5.3 won't start

race_jeep · Nov 25, 2011

I've swapped a 5.3 into my buggy, we wired it up last night, tried to start it, and it won't crank, it won't even hit on ether.
We have checked the harness a dozen times everything is correct, it's getting spark, and all the injectors are firing, it just won't start, any ideas? :dunno:

wontwork · Nov 25, 2011

Start working earlier on ur stuff.

87yjtoy · Nov 25, 2011

fuel PSI?

doctordick · Nov 25, 2011

Do you know for sure that this engine ran before you got it? If you have fuel and spark, it should at least try to run. Pull all the plugs and make sure they're dry (engine not flooded). Check for compression, crank the engine over and stick your thumb over a sparkplug hole. Do you have access to a scantool? Check codes. Put a timing light on it and crank it over, you should see timing at TDC.

POPS58 · Nov 25, 2011

A simple test is spin it over and skeet a little starting fluid in the intake and if it hits check fuel pump or fuel pressure.Thats where I start at

race_jeep · Nov 25, 2011

I haven't checked fuel pressure yet but it won't start on starting fluid so I didn't think that would be the issue, it has compression and no codes.

doctordick · Nov 25, 2011

Does it backfire or do anything at all? How did you determine that the injectors are firing? Can you hear them or did you verify that they're actually spraying. There is a schrader valve on one of the fuel rails, CAREFULLY push the valve stem and see if you have pressure there, it should spray, so put out that blunt. ;D That said, if it doesn't even try to fire on ether leads me to think a timing problem of some sort. Are you sure it's not just badly flooded or did someone oil the cylinders heavily while it was out. Most ECMs have a flood clearing mode, when you hold the pedal to the floor while cranking, the injector flow is cut way back to clear the cylinders.

race_jeep · Nov 25, 2011

Nothin just turns over

doctordick · Nov 25, 2011

Have you tried putting a timing light on it?

doctordick · Nov 25, 2011

Did you do anything at the front of the engine which could have changed the crank position sensor in relation to the balancer?

86tank · Nov 25, 2011

Mine did about the same thing when we were trying to get it going the first time. If you know where another truck is with a 5.3 try pulling the fuel rails and putting them on yours with all the injectors. All of my injectors were bad and we figured it out by doing that. If it has set up for a long time my bet is injectors.

doctordick · Nov 25, 2011

86tank said:
Mine did about the same thing when we were trying to get it going the first time. If you know where another truck is with a 5.3 try pulling the fuel rails and putting them on yours with all the injectors. All of my injectors were bad and we figured it out by doing that. If it has set up for a long time my bet is injectors.

Should have at least tried to fire on ether, even with all the injectors bad.

race_jeep · Nov 25, 2011

No I haven't changed anything on the front of the engine, lay and I pulled the fuel rail and turned it over and all the injectors r firing gud

86tank · Nov 25, 2011

True. Scan tool will be the best then. It probably is a timing issue or a bad sensor.

Draco · Nov 25, 2011

I bet it's out of time somehow.

Has it had a cam put in it before you got it? Reason I ask is I had the same issue on one of my motors and it was the valve springs. Same issue as you describe...Adjusted my valves and it fired right up. Good luck with it! (Aggravating bastards at times.)

Draco · Nov 25, 2011

This is the way I did my adjustments and it fired right up. (after days of cussing and throwing ****.)

Worth a try... :dunno:

Here are step by step instructions:

Remove the valve cover.

Identify the number one cylinder. See the page on Firing Order on the menu to the right if you are not sure which cylinder is number one.

Turn the engine over until you see the number one cylinder exhaust valve rocker arm JUST START to move from the closed position to open. You may need to turn the motor over a couple of times to reach this point, but do not turn any further.

Locate the intake valve.

Loosen the rocker arm adjustment nut until you feel some obvious lash or clearance in the adjustment.

Using the thumb and index finger of one hand, grasp the intake push rod below the rocker arm, and rotate it back and forth (clock-wise and counter clock-wise successively to be sure there is no remaining pressure on the push rod from the rocker arm as you loosen the rocker arm adjusting nut.

Using the other hand, while continuously performing step 6, with a 5/8 socket and ratchet, tighten the rocker arm adjustment nut slowly until you feel a resistance of motion on the push rod.

This will be the zero lash adjustment point. For hydraulic lifters, tighten the rocker arm adjustment nut 3/4 of a turn. For solid lifters, back off the rocker arm adjustment nut until your feeler gauge just fits under the contact point between the valve stem and the rocker arm. Fine tune the adjustment by checking it with a feeler gauge just slightly thicker than the preferred clearance to be sure the clearance is not greater than it should be. If the larger feeler gauge will fit, it needs to be re-adjusted. A lash tolerance of 1-2 thousandths of an inch in the valve adjustment for solid lifters would be acceptable since it may be difficult for someone who is in-experienced to be more precise than that.

Turn the engine over until the intake valve opens and then is almost closed.

On the exhaust valve, repeat steps 5 through 8 for the exhaust valve adjustment.

Repeat this procedure for each cylinder. Be sure to do each cylinder sequentially, either following the firing order, following the cylinders numerically, or in the case of a V8 doing one side of the engine at a time. I prefer to do one side of the engine at a time.

doctordick · Nov 25, 2011

Good idea. You can also confirm timing while you're at it. Bring #1 piston to TDC with both valves closed, timing mark should be centered under the crank sensor.

KILLERB468 · Nov 25, 2011

quick thing i do for an engine that sits for a while. even if it shouwed compression it can still have low initial comprression"first stroke of the piston. With it having spark and won't hit on fuel or ether. Take and squirt some oil in every cylinder, rotate a few times with with the coils and injectors unplugged. after 10 seconds of cranking plug all the stuff back up and try it. I bet there just isn't enough initial compression from sitting for some time.