Just trying to take all the steps to keep my vp going strong as I don't know its history as iv only owned the truck little over a month now. So with meter on DC engine running = 13.97 V switch to AC =.03 - .04 according to Mikes vid .1 is the limit ? so im hoping im good to go for a good while its a quik and ez check. with over 300,000 miles im assuming the VP maybe its been replaced but I don't know, it did still have a carter LP but its replaced now with a airdog 100.

I don't see any issues with your results. 0.03 to 0.04 VAC is fine. As for the VP44 I'm curious what fuel pressure you are seeing?

  Mopar1973Man said:

I don't see any issues with your results. 0.03 to 0.04 VAC is fine. As for the VP44 I'm curious what fuel pressure you are seeing?

It was at 18psi but then was getting the hard to start so I backed it down to 15 psi to able the starts a little easier as far as the VP psi output I haven't seen any test for that are there any ? Maybe I should crank the LP psi and do the relay ? I was thinking while at cruising rpms the fuel is going through the VP isn't that suffiecient to keeping the pump cool and while at idle at 15 psi the return is allowing the fuel to pass and cool ? im no expert by a long shot so plz educate me on this.

Ok. Lets clear this up some more. What is...

[*]Crank Fuel Pressure

[*]Idling fuel pressure

[*]WOT fuel pressure at highway speed

Give you an idea mine as of lately is...

[*]9-11 PSI Crank Fuel Pressure (bouncing from the ECM modulation of power)

[*]18 PSI Idling fuel pressure

[*]16 PSI WOT fuel pressure at highway speed

Yo need at least 14 PSI under full load to keep return flow happening for the VP44 for the cooling and lubrication of the Bosch VP44 injection pump. As for cranking pressure you can test it by pulling the fuel pump relay and cranking on it and see what the pressure is.

Notes

This will set a P1689 code so don't panic. Just reset the code with your code reader.

The rest of the numbers are seen on the highway.

What is the spec on the AC thing? How much is too much before it causes issues?

  Mopar1973Man said:

Ok. Lets clear this up some more. What is...

[*]Crank Fuel Pressure

[*]Idling fuel pressure

[*]WOT fuel pressure at highway speed

Give you an idea mine as of lately is...

[*]9-11 PSI Crank Fuel Pressure (bouncing from the ECM modulation of power)

[*]18 PSI Idling fuel pressure

[*]16 PSI WOT fuel pressure at highway speed

Yo need at least 14 PSI under full load to keep return flow happening for the VP44 for the cooling and lubrication of the Bosch VP44 injection pump. As for cranking pressure you can test it by pulling the fuel pump relay and cranking on it and see what the pressure is.

Notes

This will set a P1689 code so don't panic. Just reset the code with your code reader.

The rest of the numbers are seen on the highway.

As far as cranking pressures you hit it, it bounces 9-11. Like I said iv backed down pressure it idles 14.5 - 15 psi . Ive never put my foot to the floor but at 16-1700 rpm about 65mph its about 12 - 13 psi and seem to be at that psi at even lighter throttle . I seem to remember when the idle psi was at 18psi it would cruise at 15 - 16psi . I just don't wanna start doin wot runs and get bugs coming out that I don't want to see lol, I did run it about 3/4 throttle one time and pressures stayed at about 13 and seemed to loosen or wake things up in the motor because it has ran smoother and accelerates better and gauge on turbo seems to spool up better than it had before and probably because it had its first drink with 2 cycle lube mixed in it. Im a little lost on the cranking pressure test you just described by pulling the relay ? Will I then need to hook a gauge to the VP to test the pressures coming out of the VP ?

- - - Updated - - -

  Mopar1973Man said:

Ok. Lets clear this up some more. What is...

[*]Crank Fuel Pressure

[*]Idling fuel pressure

[*]WOT fuel pressure at highway speed

Give you an idea mine as of lately is...

[*]9-11 PSI Crank Fuel Pressure (bouncing from the ECM modulation of power)

[*]18 PSI Idling fuel pressure

[*]16 PSI WOT fuel pressure at highway speed

Yo need at least 14 PSI under full load to keep return flow happening for the VP44 for the cooling and lubrication of the Bosch VP44 injection pump. As for cranking pressure you can test it by pulling the fuel pump relay and cranking on it and see what the pressure is.

Notes

This will set a P1689 code so don't panic. Just reset the code with your code reader.

The rest of the numbers are seen on the highway.

As far as cranking pressures you hit it, it bounces 9-11. Like I said iv backed down pressure it idles 14.5 - 15 psi . Ive never put my foot to the floor but at 16-1700 rpm about 65mph its about 12 - 13 psi and seem to be at that psi at even lighter throttle . I seem to remember when the idle psi was at 18psi it would cruise at 15 - 16psi . I just don't wanna start doin wot runs and get bugs coming out that I don't want to see lol, I did run it about 3/4 throttle one time and pressures stayed at about 13 and seemed to loosen or wake things up in the motor because it has ran smoother and accelerates better and gauge on turbo seems to spool up better than it had before and probably because it had its first drink with 2 cycle lube mixed in it. Im a little lost on the cranking pressure test you just described by pulling the relay ? Will I then need to hook a gauge to the VP to test the pressures coming out of the VP ?

