A brief look at the B series Cummins engine that gives Dodge its diesel power.
When pickup trucks started going diesel ‘way back in the early eighties, Ford opted for the International Harvester (Navistar) 6.9 in its heavy duty pickups, while Chevy nestled a 6.2 under the hoods of their heavier duty units. Dodge remained dieselless in their pickup line until the ripe old year of 1989, when the 5.9 liter ISB Cummins became available on pickups heavier than the ½ ton platform.
The B-series Cummins engine has since found a home in a wide range of platforms from the D-250 all the way up to motor homes and Ford medium duty trucks.
Cummins 24 valve rocker cover
A Quick Scan of the Gut Numbers
The turbocharged Cummins ISB series engine is slightly undersquare, with a 4.02 inch bore and a 4.72 inch stroke for 5.9 Liters (359 cubic inches) of displaced air with every two crank revolutions. The compression ratio is moderate for a diesel; 16.5:1 (as opposed to 17.5:1 for the 12-valve engine) and squeezes the full volume of the combustion chambers with High Swirl Bowl aluminum pistons, bringing the air in the cylinders to the superheat required to light off fuel spray from injectors that “pop” at a brawny 4,500 pounds per square inch of pressure. The firing order is the extremely familiar 1-5-3-6-2-4 we’ve all been accustomed to for decades on straight-six engines (not that you’d cross the injector lines anyway!). The crankshaft is Induction Hardened Forged Steel, while the camshaft is “Chilled Ductile Iron” according to Chrysler’s shop manual.
Horsepower on the automatic trans equipped diesel Dodge peaks out at 215 (from 1600 rpm to 2700) with 420 foot pounds of torque, while the manual trans equipped counterpart is tuned for an additional 20 horses and another 40 foot pounds. of torque. Average engine-life-to-overhaul figures are an astounding 400,000 miles!
Cummins“High Swirl Bowl” piston
(all photos Richard McCuistian)
Fuel Delivery Overview
Fuel systems differ from one application to another in the B-series line; newer Cummins medium duty truck engines appropriate solenoid regulated top-stop injectors with a 17,000 psi gear type fuel pump, the inevitable Cummins Engine Control Module (ECM, mounted on the driver side of the engine in true Cummins style), and a common supply rail. As for the B-series Dodge pickup engine, the fuel is handled by a Bosch VP44 solenoid-controlled-radial-piston-distributor type “Smart Fuel Injection Pump” that supplies the gutsy 4,500 lbs needed to “pop” the vertically centered injectors that spray directly into the combustion chamber. There are no ignition prechambers on the 24 valve Cummins. The Holset turbocharger is matched to the engine and waste-gated for improved performance at all speeds.
The “Smart Fuel Injection Pump” itself is gear-driven (on a tapered shaft with a special keyway; more about that later) at half crankshaft speed by way of the camshaft and contains an integral top-mounted Fuel Injection Pump Control Module (FPCM) that is non-serviceable without replacing the whole pump. The FPCM is energized by the Engine Control Module via the Fuel Injection Pump relay in the Power Distribution Center (PDC). Fuel is supplied to the VP44 pump through the filter/water separator by an vane-type electric transfer pump which is mounted near the ECM. The Transfer Pump is driven at 100 percent duty cycle with the engine running and should produce at least 10 psi. During engine cranking, the pump duty cycle is a mere 25 percent, producing only 7 psi, to limit injector pump inlet pressure until the engine fires up.
Diesel guys will be familiar with the concept that most of the fuel (about 70 percent) passing through the hard-working injector pump is used to keep the pump cool and returns to the fuel tank. And like most other diesels, if you run one of these babies out of fuel the air will have to be bled from at least two injectors before the engine will receive enough fuel spray to light off. Personally I like to bleed ‘em all. The electric transfer pump is kind-hearted enough to be self-priming.
Keeping Things Timed;
The All-important Keyway.
