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

[dbrannon79]

Played with the 93 some while I was charging batteries. wired up the cold advance on the IP so it would work. had to splice in a diode to the fast idle solenoid that pushes on the throttle since I have it wired into the AC so it bumps the idle with the AC running. tested it out to make sure it wasn't going to back-feed into the relay I had for the AC and electric fan. That all seems to work fine.

I also was reading up on this 93 and found what exactly the PO did with turning up the fuel on the IP that's in it. both the transfer pump adjustment and the fuel rate adjustment have been moved. increasing the transfer pump pressure (adjustment inside the IP fuel inlet) also limits the amount of timing advance the solenoid on the IP gives. this would explain why when I manually energize the cold advance solenoid it hardly changes anything other than me seeing fuel flowing faster in the clear return line.

I wonder if I need to attempt to un-do this so it can work properly. I also need to figure out if a fella like me with limited knowledge can get it done without pulling the pump. Maybe @Will L. and @Rockabillyrat can give me some input. whether I should attempt, and if / how to know it's close the normal again.

Last night I searched up and down on the innerweb for the instructions he used on the transfer pump but could not find anything about adjusting it, even on a test bench.

Here is the link to the thread and a screenshot of the post.

DB2: Increase Case Pressure-Turn Up Fuel: Questions...........

i have done both per these instructions: "Transfer pump: This increases case pressure. Looking at intake of pump inside inlet fitting, there's a 5/32 allen screw, turn clockwise looking at it, increasing case pressure and timing advance across board. Be careful, too much and it will blow seals...

www.thetruckstop.us

 

[dbrannon79]

Been working on searching the forums to compile the full history of this 93 together on a timeline. been searching posts here and in DP. Once I have most of all the major things listed I will post something in the build threads here with all the links.

 

[Rockabillyrat]

Played with the 93 some while I was charging batteries. wired up the cold advance on the IP so it would work. had to splice in a diode to the fast idle solenoid that pushes on the throttle since I have it wired into the AC so it bumps the idle with the AC running. tested it out to make sure it wasn't going to back-feed into the relay I had for the AC and electric fan. That all seems to work fine.

I also was reading up on this 93 and found what exactly the PO did with turning up the fuel on the IP that's in it. both the transfer pump adjustment and the fuel rate adjustment have been moved. increasing the transfer pump pressure (adjustment inside the IP fuel inlet) also limits the amount of timing advance the solenoid on the IP gives. this would explain why when I manually energize the cold advance solenoid it hardly changes anything other than me seeing fuel flowing faster in the clear return line.

I wonder if I need to attempt to un-do this so it can work properly. I also need to figure out if a fella like me with limited knowledge can get it done without pulling the pump. Maybe @Will L. and @Rockabillyrat can give me some input. whether I should attempt, and if / how to know it's close the normal again.

Last night I searched up and down on the innerweb for the instructions he used on the transfer pump but could not find anything about adjusting it, even on a test bench.

Here is the link to the thread and a screenshot of the post.

DB2: Increase Case Pressure-Turn Up Fuel: Questions...........

i have done both per these instructions: "Transfer pump: This increases case pressure. Looking at intake of pump inside inlet fitting, there's a 5/32 allen screw, turn clockwise looking at it, increasing case pressure and timing advance across board. Be careful, too much and it will blow seals...

www.thetruckstop.us

View attachment 90913

When you turn up thr fuel screw you will also advace the base timing since the rollers will hit the cam ring earlier.

Transfer pump pressure you need to be careful with. At 130psi is will lock the rotor. I normally set mine to 65-70 psi at 2k rpms. Which is the normal spec for a 4911.

The HPCA solenoid only advances the cam ring about 2* (4* at the crank) so it's not alot of movment. If you increasing TP pressure it will advance the timing. The opposite end of the advance piston is controlled by housing pressure. So if you increase housing pressure then it retards timing. That's how the HPCA works. The check ball holds pressure in the housing and thus keeps the advance piston slightly pushed back. When you energize the HPCA it pushed the check ball open. That drops housing pressure to zero and advances the timing since the advace piston has no housing pressure pushing on it anymore.

Too much housing pressure can cause issues and indicate a leak in the TP system.

 

[dbrannon79]

@Rockabillyrat Is there a way i can check the transfer pressure with the pump still in the engine? a way to connect a gauge just to see if it's "ok" I was just backtracking reading up on what all has been done to this truck in the past. the engine has been running on this pump since 2016 from what I am reading in the forums. Or is this anything I need to worry about.

