Paccar DAVIE4 diagnostic program problem

Did you buy and install the Paccar DAVIE4 diagnostic program, but can't get it to work on 2016 and later Peterbilts and Kenworths? Does it identify the vehicle, but won't display codes or data items?

If so, this post may help.

Thank you for checking this post out. It outlines the frustrating process I went through and the lack of help and information available. 

Getting help to get the program to work, proved as frustrating as the solution was simple. Hopefully this post will keep someone else from having to go through the same process I did.

Here's the story.

DAVIE4 was downloaded from the Paccar site, installed, and licensed.

After installation and updating the program, I tried it on a 2016 Kenworth tractor. The program successfully identified the vehicle, and the "vehicle check" button seemed to scan. This brought up a home screen with options for diagnostic functions as shown below. Note at the bottom of the screen, the vehicle vin and engine model.

When the "vehicle check" button was clicked, the following screen appeared. Note the red connection blocks indicating no connection between the engine and aftertreatment system, to the program.

Clicking the vehicle icon on the upper left took me back to the home screen with the diagnostic options. When the "monitoring" button was clicked, this screen came up. The options were grayed out, and when any option was clicked, nothing happened.

Obviously there was a functionality problem.

I called Paccar tech support, and their answer was that I was using an older Nexiq interface, and that the program required the newer Nexiq2. I bought the new interface and installed the drivers for it. The results were exactly the same. I checked again for updates to Davie 4 and Nexiq drivers.

Another call to tech support had them conferring with software engineers, who came up with the idea that it was a problem with the vehicle I was connected to. I explained that between myself and another tech, we had tried it on several Paccar products, with the same problem every time. They indicated I should hook up to another truck and see what happened. I did so, with predictable results. The next tech support person I talked to suggested I attend a class on how to use the program. 

Over the next several weeks, when I had a chance to work on it, I repeated calls to tech support, called  the company we bought the license from several times, rechecked the laptop settings per the installation guide, and was promised calls back that never happened.

Every call to tech support started the same way. "What version of Davie4 have you got?" "What interface are you using?" "What are the interface settings?" 

One support person had me send him a log file and he and two others requested a screenshot of the grayed-out page. I asked if they could hook to my laptop remotely and look at things, they said they couldn't do that. I had a feeling they didn't know how.

I finally gave up on DAVIE tech support and  called support for the interface manufacturer, Nexiq. The tech there connected to my laptop remotely and had the answer literally in 20 seconds. "You aren't using a crossover cable." he said. A what? He explained that starting in model year 2016, Paccar (and Volvo) moved powertrain traffic from CAN 3 to CAN1, so a cable is needed to reposition the powertrain data to be readable to the interface. He gave me a part number for the Nexiq cable, (#406004) and said a version is offered by Paccar and other manufacturers. Shown below is a similar one we bought on eBay for $70.00. 

Follow this link:  crossover information  for more information on the change and several more cable options. The first part of the page concerns the newer green connector. If you scroll down you will find information and crossover options for the newer Paccar products.

When the cable arrived, I connected to a 2016 Kenworth and the program finally worked. The vehicle connection page came up showing a connected truck as shown below. The orange box between V CAN and connector means there are codes present.

Codes display on another page as shown below.

So, that's my story on this problem. In retrospect, I maybe should have pursued the possibility of a connectivity problem earlier, but we just haven't worked on that many late model Paccars at our shop, until lately. 

I would think that somebody, maybe the company we bought the license from, Paccar tech support, or the software engineers, should have been able to offer the answer in short order. Especially four years after the change. I often had the feeling that they were more interested in getting me off the phone, than actually helping. 

Also surprising was the fact that myself and another tech looked online for a possible solution, and found no information on the problem, and very little on DAVIE4 in general. 

So I hope this post helps somebody, and so long until next time.

Bruce

 

Fuel Pressure Regulator Basics

Caterpillar C7 fuel pressure diagnosis.

This post concerns how fuel pressure is developed and regulated. I’m writing it after getting a fuel pressure problem in the shop the other day. It was a Caterpillar C7, EPA 04 model. The 3116/3126/C7 Cat engines have the same type HEUI fuel system as the Navistar DT/EGR/Maxxforce engines. In fact, Cat and Navistar developed the system together. The fuel system is (relatively) low pressure, and the injectors are actuated with high pressure engine oil.

The symptoms on this Caterpillar C7 were a long crank to start, under all circumstances.

