HOW YOU CAN DIAGNOSE THE VP44 FUEL SYSTEM ACCURATELY

FROM BLUE CHIP DIESEL

If your truck "Bucks" under hard load or towing this is an indication the engine is probably starving for fuel. To test fuel delivery or pressure, install a fuel pressure gauge with a long hose on it after the fuel filter and before the injection pump. The long hose allows you to drive the truck and watch the gauge at the same time! You can install our “Low Fuel Pressure Warning Kit” and it will diagnose low fuel pressure too. To diagnose lift pump performance click the ignition key to the start function quickly, so the engine doesn't start, and let go, leaving the key in the run position; the lift pump should run 25 seconds. If you don't hear the lift pump, test for 12 volts going in to it and if it doesn't run with 12 volts going into it, replace it. If you do hear it run and it doesn't make at least 5 PSI replace the fuel filter. If, after changing the filter, it DOES make at least 5 PSI go DRIVE the truck UNDER LOAD. If it doesn't make at least 5 PSI after changing the filter, or if you have to pressurize the fuel tank to bleed the system to get the truck to run, then change the lift pump. Revving it up proves NOTHING. If DRIVING UNDER LOAD the pressure drops below 5 PSI, replace the fuel filter (if you haven't already done so) and if that doesn't fix it, you need a new lift pump if the fuel lines aren’t rusty and or sucking air. We proved on a dynomometer in 1998 that if you have 5 PSI, under load, you can make all the power available from a VP44. We do not recommend running more than 12 PSI or you will diminish fuel delivery to the rotor and make the truck run worse at high RPM and possibly overheat and damage the fuel bypass solenoid. This diagnosis is only for the lift pump, but is necessary for the successful diagnosis of injection pump issues. If you don’t have enough lift pump pressure it will cause low power or bucking under load. All other drivability issues usually are caused by the injection pump.


If you have an intermittent "Dead Pedal" this can be caused by either a faulty APPS (Accelerator Pedal Position Switch) or a faulty computer on the VP44 injection pump. Since the APPS is only $460.00 from D/C and it is cheaper than a replacement injection pump, we recommend getting someone to "scan" the ECM (not the PCM) in your truck to check for any DTC codes pertaining to the APPS. If there are none pertaining to the APPS you DON'T need an APPS, as a bad APPS always displays a code. If you don’t have access to a scan tool, the difference between a bad APPS and an injection pump is that an APPS usually is just a flat spot at a certain throttle opening, usually 65-70 MPH and smacking the pedal a few times usually clears it up. This usually is worse during cold and or wet conditions. If it is an injection pump the “Dead Pedal” is dead at all throttle positions and may reset and play if you let the pedal go to idle for a brief time and reestablish “Idle Validation”. This one is most often when hot, but sometimes right after start up when cold.

If you see the code 216, or if there are injection pump codes, or even if you have NO codes for the injection pump AND you have ANY of the above listed drivability complaints, YOU NEED AN INJECTION PUMP! Code 1693 only means there are codes in the other computer, which have NOTHING to do with the fuel system.

There are basically only two other components to the fuel system in a VP44 fueled truck and they are the ECM (Engine Control Module) and the injectors. Neither of these give any trouble typically. In 13 years of doing ONLY Dodges every day I have never seen or even heard of a bad ECM and or injector. It is highly improbable that either component could cause any of the aforementioned drivability issues. Symptoms are different for these components.

The other situation that is pretty easy to diagnose is when the truck dies driving down the road, for no apparent reason, or when you let off the throttle, especially at high RPM. This is usually a seized rotor in the injection pump and most common on 1998 and 1999 trucks. The cause of this failure is a poorly "deburred" rotor which seems to have been mostly limited to those years of manufacture. If you run any year truck out of fuel at high RPM or heavy load you CAN seize the rotor also! If this happens to your truck and you want to diagnose it simply, positively and accurately, do the following. Loosen three injector lines at the valve cover. Crank the engine a few times for 30 seconds and if fuel only comes out one line or none of the lines, this indicates a seized rotor. I know this because we proved you can not put this pump in a hydraulic lock, so therefore fuel has to come out of an injection line even if the rotor is not turning. If you have fuel coming from one line only that is where the rotor is stuck. The feeble flow is due to having only lift pump pressure moving fuel. If you have no fuel from any line opened then it is stuck at one that is closed. If you get fuel from all three lines you must bleed the engine to get it to run again and then you have to figure out why it ran out of fuel.

