compression numbers

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i8av8

Donating Member
on my road to recovery i thought i would start with compression and these are my results>

cylinder #6--160 #5--160
#4--165 #3--160
#2--145 #1--145

i added a cap of oil to cylinder #2 and compression jumped to 160. did not bother to add any to #1 cause i thought it would be the same results.

i am also trying to figure out a no injector pulse. i have a used computer that i borrowed from a board member and it worked perfectly for about an hour and then i believe my truck corrupted his computer so i had no choice but to purchase it. bought a brand new computer from gm parts direct and it did not want to work at all.

capacitors in msd box blew up so i deleted that and i went ahead and deleted my ultimate box with a hoodtuned ultimate delete for 3bar/50lb/412 cam and all that. that didn't work.

i let a year go by and the gm computer ends up working... sort of. i try it again today and it doesn't work. i put the ecm that i got from the board member and my truck fires up but will not stay running. have to give it gas to stay on.

mysterious injector pulse?
bad ecm/prom?
bad injectors?

where do i go next? need more info because i can provide it? thank you,
nick
 
littleblackpsycho

littleblackpsycho

Donating Member
Re: compression numbers

Did anything happen the last time the truck ran good? If not what have you done to it since it ran decent?
 
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i8av8

Donating Member
Re: compression numbers

it's a brand new distributor with maybe a mile put on it in the past 2 or so years. it's the billet one from ebay. bought because i was having trouble with the msd distributor before.
i even rewired from the module to the ecm just to try and eliminate the code 42 that kept popping up. ty has been sitting for about 2 years so i don't know if the rewire did any good since i can not drive it. tach does move when cranking.

my problem has been ongoing pretty much since i bought it in 2008. there has always been a stumble around 50-60 mph and a hiccup at idle. before it would idle smoothly and then it would jump from 800ish rpm to 1500 then drop to about 500 then back up to 800ish. all at on e. bought the distributor to eliminate that but again, i can't drive it so i don't know if it helped.

tonight the rpms did jump but i do have a bad plug wire and the weird no injector pulse or lack of.

truck is a mess and there is no one near me i can get help from for this. i am trying to do my best with what very little knowledge about cars i have.
nick
 
littleblackpsycho

littleblackpsycho

Donating Member
Re: compression numbers

My suggestion for right now is to try to get this narrowed down a little. Fix the plug wire first. Find tdc and restab the distributor and check the base timing maybe your a tooth off. Get it to start and idle for a few minutes so you can read the plugs. What do you have for a scan tool can you post a data master file?
 
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i8av8

Donating Member
Re: compression numbers

that'll be my next step. thank you

my plugs are 2 years old with about a mile on them and were black (possibly fouled) due to trying to get the truck to start. i just brushed them with a wire brush and made sure they were still gapped properly.

no datamaster or anything like that. just have a snap-on scanner.
 
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