HI, I was reading the article on Fuel pressures for the VP44. I have a couple of questions.
My truck is a 1999 and has 87,000 miles, the stock lift pump went out in 07, 57,000 miles and was retrofitted with a new lift pump in the tank, along with a new filter assembly. The truck was running good, the other day I stopped for about 30 minutes got back in the truck, started right up idled perfect, but stumbled above an idle, so I idled home, changed the fuel filter, had a very hard time starting it. I primed the system about 5 times before trying to start it, it finally started but real rough. The next day I rented a fuel pressure gauge, I have 10 lbs at the filter, I checked fuel at the pump have fuel, no fuel except #4 injector, 12 volts at the VP44. 2-codes at first, PO252-P1688, now just the P1688.
So I was set to order a pump, then I wanted to check the pressure one more time, I still have 10lbs, but when cracking it drops off to 0, I thought the other day I had 10 lbs all the time, but not sure anymore.

Questions

1st the pressures listed in your article are those for the stock frame mounted lift pumps or the retrofitted one in the tank like mine.

2nd, should my pump be pumping when cracking, I know the pump comes on for only 30 seconds when you bump the switch, but how often does it run when the truck is running?

3rd, with the codes I listed does it sound as though the pump is dead, and do they go out like that?
 

1688 is bad injection pump. And if I remember right, the intank pumps are a flow test not a pressure. I know this is true on the 3rd gens but not certain on the 2nd.

The lift pump should prime for about a second when you first turn the key on. It will not run while you are cranking but should run continuously after the truck has started. I am not sure what the specs are for the stock lift pumps to be honest. Bosch does not want anything less than 10psi getting to the injection pump though. Anything less than 10 is damaging and as you can see, results in taking the injection pump out. Most reman injection pumps need at least 10psi or it will void the rebuild warranty, at least thats how DAP is.

I would strongly suggest going with a LP/VP44 combo from somewhere like DAP. Usually they have really good combo deals and that way you wont have to worry about the lift pump system failing on a new injection pump.

When I first got my truck I did not drive it until I got rid of the stock lift pump and got the fuel pressure gauge installed. It should be a minimum of 14 to keep the VP cool/ not overheat.

 

My strong recommends;

 

Good aftermarket FP gauge and lift pump on the frame

 

1/2 inch fuel lines all the way... no bajo bolts.

 

Get rid of the intank screens and fuel filter in the bottom of the tank module,

 

Put on your own filter before the lift pump to keep it changed and happy.

 

One qt. of stroke oil every new tank of fuel.

Edited March 2, 201411 yr by JAG1

The lift pump should prime for about a second when you first turn the key on. It will not run while you are cranking but should run continuously after the truck has started. I am not sure what the specs are for the stock lift pumps to be honest. Bosch does not want anything less than 10psi getting to the injection pump though. Anything less than 10 is damaging and as you can see, results in taking the injection pump out. Most reman injection pumps need at least 10psi or it will void the rebuild warranty, at least thats how DAP is.

I would strongly suggest going with a LP/VP44 combo from somewhere like DAP. Usually they have really good combo deals and that way you wont have to worry about the lift pump system failing on a new injection pump.

Mine runs around 1/2 normal psi while cranking. Mopar Man has a video showing how his pump does push fuel while cranking. 

HI, I was reading the article on Fuel pressures for the VP44. I have a couple of questions.

My truck is a 1999 and has 87,000 miles, the stock lift pump went out in 07, 57,000 miles and was retrofitted with a new lift pump in the tank, along with a new filter assembly. The truck was running good, the other day I stopped for about 30 minutes got back in the truck, started right up idled perfect, but stumbled above an idle, so I idled home, changed the fuel filter, had a very hard time starting it. I primed the system about 5 times before trying to start it, it finally started but real rough. The next day I rented a fuel pressure gauge, I have 10 lbs at the filter, I checked fuel at the pump have fuel, no fuel except #4 injector, 12 volts at the VP44. 2-codes at first, PO252-P1688, now just the P1688.

So I was set to order a pump, then I wanted to check the pressure one more time, I still have 10lbs, but when cracking it drops off to 0, I thought the other day I had 10 lbs all the time, but not sure anymore.

Questions

1st the pressures listed in your article are those for the stock frame mounted lift pumps or the retrofitted one in the tank like mine.

2nd, should my pump be pumping when cracking, I know the pump comes on for only 30 seconds when you bump the switch, but how often does it run when the truck is running?

3rd, with the codes I listed does it sound as though the pump is dead, and do they go out like that?

