ds4 injector pump question

[Jim P]

I bought a used injector pump off of ebay for $25.00. I took it all apart and it doesn't seem to have any major problems with the mechanical parts. It has ceramic rollers and they look real good.I am not sure about the electronic parts. I did take off the pmd and remove the covers on the back. The little nuts undernieth were almost a whole turn loose. I am thinking that the truck was stalling because of this and the whole pump was replaced.

Inside is a a rotor with 4 plungers that move up and down in there bores to inject the fuel. I am thinking about using my I.D. grinder to make these bores bigger and then make some bigger plungers to match the new bore size. My theory is that this would make the pump capable of pumping more fuel. Is my theory correct? Two of the plungers are longer than the other two and have two grooves around them. Does anyone know the reason for this?

If all the electronic parts are good, the only cost I will have in this is whatever a seal and o-ring kit would be.

Also, this pump came of a 98 so will it work on my 95?

[Barry Nave]

Sure will ;)
Whats the pump numbers? :D

[Jim P]

The pump number is 5288.

Was that a sure will to the pump fitting a 95 or that if I install bigger plungers, it will pump more fuel.

[Barry Nave]

Best pump made and it will fit. :D
Plungers :eek: Out of my line ;)

[rjschoolcraft]

I don't see why it won't pump more fuel. I've thought of doing this along the way, but don't have a spare pump to play with. If you look at the DB2 and DB4 pumps, you'll see ones with bigger plungers as the power requirement increases. In fact, the stanadyne website shows how to identify the plunger size from the ID numbers.

You may have to recalibrate some sensors, though, to make the electronics happy.

[Jim P]

Here is my understanding of how the pump works, just from looking at it after disassembly.

The fuel solenoid is just an electromaget that pushes in on a little spring loaded valve in the end of the pump rotor. This valve controls how much fuel is allowed to enter the rotor and be compressed by the plungers. The solenoid is working the hardest at idle because the little valve I was refering to has to be forced almost completely closed. When you put your foot to the floor the computer cuts back on the juice to the pmd so the solenoid has little or no magnetism at all. This allows the little valve to be completely open and then the pump will pump the maximum amount of fuel that it is capable of. This I feel is limited by the displacement of the 4 plungers. The stroke of the plungers is limited by the ramps on the cam ring. If the diameter of these plungers was increased, it would increase the displacement of the pump(just like boring an engine oversize). Then when the computer called for wide open throttle, it would actually pump say 100 mm3 instead of the factory 80 mm3.I think it would be like installing high flow injectors. I don't feel that computer would even know the difference. You would have to keep the egts in check though.

If I am all wet on how this works, let me know.

[ucdavis]

The work you are envisioning is very close tolerance stuff. The early pumps ground themselves up inside due at least partly from poor material selection, but I'm guessing that once out of tolerance the plunger galleries and maybe plungers would self destruct pretty fast.
You can program the chip for higher fuel rate, and vendors (Kennedy, Heath, BD) offer aftermarket programmed chips for the '95 PCM. Brands K & H have variations of performance so you can tell them what you want. I gotta believe that'd be easier, but if you have a metallurgical experiment in mind, your way would be lots more fun.

[rjschoolcraft]

Ucdavis,

I think the idea is to attempt to get fuel rates comparable to the DB4. Stanadyne's website says the DB4 is capable of 40 hp per cylinder while the DS4 is only capable of 25 hp per cylinder. The bigger plungers in the DB4 gives it that flow capability.

[ucdavis]

I forgot to mention, the pump is a two stage gizmo.
Shut off solenoid is simply a valve, open for running or shut for no-go.
Fuel enters thru solenoid valve, gets pumped to 175 psi or so (maybe it was 125?), then thru the plungers to make 1700 psi to the injection lines.
Fuel solenoid fires the 1700 psi to each injection line as the engine/IP-internals rotate, so the FS fires @ engine speed x 8 cylinders / two cycles of compression. @ 3000 rpm that's 3000 x 8 / 2 = 12,000 firings per minute or a helluvalotta cycles of the FS. Even on a per plunger rate which'd be 12,000/4 or 3,000 per minute or 50 per second at 3000rpm, that's alotta cycling, so the tolerance issue is important. You may want to get ahold of a Stanadyne rebuilder's manual B4 doing the hone job & plunger replacement. Might be hard to do thru a dealer (trade secrets?); maybe Ebay?

[Jim P]

ucdavis,

I agree that a chip would be easier but even with the chip, the stock pump can only pump 80 mm3.
If my calculations are right and this works, my new pump will put out about 120 mm3 of fuel.

I know that this is precision work but that is what I do. I am a machinist. I also have a grinding shop at home where I grind cutting tools like endmills, drills and other metal cutting tools.

I am not sure but I think that what got all chewed up in the early pumps was the rollers that ride on the cam ring and push in on the plungers. These early ones were steel. The later pumps had ceramic rollers to help with this problem. This pump is from a 98 and it already has the ceramic rollers and they are in very good shape.