What the common VP44 problems are….

The housings on the VP44 wear out due to low fuel pressure from weak lift pumps causing the diaphragm in the front of the VP44 pump to rupture. This causes the steel timing piston to vibrate in the aluminum bore of the housing and the result in a short time is the housing wears to the point that fuel bypasses the piston and full advance cannot be accomplished which causes the code 216. This makes perfect sense to me as it explains why as 24 valve trucks get older the fuel mileage goes down steadily, and when we replace the injection pump with one that has a new housing we get the mileage back! In a typical competitor's rebuild, if the case isn't worn out completely and the timing can be reached on the test stand then it passes the test and a partly worn out case gets to the customer, just to fail sooner. It should also be pointed out that the replacement housings we use, have an insert for the timing piston, which the original housings did not have. The code 216 only tells you that the housing is worn out, but does NOT cause any drivability issues, other than lost power and fuel mileage. As these symptoms come on slowly the driver isn't aware of the change until they drive one of our replacement units and get back the power and mileage.

The other component that causes almost all of the drivability issues is the computer on the top of the injection pump. The computer gets intermittent because of too many heat cycles. When you shut the truck off the latent heat in the engine heats up the computer and after many heat cycles the solder that holds the electrical components to the circuit board of the computer becomes crystalline and no longer makes a good electrical connection, causing intermittent drivability issues, such as "dead pedal", intermittent hard cold start, intermittent hard hot start and white smoke. These drivability issues usually get so bad that the customer finally takes the truck in for diagnosis, only to find none of these issues create a diagnostic code or a so called DTC. This makes it hard for the inexperienced mechanic to advise the customer honestly or accurately.

 

BOSCH VP44 INJECTION PUMP AND LIFT PUMP FAILURES EXPLAINED

The best way to start this explanation is to quote an e-mail that was found on the Cummins website. “The Bosch VP44 has not been as reliable as we had hoped”. Depending on who you talk to and who you think is being honest, you will most likely get only some of the information you need. I will endeavor here fill in the gaps and get you up to date and informed; the reason I can tell you more is because Bosch had not, until 2004, allowed any franchised dealer to do anything except to send defective pumps back to the remanufacturing facility. Long before that Blue Chip had dismantled many pumps to figure them out and diagnose what failed and what caused the failure. We do not pretend to be any where near as smart as Bosch, but since there was no experience or information or truth out there, we felt we had to get the best information we could any way possible. Probably the most informative source were the applications for the patents applicable to the VP44. It was this dismantling and learning process that allowed us to get a patent and a performance product to market first.


The most common MECHANICAL failure with the VP44 pump is the cause of the code 216. This is when weak lift pumps with low fuel pressure over a perioid of time rupture the diaphragm in the front of the injection pump and the timing piston then vibrates and wears the housing of the pump until fuel bypasses the piston and full advance can no longer be attained. When full advance can't be attained for more than 5 seconds the code 216 is set. This means your pump has lost a lot of its power and fuel mileage and needs to be replaced and upgraded.


The next most common MECHANICAL failure is that the rotor seizes in the distributor section of the pump. I should note here that all previous rotary style pumps have had this problem too, to varying degrees. The most common cause and most accepted reason for this failure on rotary pumps is lack of lubrication due to running out of fuel or the possible lower lubricity of the newer low sulphur fuels.


In the case of the VP44 it is more common for the rotor to seize in the distributor because the pressures are MUCH higher and therefore mechanical tolerances have to be much smaller. Add the fact that the rotor was not "deburred" enough or correctly during manufacture, and these failures can be easily explained. Under the higher working pressure in the VP44, the edge of the slot in the rotor deflects and interferes with the distributor. Sooner or later the result is a galling of the two parts and then binding and then seizure. The seizure causes the "Drive Plate" to break and the truck stops running, never to start again until the VP44 is replaced. There is less than a half a thousanth of an inch clearance between the two parts, so it doesn't take much to make the rotor interfere with the rotor. Pumps made recently (since about 2000) are experiencing fewer of these kinds of failures, it seems to me.