1. Order No.
2. Bosch Part No.
3. Factory Code
4. Cummins Part No.
5. Manufacture Date
6. Pump Serial Number
7. Last three digits of key
Engine timing and injector pump timing are matched by an offset keyway that is specifically numbered and calibrated to match its own pump. If you bobble the key and it falls down the drain or something, simply check the pump data plate (see illustration) to see which key you’ll need to order. The three digit number stamped on the pump represents the last three digits of the part number of the key for that pump, and the same three digit number will be stamped on the key itself.
Always use a key with the same number stamped on the pump and always aim the arrow on top of the keyway toward the rear of the pump. If the offset key isn’t installed with the arrow pointing toward the pump, or if the gear has slipped on the pump shaft, an “engine sync error” or “static timing error” code will be stored. If such a scenario appears to be the case, simply pop the plastic gear access cover for a quick inspection. If the gear has to be removed for a double check of the key, a T-type puller and a couple of M8 X 1.24 screws will do the job nicely. Don’t move the gear too much or you might break the gear cover. Also, make sure to rotate the engine (Snap-On barring tool No. SP371 is really nice for this) so that the pump key is at the 12 o’clock position before you pull the gear or it can tumble down into the gear housing for a day-ruining foul-up!
Injector Pump closeup Illustration of numbered key (Courtesy Chrysler Corp)
(with FPCM module mounted up top)
photo: Richard McCuistian
Note: The Injector Pump keyway is also used for reference when performing valve adjustments on the Dodge Diesel. The intake valves optimum lash spec is 0.010 inch (0.006 -0.015). and the exhaust valves optimum adjustment is 0.020 inch (0.015 – 0.030).
Keyway positions (Courtesy Chrysler)
Three Brains are Better Than One…
The 9-pin Fuel Pump Control Module (FPCM) built into the VP44 pump partners with a separately serviceable 50-pin Engine Control Module (ECM) in controlling fuel delivery, while a third module more familiarly named the “Powertrain Control Module” (PCM) is used to regulate and control the Climate Control, charging, and speed control systems, as well as certain automatic transmission components and it also interfaces with the ECM regarding some of the instrument panel indicators. Engine idle speed and injector pump timing are obviously handled electronically. The PCM is mounted in the same place it can be found on gas burners, over on the passenger side of the engine compartment bulkhead, while the ECM is mounted on the driver side of the engine block the way most Cummins Engine Controllers are. One point that might be of interest is that the Cummins ECM for the Dodge Truck Application has only one connector instead of the two connectors found on medium duty truck controllers.
|1||K240 20 LG/PK||Fuel Injector Pump Data Link (-)|
|2||K242 20 WT||Fuel Injector Pump Data Link (+)|
|3||Not Used||Not Used|
|4||K44 18 VT/OR||Camshaft Position Sensor Signal|
|5||K45 18 LB/RD||Knock Sensor Return|
|6||Z12 14 BK/TN||GND|
|7||A40 14 RD/LG||Fuel Pump Relay Output|
|8||K48 18 DG||Fault Signal|
|9||Not Used||Not Used|
Fuel Pump Module Connector Layout according to Chrysler Shop manual. Below is the Chrysler wiring map
for the FPCM and the Engine Controller. (both illustrations courtesy Chrysler Corporation)
The ECM and PCM communicate with each other and the scan tool through Chrysler’s CCD bus circuits (“Chrysler Collision Detection,” which has everything to do with mixing and matching serial data transfer between modules and nothing whatsoever to do with actual collisions), receiving parallel signals and acting accordingly.
Engine Control Module Connector
Accelerator pedal position information is sent to the ECM in the usual way, i.e., as an analog voltage signal proportionate to throttle angle, with the standard 5-volt reference voltage filtered through a linear potentiometer, then the ECM loops it back over to the PCM along with Crank Position info gleaned from the CKP sensor. The Cummins-equipped medium-duty Ford truck Accelerator Pedal Position Sensor (APPS) is mounted on the pedal assembly along with an Idle Validation Switch (IVS) as a backup. The engine won’t rev above an idle if the switch and sensor don’t agree, but on the Dodge, the Accelerator Pedal Position sensor and IVS are actually mounted on a bracket at the injector pump. Earlier units had linkage and bellcranks between the cable-driven sensor shaft and the pump, but the linkage and bellcranks evaporated from the Dodge pickup line late in the ’97 model year, leaving only the APPS attached to the throttle cable, and giving the FPCS control of fuel delivery via the electronic manipulation provided by the ECM.
