Help, truck will not start

[turbosonoma]

weird problem.....i put my truck together after being apart for about 6 months, i got a new chip and injectors, it started and ran as good as i could expect it to right off the bat. So i went home, and went to work on it and finish it up a couple of days later and it would not start at all . It ran for a total of about 20 min at first start up. It has fuel, spark, i bought a new computer, the timing is set to 0. plug #3,4,5 are very black, but the other ones are clean and they are getting fuel. Doesnt make much sense to me. Please help.

 

[Bill Z]

Help, truck will not start

I will try to help.

First: Tell me how you know that you are getting fuel. Are you checking the fuel pressure at the rail? This will only tell you that your fuel pump is working (and that is a good thing). You need to check to see if there are pulses at your injectors. This is done using NOID lights or something like that.

What sometimes happens when these trucks are not tuned, is that one or more of the sensors pick up on a rich or too much air or something and it shuts down the pulses to the injectors. This may explain the black plugs in cylinders 3, 4& 5 (weird combination).

Do you have a code on your computer indicating one of the sensors found something?

I had a 4.3 S10 that just had a tune up. It ran great a while and then just stopped. The final problem was that the distributor cap was not on solid and came loose and busted the rotor bug.

Tell me what you find.

 

[turbosonoma]

it is getting fuel at the rail according to my gauge. i do not have any of the noid lights, that was going to be my next step. no code on the computer as i cant even get it running.

 

[Bill Z]

Help, truck will not start

Another thing to check is the spark to your plugs. Are you running an after market ignition like MSD or std. GM?

Check your spark at all spark plugs (after you clean or replace those black plugs) with a timing light. Mark the crank pulley so you will know that the plug is firing at the correct time.

By the way, O’Reillys had the Noid Light sets for $18.00. Worth the money.

Let me know.

 

[turbosonoma]

all plugs are firing....

 

[Bill Z]

Help, truck will not start

I know you know the basics. All you have to have for any gasoline engine to run is the right amount of air/fuel, compression and spark (all at the right time).

You said that you have spark. You did not say if you knew if the spark was at the right time but I will assume that it is.

I also assume that there is compression because you said that it had been running.

Try to squirt just a little fuel into 3 or 4 cylinders through the spark plug holes (replacing the plugs and connecting the wires really quickly). Then try to start it. It should try to fire over (until the gas fumes are used up). If you hear it fire, then you can figure that the injectors are not firing. Another way, but somewhat dangerous< is to spray fuel into the plenum while trying to start. The problem here is backfires.

Remember that the ECM will shut down the injectors if certain sensors do not respond right.

Also, check all of your cables and connectors for disconnects or burned wires.

By the way, did you get any codes?

Let me know

 

[TyMeUp]

Check the TPS (throttle position sensor) - make sure it isn't stuck in the wide open position.

Almost all electronic fuel injection systems use the TPS to signal a "clear flood" condition. When the ECM sees a high voltage (>4.0 V) from the TPS, it will shut off the injectors while cranking.

Normally we could look at the TPS signal on a scan tool to verify normal closed throttle voltage. If you don't have that capability, and you suspect a problem, temporarily disconnect the TPS connector and try to start the engine without it.