The other reason injection pumps fail is ELECTRCAL issues and failures. These are the problems that cause 99% of the drivability problems. The computer on the top of the VP44 is susceptible to heat and many many heat cycles. The components on the circuit board develop bad connections due to crystallized solder over time and the result is intermittent hard start, white smoke and drivability issues such as the common " Dead Pedal". Rarely can these issues be verified or diagnosed by codes set in the ECM.


A lot of people have heard about bad lift pumps and think they are the cause of VP44 drivability issues and therefore electrical failures; NOT SO! Starting with the early 98’s, not only were they weak pressure wise, but also had exposed terminals on the bottom that corrode off in salt environments. The way to tell if you have a corrosion sensitive pump is to see if the electrical connection is a plug on a 6-inch pigtail coming from the bottom of the pump. If the plug is on the top cover of the pump you’re all set, for that problem anyway!


If the lift pump is not delivering fuel pressure the truck stays running because there is a gear pump in the front of the injection pump, which keeps the fuel flowing, albeit at a much lower pressure than desired, and hopefully maintains lubrication to the rotor. As long as there is return fuel flow from the injection pump there is lubrication to the rotor, so low fuel pressure and certainly less return fuel makes it much easier to starve the rotor for lubrication. The only accurate way to test a lift pump is to monitor pressure UNDER LOAD and if it is above 5 PSI, no performance is lost and the pump is OK. If pressure is less than this, a modest reduction in horsepower results. The usual scenerio is a customer puts a performance box on his truck and the lift pump can't produce enough fuel to make more horsepower, and the performance product gets the blame.This sympton is most always a "Buck" as opposed to a "Surge" under load.


Often people have mistakenly said that increased pressure from add-on performance devices causes the injection pump failures. This statement only indicates their lack of knowledge, because, unlike most pumps, the VP44 pump does not create more fuel delivery by increasing lift pump pressure. The VP44 creates more fuel delivery by holding the fuel bypass solenoid closed longer. Fuel delivery pressure is controlled by the “pop off pressure “ of the injector.


The reason any aftermarket device that hooks up to the solenoid wire is blamed for the failure is that the failure 99 times out of 100 (honest numbers here) the pump fails within 20 minutes of installing and running with power enhancement. The reason this happens is because the fuel solenoid is held closed longer, therefore using more length of the slot in the rotor. The slot in the rotor overlaps a hole in the distributor to allow for different timing and amounts of fuel to be delivered to the injector and when the solenoid holds the bypass solenoid closed longer, then the high “pop off” pressure is still there when the middle of the slot overlaps the hole. The middle of the slot is the weakest area and therefore deflects, interferes with the distributor and seizes. Pump failure with fuel enhancement devices is not CAUSED by the enhancement device, but PRECIPITATED by the device. WE think this is a “glass half full” scenario rather than a “glass half empty” one, because the potential, eventual failure can be determined within controllable parameters, namely on the test run at higher power, close to home or the local dealer. The other side of the coin is, honestly, if your truck is still running 20 minutes after the installation AND BEAT RUN, you have a 90% chance your pump will not fail for a mechanical reason and therefore last until electrical issues start to show.


Lastly the installation of bigger injectors; do they alleviate the high pressure or raise the pop off pressure and therefore cause many failures of the VP44? Absolutely NOT. They are a bigger hole so fuel volume is increased at the same pressure. Remember fuel pressure is controlled by “Pop off” pressure more than the size of the hole! Aftermarket injectors that DO raise the pop off pressure do not appear to cause any problems. Bigger injectors do get more fuel into the combustion chamber sooner, therefore giving the engine better throttle response.Bigger injectors are worth it but not for the reason of saving the pump.

 

Let me add this to this guide so folks can tie all the problems together and understand more of why these problems happen.

Fueling System Trouble Shooting Guide


This guide will start with the fuel tank and make its way step by step through the system. I am sure there will be other things to add to this but these are the problems I have come across.

1. Fuel Tank:

A. Rollover Protection Valve sticking shut. This will prevent your system from being able to pull air in to replace the fuel you are using, thus creating a vacuum. This vacuum will slowly pull your fuel pressure down as you drive. When removing the fuel cap you will hear the air pressure release. To test this try driving with the cap loose and see if that corrects your problem.

