DS4 IP rebuild time(mechanical aspect only)

[chevyCowboy]

hey guys been awhile but i was talking to a guy the other day and he claims to have a shop that rebuilds ds4 pumps for him and they re-clock them 15* internally and get more fuel, iv been around these trucks for a while and didnt know there was a way to do this? What do you guys think?

 

[schiker]

15 degrees sounds like a lot I think but don't know. I wonder if its some optic bump they do that is more stable with some machined precision?????

 

[reddtekk]

OK I've got an interesting one...

I'm a 6.5 noobie. Just bought one this past November and thanks to folks from this forum and others I've been able to get it running. The trick is that it has a loud rap when you blip the throttle. Idle is a little uneven but not terrible. It sounds like a bad injector but I just swapped them all with ones from another engine which, I was told, ran great until someone grenaded the turbo. Many of the original injectors blew compression out the back of the injector when the lines were cracked open, so I was pretty sure that they were the culprits. Not so...the engine sounds better, but the rap is still there and its beat is identical. I bought some "good tested" military surplus injectors and I'll install them to be sure, but a friend of mine had a suggestion:

What if one of the vanes in the transfer pump was stuck in the slot??

From the photo Simon posted, it seems that the vanes are trapped by a Teflon ring on one side and the outer housing on the other - so unlike the TP in the DB2, this one is driven in BOTH directions. My friend saw this pattern of running in a backhoe one time - it sounded like there was one hard (advanced/over fueled /both) hit followed by the remainder of the detonations sounding less intense in progression, until the last sounded a bit weak. This is exactly how my truck runs. In his case, it was a stuck vane in the transfer pump altering injection pressure on some of the cylinders. In the case of our pump, it could also affect timing to have a pulsation on the transfer pressure, since the advance cylinder is driven by transfer pressure. I've got three DS4's in various states of assembly. I will probably pull my pump and put on the most complete one that I have, but I know very little about them so who knows what I'll find.

Also in the TSB that was posted earlier it stated that "uneven cylinder to cylinder fuel delivery at 3000 rpm\70mm3/str" could be related to an issue with the snubbers or delivery valves. Does anyone know what tends to go wrong with these items or what I can look for to make sure that they are OK? Looks easy enough to swap the delivery port assembly on the vehicle so if anyone has suggestions I'd happily try that before starting all over with a new mystery.

Thanks in advance, and thanks to all who have contributed to this post as reference material for these pumps is very VERY difficult to come by for the average Joe...

Thought provoking comments are welcome.

 

[reddtekk]

Hey everyone. I just was dealing with another issue with my truck and was searching for information. In this search I noticed that I never updated everyone on what went on with the issue I wrote about in my previous post, so I'll start with that.

The issues with my truck were a little beyond plain and simple because of the computer firmware issues I had, but the rap was one of those dumb overlook things that really made me want to turn in my wrenches. I did try measuring transfer pressure with the engine running using a home-made fitting with an Ashcroft pressure gauge I had kicking around. The pressure pulsates pretty heavily and it makes it difficult to read, but averaged around 150 psi IIRC. I figured that there was something else up with the pump so I swapped it with another used 5521. The truck sounded the same. After the swap a friend listened to my video and insisted that I double check my firing order. I had carefully labeled the lines and installed them back where they came from but checked anyways. The previous owner had put a (assumed good used) 5521 pump in the truck in their attempts to get it running (without installing the right firmware, but that was another issue). Apparently in the process they switched the lower two lines and the firing order was incorrect. I straightened it out and have been driving the truck ever since November 2014.

Lately I had a couple stalling issues and it wasn't PMD or computer (I had both in the cab and swapped them on the side of the road, no luck). It was always tough to start and beat was a little uneven so I decided to put another pump I acquired into it - a -5521 I stripped off a mud-covered engine that threw a rod, with the stock black Stanadyne PMD still on it and connected (which is now next to the GM/FS one in the glovebox). I got it all set up and timed with GMTD ScanTech (which I highly recommend to others) and noticed that it was leaking fuel, in addition to the occasional code 36 (fuel solenoid response too long). I pulled the manifold back off (and made some block off plates to cover the exhaust crossover ports so that it could be run like that) and found that the leak was coming from somewhere in the rear half of the fuel solenoid. The rubber boot was full of fuel and it was dripping off the back of the solenoid. I read somewhere that these can be finicky but despite my searching I couldn't figure out much about what lie under the hood - most specifically, how the fuel is supposed to stay in the pump at that point.

So I did an exploratory on another pump and there are the results:

There are two shoulder screws with threaded studs on the backs of them that make up the electrical terminals. 6mm heads and self locking nuts hold the wires onto them (also 6mm). These tighten against a white plastic (probably nylon) spacer with a flange on one end. Below the spacer is an O-ring which expands when the shoulder screw is tightened and seals against the shaft of the shoulder screw and the screw hole in the anodized aluminum end cap of the fuel solenoid. Below the O-ring is another white plastic spacer which bottoms against the body of the solenoid itself, where the shoulder screw threads into the electrical contacts of the coil.

