performance variance on different start ups?

[peyton4x4]

Well as said in one of my other posts, if I start my 5.7 vortec say Monday, it runs well. If I start it up the next day, I couldn't beat a minivan in a street race. What would cause these variances?

 

[peyton4x4]

Also, when it performs poorly, the ticking in my heads get louder. The radio doesnt work sometimes but turning off and cranking again usually helps that, but not the tick or poor performance. I've got a recomendation to check fuel pressure. How do I do this? And what what else should I look for to be causing this problem?

 

[98_k1500]

Grounds would be a good place to start. They need to be clean, and it does not hurt to upgrade them if you don't mind spending a couple of dollars. You can usually suspect grounding issues when 2 completely unrelated systems start having problems that affect one another. (window button changing the radio station was the craziest one i have seen to date) Clean the battery cables, the connections at the starter, back of the alternator, and fuse box. Be sure it is charging properly. Check the battery voltage when its running bad with a multimeter and be sure its identical to voltage when its running good. Low voltage can make a fuel injected engine act all kinds of stupid. Fuel pressure can be checked with a standard fuel pressure gauge at the schrader valve on the fuel line at the rear of the intake (slightly to the drivers side, should have a black cap screwed on it).

 

[peyton4x4]

I've noticed the gauge on my dash showing the voltage usually varies on different start ups as well. I left my interior lights on in -5 cold the other day for over 8 hours and came out in the morning and it started up slowly. So if that battery can withstand interior lights and cold like that it shouldn't be the battery should it?

 

[kennythewelder]

There is a grate video on you tube about checking the fuel pressure, but after the post of your radio, I sure wouldn't rule out electrical issues. Have you codes read at autozone. If all is clear then there may be a short some where, or a computer issue. If there is a computer issue, I would look into black bear performance. They will sell you a high performance programed computer for your truck for around $250 with exchange.

 

[peyton4x4]

Well I'll check the ground today after school, and see if I can go to autozone and get a fuel pressure gauge. Hopefully I can settle this out without dropping to much money.

 

[98_k1500]

It shouldn't be the battery should it?

I would assume that would rule out the battery. Sounds like its fine. The different voltages on the gauge are normal, the gauge itself is not really that accurate. Need to check it with a volt meter and get a accurate count on whats going on. Should be between 13.4 and 14.6 volts or so at the battery terminals with it running. If its out of this range, i would assume the alternator is acting a fool, because its internally regulated.

 

[98_k1500]

There are ground straps from the back of the passenger head, to the firewall, to the frame rail. One is on the thermostat housing, Then the main block ground (follow the - battery cable to the engine block), and a body ground on the passenger fender (also off of the - battery cable). Do you have a amp/subs in the truck?

 

[peyton4x4]

No subs or amps.

 

[peyton4x4]

Can you tell me the pressure I should see at idle? And the pressure at 2000 rpms?