One other thing is that it is not going to cost me much. I have 25.00 in the pump and I will have to get an oring kit for the pump but the rest is only my time.

One other reason that I am doing it is if it works, I am going to try to start doing this for local tractor pullers to increase their fuel delivery and make more power.

[Jim P]

I know about the vane pump that supplies fuel to the rotor but I think it will be plenty big enough to supply the extra fuel. If it's not I will do like the tractor pullers do. They take out the vanes and use a hydraulic pump that is belt driven, to feed the ip.

All four of these plungers pump fuel for each cylinder. They only move .025" up and down in their bores at full throttle. I think that most of the wear is with the rollers. These have to roll up and down the ramps 8 times for each revolution of the pump.

I am planning to use rollers out of roller bearings to make the new plungers.

[rjschoolcraft]

Try to stick with the ceramic if you can. You may need to look at some industrial machine tool bearings to acquire rollers. Ceramic is incredibly stiff... much stiffer than steel. In bearings with ceramic balls, the groove geometry is specially designed for the ceramic balls to keep the contact stress in check. This same groove geometry will not work for steel balls. I don't know the specifics of the IP design, but I bet a lot of these principles apply.

[Jim P]

The original plungers are not ceramic. They are steel. It is the rollers that are ceramic. I will not need to do anything with these.

[rjschoolcraft]

I mis-read your post...

You're planning to use rollers to make plungers! I assumed you were going to scavenge rolling elements to replace the balls that ride on the cam plate.

My bad! :(

[kowsoc]

Would it be possible to increase plunger displacement by increasing the plunger stroke? You mentioned it only moves .025". Just like a "stroker" crankshaft can increase engine displacement maybe a reground cam ring in the pump could do the same. Just a thought. smile.gif

[Jim P]

I am sure that increasing the stroke would increase the fuel delivery but I really don't have the right equipment to grind a cam. Excellent idea though.

[Marty Lau]

WOW;
Jim you blow me away, please keep us posted with your progress.

[Jim P]

After studying the drilled fuel passages in the pump rotor, I feel that my first theory of how the pump works is wrong.

It seems that the only time that the pump can build enough pressure to pop the injectors is when the fuel solenoid is holding the fuel delivery valve closed. So now my theory is that at idle, the solenoid closes for a very short time to just allow a little fuel to be injected. At wide open throttle the solenoid closes for a longer time which allows more fuel to be injected.

The problem with this is, if the computer is only programmed to hold the solenoid closed for a set time, it will only allow as much fuel as the program is set up for. Assume the computer is set for 80 mm3. Even if the pump is capable of 100 mm3, the extra 20 is just returned to the tank unused.

Now if the solenoid holds the delivery valve completely closed at wide open throttle, then it should benefit from having bigger plungers in the ip.

Does anyone know if the fuel solenoid does hold the delivery valve completely closed at wide open throttle?

[Beedee]

I ran a search on Google the other night, looked under "Roosa Master", found a site that explained how a distibutor type pump worked, unfortunately I was tired at the time and forgot to post the site or bookmark it. I'll try again tonight and if I can find it, I'll post the link.
I threw out all of my old fuel injectinon books last year because thesy were getting to out dated, should know better.
Roosa Master, and CAV are a couple of well known pumps, used on lots of different types of diesels.

[Jim P]

I read a sight that explained how the mechanical pumps work but I don't think that the electronic ones work the same way.

The mechanicals meter how much fuel gets compressed by the rotor but I believe that the electronic ones always compress the same amount of fuel. The computer tells the fuel solenoid how long to stay closed. Once the fuel solenoid opens, any excess compressed fuel that has not yet been injected is just returned to the tank.

[kowsoc]

Yes, I think the fuel solenoid just dumps the pressure to each injector. So as you mentioned, at idle very little fuel is injected before the solenoid dumps the remainder of the stroke. As load is increased the PCM (through the FSD) holds the fuel sol closed longer to deliver maximum fuel. Very interesting point you mentioned about the DS4 being capable of delivering more fuel than the PCM allows. ;)

[Marty Lau]

Jim;
If what your think is true could some sort of electronic gizmo be used to fool the PMC to think the value should be opened longer at full throttle just like JK "Boost fooling" controller?
I know about zipp about electronics other than it works on the PFM & Smoke theories.

[JohnC]

The Fuel Solenoid controls how long the injection cycle is for each injection event. If the pump displaces more than standard, then in a given time it will inject more than designed. At full throttle your modified pump will be injecting more fuel. You'll need to increase boost as well, though, as you will skew the balance between measured air and expected fuel, as far as the PCM is concerned. One thing that may be a problem is that at idle the fuel injected will be so much more than expected the PCM may not be able to compensate. Interesting experiment, though...

[Jim P]

16ga SxS,

I was thinking the same thing today.

I have read that the ds4 is capable of pumping 80 cubic millimeters of fuel. But the pcm in my truck is only programmed for 64 cubic millimeter if I remember right. I think that the after market chips just reprogram the pcm to 80 or whatever you specify.