- - - Updated - - -

  ISX said:

What is the spec on the AC thing? How much is too much before it causes issues?

.1 VAC Mike has a vid of the test, its in the article section on what 4 things will hurt the VP. I hope I remembered that correctly.

  ISX said:

What is the spec on the AC thing? How much is too much before it causes issues?

Optimal is to have ZERO AC noise at all. But you got to remember the logic chips in the computers don't like AC noise. I guesstimate roughly 0.1 AC volts to be excessive for the system. Like I said optimally you want ZERO AC voltage. Typical Alternators I've tested run about 0.01 to 0.03 VAC.

  Cheatham said:

As far as cranking pressures you hit it, it bounces 9-11. Like I said iv backed down pressure it idles 14.5 - 15 psi . Ive never put my foot to the floor but at 16-1700 rpm about 65mph its about 12 - 13 psi and seem to be at that psi at even lighter throttle . I seem to remember when the idle psi was at 18psi it would cruise at 15 - 16psi . I just don't wanna start doin wot runs and get bugs coming out that I don't want to see lol, I did run it about 3/4 throttle one time and pressures stayed at about 13 and seemed to loosen or wake things up in the motor because it has ran smoother and accelerates better and gauge on turbo seems to spool up better than it had before and probably because it had its first drink with 2 cycle lube mixed in it. Im a little lost on the cranking pressure test you just described by pulling the relay ? Will I then need to hook a gauge to the VP to test the pressures coming out of the VP ?

WOT will not hurt it at all with a empty truck. It's actually a good thing to get the engine nice and hot now and then to burn the carbon off the injectors and clean up the cylinders. Carbon starts to burn at 1,000*F so getting 1,100*F EGT's will clean up the nozzles and keep it running good. Not to mention at WOT or very heavy throttle you maximize the VP44 injection pressures and blow any carbon out of the nozzles as well. You should aim for the lowest pressure at 14 PSI this way to keep the VP44 cooled. As for the cranking test...

http-~~-//www.youtube.com/watch?v=NCJjMzRImpA

Ill be mainly driving empty no loads nor trailer so ill give the throttle a good stretch, im in flat area except for a tall bridge which I hope the VP will never go out on me on anyways the tall long bridge is a good test road to put a load on a vehical, ill have to find your diag. to the fuel pump relay and bump the pressure back up. the truck is all stock , no programmers, just straight piped.

+1 to Mikes numbers. I see the same with my set-up. The only time I ever had starting problems is when I had the the new lift pump on a bad injection pump. Once I replaced the VP44 the hard start issues went away.

  Cheatham said:

Ill be mainly driving empty no loads nor trailer so ill give the throttle a good stretch, im in flat area except for a tall bridge which I hope the VP will never go out on me on anyways the tall long bridge is a good test road to put a load on a vehical, ill have to find your diag. to the fuel pump relay and bump the pressure back up. the truck is all stock , no programmers, just straight piped.

If you can get a load on it it would help you get the temp up and hold above 1000*. The longer you do that the easier it will burn the carbon off. When I bought mine new in 01 I strapped a 12k # trailer on it that day and took off. 285k miles later, she pulls better than that first day. The owners manual even recommends loading it up and driving to break it in. you wont hurt it by loading it up and driving it.

  Cheatham said:

Ill be mainly driving empty no loads nor trailer so ill give the throttle a good stretch, im in flat area except for a tall bridge which I hope the VP will never go out on me on anyways the tall long bridge is a good test road to put a load on a vehical, ill have to find your diag. to the fuel pump relay and bump the pressure back up. the truck is all stock , no programmers, just straight piped.

You mean this one... http://articles.mopar1973man.com/2nd-generation-24v-dodge-cummins/25-fuel-system/49-fuel-pressure-specification-for-bosch-vp44-injection-pumps

Will a Autozone RL44 relay work ? it has 85 86 87 an 30 There is no 87 and 87a only 87.

Got the proper relay from autozone 19273 wired it up cranked fuel psi back up to 19 and it starts with just a quik blip of the key. I cut and spliced the wires from the LP so I didn't have to cut into the factory wiring. I think I will do like my drag car and drop the tank install a #8 bulkhead at the Bottom lowest point and move the airdog 100 closer to the tank and replace the banjos with AN fittings extend the wires, the pump will then be gravity fed and work ezr and supply all the fuel it needs and maybe add a t fitting to sump the tank now and then to keep it clean.

- - - Updated - - -

Got the proper relay from autozone 19273 wired it up cranked fuel psi back up to 19 and it starts with just a quik blip of the key. I cut and spliced the wires from the LP so I didn't have to cut into the factory wiring. I think I will do like my drag car and drop the tank install a #8 bulkhead at the Bottom lowest point and move the airdog 100 closer to the tank and replace the banjos with AN fittings extend the wires, the pump will then be gravity fed and work ezr and supply all the fuel it needs and maybe add a t fitting to sump the tank now and then to keep it clean.