I have my engine all rebuilt and sitting on the break-in-stand. It wont start. Checked the fuel pump, it was bad, replaced it. Changed coils, still wouldnt start. Got fresh 87 oct fuel (ignites easier)and a fully charged battery, still wouldnt start. It turns over fine, and is timed right. We got a couple of pops out of it, but it just wont go. The carb has been sitting for a while, but it was delivering at least some fuel, if not all. Im gonna put a new carb on to try, but if that dosnt work, what might it be?

 

Just for sh*t's and giggles, re-check your valve lash. Might have it too tight.

 

Recheck your distributor

 

Double check that!

 

make sure you dont have a plug wire crossed or you could try putting the engine at top dead center on the number one piston on the compresssion stroke and restab the distributor and see if that helps out at all........

 

The distributor is fine, im thinkin it might be the valve lash( cuz i set them ) My friend checked them though, and said they were good.

 

hmmmmmm only other thing i can think of if your gettin good spark and fuel is maybe the plugs are bad or fouled ....or you have a vacuume leak......

 

Here is a good list of things to check:
go through your standard check list, for carb cars,(some of the info works on all cars)

check that theres spark at all the plugs and the plugs are burning cleanly

check that your getting the correct voltage at the coil/ignition and plugs are not loose and gapped correctly,

check that the wires and coil are not arcing or shorting out

check that the throttle linkage opens fully

look for coolent on the plugs or coolent leaks under the car

look for loose vacume hoses, crimped lines, ETC,

check your oil level is correct

do a compression test if anything looks bad on the plugs or engines seems to not be running on all 8 cylinders

look for rocker arms that are not moveing correctly,bent push rods, loose rocker arm studs, broken valve retainers, or valve springs

check that your getting good oil pressure at idle(pressure switch can turn off ignition)

check that cam and ignition timeing is ok/not changed (timeing light,

loose timeing chain on cam drive, check that the distributor has not moved, check with a timing light)check that the rotors not loose under the distrib. cap and the distrib. cap itself is not loose or cracked

check that you have not wiped a cam lobe, broken a valve spring or valve spring damper.

look for loose rocker arm adjustment

look for vacuum leaks

look for loose electrical connections, fan belts or accesories that might be having a bearing or electrical failure putting excessive drag on the engine

look for low fuel pressure/clogged fuel filter, bad fuel, water in gas, rust in the gas or just low on fuel.

look for plugged up air filter/bad pvc/egr

check catalitic converters not plugged/restricting the exhaust flow

check for moisture in distributor cap.

check that the damper on the crank has not come loose and moved the timeing marks on the outer ring by having the elastic break loose between the rings on a stock style damper or that the key in the crank has not sheared allowing the damper to move possition

do a CYLINDER LEAK DOWN test

make sure the fuel pressure is correct and the fuel supply system is working at 6psi-8psi before the pressure regulator and about 5psi-6psi at the carb

http://www.centuryperformance.com/timing.htm

http://www.centuryperformance.com/vacuum.htm

http://www.boyleworks.com/ta400/psp/distcurve.html (pontiac but info the same for chevy)

http://www.73-87.com/garage/101s.htm

http://www.73-87.com/garage/hei.htm




look for spark plug wires that are loose or not correctly connected

heres info later efi engines like my corvette can use

HERE TAKE IT STEP BY STEP

http://www.c4vettes.com/maf.htm

http://www.c4vettes.com/l98.htm

http://www.midniteworks.com/vettecodes/vettecodes.html

L-98 Engine Start Sequence

When you start an L-98 engine Corvette, a series of events take place that causes the engine to run. Knowing the sequence will help you troubleshoot no start conditions.

Fuel Rail Pressurization:

When you first turn the key to the “on” position, the fuel pump will run for 2 seconds pressurizing the fuel rails. There is a Shraeder valve on the passenger side fuel rail near the rear of the engine and if you measure the pressure there after the pump runs, you should see between 40-42 pounds of pressure. The reading will go to 38-40 pounds nominal once the engine is running.