 

[Rockabillyrat]

You need the adapter to put a gauge to it. You remove the torx screw holding nose cone retainer in place. Then the adapter screws in for the gauge

 

[MrMarty51]

Run you a thread chaser tap into the hole and clean out any debris

I dont have a thread chaser for the metric.
Oriellys is open and they didnt have one, neither did ACE.
Got back home after buying new bolts, took a old hard bolt from the jug, filed grooves crosswise of the thread and run that into the bores.
It went through real easy so I think all was left in good condition.
New bolts was easy to spin in with the PS bracket in position.
It is now getting closer to fire.
Drilled and 1/8” pipe tapped the exhaust manifold for the drive pressure gauge. Exhaust pipe already has a bung from when I had the pyro poked through there. Good to go for wwhen the boost gauge arrives.

 

[dbrannon79]

You need the adapter to put a gauge to it. You remove the torx screw holding nose cone retainer in place. Then the adapter screws in for the gauge

Sounds like I better leave that to an expert! I wouldn't know where to find that sort of adapter. I already know not to mess with the adjustments, since these have already been toyed with it needs to go to an expert like you for inspection.

makes me want to take the pump that's on that 6.2 engine and see if I can figure out what's with the loppy idling thing it does, open up the advance on the bottom cleaning it all out, maybe going as far as pulling the cone retainer to check the screen filter. then use it on the 93 and send it's pump to have it checked and brought back into spec. Not sure if I would be able to find anyone willing to do that.

 

[dbrannon79]

I forgot to post this morning about the 93 leaving for work. I had wired up the cold start advance solenoid on the IP yesterday. I had already tried it manually but I guess when the engine is slightly warm already you can't tell any difference in it running. Well this morning I was reminded why I disconnected it!! fired it up and the engine sounded like I had a dozen ball pien hammers banging against a steel plate at uneven rythms!! And LOUD! I'm sure I woke up the neighbors LOL

Maybe I need to re-visit this and see if anyone knows just how noisy it should be on a cold (60 degree) start like that. if I didn't know any better it sounded like all 8 rods were about to be ejected!!

I might try to do a video on my phone as I'm starting it up leaving from work. it's sat in the parking lot for 10 hours now and it's 76 degrees so maybe it will sound just as it did this morning.

 

[dbrannon79]

Tried to video it for the sound but it wasn't near as loud as this morning, will try again in the morning if I remember. it's supposed to be down in the mid to high 40's. I am thinking I have the IP turned slightly too much one way or the other. if that's the case I can possibly mess with it this weekend once I figure out which way to bump it.

 

[dbrannon79]

Someone maybe can verify this. I think I am just a tad too far retarded on the timing (probably me and the timing HAHA). with the symptoms I get are by pressing the advance piston (lever on the passenger side of the pump) engine stumbles and a little smoky. also under acceleration engine is quiet (no rattling) and will throw quite a bit of grey smoke. remember a while back I did adjust the cam on the throttle shaft to match the other IP I have, it was way out. I might need to adjust it back slightly after moving the pump again. I did mark the original position on the shaft so it could be put back.

correct me if I am wrong... when the cold advance solenoid is powered, it actually retards timing not advance.

I found this on DP explaining how to time by ear and sight.

First, the two marks should be as follows, on the timing cover, the mark should fall dead center of the top injection pump stud. On the injection pump, the mark should be centered with the slotted hole.

Advance pump to drivers side, retard to passenger side (drivers is right side as stand in front and look at vehicle)

On your injection pump there is a long metal arm, opposite side of pump from the throttle linkage. At the bottom of this arm is a plunger called light load advance. Take a screwdriver and with the Engine running, depress the lever(this pushes on the plunger) and listen. If the engine did nothing, you didn't push far enough, or its bad.

If when applying the light load advance lever the engine slows, but doesn't really do any thing else, your likely too advanced.

If the engine stumbles just a little bit (fishbite) then your timing is pretty close to good.

If it really stumbles, runs rough, smokey, you're way to retarded.

I've found the best spot is a hair advanced of the timing cover mark.

DB2 Timing Questions

www.dieselplace.com

Going by the post I found, I think I am somewhere between "close to good" and "way too retarded" along with the above mentioned cam adjustment is slightly too far.