B. Fuel Pickup Tube corrodes on the outside or cracks inside the tank. The fuel pickup tube on the early models of 2nd generation trucks have a tendency to corrode and leak air into the system right on top of the module where the fuel line connects to it. If it cracks on the inside your truck will run fine until your fuel level gets below the crack. Then it will pull air mixed with the fuel. This is the same thing as putting a hole in your drink and trying to suck through it, you will get some drink but it is mixed with air. This will create low fuel pressure and a loss of power.

C. Fuel Pickup Screen clogs with debris inside the tank. On the bottom of the pick up tube is a fine mesh screen that sometimes will clog itself up if you have gotten bad fuel. This will sometimes fall lose when you shut the truck off and then re-occur as your driving. No real way to diagnose this except to get inside your tank and check it.


2. Lift Pump:

A. There is only one thing to say about the stock OEM lift Pumps, regardless of which type you have. They are not sufficient to provide enough dependable fuel flow to the VP44 to keep it cooled off. If you are running any type of performance mods this just increases the weakness of the stock system. A fuel pressure gauge that is visible to you as you drive is the only assurance you can have to know if your lift pump is functioning properly. You can have 20psi at idle, but when you get on the go pedal that could drop to 0psi and then the very expensive VP44 is on its way to the graveyard. If you only do one Mod to your truck, make it a fuel pressure gauge.


3. Fuel Filter:

A. The Water Drain Valve sometimes leaks fuel. If your lucky you can jiggle it around and break lose whatever is blocking it from closing completely, if not it will need to be replaced.

B. Seals go bad. Many of us have a tendency to change the filter but not use the new seals that come with the filter. It is important to change these to maintain to maintain an air tight seal.


4. Injector Pump:

A. Also known as the VP44, the injector pump is fuel cooled. The lift pump is expected to not only pump enough fuel to feed your injectors but enough excess to provide cooling action to this pump. The main failures to this pump are to the electronics that overheat and lose there ability to control the fuel flow. There are many different symptoms associated with this. Among them are a noticeable loss of power, loss of fuel mileage, hard starting when warm and/or a code of 0216 on the code reader.

B. Fuel Pressure Regulator is nothing more than a banjo bolt on the outgoing side of the fuel flow that maintains 14psi of fuel inside the VP44. If this goes bad it could either stick in the open or closed position or just get weak and not hold enough fuel pressure to the pump. If it sticks open or gets to weak to maintain pressure it will let the fuel just bypass the pump and return thru to the tank, not feeding the injectors. This will result in low to no power situation. Many $1000 pumps have been replaced because this $12 banjo bolt went bad. Test it before you replace the pump!!!


5. Banjo Bolts:

A. You have several Banjo Bolts throughout the fueling system. These are the most restricting part of the fuel system. They are just a brass bolt with a hole drilled through the length of it and another that meets it drilled high on the threads to meet together. They allow fuel to pass through this hole when transitioning between fuel lines and the components on your truck. There are two on the fuel filter, two on the VP44 and two on the lift pump. Some people have drilled the hole out bigger on these bolts to allow more fuel and some have replaced them with High Pressure fittings and gotten rid of them all together. The only one you cant do anything with is the Fuel Pressure Regulator bolt, which is the outgoing line on the VP44. resulting in codes being thrown and eventually putting your VP44 into self protection/limp mode.

 

check this one, have a load of pic's

http://www.turbodieselregister.com/u...&albumid=17275

 

*Defective VP44 Engine Codes

Tampering with the The retrieval of codes does not constitute an engine diagnosis. However, there are some codes that usually indicate a defective injection pump. A current P1688 always means that the pump is bad, there is no further diagnosis required. Code P0216 is probably the most common code for VP-44 Pumps. If transfer pump pressure has been checked and is O.K., the injection pump is defective. Other codes that are less common are P0180, P0181, P0215, P0251, P0252, P0253, P0254, P0370, P1287, P1689 and P1690. These codes USUALLY, but not always indicate a defective pump. There are wiring and power checks to be performed if these codes are present. These codes relate to Dodge pickups only, and are not for any other ISB application.

 

Check out these threads for more info on these issues and the Timbo APPS. Seems as though a noise filter also fixes some of this.
https://www.dieselbombers.com/24-val...up-issues.html

https://www.dieselbombers.com/24-val...up-issues.html

https://www.dieselbombers.com/24-val...i-believe.html

https://www.dieselbombers.com/24-val...imbo-apps.html