style timing cover" are you indicating the 94's unvented Opti was upgraded to a vented Opti, with new timing cover, new timing set and new cam with the correct hole in the nose for the vented Opti pilot shaft, and longer dowel pin to drive the vented Opti? That's the only reason to go to a 95, or a 96/97 timing cover. Since the MSD is "vented" for all years, the reason for the change is unclear.

Are the Bosch plugs the multi-electrode type? They do not appear to work well in the LT1.

Didn't see any mention of scanning for codes. Probably a good first step. Consider the free download of Scan9495 data logging software, linked in a "sticky" at the top of the "Computrer Diagnostics...." forum.

SCNGENNFTHGEN

I didn't put the opti on, so idk if the screws were locktited. My brother told me, back when he was getting the msd, that he needed my later style cover because the didn't have an early style opti. It does burble and try to start when I let off the key and stop cranking. I didn't know about the screw, so I will check it out, and ask my brother about the screws. Just regular bosch platinums. Ireally appreciate the advice man!!! I will put my brother on the computer stuff. This is why I am building one (LT1)with hei, and a simple carb for my 2nd gen. My 4th gen is going through some changes while I ride and enjoy the sunshine. In the back of my mind, when I get the hood, and paint done, I'm praying my opti is still good! I've got so much going myself, he sorta gave it back so I could do some work on it. It need a rocker panel, and a lil body tlc so we can paint it. Everything is slow going due to finances, and working all the time on both our parts too. He keeps talking LS/T56 for it, but I do love the LT1's...Really wish he'd have put a cam in though, so he could get a taste of their true potential!! Your help on this is greatly appreciated and respected!!!

Injuneer

The MSD Opti is available in both the 93/94 unvented unit, and the 95-97 vented unit. There was no need to change the front of the engine to accommodate the vented unit. Both the unvented and vented MSD units are "vented".

93-94 is part # 8381

http://www.msdignition.com/product.aspx?id=5377

SCNGENNFTHGEN

OK, so it sounds like my brother "wanted" to switch to the vented opti for whatever reason! Thanks again for all your help!!!