Engine/Transmission (1998.5 - 2002) Need some answers,,,,injector gurus

[SHobbs]

Picked up a set of 275's dropped them in the truck and had a dead miss. Turns out one injector was not firing. Tried it in every cylinder with no luck. Had another injector sent for replacement, no luck. Injector number three, no luck. Took the original 5 plus the one I received Thurs to have tested. All 6 injectors popped at 4300-4350psi give or take a little and not below 4300psi.

My vendor has been great in all this and is stumped as well and trying like mad to help me figure out what is going on. The head man at the shop that tested them told me it could be my VP44 not puttin out enough pressure to pop them or an internal problem within the pump. How could that be when it can pop 5 of them?





Here's my questions

What is the pop pressure in a stock injector for my year model?

Can the 275's perform like they should with a pop pressure at 4100psi?

Is this an injector problem or possibly my VP44?



If I put the stock injectors back in all is well and runs like it always has. I did put the one injector that is not firing in with 5 of my stockers with no luck still a miss. I also took the spring and shim out of my stock injector and placed it in the 275 body with the 275 nozzle, again no luck. I asked about lowering the pop pressure thinking that maybe it will allow all 6 injectors to pop and allow me to utilize the added gains from them.



Has anyone experienced this? I am at a loss here trying to figure out or understand where to turn now and so is my vendor.



Thanks

Scott

 

[JHansen]

Very strange... . maybe something to do with a connector tube? Just a thought as I can't figure out why it would not fire moving around from cylinder to cylinder.



Anyways, from the FSM, pop pressure is 4500 psi +/- 250 psi and leakdown is approximately 300 psi less than pop pressure.



Jason

 

[WrenchRat]

Scott,



Seems to me like you've gone beyond the call of duty in swapping and bench testing. Even though pop off pressures checked out ok and it still doesn't function where ever you put it, INSIST ON GETTING A REPLACEMENT so you can get on with life. Let the OE (Bosch?) figure out what is wrong with this one.



The logic is solid:

If you've put one of the other five 'good ones' in hole #3 and had successful operation, it is not your VP44. -AND put the bad one in another hole and it still doesn't function, you have successfully isolated the problem to the injector.



Get it replaced and be done with it.



I had a nearly indiscernible misfire after I put my 275's in (my labor). The idle just was not as smooth as the stock 235's. I was bummed to be sure. The folks I bought them from said that my situation was not uncommon and after actually listening to it, recommended putting cycles on them before going to the trouble of R&R. If it did not improve, they would swap the WHOLE set. Based on the dealer's comments and since the performance was soooo much better (and I'm lazy), I elected to just run'em. After several thousand miles, they settled down and all is smooth. Don't know what the issue is/was. I'll call it break-in.



We are dealing with tolerances in millionths of an inch and surface finishes below 4 microinch. Any extraordinarily minor (including corrosion or even a mega minute spec of dirt) flaw could cause an issue. The exact answer can only be properly answered by a knowledgeable Bosch engineer or likewise experienced individual after a thorough examination of the offending assembly... May be the same for an explanation in your case.

 

[SHobbs]

WrenchRat,



The injector that is not firing is the third replacement injector. With all six in the engine I have a dead miss, not a rough idle and not something that will go away, I drove the truck 20 miles and the miss was still there. I had a sit down with Larry at my local Cummins shop, he is the pump and injector man there. He pop tested all six and found that they are functioning correctly. They all pop around 300 bar or 4350 psi. He said the new ones were just a tad tight but where they should be. Being that I have no problems running the stock injectors which might be just below the 300 bar mark making them easier to pop.



He told me that all injectors pop under the same pressure and that the shims are what determine the "pop" pressure. He also said that no one makes these shims and I would have to shave a certain amount of each one to lower the pop pressure. They are very hard and it would very difficult if not impossible to thin down a shim. He did tell me that my pump should be able to pop all six injectors which apparently isn't happening.



His theory is one I don't want to hear. He thinks that my VP$$ has lost it manhood (for lack of a better term ) and cannot fire all six of the new injectors and that there might be a weakness in my VP$$. Either it cannot maintain adequate pressure or not putting out enough to fire every injector. Not sure. I replaced the inj. pump just over a year ago and it only has about 30k on it which by the way the warranty ran out in Feb. this year, go figger.



So here is my options as I see it

1) New VP$$

2)Have my VP$$ tested which is difficult with my truck being my only vehicle

3) Just forget everything and wait and see if the VP$$ goes belly up then replace it

4) Punt

 

[KLockliear]

Scary that the "pump shop guy" either doesn't know or is lying to your face - those shims are available from a Bosch distributor/dealer. They aren't cheap, but definitely available.



Set the injectors to pop at 305bar.



Could be a delivery valve in the VP pump for cyl #3.

