What kind of lift pump are you running? Is it still the oe pump on the block? How are you checking your codes? The 1689 code is leaning toward computer issues. It your are still stock on the lift pump it could be bad and providing enough pressue for the vp. Do you have a fuel pressure gauge?

 

Here is the diagnostics...
Mopar1973Man's Dodge Cummins Articles - P1689 No Communication Between ECM And VP44

 

I have no idea which lift pump it is, im assuming it was a stock replacement, i was told it has a new lift pump as well as a new vp44. i do not have a fuel pressure gauge, i just bought the truck yesterday.

 

A restricted filter might cause. A pressure gauge at VP44 is required to diagnois.

 

Which would still lead to the path of the P1689 code because once the pressure falls below 14 PSI the overflow valve start closing and the cooling fuel is gone so the computer can overheat. Hence P1689...

But its funny no one has ever seen a P0168... But the computer don't tolerate heat very well.

Mopar1973Man's Dodge Cummins Articles - P0168 High Injection Pump Fuel Temperature

 

When you say restricted filter which do you mean? The fuel filter?

 

Im going to go through as many of the steps in the link you supplied me Mopar1973man, Im no diesel tech, and honestly this is my first diesel, so i have no idea how to tst voltage and all the other stuff you alluded to, but i will check all the grounds and electrical connections.

 

Also when talking to the mechanic who serviced the truck before i bought it he said he replaced the vp44 as well as replacing the lift pump, he said he put in the upgraded in tank lift pump??? i know little about the fuel systems in this truck, but he said the old one was mounted on the engine somewhere but the new one is mounted in/on the tank?? What should i look for to verify this?

 

If you bump the starter and not start the engine, you should be able to hear it running in the tank. They arent any better than the oe lift pump. I had one and it was bad news. Cost me alot more than installing a top of the line AD or Fass. With me doing the work that is.

I yu can get acces to a test gauge, there is a port on the VP at the inlet line. It is a schrader valve and you can connect one there to check the pressure. you still want to get a fuel so you can monitor it all the time.

 

he said he put in the upgraded in tank lift pump???

Oh No!

You need to install a fuel pressure gauge! Then once you do that you need to keep the fuel pressure above 14 PSI for good VP44 health.

Mopar1973Man's Dodge Cummins Articles - Fuel Pressure Specification For Bosch VP44 Injection Pumps

 

Sounds good, I intend to get a fuel pressure gauge ASAP so check the pressure. or at the very least have a pressure gauge check to make sure im within specs before i get the time to add the permanent gauge.

 

Make sure you check both pressures... Idle and WOT at highway speed. If it drops below 10 PSI its a instant fail.

 

problem is most times when i try and go WOT the truck will shut down under hard accel and throw the 1689 code. It runs perfect up until the point where i stomp on it and it starts building max boost.

 

So the truck blew a brake line and i just got it back from the shop, I started to test the truck to see how often it throws the cel. 1689 every time.

It will cut the power for a few seconds EVERY time it hits 2500ish rpms, it only happens at 2500rpm's. why would it be doing it at a specific rpm? I thought for a while it was only doing it under hard acceleration but its cutting out at 2500??????

Any ideas???

 

Any one have any ideas? Tested the truck some more and it will also throw the code while revving the engine in neutral, so its not specific to driving under a load, it will throw the code everytime it hits 2500rpms, under load or in neutral.

 

Well the trucks at the shop now, ill let you guys know what the find out.

 

Mechanic says they tested everything and the Ecu is shot, So i bought a new Ecu, and they will be programming it and installing it tomorrow, we shall see if this was the problem........

 

Sounds like you need to let them buy the truck back and buy one that has a better background.


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Thats not an option, Im keeping the truck, Either way i don't care what it cost, I just want the truck fixed and running the way it should.

 

Let us know what they find. Best of luck!


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