What did you do with your GMT400 today...or yesterday....

[Will L.]

Yes the advance works by limiting the outgoing fuel- which raises pressure inside. The increased pressure forces the advance.

 

[dbrannon79]

What I'm leading to is wondering if things are happening inside the pump while driving where something might be pushing this solenoid or the check ball in the return fitting causing this random timing advancement I was just reading on another forum where they are saying it opens that check ball causing a pressure drop in the pump for the advance.

it's very random with it happens and far and few in between. I could drive through a couple of tanks of fuel before it happens again. it's just this last occurrence lasted longer than it had in the past. time before that when it happened my wife was with me, it was just a split second but enough for her to notice and us both to say "what the ___ was that" each time I witnessed it, I just chalked it up to oil from blow by pooling up in the intake and then one or two of the cylinders swallowing it.

 

[Rockabillyrat]

@ak diesel driver I believe you are talking about this part of the IP in this video. time starts at 1:32 and continues till 6:58. I do know the little plunger behind the advance lever does not return when the engine is off if pushed in. I discovered this when I adjusted the piece on the throttle shaft. I had adjusted it since it was not contacting the lever until about 1/2 throttle a while back. I had compared it to the IP on the 6.2 engine and set it accordingly. this adjustment made a major difference on how the engine is much quieter under acceleration.

I'm not sure I want to attempt to pull the IP and mess with this in the way this guy did. I wonder if it did have water in the IP if over time that water would evaporate out with heat and running where I could possibly fill the filter with ATF or some other oil that would help clean it, work that plunger pin and lever without pulling the IP and then let the engine run flushing the ATF out with fuel.

Maybe @Will L. or @Rockabillyrat can help with their vast knowledge on this and the symptoms I witnessed this morning as well.

The issue with the advance piston bore was Stanadyne never sleeved it from the factory until recently. So all the pumps on our trucks would wear out the bore from the steel advance piston riding on the aluminum housing. The fix used to be to bore them out and put in an oversized advance piston, once you reached the max bore size then they could be sleeved with a metal insert and the advance piston is machined down to match. It also doesn't help that the bore for the advance piston is at the bottom of the pump so it collects a lot of junk.

I preferer to sleeve all the pump housing and be done with it. its a better fix and it saves my from buying all the reamers which are expensive,

 

[dbrannon79]

The issue with the advance piston bore was Stanadyne never sleeved it from the factory until recently. So all the pumps on our trucks would wear out the bore from the steel advance piston riding on the aluminum housing. The fix used to be to bore them out and put in an oversized advance piston, once you reached the max bore size then they could be sleeved with a metal insert and the advance piston is machined down to match. It also doesn't help that the bore for the advance piston is at the bottom of the pump so it collects a lot of junk.

I preferer to sleeve all the pump housing and be done with it. its a better fix and it saves my from buying all the reamers which are expensive,

@Rockabillyrat How safe is it for me to pull the pump and open up the large nuts to pull this piston for checking and cleaning any debris without changing any adjustments or causing damage to the pump?

would the symptoms I am experiencing also have anything to do with the advance solenoid or return fitting in the top cover?

 

[dieselolds]

Today I picked up a Napa gold 6441 air filter to go along with a couple red silicone elbows I got from Amazon.I’m still using the K47 in my 96 gmc truck.I picked up a plastic 5/8 barb fitting from Napa and used a hollow punch to create the hole I needed in the silicone elbow.I think it looks pretty good overall.I’ll install this setup and take another picture under the hood when the rain stops.Its pouring here today.

I used the silicone elbows as the factory K47 air duct elbow is somewhat restrictive and narrow so I wanted to open up that area by going this route.I also used one 4” aluminum adapter to connect both elbows and another adapter was used going into the filter.

 

[Big T]

OK replacement power steering pump arrived. Got it installed before a 1.5 hour quarterly staff meeting. Tested it after the meeting and knew immediately that it was working. Did some bleeding with it up on stands, engine off and engine on. Pulled reservoir cap and the fluid looks fizzy like soda pop. Took the truck off the stands and started it, have power steering but the same sounds as with my original 241.5K mile pump. Hmmmm.

I drove the truck 12 miles one way to Napa to return the pump pulley remove and install kit. Groaning sound when hitting the brakes and while turning. Sound continued all the way back home for a total of 25 miles. Pulled the cap on the reservoir and the fluid was half way down and fizzy. Topped it up and went for another short drive. Sound is now 98% gone and steering is normal. I am wondering whether it is possible to have an air leak at the hydroboost which causes the fizzed air in the fluid, which then causes the noise.

 

[Big T]

After success with the power steering pump, I went to work installing the 4wd actuator. New GM actuator and I now have 2Hi, 4Hi and AWD working as verified on pavement. 4Lo only flashes and does not shift into 4Lo, no matter whether it’s in Park, Neutral, Reverse, rolling in neutral or reverse, etc.This is the closest it has been to full function in years. Have not had 4Lo for over 10 years.

 

[dbrannon79]

Are you able to pull the actuator motor out having it in hand while switching between 4hi and 4lo seeing if it moves into place? I assume it's an arm on the actuator that pushes a plunger within the axle to lock it into the different positions? maybe that plunger is sticking?

That or there is another actuator on the transfer case that needs some love?

 

[Big T]

Are you able to pull the actuator motor out having it in hand while switching between 4hi and 4lo seeing if it moves into place? I assume it's an arm on the actuator that pushes a plunger within the axle to lock it into the different positions? maybe that plunger is sticking?

The actuator merely locks the front axle. It is a plastic jack screw that pushes out and locks the axle. The shift positions are at the transfer case. The shift or encoder motor is what moves and shifts the transfer case into 4 hi and 4 Lo. The encoder motor does rely on a signal from the actuator that the front axle is locked into 4wd.