 

[SHobbs]

Keith,



It's not the cylinder this thing won't fire in any cylinder. I have had it in every cylinder and each time it comes out clean. 305 bar is where they are now and won't fire. I think I need to go to 290 or 295 if thats possible. If that is possible how will the injectors act at lowered pop pressures? He was going to call a guy he knows with Bosch to get his idea on this

 

[KLockliear]

Don't lower the pop pressures - that affects your injection timing. If the injector won't fire in the motor, replace the injector. Perhaps the pintle is stuck.

 

[WrenchRat]

I just related my 275 situation for S's and G's and maybe to help someone else, not that it was the same kind of failure you are experiencing. Obviously with a 'dead' or severe miss, the truck shouldn't be driven. Sorry if I misled you in any way.



Wow! The third unit to be 'faulty'? This is sounding suspicious. While it's certainly possible to get several 'bad' injectors in a row, I strongly doubt it.

So here is my options as I see it

1) New VP$$

2)Have my VP$$ tested which is difficult with my truck being my only vehicle

3) Just forget everything and wait and see if the VP$$ goes belly up then replace it

4) Punt

Along the lines of option #2;

If you really want to run the 275's, is it worthwhile to get a 'borrowed' VP and confirm that the pump is up to the task? Based on what you've said, it doesn't seem logical, but the only way to know for sure is to R&R for at least a bench test of the VP. I know that is a BUNCH of trouble, but what else can you really do at this point? Oh, yeah, option #4, PUNT.



Would it be worth calling Industrial Injectors and relating the situation to see what they say? Or another Bosch authorized rebuilder of your choice? Even if you thoroughly trust the guys your working with, another expert opinion or two might solve this? (No, I am NOT in the expert class)



If you can't find a VP to borrow, maybe get a 'rent a wreck' for transpo while you get the VP tested? If it comes back 'bad', you'll know the 'easy way' rather than being stranded. If it's good, well, you know where NOT to look.



As for option #3, I don't recommend it. My single VP failure left me stranded in the boonsticks at the side of the road. #@$%! No warning at all. Just like I turned the key off. I was lucky to be near a phone and not hauling a load. I am strongly considering carrying a spare VP with me ($$$). At the least, I can get a VP drop shipped to where ever I am from Industrial Injectors in 24hrs. Money, money, money, monnnnnneeeey. (Pink Floyd :-laf)



Regardless, you've got your work cut out. Good luck. Please let us know what the verdict is.

 

[PRout]

If I put the stock injectors back in all is well and runs like it always has.

Like Wrench is saying. . This statement above makes it hard to believe all your new 275's are good.

Just curious if these injectors are coming in genuine bosch boxes, or could they be knock-offs? Mine came in individual Bosch boxes. Not pointing fingers at any vendors, but 3 baddies in a row? Hard to believe the VP is right on the ragged edge of not being able to fire off the same injector that has been replaced twice, but it will fire off your stockers ok. Thats really splitting hairs. Long odds on it being the VP. Sounds like bad luck on injectors, or something else is going on that isn't obvious yet. But Keith has more experience so my opinion is only that. . like a bb, everyone has one.

Added: Just noticed you are running B100 fuel. Wondering if that has anything to do with the equation.

Have to ask the obvious questions. You're torquing the injector tubes to 29ft/lbs, good fuel pressure/filtering, known good fuel, no water or glycerin or algae problem right?

 

[SHobbs]

Phil,



Currently I am running B20, nights are still too cold. Tubes are correct, fuel pressure is 11-12 psi at idle and never below 7 at WOT. The bio I run is good quality never a water issue or any issues with algae. My fuel filter looks the same on bio as it does running diesel. As far as the injectors, no they did not arrive in Bosch boxes.

 

[PRout]

Ok, Just throwing it out here for consideration. .

I got my 275s from Rip at sourceautomotive. biz (Thanks to Bob Wagner who assisted). These have been flawless and did come in "individual genuine bosch boxes".

Knowing a VP44 removal, test, and or replacement is time consuming and could add a larger cost to finding the problem and the VP already seems ok with your stock injectors, I would consider buying another complete set of 275s from a different vendor for around 320. 00, and with hopefully another one-time injector swap, would tell you a lot.

It will either run right and the nightmare will be over, or it would indicate that your VP may be on its way out in which you can fix that problem, and then sell your original 275s in the classifieds and recoup some costs since they would most likely be good (recently pop tested) and there is a demand for them out there.

Since the reliability of the guy doing the injector tests has been questioned, it seems like a different way of validating the injectors would be least costly. Either way, you can sell (good) 275 injectors, so they arent a total waste of money.

 

[aircop]

Buy brand new bosch rv275 from Midwest Fuel Injection. Good price good people to deal with.