Hot or cold, initial startup or after road time, it cranked 15 to 20 seconds or even more, before starting. A warm engine should start almost instantly.

Even before scanning it for codes I had a feeling I was dealing with a fuel problem. However, I’ve learned the hard way that it’s best not to make assumptions until I see evidence. There was a code for low fuel pressure and none for injection control pressure, so I was comfortable starting with the fuel system.

Checking fuel pressure on this engine was easy – there is a Compuchek port on the filter base, so an adapter just snaps onto the port. When I cranked the engine the fuel pressure built slowly, taking 15 seconds or so to build to spec, and the engine started. After it was shut off, the pressure dropped to 0 within a few seconds.

  

Fuel pressure is regulated on pump output.

To address a fuel pressure problem, you first need to know how pressure is developed and regulated. These same principles apply to any hydraulic system, whether it’s power steering, auto trans, or engine oil supply. If you don’t understand how it works, you are destined to just replace parts one by one, hoping you replace the right one before the customer’s money runs out.

The first principle is that PUMPS DON’T PUMP PRESSURE! Pressure is developed by a restriction in the pump output. Think of a garden hose. With the end of the hose open and water flowing, there is almost no pressure in the hose. If you put your thumb over the end you can feel the pressure build and the water stream comes out harder. The same principle applies when making fuel pressure. Restrict the flow, and the pressure goes up.

Caterpillar C7 Fuel schematic

One of the most common misconceptions is that fuel can be regulated on the supply side, in other words on the pump input side. If you restrict on the pump suction side such as the fuel pickup it will starve the pump, like ice in the pickup line or a restricted separator. This may also cause low fuel pressure, but the point is that pressure is regulated on the pressure side, and fuel must FLOW THROUGH the regulator to control and limit pressure.

Fuel can be returned back to the tank, or to the suction side.

Depending on the system, fuel after the regulator can be routed back to the tank or to the suction side of the system. This Cat C7 and the late, great Detroit Series 60 route it back to the tank, through the regulator on the back of the head. Older Mercedes 900, Volvo, and some Navistar engines return it back to suction, or pickup side. The advantage to returning fuel to the tank is that any air getting into the system, like during filter changes, is quickly bled off to the tank. Returning to suction means any air needs to go through the injectors, and it sometimes takes lots of time and effort to get an engine running right after a filter change or especially after running out of fuel. Air in the fuel can lower indicated fuel pressure, because the air is being compressed, instead of properly pressurizing the fuel.
 

Modern high-pressure common rail systems differ in that there are actually 2 fuel systems, a low-pressure system and a high-pressure system that supplies the injectors. Here, the two systems need to be diagnosed separately to see which is causing a problem. The low-pressure system is controlled like the traditional unit injector systems like on the C7.

The C7 application had a Racor separator with the same size line in and out, so it was a simple matter to bypass the unit by taking the lines off and connecting them together. This showed no improvement. Looking in the fuel tank with the engine running, no bubbles were emitted from the return, so no air was being sucked into the system. There was no fuel smell or overfilling of the engine oil, so it wasn’t a leaking injector. The only other realistic possibility was a leaking or stuck open regulator. This was supported by the fact that fuel pressure dropped off so quickly after the engine was shut off.

  

The regulator on the C7 is on the rear of the cylinder head. 

Removing it for inspection was easy, just had to crawl under the truck and wedge myself up by the transmission. (No doghouse in a Freightliner M2)

The problem was obvious. The hole for the check valve was worn oversize and the end of the valve was sticking out of the valve body. Replacing it cleared up the long crank and the engine started repeatedly after a few revolutions, hot or cold.

C7 fuel regulator. Failed (left) and replacement.

C7 fuel pressure regulator design has two parts.

The design of the regulator is interesting, with two parts. The upper part is a check valve with a very light spring that holds some pressure in the head when the engine is shut off. The lower part regulates fuel pressure during operation. The regulator plunger has a tiny pinhole in it. When the check valve failed to seal with the engine off, the fuel leaked through the pinhole, into the return. Thus, zero fuel pressure seconds after shutdown. I can only guess at the purpose of the pinhole, maybe to prevent hunting at idle or to dampen regulator oscillation.

Caterpillar C7 fuel pressure regulator

Detroit Series 60 fuel pressure regulator has two parts.

