Engine/Transmission (1994 - 1998) Blocking the Injector return line

[Highfinance97]

Has anyone blocked off the return line??

What would be the Pros and/Or cons???



Michael

 

[Bob4x4]

Has anyone blocked off the return line??



What would be the Pros and/Or cons???







Michael

That would be a mistake :-laf



Bob

 

[Highfinance97]

That would be a mistake :-laf

Bob

Thats what I thought but if you look in the new Diesel PWR Mag. (Jan. 08) on page 132 in the Readers rides Titled "Scotts Dodge" it says and I quote

"He has Installed 330-HP injectors(with return shut off at each injector)"

What is the all about:-laf


Michael

 

[GDMRTN]

I read that too. I don't know how it would work. I don't buy diesel power mag. My brother got one and I paged thru it. Anybody know how it would effect the engine and/or injectors?

 

[Gene Arnold]

I'm watching this subject out of curiosity with no interest in upgrades. However, the first few trips I made with my old 6. 3 Chevy diesel I had a big problem with how it ran on the left tank. It was OK on the right tank but when on the left tank it had very little power. Long story short-- I discovered that the factory had installed a flex hose in the return line at the tank that was about a half inch too long. This caused a kink in the return line and the lack of power was unbearable (compared with the normally underpowered 6. 2 thats really bad). When I was pulling really hard, the restriction was bad enough to cause the line to pop off at the #1 drivers side injector. I raised the box at the front, shortened the hose, reattached it, and all was normal. I found thereafter that if I pinched a return line under the hood I could stall the engine. Granted, the pump and return system is altogether different on the Cummins, but I think there might be problems with a lack of return.



Gene

 

[DieselDoghouse]

I would think that blocking the return from each injector (and since the fuel rack and distribution valves meter fuel to each injector pretty carefully) would be a much less dramatic step than blocking the return from the pump itself. Could you toast a P7100 doing that??

 

[R.ebel]

Dsl Pwr

Be warned, I have noticed A LOT of misprints or just flat out bad info in that Rag (DSL PWR) since it been in circulation.



If blocking off the injector return line was a cheap and effective way to increase PWR, I would think that it would have been done years ago on the 12 valve trucks.

 

[tony597fitter]

Be warned, I have noticed A LOT of misprints or just flat out bad info in that Rag (DSL PWR) since it been in circulation.



If blocking off the injector return line was a cheap and effective way to increase PWR, I would think that it would have been done years ago on the 12 valve trucks.

^^^^^^AGREED^^^^^^

 

[Dieseldemon]

The inj will get hotter than h$%# that is what cools the injectors.

 

[TJarecke]

Does the banjo bolt in the injector return line already block some of the return or is just to keep from losing prime? There isn't much room for fuel to flow by the ball in the banjo bolt on the factory system.
I am curious about this because I eliminated this banjo bolt in my custom fuel system.

 

[Dieseldemon]

There ia a check valve on the top of the filter in the return line the fuel that is returned to the tank is used to cool the inj.

 

[Hammer]

There ia a check valve on the top of the filter in the return line the fuel that is returned to the tank is used to cool the inj.

Thats not correct...

The returned fuel from the fuel injectors is returned back into the top of the fuel filter housing and held in place with a banjo bolt and fitting. There is no check valve associated with the injector return line at all. I have looked at both my factory hard parts which were removed from my truck when the FASS was installed and to make sure I didn't miss anything I looked at the Cummins Quickserve site and none is shown.



I am in belief that either the writer or the owner who sent the info in are half baked on this idea. Diesel Power is well known for its screwed up print... ... Andy

 

[starring]

This myth does have some truth to it. I work on old sno gos with a cummins 855 in the back and on thoes engines this does work. There are small power gains with this but I have no herd of this working on an engine newer than about 1975

 

[JGK]

I asked a local Bosch certified injection pump tech with about 20 years experience about this yesterday. He said the return line returns excess unused fuel to the filter after the injection pulse and helps keep the injection line pressures in spec, and to a degree helps cool the injector, as mentioned. Blocking it off would cause huge hydraulic pressures in the lines and injectors with eventual damage of the injector.



I think I'll leave mine as is.



I also asked him about blocking the overflow valve on the pump. He said that can cause problems with the plungers and barrels. There apparently is a "permanently" lubed O-ring in the barrels that can have the lube washed away if the excess fuel pressure is not relieved by the overflow valve. When that o-ring looses its lubricating/sealing capabilities, the plunger can sieze in the barrel. That will shut down that barrel and even stop the rack from moving because the plunger can't move (rotate) in the barrel.



For what it's worth,

-Jay

 

[Dieseldemon]

How long have you been working on this engine not very long i suspect there is a check valve in the return line on top of the filter hsg. The part # of the CHECK VALVE IS 3924726 Call any Cummins dist and give this # to them and ask them if it is a check valve I have been working on this engine longer than you have owned one I think I know what I am talking about Who are you calling half baked.

 

[Highfinance97]

Who are you calling half baked.

Im pretty sure he meant The guy From Diesel Power that said he blocked his return line intentionally



Michael

 

[highmilage94]

Back to basics.......

Whether or not it helps can be easily figured out by the god 'ol Cummins basics... ... ..... If blocking the return on individual injectors made the engine more efficientOo. , made more powerOo. , or increased longevityOo. Oo. there is about a 99. 9% chance that Cummins would have used this concept on the b-series from the factory... ... ... ..... The same thing holds true with the turbo muffler ring. The ring was installed by Dodge to decrease turbo noise, not Cummins, and my turbo barks with it in and doesn't when it's out... ... ... . Also a small boost increase is noticable with out it installed... I run 42 p. s. i. with the original 275,000 mile turbo and no boost elbow...

 

[bmoeller]

This myth does have some truth to it. I work on old sno gos with a cummins 855 in the back and on thoes engines this does work. There are small power gains with this but I have no herd of this working on an engine newer than about 1975

It works on a 855 because there is no fuel injection pump, just a gear type fuel supply pump, and how the fuel is metered. PT and PT-G pumps use pressure and time (hence the PT in the name). The "G" is one that has a governor. The PT setup is the only fuel system I know of that will allow the engine to be self regulating, and not require a governor to keep the engine from running away. Pinching the fuel return line on those engines DOES increase the power. Just not the best way to do it. Changing buttons in the pump and orifices on the injectors is the best way.

 

[bmoeller]

the fuel that is returned to the tank is used to cool the inj.

Also lubes the injector.

 

[Joe G.]

How long have you been working on this engine not very long i suspect there is a check valve in the return line on top of the filter hsg. The part # of the CHECK VALVE IS 3924726 Call any Cummins dist and give this # to them and ask them if it is a check valve I have been working on this engine longer than you have owned one I think I know what I am talking about Who are you calling half baked.

Jim, where exactly is the check valve? The double stacked banjo fitting at the input to the fuel filter on my '95 leaked a couple of years ago and I replaced the washers. The lower banjo fitting is from the lift pump and the upper smaller one is from the fuel return manifold (AKA return line) at the injectors. I didn't see any check valve there. Both banjo fittings looked like normal fittings to me. Is it in the fuel filter housing? In there one somewhere else close by? As far as I can tell the fuel from the injectors does not go back to the tank. It goes into the fuel filter and back to the P7100. Am I confused about this stuff?