91 wont start with new motor

[madstacker]

Hi I just rebuilt the motor in my 91 vette and it wont run.The motor has all new parts except fuel injectors.I put in zz9 cam,afr190 heads,eddlebrock intake,bbk throttle body,1.6 rockers,steel crank,hbeams,forged speedpro pistons,and fluid dampner. I can get the motor to fire up for 2 or 3 seconds then it dies also the car is flashing a code 43.Ive checked the fuel preasure and it goes to 45 pounds while cranking and spark is good. The car hasnt run in 8 months and i hate seeing it just sit in driveway any help would be aprecaited.

 

[1992]

I do not know what you have checked, but a good start would be to make absolutley sure you aligned the distributor correctly when you installed it. Also, are all the valves adjusted correctly. Check to make sure you do not have a vacuum leak anywhere. A code 43 is for the esc(knock sensor). However, that would probably not keep the engine from running. There are some other things, like are you using the stock chip or a custom made chip? Also, recheck that all the wires that you disconnected are in hooked up.There are a few other things to look at, but try the ones a mentioned first. Cheers!!

 

[Chick]

Code 43 is a knock sensor. But you have other problems. It needs to go to the professional for a scanning. :eek

 

[-=Jeff=-]

Code 43 is a knock sensor. But you have other problems. It needs to go to the professional for a scanning. :eek

Can't really scan much other then codes when it is not running.

I would be absolutely sure the Distributor is in correct, you might be 180deg off which would cause what you are seeing too

 

[8388]

I agree with Jeff, start by rechecking your timing. Look at all your electrical connection, ground, vacumm lines etc.

 

[madstacker]

The chip is stockand tpis said the motor should run with it but i should get a better one.I have checked the timing and adjusted the valves about 3 times.The wire harnes isnt in the best shape.Also the car was dying before i put the new motor in.

 

[8388]

A word about chips. I had a 91 GTA 5.0 ltr 5 speed. I did an engine swap, built a 383 mini ram for it. After several attempts with custom chips I found that the car ran its best with the original chip piggybacked with a Hypertech chip, which only served to turn the fans on sooner. Note this was a 305 ci going to 383ci with an entirely different intake and fuel requirement. I did have to reset the fuel pressure since I had gone from 24lbs injectors to 30 lbs injectors. So long as the engine is creating good vacumm, the factory chip should be ok, and not cause your problem.

 

[madstacker]

is there any way leaking injectors could be causing it not to start? the plugs are gas fouled and i can smell gas in the tail pipe.the car had quit running before i rebuilt the motor .

 

[-=Jeff=-]

is there any way leaking injectors could be causing it not to start? the plugs are gas fouled and i can smell gas in the tail pipe.the car had quit running before i rebuilt the motor .

I still say it is timing.. you are trying to start it, injectors are squirting, but the car is firing at the wrong time

 

[steve1ph]

code 43 in my `90 l98 gm books are telling me "electronic spark control" circuit or knock sensor. for the hell of it unplug the sensor at the block and see what happens.

 

[madstacker]

I rechecked the timing again and it is good but car will still not run.I have a wire going to the starter from the ignition that was put on by somebody to bypass factory wire is there anyway this could be keeping it from running?I tried using the purple wire that is in the wiring harness but it is not getting any power.I am starting to think maybe the vats is keeping it from running.

 

[Top]

If the Vats is engaged the engine won't even turn over. Vats 'disconnects' the starter circuit for approx 5 minutes

How are you checking the timing if it won't run? Just lining up the rotor with the number one plug? Are your sure it is firing on the compression stroke? Sounds like you could be 180 out on your timing.

Good Luck

 

[madstacker]

im sure the timing is rite on i waite for thecompression to blow out of sparkplug hole and watch both liffters to make sure there closed.

 

[steve1ph]

just a thought, but what about the oil pressure switch. i think there is somthing about if your in a accident and the pressure drops below a certian point the car will shut down? or it could be the cam sensor. does this car have the coil packs or distributer? if its got the packs try the crank trigger or cam sensor.

 

[8388]

I'm not sure what the codes are, for your model, but if it has anything to do with spark as someone else mentioned, it may be the dist. module. Some part stores have a way to check to see if it's defective. Just another suggestion.

 

[vigman]

Opti?

Did you replace your opti spark module?( 91 was the first year of opti I believe)

Do you have spark?

Did you hook up a test light to see if the injectors are pulsing?

Did you hook up a pressure gauge to the fuel rail to make sure you have OVER 30 psi in the rails?


Vig~

 

[-=Jeff=-]

Re: Opti?

Did you replace your opti spark module?( 91 was the first year of opti I believe)

Do you have spark?

Did you hook up a test light to see if the injectors are pulsing?

Did you hook up a pressure gauge to the fuel rail to make sure you have OVER 30 psi in the rails?


Vig~

Hey Vig, 1992 was the first year for the opti, not 1991

 

[WhalePirot]

code 43

I doubt that code 43 has much to do with your problem.

The '90 manual says the ECM runs two tests to check the knock circuit for proper ops. The first may be of interest.
#1-- If CKT 496(dk blu)[wire from knock sensor to ECM A11] opens or shorts to GND, the voltage goes above 3.62 or below 1.44. If so for >.5sec., code 43 is set.
#2-- the ECM checks the sensor (coolant>203degF/95C and high engine load, based on airflow). It awdvances timing and looks for knock. If none is detected, code 43 is set.

Always use a digital VOM!! Knock sensor resistance should be between 3300 and 4500 ohms. With ignition ON, CKT 496 should be 4-6vdc.

Fuel pressure should be 32-47 with ignition ON. Watch the pressure to see if it maintains during the brief run. A drop may indicate a low oil pressure sensor signal.

With one injector unplugged, will a test light blink. Check boh sides.

Check two plug wires for spark while cranking.

Ensure the MEMCAL is securely installed in the ECM, locking tabs secure and all pins are properly contacting.

Defective MAP sensor may cause no start or stall after. Disconnect it and start up. The ECM will use a default value for it.

I hope you are using new spark plugs. I learned this the hard way.

Recheck, with a friend's fresh eyes, your TDC timing, as has been said.

Frustrating, ain't it. I KNOW!

mike

 

[madstacker]

I rechecked the distributor and it looked good.If it is off 180 degrees it would have to be in the cam installation.