350 vortec no start help

[prairiehotrodder]

2000 chevy 3/4 ton with the old style 350 vortec.

Has spark and fuel

cranks really hard like the timing is far advanced

kicks back as it cranks.

won't start

timing chain seems tight.

Tons of parts have already been replaced by the owner searching for the problem . Cap, rotor, MAF, plugs, wires,

[In-Tech]

Hiya Brian,
The timing is controlled by the front crank sensor, the cam sensor distributor is basically for rotor phasing and sequential sync so it will run "non batch" fire.
Pull the front sensor and check for metal "fuzz" then check to make sure the reluctor wheel hasn't spun on the woodruff key.

[BOOT]

Dist gear is another possible cause and easy to check if if the rotor moves.

[prairiehotrodder]

reluctor looks ok from what i can see through the hole. Crank sensor was replaced.

distributor also looks ok. Rotor doesn't turn on the shaft.

Cranking psi is about 125 cold so i don't think the chain has moved.

Spark plugs get soaking wet.

[BOOT]

Test the gas, knew a guy who went n replaced/checked it all to find out he just filled up with mostly water.

[Matt Compton]

Also if distributor was removed at anytime, you need to be sure its sync'd with a scan tool.

[prairiehotrodder]

pulled the balancer off to better check the reluctor wheel and it appears ok. Timing chain feels ok / rotor moves immediately when i turn the crankshaft.

[In-Tech]

dot to dot on the chain should have the rotor pointed at #6 if you want to check that. That flat cap can be a bit confusing. Look closely. It's very easy to mess up the firing order.

[1980RS]

I always remember those spyder injector systems causing all sorts of problems. I know this, anything less than 50psi fuel pressure and that 350 won't run.

[rebelyell]

^^^this^^^ had one acted up w/ same symptoms --- fuel pump --- common failure --- fuel pump

and --- oh joy --- pump's in top of tank --- either drop tank or cut access panel thru bed.

also, test cam sync sensor --- it's inside distributor --- looks like an ignition pickup or trigger but it's a cam sync sensor.

also, ensure dist vents are open & clear

[travis]

Something is definitely rotten in Denmark. Cranking compression should be 50+ psi higher. The timing chains on these things seem to last forever. Definitely make sure fuel pressure is 50+ psi with key on engine off. The ignition module is also something that will bite you in the arse...when they fail you can get all kinds of crazy popping and misfiring. Does the engine start then stop immediately, or not fire at all? Verify plug wires are on the right terminals (easy to get wrong). Don't even bother with parts store distributor caps and rotors...get a good brass terminal cap like an MSD (makes a world of difference). Check plugs for signs of antifreeze (intake gaskets are a common failure point on these). Double check for vacuum leaks as well...these things seem quite sensitive to them. Make sure the valve adjustment isn't too tight, and check for bent pushrods.

Just thinking aloud the issues I've seen on a handful of L31's myself

[rebelrouser]

I always remember those spyder injector systems causing all sorts of problems. I know this, anything less than 50psi fuel pressure and that 350 won't run.

Yep if it has the old spider injectors pull the intake and look at them. I have seen them backfire in the manifold and melt the lines, and somebody mentioned water in the fuel, those injectors will not pass water through the nozzles. Years ago I helped a guy get one running that was flooded.

[Tom68]

Seems to be a lot of going about this the long way, mechanically.

1. Spark. Test with a big gap, so you know it can fire a shitty mixture.

2. If you thing the spark is at the wrong time, get at least a rough TDC mark, use a timing light and confirm the spark is before TDC.

3. Fuel, all the advice for this is in the responses, I've never physically seen an L31, not true I walked under one on a hoist.

4. Comp, you done that and you would have done it making a TDC mark otherwise, although not with a gauge.

5. Well it's not 5, but cam timing has been mentioned, when you're rough TDC shows No 1 at the end of the compression stroke, the valves on number 6 will be in overlap. But you'd already confirmed spark was at approximately the right time.

Fresh fuels been mentioned, if the fuel is in an atmospheric vented tank you need to check it, spill some on the floor, light it, and if it burns like kerosene it won't be good enough to start an engine. That's normally many years old fuel that does that though.

[BB70]

Anyway to drop the exh before the cat convertor(s). Had this happen a time or two. Good luck.

[Tuner]

Anyway to drop the exh before the cat convertor(s). Had this happen a time or two. Good luck.

Remove the O2 sensor.