#3 VP44 No Start

cumminscruiser said:

This is my 3rd VP44 in a few years less than 1000 miles. Couple months ago installed #3 it actually started, drove it a couple miles came home turned it off and it would not restart. I connected a Cumming tool 3163834 to the VP44 and it started.

Now a couple weeks later still no start.

I check the VP44 connector wires #5, 6 and 7.
No power between 5 and ground, no power between 5 and 6.

12v between 7 and 6, 12v between 7 and ground.

6 is grounded.

I retry the Cummins tool and no start.

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cumminscruiser said:

Update for today.

1) I waited a couple hours and retried the Cummins tool, still no start. I let it crank 15-20 times.

2) I plugged in the truck wiring harness and tried starting it again. To my surprise it started the first crank. arty018:

3) Fuel was low so I drove it about 5 miles to a gas station and back, I did not turn off the engine.

4) Drove the truck home, turned it off, I waited about 30 seconds and tried to start it but NO start again.

Fuel pressure stayed at 25 psi.

I'm lost :confused013:

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99coalroller24V said:

Fuel Pressure is entirely to high! I had mine set at 19 and it wouldnt start to well, turned it down to 18 and it starts everytime. 25 can cut the diaphragm in the VP

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Mopar1973Man said:

Fuel pressure is way too high. Get your pressure back down below 20 PSI. Cranking pressure should be 7-12 PSI optimal for quick easy starting.





Please show where this diaphragm is? It doesn't exist...
Mopar1973Man's Dodge Cummins Articles - Bosch VP44 Injection Pump Exploded View

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99coalroller24V said:

I have picked false knowledge up on here I guess. Always thought people said there was a diaphragm somewhere. The psi is too high like I said though


Not trying to start a War but,

" The most common mechanical failure of the VP44 pump is rupturing of the diaphragm in the front of the injection pump. The diaphragm ruptures allowing the timing piston to vibrate and damage the front cover until fuel bypasses. This will cause the dreaded check engine trouble code P0216. When this occurs your Bosch VP44 Injection Pump must be replaced. The rupturing of the diaphragm is caused by a poorly designed lift pump. When the lift pump does not supply the Injection pump with the correct amount of Fuel Pressure (a minimum of 5psi under load at wide open throttle) the diaphragm then doesn’t have enough positive pressure and ruptures. Dodge has recognized this problem as they will no longer even sell the lift pump that goes on the side of the block, they replace it with a unit that is now mounted in the tank. The average cost of having the lift pump put in the tank is about $800. "
-Thoroughbred Diesel

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I've seen several times where people will link back to performance pump builders and quoting where they say, "(Un-named) proved that 5 PSI, under load, made all the horsepower the VP44 pump could make, even with stock fuel lines, fittings and supply pump." This might be true but there is nothing ever said about the life span of the pump at these conditions. So... Please do not follow these performance crowds into destroying a perfectly good Bosch VP44 injection pump.

The fact still remains from Bosch the actual designer of the Bosch VP44 injection pump states that injection pump should return 70% of the fuel back to the fuel tank for cooling and lubrication purpose of the VP44. Being the only way a Bosch VP44 injection pump can do this is to have fuel pressure above 14 PSI to open the overflow valve. Then if the stock Bosch VP44 injection pump with an enhancement box say an Edge Comp on 5x5 can consume 15-20 GPH that means the stock 35 GPH pump cannot keep up with Bosch's design of 70% return volume. So this why products like AirDog, Raptor and FASS was created because they actually meet the demands of the Bosch VP44 injection pump. Then another fact that Bosch will let you know of is that diaphragm damage occurs from operating the Bosch VP44 injection pump at low fuel pressures. Making matters worse is that no Bosch injection re-builder will void warranty a VP44 injection pump with diaphragm damage. Dead give away that you had a bad lift pump or low fuel pressure problems.

Then the other fact is right from the Dodge Factory Service Manual has the minimum fuel pressures (picture at the top of the page). It even states the pressure that the overflow valve requires to open. Refer to the Overflow Valve Testing from the Dodge Factory Service Manual and see that the overflow valve should remain closed at 10 PSI and open by 14 PSI. So if the overflow valve is close by 10 PSI, then you extra cooling and lubrication just disappeared.

So ultimately it suggested to have a fuel system of no less than 100 GPH supply that can maintain a minimum pressure of 14-15 PSI at WOT. This will great extend the life of the VP44 because it keeps the electronics cooler longer and keeps the rotating parts lubricated properly.

So please people let the facts and information from the actual designers of the injection pump (Bosch) and engine (Cummins) provide you proper information for your fuel system for your engine. Don't be swayed by performance shops claim of high horse output with little fuel pressure. As I proved right here doesn't work for longevity of the VP44 injection pump...

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