Now if the fuel solenoid is held closed during the entire injection stroke to produce the 80 cubic millimeter then it is possible that a maximum fuel switch could be rigged up to put juice to the fuel solenoid. When ever this switch was activated it would allow maximum fuel(even without a chip) and would bypass the pcm control. When I say bypass, I mean it would have no governor or speed control or any other safety feature built into the pcm. It would basically be running wild. If the engine was not under a significant load, it would probably run away with itself and self destruct.

That being said, it would be pretty cool for a little extra boost at a truck pull or when that powerstroke or dodge was trying to pass you. :D

I have no idea how the pcm would react to this but I assume it would set more codes than you can count.

I am going to experiment with this a little though. ;)

[ 02-25-2004, 04:36 PM: Message edited by: Jim P ]

[Jim P]

JohnC,

I have thought about the idle possibly being a problem. The stock plungers in the pump measure .310" and I was going to install new ones that measure .375". I am now having second thoughts and I think I will start off with .350" and see what it does.


I realize that in order to use the extra fuel, the boost will have to be increased but on my truck anyhow, the pcm has no way of knowing how much air is being forced into the engine. The trucks that have the maf sensor may tell the pcm how much air is being forced in but I don't have maf sensor.

[kowsoc]

I don't believe the modified pump would have trouble with idle full metering. The electronic signals operate extremely fast and could deliver very small volumes. As far as the fuel solenoid being energized constantly i don't think this will work as I believe the fuel solenoid has to be de-energized to allow fuel into the plungers then closes again during delivery and opens again, dumping fuel at the right time to give the desired fuel delivery. I think this is how the pump works and is the reason you can kill fuel delivery to selected cylinders with a tech 2 to check cylinder imbalance. To add an interface between the PCM and fuel solenoid to increase fuel delivery would be tricky as the PCM receives feedback signals from the FSD to know whats going on with the solenoid. Hmmm, gotta love electronics. Keep testing, you may be onto something....nothing like a challenge! smile.gif

[Jim P]

Kowsoc,

I think you are right about the fuel solenoid energizing and deenergizing in between each injection. I also think that the reason that a tech II can disable a cylinder is because the pcm just never energizes the fuel solenoid for that cylinder. The fuel solenoid is nothing more than an electromagnet. It has two wires, one going to the pmd and the other to ground. The solenoid when enegized just pushes on a little valve that I call the delivery valve. This delivery valve is basically just a pop off valve. If this valve is not held closed, the pump never develops enough pressure to pop the injectors. At idle the solenoid only holds this valve closed for a very short time. When the solenoid is deenergized the remaining fuel that had been compressed by plungers is just dumped and allowed to return to the tank.

The thing I don't know is whether the solenoid is energized contiuosly at full throttle or if is still pulsed in between the injection of each cylinder.

I am not sure but I feel that the timing is still adjusted mechanically inside the pump. I feel that this is accomplished by the stepper motor. It is attached to a piston in the pump that is attached to the cam ring. This cam ring can turn to change when the plungers get compressed. This changes when the fuel pulses occur. This part of the pump operates almost exactly like the older mechanical ones did.

Last night I had the truck running and I checked the voltage of the red wire that goes to the fuel solenoid. On dc, my digital volt meter would only register a few volts but on ac it would show about 2.7 volts at idle but when I had my wife mash the pedal to the floor, it would increase to almost 12 volts. I am just wondering if you cut this red wire and hooked 12 volts to it, if it would make the truck rev up and make the pump produce its maximim amount of fuel. If you also hooked up a diode between this connection and the red wire leading to the pmd, this would allow the pmd to function normally and when you energized the solenoid manually, it would prevent any juice from flowing back to pmd. This might prevent the pcm from throwing codes.

This all depends on whether the solenoid is energized continuosly at full throttle, if it is not, it probably won't work and will probably burn out the fuel solenoid.

If nobody knows if the solenoid is energized continuously at full throttle then I guess I will have to be the one to try it. I will just drive down a back road and then enegize the fuel solenoid and see what happens.

[Jim P]

I did a little more experimenting tonight.

I took the fuel solenoid from the pump that I have apart and put 12 volts to it using my battery charger. The amp meter goes up to 12 amps on my battery charger and it just pegs the needle.(no wonder the pmd's go bad so quick). If you leave juice to it very long, the solenoid gets hot so I am assuming that the solenoid does not have power to it continually at full throttle. I also feel that if you put continuous power to it that it would burn up pretty fast.

So this idea is probably going to get scrapped. Now I have to get back to grinding out the bores for those plungers and get the pump back together.

Does anyone know where I could get a seal and o-ring kit for the pump? Preferably someplace that would mail it to me, so I don't have to drive a long ways to pick it up.

[whatnot]

They probably use AC and change the frequency with speed.
You meter is probably too slow to show the correct voltage at higher frequency.

[CaseyR]

You could probably figure out what is happening with the input frequency and voltage by hooking up a small oscilloscope. Probably a fairly simple one would do the trick. If you know any serious electronic hobbiests, they might have one. I don't know if the ones they typically use in auto repair shops would do the trick.