i have a gen2 block lt1 in my 95 s10 and im having some troubles:

about a month ago my truck started acting up- it would idle really rough and just about die unless i gave it some gas, then run fine once i got going, then i made a turn and tried to accelerate but the engine just bogged down and died, would not restart

thought i blew a head gasket since it was getting hot, tore it down and found the aluminum heads were warped, so i got them fixed and put it all back together, but it is still not starting
it has a rough start, similar to when i tried to restart it after it died, rather than the smooth start of before it was acting up
i have checked and rechecked everything from the wire connections and grounds and pulg wires
earlier it would actually start and run really rough and die, now it will not even start anymore

so im not sure what the problem is, i have read and tried many solutions on the board but my situation is unique
i also have an msd 6a box on it

any help is greatly appreciated!

 

Did you ever check the fuel pressure? Or lack there of?

 

It does sound like it's running out of fuel so definately check the fuel pressure as Speedy suggests. Then, remove the MSD box whenever you do any diagnosis to speed the process.....

 

pressure was 32pds, i smell it when i try to crank, i tried unplugging the msd box but then it would not start at all, when it was starting anyway

 

I wanna say that is a low amount of fuel pressure for a LT1, the one I have in my Sig. the book says 41 pounds to 47 pounds at prime (key on/engine off) and should sit around the same when on. I know very little but I am learning and try to help when I can. As I dont see much help I try to do what I wish I could get. lol Good Luck Man. But it does sound like it could be a fuel pump. Any more info??

 

41-47psi is OK running, with the vacuum compensation line disconnected. with the vacuum line connected, you will typically see 6-8psi less than the "no vacuum" readings, depending on your cam.

 

what if their is only a 3psi difference tops? the fuel pressure regulator is bad?

 

Or you have a VERY large cam, and there's very little intake manifold vacuum.

 

well, the turn had nothing to do with it, it was just part of the story because it was doing it everytime i came to a light and idled

i dont know man, all i know is that it ran like **** and now it wont even start
could it be a coil or the opti?

 

Have you pulled any plug wires to check for spark?

Have you tried squirting fuel in the intake while cranking it?

Have you checked compression?

??????????

 

ok, the engine is running again, but still running like hell
i ohmed my injectors- 12.3-4 all of them(my battery is on the weak side, not sure how that effects reading)
i pulled off plug wires to check for spark-im getting it(obviously)
i listened to fuel pump- it is priming everytime key is turned on

how can i check to see if my icm has gone bad? i think it might have burned up when my engine overheated

any other suggestions?
thanks

 

Have you tried disconnecting the MSD box and reconnecting the coil/ICM correctly? You can't just unplug the box.

Have you scanned it for codes?

Take the ICM off and take it to an auto/parts shop and have it tested.

Your fuel pressure seems low, if that's all you get when the pump primes. The fact that you can hear the pump prime when you turn the key to start it proves nothing with regard to adequate fuel pressure. Now that it is running, what is the fuel pressure with the vacuum compensation line off the fuel pressure regulator (hold finger over end of the line to prevent a vacuum leak)?

 

Your fuel pump might be providing barely enough pressure to start- but it won't provide the volume to keep the motor running.

Like Fred said- just because you hear it doesn't mean that it is running like it should. Get a fuel rail pressure tester. It will show you if your fuel pressure drops right off once the motor starts. If that is the case then I would say time for a new fuel pump since it is no longer providing the volume the motor needs.

 

alright so i hooked up a gauge to it (didnt unhook vacuum compensation line since i dont know where the fpr is) and found that it goes to about 36pds and immediately falls down to 32pds,
when i start it it jumps between 34-36pds very quickly for a few seconds before the engine dies
so it sounds like that is going to be the problem

if i somehow hooked a vacuum line up wrong could this cause low fuel pressure? as far as the vacuum compensation goes

 

Shoebox has a photo of the fuel pressure regulator for 94-97 engines:

http://shbox.com/1/fp_reg.jpg

When the engine isn't running, it doesn't make any difference whether the vacuum line is connected of not. Once its running, with the vacuum line disconnected you should have at least 41psi, with the factory spec 41-47psi.