Low power Cummins ISL, ISC etc

[DaveAtherton]

Good morning, following post about low power, ISL / ISC with caps system. Post on probem on right track to correct problem.

Caterpillar has had same problem with Heui injection systems with constant fuel flow in motorhomes being fuel tank location 

35 to 40 feet from engine and a singe stage piston type fuel transfer pump pulling fuel. Along with all this being said not taking

in any air leaks on the suction side pulling fuel from front. What has been mentioned is correct on tract except need to remove

Cummins electric pump from system and go direct to caps pump.  Caterpillar Update same problem on 05/02/2005  (Special

Instruction). Instruction for installation for electric fuel priming pump on caterpillar equipment. This includes COMMERCIAL 

ENGINES AND TRUCK ENGINES. The caterillar electric fuel pumps runs anytime engine running to provide constant fuel

flow from fuel tank. Good example Cat C-9 400 HP has a single stage piston fuel transfer pump along with age and other factors

air entry cannot meet the demand of constant fuel flow and maintain constant fuel pressure. The idea is great and there are

several Caterpillar owners that have gone this route with great reviews. With Cummins engines same concept remove electric

pump that only runs for 30 seconds and install a electric pump that runs all the time. Without any fault codes or event codes

on low power is telling a person basic there is not a problem when there is a builder problem putting a fuel tank 35-40 feet

away and expect to maintain constant fuel flow. Dave AthertonRetired Cat Mechanic

[jleamont]

Dave, have you read this post?

 

[dickandlois]

Dave, Think the Lift pump on my Cummins fuel supply runs all the time when the engine is running, but will run only 30 seconds if the engine does not start. That makes them hard to prime after fuel filters are replaced, if one does not pre-fill the new filter, when there is no hand operated priming pump.

[jleamont]

Rich, what engine and year engine do you have?

[jleamont]

Rich, I believe some of the confusion stems from the term "CAPS". While the ISB, ISC, ISL, ISM and ISX all had that system design there were many differences depending on the engine model and year. Some were equipped with the Bosch VP44 and others the Cummins designed and produced injection pump.

I did recently located this kit to remove the entire CAPS system and replace it with the old Bosch 7100 series mechanical injection pump found in the years prior to CAPS. If you want to throw $8000.00 at it in parts alone.

https://areadieselservice.com/diesel-power-products/product/caps-pump-replacement-kit/

 

[manholt]

Good grief....My buddy James, just looked at this, he's still walking around laughing! 

Joe.  He also, read your post on the re design and was impressed...that's a big compliment from him! 

[dickandlois]

Hi Joe, Yes the 7100 is almost bullet proof. Longer with a compression section for each Cylinder and no electronic fuel metering.

Anyway, my ISB has one of the first VP-44 pumps and the OEM design did not use the correct materials for the fuel compression pistons(time line was 1998 to late 1999) that work off the internal cam and where / are suspect to structural damage, pitting or rust. When they start to fail one needs to remember that the problem first shows up when the pumps get hot. I on the other hand  had a DUH moment and totally drew a blank in the heat of the moment. There are no new VP-44 pumps, all are reman. units and not all re builders are equal.

The real test is to pour cold water over the back of the pump, that's the end where the injector lines connect. This cools the pump just enough to reduce the friction caused by material damage an heat expansion. this allows the pistons to work freely again. IF you do not get a Code from the pump control electronics !!!

Internal structure is 3 compressor cylinders, with 2 solenoids so each one can feed 2 injectors. So 3- compression sections can supply 6 cylinders. 

The thing is we are always trying to build a better mouse trap and reduce the cost!

Engineers always need a challenge to keep them entertained. I have always enjoyed a challenge, but building something cheaper just to save money; did not fit into my mind set. The privet aircraft industry and Uncle Sam tough me well. Build it tough and make things redundant.

The one lesson that keeps getting missed, is dissimilar materials connected together or in close proximity to each other is not a good idea in a number of applications.

Note, Bosch VP-pumps number tag 04756-XXXX. The last portion of the number is needed to get the properly specked pump for each Cummins Engine application!

Rich. Old and still having fun learning !!!