kainZ

I'm having a very similar problem to one of the other members (Xaphanz) who posted below about his engine not starting after a rebuild. If you have any ideas about my car, it sounds like they might apply to his situation too, so if you have the time, try to take a look over at his thread..

Anyway, onto my problem:

My car has been sitting since last July, and now that it is all back together, the starter rotates the engine fine, but it won't fire. I did hear a couple (like literally two) pops when I first started cranking it, but after that, nothing.

The gas is the same gas that was in there in July.. but could the gas really "go bad?"

I confirmed that I have fuel at the rail (though I haven't checked the exact pressure yet).

I'm not sure if my injectors are firing or not.. I hooked up a multimeter and it looked like there was a constant 12vdc.. maybe my meter doesn't have fast enough update resolution to sense a pulse? Or maybe they just aren't firing?

I confirmed that I have spark.. though I don't know if my Opti's timing is correct yet, but I haven't touched the Opti or the cam, so I don't know why anything would have changed there.

I checked all my spark plug wires, everything's in order there.

I checked all my fuses (inside the car and under the hood), and they're all good.

I haven't checked the compression yet, that is on my todo list.

I recently (during the time that the car was sitting) swapped my heads and intake manifold for a recently rebuilt set. The intake mani is off a 97 LT1, while my car is a 95 LT1. I know that 96+ are OBD2, but all the connections seemed to be the same, so I don't really think this is the source of the problem.

At this point, I'm getting close to being stumped..

Does anyone know how to confirm that the injectors are getting a pulse to fire?

Does anyone have any ideas that I might have overlooked?

Is there some big difference I didn't notice between the OBD1 and OBD2 intake manifolds?

Thanks in advance for any ideas you guys might have .. I'm dying to get this thing running (esp. with all the great weather we've been having lately!)

J96Z

Maybe you need to go back through and adjust your rocker arms. If you didn't touch the cam or timing chain your cam timing is probably good. And yes, a 97 intake is the same as a 95. the 93's are the only intakes that are different. They don't have the fuel crossover tube at the front of the intake.

kainZ

You mean for "zero lash?"

I was just reading this website when I saw your reply:
http://shbox.com/1/4th_gen_tech2.html#adjust_valves
Is this the type of thing you are referring to?

Thanks for your quick reply, I'm definetly going to look into this!

J96Z

Thats exactly what I mean. That seems to me the only thing that could be wrong unless you have some wires hooked up wrong or something. Double check your injector wiring and spark plug wires as well to make sure nothing is crossed.

ajschult

my money is on improper rocker adjustment if you never touched the timing chain.

kainZ

I was just thinking.. when we tightened these, we tightened them to the torque specs from the Haynes manual.. is it the case that these specs might have been too tight, or does that rule this out? We didn't feel to see if the pushrod could move at all or not.. we just tightened them and called it a day.. Are the torque specs max torque?

Just want to ask this before I go ripping the valve covers off again

Thanks again for everyone's quick responses!

J96Z

Thats the absolute wrong way to adjust rocker arms. You need to be on the base circle of the cam when you adjust the rocker arms. You can't just crank them down and call it good. They are probably way too tight. Here is how I do them. Pick a cylinder, any cylinder, and turn the engine over until the exhaust valve just starts to move up. You can now adjut the intake rocker arm on that cylinder. Tightn it until you just start to feel the pushrod get tension on it while you are spinning it and then give it about 1/2 to 3/4 more of a turn. Now turn the engine over until the intake valve goes all the way up and is about 2/3 of the way down. You are now ready to adjust the exhaust rocker arm the same way as the intake. Repeat this until you have done all cylinders. Should run no problem after that. If you have tem too lose they will clatter when it is running and if you have them too tight you could possibly damage the cam lobe or destroy the lifter.

kainZ

Got it, will do! Thanks again.

Last question (and this one might sound stupid, but I'm pretty new to actually doing any internal engine work) would be how to rotate the engine that slowly.. Can it just be done by hand by a strong person with a ratchet on the crank pulley?

J96Z

Thats how I do it. Get a 1/2" drive ratchet with a 5/8" socket and it's not that hard to turn over. I would loosen all the rockers up first though. Might make it easier to turn over. As far as a maximum torque for the rocker arms, i don't really think there is one.

kainZ

Okay, so it was the rockers...

Apparently the mechanic who worked on them before torqued them to 50ft/lbs and called it a day (without even rotating the engine to the correct spots for the valves he was tightening.. he just did ALL of them at once in whatever spot it was in).

I'll have to post pictures of my pushrods later.. some had as much as 15-20 degree bends in them by the looks of it!

Anyway.. it starts now, but its still not running right.. I followed the twist the pushrods until they get hard to turn then tighten the rocker another half turn thing... and they're chattering like a mother****er..

Anyone know how to know when you've REALLY tightened them enough without trial and error until the chatter goes away?? (I'd have to take the alternator and valve covers off, tighten them and put it all back together each trial and error session!)

Thanks to everyone for the help thus far! hopefully somebody has a good idea about how to get everything perfect or if maybe the sound is something else.

I wanted to autocross it tomorrow, but I guess thats out

J96Z

You can adjust with car running as well. Did you replace the bent pushrods? Start the car with valve covers off. Lossen rocker slowly until it starts to clack a little and then tighten it slowly until the clack goes away and then 1/2 to 3/4 turn more. That mechanic sounds like an idiot.

kainZ

Yeah, I got raped by Autozone (40 bucks for 16 stock pushrods).

Yeah, I can't understand what other explanation there is for someone tightening rockers that way.. esp when the haynes manual which he claimed told him to torque them all to 50ft/lbs (which doesn't say that anywhere) clearly stated the same instructions that are on the web about getting cyl #1 compression stroke to TDC and then doing the specified rockers until the pushrod's play goes away + half - 3/4 turn, then cyl #6 TDC, do the rest of the rockers the same way.

one question about doing them with the car idling.. won't oil come shooting out at 40+ psi??

J96Z

No it will come out but not that hard. You do want to be a little hasty about it though because it will start to spill over on the exhaust manifolds if you run it too long with the valve covers off. It will just come out of the ends of the rocker arms a little on the side where the pushrod goes into the rocker. A little oil smoke won't kill ya.

kainZ

Oh, I forgot to mention.. I put 1.6 aluminum RRs in place of the stock rockers.