CUCV glass ball check valve and idle

[Barrman]

This weekend makes 4 months of M1009 owner ship. I have put almost 5000 miles on it in that time. The engine starts and runs good. The idle always seems a bit off, but being my first 6.2 I don't know any better.

Last weekend I was able to hook a tachometer up to it. 900 rpm hot engine idle. I turned it down, and down and down. I went all the way down to 650 like the book says it should be at. However, it sure shakes and lopes and skips a few beats. It still starts great, idles in gear great and does fine. Just a lopy idle.

I was also around people that have 6.2's when I set the idle. They all said it isn't right. Again, I don't know any better and thought it was just the way it was.

Now that I have been told it isn't right, I need to work on it. My first step was to use a thermometer to check exhaust port temps. All within 20 degrees of each other and with a cooling fan blowing, I figure that is pretty good. Next I pulled the return line off the top of the pump and removed the fitting with the glass ball inside.

No glass ball and the fitting is clean looking. So is the pump at that spot inside. Here is my question to those that have busted out the glass ball. Did your idle quality go down afterwards, but the truck still go down the road great?

Thanks.

 

[CUCV85]

Glass ball gone from return line valve indicates someone thought the IP was going, usually indicated by crap clogging the return line valve from the internals of the IP failing.
Replace the return valve, check timing - adjust timing/
possibly turn up IP/IP idel... your IP may be going? You can stretch it a while.

This weekend makes 4 months of M1009 owner ship. I have put almost 5000 miles on it in that time. The engine starts and runs good. The idle always seems a bit off, but being my first 6.2 I don't know any better.

Last weekend I was able to hook a tachometer up to it. 900 rpm hot engine idle. I turned it down, and down and down. I went all the way down to 650 like the book says it should be at. However, it sure shakes and lopes and skips a few beats. It still starts great, idles in gear great and does fine. Just a lopy idle.

I was also around people that have 6.2's when I set the idle. They all said it isn't right. Again, I don't know any better and thought it was just the way it was.

Now that I have been told it isn't right, I need to work on it. My first step was to use a thermometer to check exhaust port temps. All within 20 degrees of each other and with a cooling fan blowing, I figure that is pretty good. Next I pulled the return line off the top of the pump and removed the fitting with the glass ball inside.

No glass ball and the fitting is clean looking. So is the pump at that spot inside. Here is my question to those that have busted out the glass ball. Did your idle quality go down afterwards, but the truck still go down the road great?

Thanks.

 

[3dubs]

Gone? Can you stick something through it? I would think there would not be much fuel pressure if it was gone. But I have not tried it. I know when I looked through mine I could not see anything but when I tried to spray carb cleaner I found out it was there.

 

[dilvoy]

I've broken out the glass plunger and spring on a couple of trucks and I noticed no difference in either idle quality, idle rpm or drivability as compared to a truck that had a properly operating plunger.

 

[3dubs]

Cool! So I guess when they get dirty the blockage is the problem.

 

[Barrman]

Yes, I am able to stick a small screwdriver through the entire fitting. Thanks for the info about the idle not changing any with the ball removed. I will prepare my wallet for pump. Actually, I think I will find a used one and try to pull it apart to rebuild myself. Might as well learn how to do it.