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GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15181
Experience:  GM Grand Master Technician 2007. 14 years experience.
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Chevrolet Silverado 1500 Classic LS: i have a 05 silverado

Customer Question

i have a 05 silverado 1500 that wont start. has 55psi of fuel pressure has spark but has a funky injector pulse. the first three sparks of the plug and injector are on time with each other but then i get 2 sparks per 1 injector pulse. kinda stumped please help
Submitted: 8 months ago.
Category: Chevy
Expert:  Jared D replied 8 months ago.
That sounds like maybe a bad signal from the crank position sensor is messing up the injector pulse. Have you taken a look at the crank sensor yet?Do you have a scope to test it for a good wave signal?
Customer: replied 8 months ago.
hey jared. i was curious about that myself but didnt want to throw parts at it. i dont have a scope but i do have a snap on solus ultra with no codes and verified cranking rpm
Expert:  Jared D replied 8 months ago.
I would probably put a crank sensor in it, or at least check the wiring to the sensor really closely for frays or damage.Our Solus will sometimes show cranking RPM when the crank sensor is faulty.
Expert:  Jared D replied 8 months ago.
Check the ground on the left side of the engine block close to the firewall. This ground is bad about coming loose and creating spark issues as well.
Customer: replied 8 months ago.
ive seen that rare occasion also lol. would like to think thats all it is. the ground isnt loose but it may be dirty. i checked the wires to the crank sensor last night and didnt see any signs of fraying or so forth.
Expert:  Jared D replied 8 months ago.
I've seen a handful of these trucks with a crank, no start condition that had too much paint where the ground mounts to the block. A wire brush usually takes care of it.
Customer: replied 8 months ago.
ill give it a shot. let me run to the parts store. be back in 30 or so
Expert:  Jared D replied 8 months ago.
Sounds good.
Customer: replied 8 months ago.
well cleaned ground and replaced crank sensor no change
Customer: replied 8 months ago.
the truck was running great and i pulled in the driveway and it stalled. re started it and it fired right up. drove down the driveway and shut it off. went back out to leave 6 hours later and it would start and die. start and die. now its at the point all it does is turn over and not even try to run.
Customer: replied 8 months ago.
have checked all fuses and both injector power fuses.
Customer: replied 8 months ago.
squirt with starting fluid or gas bottle and will run as smooh as ever as long as u keep sprayin
Expert:  Jared D replied 8 months ago.
So it's a fuel delivery issue then?Do you have pressure gauges to see what the fuel pump is putting out?Can you hear the pump buzz when you first turn the key to run?
Customer: replied 8 months ago.
yessirr. pumps runnin. 54 psi on fuel rail
Customer: replied 8 months ago.
koeo of course
Expert:  Jared D replied 8 months ago.
What does it do if you try to start it with the MAF unplugged?
Customer: replied 8 months ago.
same. no change
Customer: replied 8 months ago.
i would think it would try to start but its not. i have physically taken a stethascope to the injectors and i can hear them click but what is really odd is they appear to be firing at every other injection cycle. like same cylinder with inline spark checker and same cylinder with a noid light and the plug will fire twice to every once of the injector.
Customer: replied 8 months ago.
but the first 3 or 4 cycles they are right on queue with each other then all the sudden u get every other time
Expert:  Jared D replied 8 months ago.
Check ground G102 also.
Expert:  Jared D replied 8 months ago.
You already checked g103 and g104 right?
Customer: replied 8 months ago.
i only checked 103. 104 i looked at and it appeared to be just a body ground it tuns to firewall. didnt check 102. will do now. brb
Expert:  Jared D replied 8 months ago.
You might pull the PCM connectors and make sure nothing is loose/corroded there too.
Expert:  Jared D replied 8 months ago.
I'm leaving the shop for the day. I'll check back in this evening to see how things are going.
Customer: replied 8 months ago.
well pulled and cleaned all grounds. no change.
Customer: replied 8 months ago.
man that one on the back of the drivers side head is kinda a pain lol
Customer: replied 8 months ago.
pulled pcm connections and all are clean and tight
Expert:  Jared D replied 8 months ago.
Still no luck after checking all of the grounds huh?Let me see if I can look at the schematic and see where we might be losing injector pulse while cranking.