 

 

#1. I am not sure which article you were reading, but keeping the pressure between 14 and 20 is safe level to run. This insures adequate fuel for cooling and lubricating the VP. the 1688 code is for the computer, FPCM, on the VP. Maintaining the pressure above 14 will keep the most fuel circulating thru the VP. I personally run mine at 19 at Idle and it drops to near 16 at WOT. A fuel pressure gauge is recommended to monitor the pressure so you know when there is a problem. Low pressure puts a lot of wear on the VP.

 

#2. Your pump will run when cranking. The ECM will cycle it on and off during cranking reducing the pressure by about 50%. After cranking the lift pump will run constantly.

 

#3. The 1688 code is for failure of the FPCM on the VP. You might clear the codes, clean up the connector on the pump, and try starting it again, If the code comes back or it wont run the VP is shot. And yes a pump can fail at any time. The in tank pump is the likely culprit. My guess would be under WOT your pressure is near 0. I had one in mine and had trouble with it less than 6 months later. They are no better than the OE pump on the engine. As stated before, you really need a fuel pressure gauge.

1688 is bad injection pump. And if I remember right, the intank pumps are a flow test not a pressure. I know this is true on the 3rd gens but not certain on the 2nd.

Thanks, yes I did read a blimp put out by ALLDATA that on the retrofitted in the tank pumps you can't just test on pressure, its more on flow the sheet said to use the testing procedures for a 2005 Dodge diesel, which I haven't located yet., No matter what I plan on installing a gauge I just need to see whats better mechanical or electric and where to install after the filter.

Thanks

The lift pump should prime for about a second when you first turn the key on. It will not run while you are cranking but should run continuously after the truck has started. I am not sure what the specs are for the stock lift pumps to be honest. Bosch does not want anything less than 10psi getting to the injection pump though. Anything less than 10 is damaging and as you can see, results in taking the injection pump out. Most reman injection pumps need at least 10psi or it will void the rebuild warranty, at least thats how DAP is.

I would strongly suggest going with a LP/VP44 combo from somewhere like DAP. Usually they have really good combo deals and that way you wont have to worry about the lift pump system failing on a new injection pump.

Thank You, a rebuilder in Oakland CA, requires the lift pump to be changed also; however if you already have the retrofit pump in the tank, they will give the 12 month warrenty.

#1. I am not sure which article you were reading, but keeping the pressure between 14 and 20 is safe level to run. This insures adequate fuel for cooling and lubricating the VP. the 1688 code is for the computer, FPCM, on the VP. Maintaining the pressure above 14 will keep the most fuel circulating thru the VP. I personally run mine at 19 at Idle and it drops to near 16 at WOT. A fuel pressure gauge is recommended to monitor the pressure so you know when there is a problem. Low pressure puts a lot of wear on the VP.

 

#2. Your pump will run when cranking. The ECM will cycle it on and off during cranking reducing the pressure by about 50%. After cranking the lift pump will run constantly.

 

#3. The 1688 code is for failure of the FPCM on the VP. You might clear the codes, clean up the connector on the pump, and try starting it again, If the code comes back or it wont run the VP is shot. And yes a pump can fail at any time. The in tank pump is the likely culprit. My guess would be under WOT your pressure is near 0. I had one in mine and had trouble with it less than 6 months later. They are no better than the OE pump on the engine. As stated before, you really need a fuel pressure gauge.

I read a article from ALLDATA that if you have a 1998.5 to 2002 Dodge with the retrofitted pump in the tank you can't go just by pressure, it states you have to use the test procedures for a 2005 Dodge, which I haven' found yet.

When I checked the pressure when cracking yesterday it dropped off to zero so that concerned me.

I have cleared the codes a few times, but I haven't cleaned the plug I will try that, I also read today that you can try unplugging the lift pumpcuircut breaker and try to start the truck the article stated that if there is a crack internal in the VP the lift pump does not let it buld enough pressure in the pump to start it?

No matter I plan on installing a gauge just need to see which is better mechaical or electric and where and how to install it

 

Thank You

Mine runs around 1/2 normal psi while cranking. Mopar Man has a video showing how his pump does push fuel while cranking. 

Thanks

I read a article from ALLDATA that if you have a 1998.5 to 2002 Dodge with the retrofitted pump in the tank you can't go just by pressure, it states you have to use the test procedures for a 2005 Dodge, which I haven' found yet.

When I checked the pressure when cracking yesterday it dropped off to zero so that concerned me.

I have cleared the codes a few times, but I haven't cleaned the plug I will try that, I also read today that you can try unplugging the lift pumpcuircut breaker and try to start the truck the article stated that if there is a crack internal in the VP the lift pump does not let it buld enough pressure in the pump to start it?

