***Update***
The problem was, most of the pushrods got bent really bad on first fire up. The dumbass that put the engine together didn't install the stock pushrod retainers and it bent almost all of them. New 7.4" hardened pushrods, fired right up. Another dumbass thing this shop did, was drill a hole in my TB blade, to try to get it to idle. That ended up screwing me over for the following 4-5 months trying to fix my idle.




My '98 vette just got finished getting a new engine installed today, the mechanic tried to start it, and it won't fire up. The previous engine ran fine when it was pulled, besides a massive oil leak and spun bearings.

He says there is both spark and fuel, but he is by no means an expert on LS1's. It's not throwing any engine codes. He seems to think it has something to do with cam timing and the previously tuned PCM. I have plans to take the vette to a tuner in oklahoma city next week, but I need to figure this problem out before it gets trailered over there. My tuner says that there is no way the old PCM or camshaft is to blame for the engine not firing up. My only guess so far is that the spark plugs are the problem. I am going to the mechanic tomorrow morning to have him replace the spark plugs and help him look for a solution.

Here is what I have currently installed on the new engine currently:

Comp Cams LSR lobe
317 heads - ported / milled
LS6 intake manifold
42lb green injectors
Racetronics fuel pump
Vararam B2
85mm MAF
new iridium plugs / new bosch wires


This is what was on the previous engine that the car was tuned for:

forged 408ci stroker , 243 heads, anywhere inbetween 8:1 and 9:1 compression
custom cam grind 235/235 .581 112 LSA
cam timing advanced +4 degrees.

Everything else above stayed on the new engine. Can anyone out there offer any advice or ideas? I just bought this corvette a couple months ago only to find out on the drive home from out of state, that the engine had been destroyed. I am completely new at this stuff. Any help is greatly appreciated!

 

Where is your cam pickup located and what generation was your cam specd for?

 

If you mean the cam sensor location, it is located on the upper part of the engine on the rear side. Also, I called Comp Cams service department. They told me that all of their cams are pretty much the same, and wouldnt be any different for a GEN IV or GEN III. That is just what they told me, I dont know if it is true or not.

 

Yep thats true, just trying to figure out your build. My experience with Comp is that the pickup is in the back of the cam wether you need it or not, so I guess that rules it out.I guess the next dumb question.. is the cam sensor plugged in?
What a minute... Upper part on the rear side? to be clear it should be next to the oil pressure sensor behind the intake manifold correct?

 

I cant explain the exact location, I am just going off the general area of the engine that the mechanic said the sensor was located. He didnt have to use a wiring harness extention though, so would it be fair to assume that the sensor is not the 58x version? The crank sensor is black color, people on LS1tech have told me the 58x sensor is a grey color.

One thing I just realized, is that the short block was painted right before it was dropped in, and I doubt that the sensors were masked off.

 

Interesting scenerio, This one would definately require hand on aproach. And yes paint will screw you.

 

Just want to be sure - advanced camshaft timing couldnt cause this?

 

I am crossing my fingers on paint being the issue

 

Well if the motor has the same 24x reluctor then there should not be an issue; the old crank sensor should work unless it was damaged. The car will start an run without the cam sensor it will just have extended cranking times. Make sure that all of the grounds are hooked up on the back of the heads and the side of the block. If there is spark, and there is fuel pressure and the injectors are firing, then the car should run. Any other questions just let me know.

 

thank you for the advice...I believe we ruled out all of the above ^^^ this morning

I must have misunderstood the mechanic yesterday. It DOES "fire up", but it barely idles and back-fires violently until dying seconds later. The RPM gauge works, and there are no engine codes.

The mechanic is completely confident that the engine is just getting to much fuel due to a the aggressiveness of the original camshaft and the timing.

But I called my tuner in the city and he says he has never ran into a problem like this with back firing etc.

Now I am getting a little bit worried...

I guess I need to find out if a wild camshaft tune (or a shorter piston stroke) could have actually caused this. If not, then I am out of ideas.

Anyway it will be another week before I can get it trailered to the city.

 

Was the new cam degreed when installed? Was it set at zero degrees or changed? Sounds like the cam is way out of time (backfiring)

 

The cam in the old engine was degreed +4, the new cam is set at zero.

 

Sounds like the cam was installed 1 tooth off zero. Who did the installation?

 

I think you need to go back to the basics check for massive Vac leak, recheck fireing order, plug wires, all grounds, cam sensor, pull plugs see if they are gassed,valve readjusting , check for glowing header tube or tubes, still sounds like vac. leak to me

 

Hmm vac leak, that may have something to do with it.

The original engine had the PCV deleted for a supercharger set up (was later removed and retuned), and we had to reverse engineer a new PCV system so I suppose I need to look into that.

As far as everything else you listed, most of it is beyond my technical experience. I am going to make a big check list, and hope my new tuner can figure this thing out.

 

sounds like a real nightmare... scary, in fact! best of luck

 

Probably the best suggestion in this thread that was not followed.....



http://forums.corvetteforum.com/c5-t...e-grounds.html

 

Was this engine running before you installed it?

I've put heads/cam, 36lb injectors and my car started right up. I spun a bearing on that engine, put a new 402 in and the car started up even with the wiring on the cam position sensor wrong. It just would misfire while starting every now and then, but once it was running, it was fine. The point being, the car seems to be pretty robust in starting. I wouldn't jump in car and go head for the drag strip, but it takes a lot to a make the car not idle.

A loose hose between the MAF and the throttle body will keep it from idling, but after that I would think about pulling that front timing cover off and make sure the cam and crank shaft markers are lined up.

 

*****Update*****


I got a call from the tuner today. My problem is indeed an electrical wiring issue. The ECM was locked, but after he got the appropriate files he was able to dig through everything. But after 5 hours of labor involved in troubleshooting, there is no solution in sight. He is at the point where his next step is to just pull the engine out of the car and go from there.

This is what I know about my issue...



- The car will start, rev, backfire and die shortly after (it ran just fine before engine was pulled)

- The ground wire on the drivers side of the block will spark if touched against the header. So I am assuming there is some sort of power source on that ground.

- Some of the grounds were slightly altered and rewired by Aaron the original mechanic (without my knowledge of at the time, or permission)

- The battery has been drained dead at least once, just from sitting in the garage

- The ECM and cam timing seem to be fine.

I've made plans to trailer the vette back down to the engine installer so he can "try again" to get it right this time. I cannot afford to pay for an engine swap twice. I am looking at $2100 minimum if i leave it with the tuner. He talked about trying to get my money back from the other mechanic, but I can almost gaurantee the only way that will happen is through a lawsuit.

What should be my next step? I don't really know much about working on cars, but I am almost to the point where I just want to trailer the vette home and try to fix it myself.

 

How old is the fuel in that car? Sounds like it has been down for a while. Are the fuel injectors new?

Another thing is, have they actually watching a timing light/noid lights to see if the lights are firing consistently? If they're not it should at least narrow down your search for the electrical issue.