Initial Crank Action:

If you then rotate the key to the start position (assuming the anti-theft system has not disabled the starter), the engine will rotate.

Once the oil pressure has reached 4 PSI, the oil pressure switch will close allowing the fuel pump to run. (Note that you should have a black oil pressure switch/sender. It is mounted behind the distributor on the driver’s side and if it is not black, it is suspect due to a run of bad units that stayed in the GM parts pipeline for some time).

The distributor will send a string of pulses to the ECM (Engine Control Module) in response to the engine being rotated by the starter. These pulses continue as long as the engine turns (both starting and running) and if they are not present, the engine will not run.


Summary:

If you have a no start condition or if the L-98 starts and then dies, check the above items in sequence to see if all the events are occurring as required.


Theory of Operation

As the air travels past the heated wire enroute to the intake manifold, it will cool the wire and additional current is added to again heat the wire to the design temperature. Since the amount of air moving past the sensor is directly related to the amount of cooling experienced by the heated wire, a feedback condition is established whereby the exact amount of moving air is directly related to the amount of current passing through the wire and the intake air is therefore precisely measured.

Once the amount of air is known, the computer controlling the engine can add or subtract fuel as required to maintain the magic 14.7:1 air-fuel mixture resulting in the cleanest burn possible from an emissions (pollution) standpoint.

It does this by varying the "on time" of the fuel injectors. The injectors are pulsed on and off and the width of the pulse is lengthened or shortened as required. When you first start a typical engine, the pulse width is around 4 milliseconds but as soon as the engine "catches" the pulse width is shortened to about 2.2 milliseconds for idle. During operation, the measured air flow through the MAF will cause the computer to increase or decrease the pulse width as explained above.
good luck

 

Thats quite a list.

What do you mean by " wires arching"?

 

Check your distributor placement.

I'd be willing to bet it's 180° out.

Take out the #1 plug; stick your finger over the hole; have somebody bump it wth the starter until you feel compression; turn the engine slowly after that until you can look in the hole and see the piston at TDC; and check where the rotor is pointed. If I was the betting kind, I'd bet the rotor would be found pointing at #6; that's the cylinder that's 180° away from #1 in the firing order, that fires at the other instance of #1 TDC.

 

RB you must fix that keyboard...LOL its cracking me up!!

 

Don't forget valve timing. Took me 2 weeks to figure that one out.

 

That spark plug wires are touching cause them to fire on the wrong cylinder or broken wire touching metal, cause it to fire..

 

open the hood in the dark...if you have arching..you will know what it means...

 

I put a new carb on, pushed the start button, and it spit fuel out, so the timing was 180 out. But it was actualy the cam timing that was out, so I just flipped the rotor to 180 out. Started up with just one touch of the button, and it sounded awesome!

 

Glad to see you have it running..

 

yep, having the dist. 180* out is one of the easiest things to do wrong with a new motor.

glad that its running

 

yep , it feels like cam / crank alignment, remember, when the 2 dots are together is firing at #6 ?
it happened to me before
Fernando.

 

Here is what happen and why the distributor will be 180* out.
When you line the cam and crank gears dot to dot that #6 position is used to ensure that your cam is phase correctly. Now once you have it Dot to Dot you must rotated it 360*, which would put the cam gear at 12 o'clock and the crank gear at 6 o'clock, at this time the engine will be firing on the #1 cylinder. This is when you drop the distributor in to mesh with the cam, Otherwise you will be 180* out everytime.

 

One thing that should be specified here for others is that dot to dot doesn't mean jack when you have an adjustable cam sprocket. Dot to dot must be done at 0 on the crank sprocket not +4 or -4 unless you're messing with your valve train timing.

 

dtl i think the dots on both gears would be at 12 not 12 and 6