No matter I plan on installing a gauge just need to see which is better mechaical or electric and where and how to install it

 

Thank You

 

I was not aware of the not being able to use a pressure test on the in tank pump. I do know that after I added a booster pump to the fuel system and got the pressure up, the issues I was having, dead pedal and bucking, went away. 

FLOW TEST.
1. Remove the fuel pump supply banjo fitting from the fuel injection pump.
2. Install Miller Tool #9014 fuel system test fitting into the fuel injection pump.
3. Connect one end of a section of fuel hose to the test fitting.
4. Put the other end of the fuel hose into an empty fuel container.
5. Use the scan tool to actuate the fuel lift pump.
6. While the lift pump is running, move the fuel hose from the fuel canister into a 1000ml graduated cylinder for 10
seconds.
7. Read and record the amount of fuel in the graduated cylinder after 10 seconds.
8. If you have more than 430ml in the graduated cylinder after 10 seconds, the test has successfully passed.
9. If you have less than 430ml of fuel in the graduated cylinder, inspect the fuel supply line from the fuel tank to the
fuel filter housing and the fuel supply line between the fuel filter housing and the high pressure fuel pump for signs
of damage, replace as necessary. If no damage is found, replace the fuel filter and retest.
10.Verify the Screened Banjo Bolt at the outlet of the fuel filter is free of debris. If debris is found, rinse screen with
water, blow dry and reinstall. Retest vehicle. If flow meets specification then trace back the source of debris, if flow
is still below spec repair damaged component.
DR ENGINE - ELECTRICAL DIAGNOSTICS - DIESEL 9 - 1583
11. If reading is still less than 430ml in 10 seconds, remove the fuel tank and fuel tank module. Inspect for damage
and/or debris in and around the fuel tank module. If module is damaged, replace and retest.
12. If the module is not damaged, replace the fuel lift pump and retest to confirm fix.

 

 

The transfer pump is self-priming: When the key is

first turned on (without cranking engine), the pump

will operate for approximately 2 seconds and then

shut off. The pump will also operate for up to 25 seconds

after the starter is engaged, and then disengaged

and the engine is not running. The pump

shuts off immediately if the key is on and the engine

stops running.

The fuel volume of the transfer pump will always

provide more fuel than the fuel injection pump

requires. Excess fuel is returned from the injection

pump through an overflow valve. The valve is located

on the side of the injection pump (Fig. 52). It is also

used to connect the fuel return line to the side of the

injection pump. This valve opens at approximately 97

kPa (14 psi) and returns fuel to the fuel tank

through the fuel return line.

Edited March 2, 201411 yr by mopartechnician

I was not aware of the not being able to use a pressure test on the in tank pump. I do know that after I added a booster pump to the fuel system and got the pressure up, the issues I was having, dead pedal and bucking, went away. 

Is your lift pump in the tank or on the frame, if its in the tank does your auxiliary pump pump through the tank pump, and how did you mount your gauge

Thanks

Is your lift pump in the tank or on the frame, if its in the tank does your auxiliary pump pump through the tank pump, and how did you mount your gauge

Thanks

I installed an ADII bout 3.5 years ago. Dodge installed my in tank about 7 years ago. When I started having trouble I installed a booster pump on the frame rail in front of the tank. So I was pulling fuel thru the in tank pump. It worked fine for a long time. I just kept worrying that one of them would go and I would loose all fuel press. Did not know much about them back then. 

Well the error code P1688 isn't good the VP44 is indeed shot. But why would you hassle with unknown shop I know DAP sell lift pump and VP44 combo packages for under $1,000... Even better yet its a FASS lift pump.

 

http://www.dieselautopower.com/product-p/vp44-combo-fass.htm

Well the error code P1688 isn't good the VP44 is indeed shot. But why would you hassle with unknown shop I know DAP sell lift pump and VP44 combo packages for under $1,000... Even better yet its a FASS lift pump.

 

http://www.dieselautopower.com/product-p/vp44-combo-fass.htm

Yes.... and I heard those in tank pumps are about as good as sending air bubbles thru your kids aquarium tank.

Sorry about that comment..... I just couldn't resist   but, I wouldn't think of a new VP until my fuel supply system was revamped properly. That means no short cuts and doing like everyone else around here is talking about.

Well the error code P1688 isn't good the VP44 is indeed shot. But why would you hassle with unknown shop I know DAP sell lift pump and VP44 combo packages for under $1,000... Even better yet its a FASS lift pump.