These were snug in my truck so I left them alone.

There are two Torx head screws also installed in the end cap. These are what actually hold the end cap to the solenoid body and they use copper crush rings of some sort to seal against the head. A T-10 is a somewhat sloppy fit and a T-15 is too big, so I'm guessing that they may be a T-12 but I didn't have anything between T-10 and T-15 so the T-10 got the job.

I have seen some testimony of others having had these Torx-head screws back out of their fuel solenoids, causing a horrid fuel leak and other issues. The ones I took off the exploratory cadaver were fairly tight. I did a finger feel of the torque on them and then checked the ones in my truck. Sure enough, they were loose. I gave them a good guess at torque (didn't go nutso on them, they aren't very big, and I don't want to distort the housing and cause issues with armature stroke).

Not only did this fix the fuel leak, it also seems to have gotten rid of the DTC for "fuel solenoid response too long" (or something to that effect). I'll see if I can put up some photos for the group later on which provide more detail of the fuel solenoid assembly. Tonight I have to put it all back together so I can really test it out and make sure that the DTC doesn't recur, but I ran it for a while last night after resetting it and the history is clear.

 

[MrMarty51]

Hey ReddTekk, thank You for the write up. It sounds like You have got Your truck to running quite nicely. Now waiting for the road report LOL

 

[Will L.]

Good deal on the fix. I had that happen in a fleet truck once where the screws came loose, we chalked it up to never got tightened after a repair, but I forgot all about that until you mentioned it. It was annoying hunting for that, I remember that much. Swapped lines- it happens- big improvement fixin that huh? haha!

 

[reddtekk]

Hey everyone, well thanks for the words of encouragement. I got it all back together and I am sad to say that although it cold starts better than before and ran great on the road, I parked it and went back an hour and a half later and it wouldn't start. I could hear a little bit of ignition on one or two cylinders but that's all I get. Oh well, time to do some more reading....

At least I don't see any more signs of fuel leaking from the fuel solenoid.

Good night all.

 

[reddtekk]

Out here again looking at IP info. Debating whether to rebuild my own or have someone else who knows a heck of a lot more do it for me. Not to mention the equipment worth more than my house and everything in it which is required to properly test it. I still have one I haven't tried out, so that may be next. I'm just getting tired of nursing old worn out junk along. Still have the pump mentioned in my previous posts on the truck. Just beating up my very new PowerMaster, ring gear and my brand new batteries unnecessarily. Oh and the jallopy feel I get when it barely starts and fills the neighborhood with blue smoke. It is time.

Yep,..is the stepper covered in there too?
If so, how does one tests it.

Hey Bison, I know this is only 5 years later so I am a bit early with this reply, but I didn't know as much about this 5 years ago...
I am just pulling this out of my backside (with some help from my interest in hobby electronics and background in industrial controls) but as far as I know the "stepper motor" is a basic 2-phase stepper driving a screw to get a linear motion out of it. If I'm correct about that, one could drive one of these motors in and out with a few push-button switches and a stepper motor driver. The drivers I use (DRV8825) take a step and direction input to run the motor forward and backwards, and a set of 5 are under $9 on Scamazon. Plenty of info on how to wire one of these bad boys up to a generic stepper motor out there, so I won't bother with those details here. Probably not necessary to set it up for microstepping (so ground the M0, M1, M2 pins). If you repeatedly press a button hooked up to the "STEP" input the motor should move in one direction. Hold the "DIR" button while repeatedly pressing the "STEP" button should result in it running in the opposite direction. Run it off a wallwart - they probably run the motor off 5v. If you really want to get fancy, get an Arduino and make it run back and forth! I have all of the above and may try it out, but who knows when I will have the chance. If anyone else gets to it before me, please chime in!

 

[NVW]

Sad to say but Simon, aka bison hasn't posted for a few years or more.

 

[schiker]

What do you want to do with the timing? Having messed with the timing its a lot of electronic manipulation. You move the IP to set base time and then check top dead center offset. My understanding is the ECM then makes adjustments to timing due to programming. I am not sure you could manually adjust it as much as the ECM does to compensate for wear.

Are you looking to "offset the offset" of the stepper timing????

Most of the smoke and poor performance of an older IP IMO is pumping losses due to wear. The injection pulse isn't as crisp from a worn IP as new and the mechanical injectors only deteriorate with age. I have noticed less launch puff when I installed new injectors.
My IP has many miles on it and think most of my loss of power is due to general wear. I have installed a timing gear set so timing is as accurate as OE. Now the injection is only as good as the IP can produce and the injectors can spray.

 

[reddtekk]

NVW, thanks for letting us know. I hope all's well. He has made a great contribution to the community with this thread.

Schiker, I was replying to Bison's request for info on how to test the stepper motor. He asked a few times in this (very informative) thread. As far as I understand it, he was just looking to be able to bench test them for proper function (not just testing to see if the coils were still OK but actually make it move). Making changes to that timing would probably be best done in the EPROM of the 'puter.