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Posted - 05/06/2006 :  10:30:39 AM  Show Profile  Reply with Quote
I'm wanting to learn a little bit more about modern diesel fuel injection. I know alot of older diesels used "injector pumps" versus the "common rail" or "unit injection" type. I'm under the impression that most diesels now are using the common rail design. Are there still large truck/bus diesels that use injector pumps? If this system is stil used, what kind of electronic controls would be used for an injector pump system? I know throttle control and injector plungers are electronically controlled via high pressure oil and solenoids on a common rail system (or this is one way of doing it). This is a rather broad topic I'm quite sure so I know it might be a little difficult to answer. I'm sure that every design varies for every manufacturer, but any insite is appreciated.

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Posted - 05/07/2006 :  08:54:31 AM  Show Profile  Visit ModMech's Homepage  Reply with Quote
Well, where to start as you have the basics of every current system figured out....

There are the following "common" fuel systems..

1) PT (pressure time), used in most Cummins engines (Cummins patent) with cam actuated unit injectors. Fuel rate is dependant on pressure and the time the injector has to fill. Has a fuel pump that delivers fuel to a common fuel rail at moderately high pressures of 120-200 psi.

2) PLN (Pump, Line, Nozzle), used on most "automotive" engines (Bosch patents) with various pump and injector types, the common thread is the pump is driven at 1/2 engine speed (like the cam) and each cylinder has one injector and a steel line that feeds it from the pump. Fuel is delivered at a fixed time, the rate is dependant on the pump supply. Has a transfer pump that delivers fuel to the injection pump at relativel low pressure (25-35 psi).

3) DDA "rack". Fuel is delivered to a common rail (drilling) in the cylinder head under low pressure (40-60? psi), and the injectors are camshaft actuated with the fuel rate determined by mechanical movement of a metering sleeve in each injector. This system is sensative to differences in cyliner to cylinder adjustments, but simple. A variation was also used by CAT on both the 3208 (sleeve metering) and more closely on the 3116.

4) EUI, Electronic Unit Injector as found on the Series 50/60, Cat 3406/C15 where the camshaft provides the power to inject fuel, but electronic controls determine when and for how long (timing and fuel rate). Has common fuel rail at moderate (60 psi) pressure.

5) EUI, a Mack variation. Each Unit Pump is directly driven by the cam, but timing is controlled by an electronic solenoid much like the EUI system, with the exception that it is located on the camshaft actuated pump, and not the actual injector. Each pump is connected to the injector with a steel line like the PLN type systems. Basically a conbination of EUI and PLN.

6) HEUI, Hydraulic Electric Unit Injector. CAT and International are the only two to use this system, and was jointly developed and patented by them. Each cylinder has one electronically controlled injector. The power to inject the fuel comes from high pressure oil (650-6500 psi) delivered to each injector via a common oil rail, fuel is delivered in the same way, via a common rail (drilling) in the head. Injection timing and quantity (fuel rate) is determined by when and how long the injector is "on" (coil energized), much like the EUI system. Fuel is deliverd to the injectors at low pressure (40-60 psi).

7) CR, Common Rail. This is another Bosch invention, and like the PLN uses individual lines to each injector and a common "injection pump". That is where the similarities end. With CR, ALL the fuel in the lines is pressurized to 20,000-35,000 psi at all times by the injection pump. The injectors are "piezo-electric" and operate much like the EUI and HEUI injectors where the timing and fuel rate is determined by when and for how long the injector is "on".

Each system has distinct advantages, and limitations. Currently, the only two systems that will meet 2007 emissions are EUI and CR.

System type & common engines using it:

1) Cummins K, L, M, N, 855

2) Cummins: B,C; GM 6.2/6.5; International 6.9/7.3; Onan, Hatz, Toyota, Continental, Mitsubishi, VW, Mercedes, BMW, Ford and many others.

3) Detroit Diesel (two stroke, and 8.2L four stroke), CAT 3116 and a distant relative on the 3208 (sleeve metering).

4) CAT, Detroit (S 50/60), Cummins N14 (although it is also PT)

5) Mack

6) CAT 3116E, 3126, 3176, International "Power Stroke" 7.3L/6.0L/4.5L (also used in Ford E/F series trucks and vans).

7) MB (Sprinter, Cars), Cummins B/C, VW, BMW, Audi, Ford, GM (DuraMax), International/Ford 6.4L (2007).

If you want customer service, you NEED an International!

Edited by - ModMech on 05/07/2006 09:16:40 AM
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Posted - 05/07/2006 :  09:43:30 AM  Show Profile  Visit 78fordwayne's Homepage  Send 78fordwayne an AOL message  Send 78fordwayne a Yahoo! Message  Reply with Quote
Wow thats very interesting. I had no idea there were so many types. The only one I worked with is the HEUI system.
There are so many people I talk to that believe diesel engines are the same today that they were 20 years ago. When I try to tell them that there is no injector pump, they say its not posable.
I love showing people that they are wrong

Robert B.

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4195 Posts

Posted - 05/07/2006 :  09:59:37 AM  Show Profile  Reply with Quote
Thank you for that ModMech! Quite educational and interesting!

I'm with ya 78fordwayne. That last superintendant I worked for could not understand why it cost so much for a Cat 3126 Reman because he just had his tractor overhauled for $1800. Clearly WE were wrong hehe.
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Advanced Member

459 Posts

Posted - 05/07/2006 :  12:23:56 PM  Show Profile  Reply with Quote
That was quite an impressive body of knowledge there John. I appreciate the response as it certainly opened my eyes a little bit on all the various types of diesel fuel injection. I've been looking for a book that basically goes into detail on what you said, but I haven't looked that hard yet. I've seen some technical books on specific topics, but nothing broad that would sort of overview and describe different systems. Thanks again.

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New Member

1 Posts

Posted - 05/12/2013 :  04:50:02 AM  Show Profile  Visit TommyA's Homepage  Reply with Quote
I will help you out! i found a site where you can learn everything about fuel injection. Checkout
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