 

http://www.dieselautopower.com/product-p/vp44-combo-fass.htm

Thanks, I have never heard of DAP, I'm in CA, are their pumps good, I don't want to be changing them regularly? do they also put a rebuilt computer on top of the new pump, one online vendors installs used computers on their base pump and then theres options from there?

When dodge retrofitted my pump, on the line from the filter to the pump they have a short section of neoprem hose, I asume when they changed the filter assembey the lines were a different length, I was thinking about putting a tee there for a gauge either manual or electric, any thoughts?

 

Tanks Again

DAP is a reputable dealer. I know one of their injection pump suppliers is industrial injection. The computers on top are new. The online vendor sounds like Blue Chip?? FYI I went through 2 Blue Chip pumps in less than a month. I now have an industrial injection that I am more than pleased with. Long story short, call DAP and get an injection pump lift pump combo. You won't be disappointed with service or quality

Learn something new every day I guess. Didnt realize the lp pumped while cranking. Thanks for the info. Definitely go with DAP. Good people and good prices. I am using a VP from them and its been great.

Here is my collection of Certified Bosch rebuilders...

http://articles.mopar1973man.com/2nd-generation-24v-dodge-cummins/25-fuel-system/247-bosch-certified-vp44-injection-pump-rebuilders

 

I've dealt with Vulcan Performance and Diesel Auto Power both and have good pumps. (Industrial Injection).

FLOW TEST.

1. Remove the fuel pump supply banjo fitting from the fuel injection pump.

2. Install Miller Tool #9014 fuel system test fitting into the fuel injection pump.

3. Connect one end of a section of fuel hose to the test fitting.

4. Put the other end of the fuel hose into an empty fuel container.

5. Use the scan tool to actuate the fuel lift pump.

6. While the lift pump is running, move the fuel hose from the fuel canister into a 1000ml graduated cylinder for 10

seconds.

7. Read and record the amount of fuel in the graduated cylinder after 10 seconds.

8. If you have more than 430ml in the graduated cylinder after 10 seconds, the test has successfully passed.

9. If you have less than 430ml of fuel in the graduated cylinder, inspect the fuel supply line from the fuel tank to the

fuel filter housing and the fuel supply line between the fuel filter housing and the high pressure fuel pump for signs

of damage, replace as necessary. If no damage is found, replace the fuel filter and retest.

10.Verify the Screened Banjo Bolt at the outlet of the fuel filter is free of debris. If debris is found, rinse screen with

water, blow dry and reinstall. Retest vehicle. If flow meets specification then trace back the source of debris, if flow

is still below spec repair damaged component.

DR ENGINE - ELECTRICAL DIAGNOSTICS - DIESEL 9 - 1583

11. If reading is still less than 430ml in 10 seconds, remove the fuel tank and fuel tank module. Inspect for damage

and/or debris in and around the fuel tank module. If module is damaged, replace and retest.

12. If the module is not damaged, replace the fuel lift pump and retest to confirm fix.

 

 

The transfer pump is self-priming: When the key is

first turned on (without cranking engine), the pump

will operate for approximately 2 seconds and then

shut off. The pump will also operate for up to 25 seconds

after the starter is engaged, and then disengaged

and the engine is not running. The pump

shuts off immediately if the key is on and the engine

stops running.

The fuel volume of the transfer pump will always

provide more fuel than the fuel injection pump

requires. Excess fuel is returned from the injection

pump through an overflow valve. The valve is located

on the side of the injection pump (Fig. 52). It is also

used to connect the fuel return line to the side of the

injection pump. This valve opens at approximately 97

kPa (14 psi) and returns fuel to the fuel tank

through the fuel return line.

I did the test twice, I didn't have the fittings, but what I did is to attach a clear plastic hose to the outlet line from the filter, i was by myslef, so I tested it by once holding the hose and once the air was out I held it with my thumb, then I shut off the key and then tapped the starter again for the duration of the pump cycle, the other time i just set the hose in the container , and just let the air purge both times they were close to the same results

test 1=1.598 liters---56 ounces

test 2=1.568 liters-----55 ounces

 

the reason for the air was because of the long tube once it filled the air was gone, so I may have lost an ounce or so in the process. I used an out board motor oil fill bottle to measure with I pumped into a gallon container and transfered to the measuring bottle.

 

At the same loacation where the dealer had inserted a 3" piece of neoprime hose from the filter line to the fuel fitting by the banjo bolt on the pump I tested the pressure there just to check before I tested at the filter housing, I still only got 10 lbs.

 

Thanks Dan