 

[dbrannon79]

I would assume the encoder is getting the needed signal since it's locking in 4hi. maybe the encoder is having issue physically shifting the transfer case into 4lo from binding or sticky linkage within the transfer case?. this would be my thinking at least. iirc I thing a while back you already replaced the encoder.

 

[Big T]

I would assume the encoder is getting the needed signal since it's locking in 4hi. maybe the encoder is having issue physically shifting the transfer case into 4lo. this would be my thinking at least. iirc I thing a while back you already replaced the encoder.

My mechanic had it narrowed down to actuator, then a faulty wire. Actuator solved 3 of 4. We’ll work on the rest. Important part is the actuator plays a binary function: Locked axle or not locked. The transfer case shifting is back at the transfer case.

Yes I am sitting on a new AC Delco encoder motor which was BOTB. We had to go back to a Dorman which is what is currently in the transfer case. It appears to be working and we will solve 4Lo.

 

[MrMarty51]

OK replacement power steering pump arrived. Got it installed before a 1.5 hour quarterly staff meeting. Tested it after the meeting and knew immediately that it was working. Did some bleeding with it up on stands, engine off and engine on. Pulled reservoir cap and the fluid looks fizzy like soda pop. Took the truck off the stands and started it, have power steering but the same sounds as with my original 241.5K mile pump. Hmmmm.

I drove the truck 12 miles one way to Napa to return the pump pulley remove and install kit. Groaning sound when hitting the brakes and while turning. Sound continued all the way back home for a total of 25 miles. Pulled the cap on the reservoir and the fluid was half way down and fizzy. Topped it up and went for another short drive. Sound is now 98% gone and steering is normal. I am wondering whether it is possible to have an air leak at the hydroboost which causes the fizzed air in the fluid, which then causes the noise.

There is no suction on any of the hoses or pipes. Merely free flowing fluid back to the pump reservoir. AFAIK.
Did You use that bypass kit to eliminate that variable orfice valve thing on the PS pump ?

 

[MrMarty51]

I wanted to do a test on that pendulum fuel tank sending unit.
Hooked battery/jumpers to the main power source for the cabin.
The fuel gauge was setting near 3/4 tank.
Turned on ignition switch and gauge dropped to 1/2, or close to 1/2 a tank.
I think it may be functioning correctly.
Before, if I allowed the gauge to drop to those reddish markers on tje fuel level, truck would sputter, die and be out of fuel.
I hope that with this new sender unit that when the gauge gets to those reddish marks that it will actually be a warning to get some fuel.

 

[Big T]

There is no suction on any of the hoses or pipes. Merely free flowing fluid back to the pump reservoir. AFAIK.
Did You use that bypass kit to eliminate that variable orfice valve thing on the PS pump ?

Tried the bypass kit and it had no effect on the bad pump.

2nd pump worked immediately and it is using the eco from the original pump.

 

[dieselolds]

Today I picked up a Napa gold 6441 air filter to go along with a couple red silicone elbows I got from Amazon.I’m still using the K47 in my 96 gmc truck.I picked up a plastic 5/8 barb fitting from Napa and used a hollow punch to create the hole I needed in the silicone elbow.I think it looks pretty good overall.I’ll install this setup and take another picture under the hood when the rain stops.Its pouring here today.

I used the silicone elbows as the factory K47 air duct elbow is somewhat restrictive and narrow so I wanted to open up that area by going this route.I also used one 4” aluminum adapter to connect both elbows and another adapter was used going into the filter.

Here’s how things look after just installing it.Thank goodness for the top post on the battery.Theres no side posts on these.

 

[Rockabillyrat]

@Rockabillyrat How safe is it for me to pull the pump and open up the large nuts to pull this piston for checking and cleaning any debris without changing any adjustments or causing damage to the pump?

would the symptoms I am experiencing also have anything to do with the advance solenoid or return fitting in the top cover?

Its safe to pull apart. Just mark the position of the LLA cam before you remove it. And of course be very clean with everything.

The HPCA solenoid is used to advance the timing for cold engine conditions. The coolant sensor activates the solenoid. It pushes the return fitting check valve open. Which drops housing pressure to 0psi allowing the advance piston to move. Just disconnect the HPCA solenoid and see if your issue goes away. I delete them on most performance pumps and knock out the check valve. It gains some timing, but more importantly cooling since it increases flow though the pump keeping it cooler. I would only keep the HPCA if you live in an area where it gets REALLY cold.

 

[dbrannon79]

Well I need some help getting the ESS oil pump drive out of the engine. I’ve pulled the bolt and retainer off. It spins freely but will not lift out of the block!

I pulled the non-ESS pump drive off the other engine with ease.

 

[dbrannon79]

Here is the current state of affairs... Maybe @Will L. or @ak diesel driver has some tips on what to do here. the top of the oil pump drive rotates easy and smooth, I can lift and feel something down lower in the block seem like it's stuck, that or the lower section is broken? I can't seem to find a good way to get a pry bar in there to get a bite on it trying to lift. all I'm doing is swapping this out for the one off the 6.2 block to stop the oil leak.

 

[dieselolds]

This evening I installed the dust seal upon the steering knuckle.I used a old 6.2 piston I had laying around to ensure the seal was driven home all the way.A new kugel brand wheel bearing is in place with dorman flange bolts.I also picked up a set of acdelco advantage brake pads.If all goes well I hope to get the driver side section completed tomorrow.

 

[ak diesel driver]

I'd be concerned the drive rod to the oil pump is stuck in the bottom.