 

[MrMarty51]

Someone maybe can verify this. I think I am just a tad too far retarded on the timing (probably me and the timing HAHA). with the symptoms I get are by pressing the advance piston (lever on the passenger side of the pump) engine stumbles and a little smoky. also under acceleration engine is quiet (no rattling) and will throw quite a bit of grey smoke. remember a while back I did adjust the cam on the throttle shaft to match the other IP I have, it was way out. I might need to adjust it back slightly after moving the pump again. I did mark the original position on the shaft so it could be put back.

correct me if I am wrong... when the cold advance solenoid is powered, it actually retards timing not advance.

I found this on DP explaining how to time by ear and sight.

DB2 Timing Questions

www.dieselplace.com

Going by the post I found, I think I am somewhere between "close to good" and "way too retarded" along with the above mentioned cam adjustment is slightly too far.

I was thinking too far advanced gives the predetonation rattle/clatter.
Retarded is quieter.
Seems after I advanced the timing on My engine from around -.45 to -1.50 it clattered a lot more.
But then too that was when I installed the newly balanced injectors that were popping at 1950 PSI so I was not sure if it was from having the injectors popping at higher pressures or the advanced timing.

 

[MrMarty51]

Guessing at proper belting length for elimination of the vacuum plump.
I tried one of two other belts and the tensioner mark was farther into the rectangle.
Got two more belts and tried the shorter of the two first with this as the results.
This belt is 100-1/4 inches in length.
The longer belts took the mark deeper into the rectangle.

 

[dbrannon79]

Guessing at proper belting length for elimination of the vacuum plump.
I tried one of two other belts and the tensioner mark was farther into the rectangle.
Got two more belts and tried the shorter of the two first with this as the results.
This belt is 100-1/4 inches in length.
The longer belts took the mark deeper into the rectangle.
View attachment 90926

that looks like it's in the right spot though check it again after it runs. I have noticed that after it runs a few minutes the belt will settle into the groves and changes where the marks line up.

 

[dbrannon79]

I was thinking too far advanced gives the predetonation rattle/clatter.
Retarded is quieter.
Seems after I advanced the timing on My engine from around -.45 to -1.50 it clattered a lot more.
But then too that was when I installed the newly balanced injectors that were popping at 1950 PSI so I was not sure if it was from having the injectors popping at higher pressures or the advanced timing.

I think your right. I was reading my own thread I had started on leaning to set timing. will and others said the same. more advance = more rattle. I will have to play with it some. I think I have two things going on. the IP is a little advanced and I have the cam adjusted too far which is compensating for that under acceleration. this would make sense why it rattles more at idle and more so with the cold advance solenoid powered while cold. then when I drive the rattles go away accelerating with grey smoke. this combo also might explain the random loud rattly blips it does from time to time, the advance plunger getting stuck when I decelerate (pump needs to come off and that piston and bore cleaned).

with that I have an idea that I need to retard the pump slightly and then move the cam back towards it's original position some. once I get it were it's a happy medium, mark it all well and pull the pump to clean and inspect the advance piston and bore. Of course I need to order a seal kit for the pump before I pull the pump. Hopefully I don't find out the bore is fubar and need another IP.

I bet there is nothing wrong with the IP on the 6.2 ether, it's just out of time and the chain is stretched beyond normal. remember that engine had a date code from the late 80's I bet nothing was done to it other than it getting plopped into another truck and rode till I received it in its current state.

I tend to over think things until I read and re-read things learning. Posting here and listening you you all helps me realize I did it wrong the first time even though y'all told me before! LOL.

 

[dbrannon79]

Well last night after thinking more about it, I ran out there and disconnected the cold advance solenoid (afraid of the engine coming apart), left the high idle one connected. This morning with temps at 45 degrees the engine was a little harder to start. had to use the GP override button on the second go. she fired right up and was quiet as a mouse compared to with the solenoid connected.

I think the hard start and quiet startup kinda also confirms I have the pump out of time.

 

[Will L.]

Seems like already too advanced so when cold advance kicks in, its WAY to advanced.
Wether thats just ip, inside the ip, if he advanced the cam & ip, whatever.
You have it going ok with the couple glow times- just run that.

The engine sounds tired, and DeeJaaa hopped it up a little so idk if I would make a ton of changes for now- just keep it running. Drive one, wrench on the other truck. Trying to learn everything about the engine, then trying to undo whatever he did- thats a fight not needed.

 

[dbrannon79]

The engine is tired, I had played with the pump trying to get it to run better. Now as the weather is cooling down I'm realizing I had advanced the timing a little too much. Just need to bring it back some. Maybe this spring I will be setup so I can pull the engine, drop the pan and see if this engine is worthy of more work. Not unless I run across another one affordable that I can run.