The old Series 60 regulator is worth mention here. Its fuel system is much like the C7. On the back of the head is an elbow on the fuel return port. The regulator is screwed into this elbow. These regulators are known for problems, not necessarily with the regulator itself. The elbow in the head looks just like a regular brass pipe elbow, but it’s not. It has a small (I think .02 in.) orifice in it. This hole actually regulates the fuel pressure at higher engine loads and is exactly the right size to trap pieces of injector seals after an injector change. When the hole is plugged the engine may run, but not well and won't have any power.

2006 MBE 4000 Hard Start and Engine Miss

I was recently involved in a repair of a 2006 Mercedes MBE 4000 with a hard start problem.
The customer said it wouldn't start without ether, and when it did run it didn't idle very well. The check engine light was not on until I got the truck into the shop.

I went out on the lot and tried to start it, and couldn't get it going by myself. It took one of the other guys to feed it ether while I cranked it, and finally got it to start and run well enough to get it into the shop.

I hooked up our Bosch scanner and pulled codes for #1 and #2 injectors, that became active while the engine was running. I then hooked up the Detroit program to verify the results and run any tests that were needed. I usually hook up the Bosch first because it is often less messing around to get running and check for codes. Detroit verified the injector codes, then I did a cylinder balance test showing a higher torque deviation on those cylinders.

I wasn't convinced two faulty cylinders could cause the hard start I was experiencing, especially seeing as the Mercedes has a unit pump injection system. Each cylinder has its own unit pump running off the camshaft and as far as I understand the system, the injectors are like old-school nozzles that just open at a given pressure. Granted they are trimmed electronically, but I needed more proof that they were the source of the issue.

Fuel aeration is indicated by air bubbles in the fuel returning from the engine  to the tank.

Next I looked in the fuel tank. The fuel looked good and there was plenty of it, but while the engine was running a problem was obvious. The fuel return could be clearly seen near the bottom of the tank, and it was emitting a steady stream of air bubbles. it looked like when you were a kid and you blew bubbles in your milk with a straw. That much air coming back from the fuel system was doubtless the cause of the hard start.

Just to cover all bases I checked the fuel pressure. This is easy on this application, as there is a compu check fitting on the filter canister. A special connector like a hydraulic coupler goes on the fitting for a quick, no mess pressure check. The fuel pressure was approximately to  spec at idle and at high idle. Note here that high idle on a diesel engine is no load, pedal to the floor.

Find the source of fuel aeration start by eliminating the fuel tank and pickup line and running the engine off a can of fuel.

On this engine that is an easy matter. The fuel lines to and from the separator are regular nylon airline, so I just disconnected the one to the tank, stuck a tight fitting piece of rubber hose to it, and stuck it in a bucket of fuel. after a few minutes of running the fuel return was still producing air, so I took the line off the other side of the filter housing and ran the engine with the filter bypassed. It still made air, so I knew the problem was neither in the tank, the pickup line to the separator, nor the separator itself. The rest of the fuel system has hard plastic lines with banjo connections, so it would be harder to check.

Check the lines and fittings between the filter housing and the transfer pump for leaks that could be sucking air.

 We have an electric pump we use for transferring fuel and pumping out tanks, so I used that to pressurize that part of the system. This would pressurize the whole system up to the regulator at the rear of the engine, but the only thing I was interested in was the suction portion from the filter to the pump. This test again showed no leaks.

Another possibility was that an injector was stuck open and cylinder compression was getting into the fuel circuit. Luckily under each valve cover is a banjo connection for the return fuel from each injector, feeding a line that routes back to suction fuel. It was an easy matter to remove the valve covers and remove the banjo bolt at each injector, one after the other, while someone cranked the engine. A stuck injector should emit air from its return, but again this test proved negative on all cylinders.

The only other possibility left for air entry, or fuel aeration, was the fuel pump.

 It is a mechanical unit mounted on the front cover, so if the pump's front seal was bad it could suck air there. Unfortunately there was no easy was to test the pump, other than just changing it out. I did so, which took about an hour, and started the engine. It seemed to start fairly well. but there was still quite a bit of air coming from the return even after a few minutes of running, and the engine still ran rough. During a short test drive, however, it smoothed out and when I got back to the shop there was no longer and air coming from the return.

A quick scan showed that the injector codes had gone inactive, and stayed away after being cleared. Evidently the codes were due to the air in the system. Fuel enters the head at the front, so the air affected the front two cylinders the most. The engine started immediately hot and cold, so I pronounced it fixed.

Thanks for reading.
Bruce