The APPS is serviced along with the bracket, and while we all like to tinker, the Mopar folks warn us not to go there, since the APPS is calibrated and permanently mounted to its bracket. You can’t get a replacement sensor without buying the lever and bracket assembly anyway.
APPS & Bracket APPS Sensor and bracket
(Illustrations courtesy of Chrysler Corporation)
The Rest of The Crew
Other ECM inputs are Ignition switch input, CKP (Crank Position), WIF (Water in Fuel) sensor, Air Temp Sensor, Oil and Manifold Pressure Sensors, and CMP (Cam Position Sensor). Pins 41 and 40 are CCD Bus pins, where the ECM receives serial data from the PCM. The FPCM talks to the ECM on a separate pair of shielded wires. Other ECM outputs besides the FPCM include the Intake Air Heater relays (two of them, one for each intake grid heater) the Diesel Wait to Start Lamp, the Fuel Transfer pump, and the Injector Pump Relay.
Data for the Driver
Interestingly, Cummins markets a hot little item called “Road Relay 4,” which allows the driver to monitor the vital (and not so vital) signs the Engine Control Module broadcasts over the CCD bus. It was once available only to 18 wheeler drivers, but Cummins has plans to market this handy little electronic device to Dodge Ram owners in the near future. A nice little alternative to the Road Relay 4 is Quick Check II, another interface available through Cummins designed to allow the Cummins Engine Controller to communicate with your PalmTM device.
Cummins Success Dealing With Nox Standards
Diesels pretty much managed to dodge the emissions bullet for a lot of years longer than gas burners. But in 1998, under a settlement of a government suit, seven diesel engine manufacturers agreed to lower Nox emissions on engines in tractors and 18-wheelers by October 2002. Cummins, Navistar International Corp.’s International Truck and Engine Division and Volvo Truck, as well as the Detroit Diesel folks are all meeting the October deadline, but Caterpillar seems to be having trouble with it.
The new government regulation calls for truck engines to certified by the Environmental Protection Agency (EPA) to the 2.5-gram NOx + NMHC standard. Cummins actually met this standard and earned EPA approval on the ISX series engine, shipping its first certified engine early in April 2002.
The primary differences in engineering that enabled Cummins to meet the October deadline seem to center around Holset Variable Geometry Turbocharging (VGT) and a cooled EGR system. The VGT will eliminate wastegating, since the turbocharger uses a single sliding nozzle to regulate turbo boost. It’s not a new idea; Over 40,000 trucks in Europe are already using the new design with tremendous success.
I contacted Cummins with an inquiry as to whether or not the ISB engine would be re-engineered to these standards, and the reply I got was that as of May 21, 2002, the ISB engine has been submitted to the EPA for certification under the new Nox standards. The EPA is expected to render their certification of the ISB early in the summer of 2002, and the ISM engine is expected to be certified by the October deadline. One wrinkle on the ISB is that only engines rated at 245 horsepower and above will receive the VGT. Lower rated turbocharged engines will probably keep their wastegates for a while longer.
Along with the VGT and cooled EGR, on the higher powered units, all the new ISB engines will lose their Bosch injector pumps in favor of a “High Pressure Common Rail (HPCR) Fuel System” for reduced noise, as much as a 2% increase in fuel economy, and improved emissions. The gear train will be moved to the rear of the engine, a change which may cause diesel wrench guys to groan, but intended by Cummins to provide increased accessory drive capability and as much as 80% quieter on engines built with both HPCR and the rear gear train. If these claims prove out, it’ll seem strange to hear a diesel that sounds like a gas burner!
CI-4 oils are recommended on the new engines, crafted to meet EGR requirements.
Changes Keep Coming
Diesels are getting quieter, smarter, more powerful and more efficient every year. Who knows what the next decade will bring? Diesel electric trucks maybe?