This problem has me stumped!

[my99ram]

First a little background.

After my last trip of about 1200 miles I decided to upgrade my lift pump because the old (new) carter was misbehaving (again).  I replace the original carter before last years 7000 mile trip, fuel filter also.  Worked flawless as far as carters do. Ran about 7-9lbs FP until about 300 miles from home.  Pressure went to '0' for about 10 seconds while entering the freeway and then returned to normal.  When I got home I changed the fuel filter and then all was well.  This year the carter went to '0' again for about a minute or so up in Sandpoint, Idaho and then came back up to 6-9 lbs. Made it back home ok and changed out the carter to a fuel boss.

After changing to the fuel boss I took the truck for a test drive.  I went about 1/4 of a mile and while driving about 40mph the engine shut down.  I coasted to the side of the road and started the truck back up.  Check engine light came on.  Fuel boss gives me a constant 17 -19 fuel pressure.

Ok, go to O'reily, read codes P1689, P1690.  Crap, never had codes before.

Checked online at other dodge sites (hadn't found this site before ordering the VP, crap) they said VP44 is bad. Crap!  I figured I needed a new VP44 because I never had fuel pressure readings above 9lbs with the carter. Mostly between 7-9.  Sometimes 3-4.

Replaced VP44.

Truck running again. Happy again. I don't use the truck much around town. Mostly for trips. I have a slide in camper. 

Had about 100 miles on the new VP44. Wednesday the 21st. Went to get some lumber for a stair project.  On my way home, about 1/4 mile from the store and going 45 mph the truck shuts off again, engine just dies.  Coast to the side of the road.  Truck won't start. Wait about 5 min. Truck starts and I make it home. I park in the driveway.  About 4 hours later I go to start the truck to put it in the garage. It won't start and check engine light is back on.  I bought a code reader and it says P1689.

Today I go to see if the truck will start.  It starts right up. Starting pressure is about 7 with the carter until the fuel boss kicks in and then 17.

 

What can I check to get to the bottom of this problem?  Would it be something the fuel boss is causing or just coincidence?  I have never had any problems with the truck except a bad ABS sensor in the differential and now this stumper.

 

[Marcus2000monster]

Where did yo get your new VP? 

[Guest 04Mach1]

1 hour ago, my99ram said:

 

Today I go to see if the truck will start.  It starts right up. Starting pressure is about 7 with the carter until the fuel boss kicks in and then 17.

 

 

 

I'm not familiar with the Fuel Boss but are you supposed to still use the Carter pump with a Fuel Boss? If I'm reading correct @my99ram still has the Carter in conjunction with the the Fuel Boss which seems like would cause a severe restriction for the Fuel Boss to suck through.

 

Seems to me that the Carter should be by-passed with the Fuel Boss just like we would do with an Airdog or Fass.

[my99ram]

1 hour ago, Marcus2000monster said:

Where did yo get your new VP? 

Thoroughbred diesel

34 minutes ago, 04Mach1 said:

 

I'm not familiar with the Fuel Boss but are you supposed to still use the Carter pump with a Fuel Boss? If I'm reading correct @my99ram still has the Carter in conjunction with the the Fuel Boss which seems like would cause a severe restriction for the Fuel Boss to suck through.

 

Seems to me that the Carter should be by-passed with the Fuel Boss just like we would do with an Airdog or Fass.

Carter only is used for initial startup then turns off using a hobbs switch.  Fuel boss then takes over.

[IBMobile]

1 hour ago, my99ram said:

Would it be something the fuel boss is causing or just coincidence? 

It's not the fuel boss causing this problem.   P1689 no communication between ECM and VP44  

 

The same thing happened to my truck when the VP44 failed just north of Riggens, ID.   It was running, died, started ran then died.  Me and @Mopar1973Manreplaced it with a pump from DAP.  All has been well since.    

 

Check your connections and wiring between the VP44 and ECM.  If they are OK then the electronics in the VP44 may be bad.

 

By the way I don't use the electric pump when starting, I have the fuse for it pulled and I have it on a relay

. 

 

 

[Guest 04Mach1]

47 minutes ago, my99ram said:

Thoroughbred diesel

Carter only is used for initial startup then turns off using a hobbs switch.  Fuel boss then takes over.

Thanks. I've heard great things about Fuel Boss but have yet to see one in person.

[Marcus2000monster]

I would go through your wiring and make sure everything looks good first. It is possible that you got a bad VP44. 

[Dieselfuture]

I find it hard to believe original VP same problem another new VP same problem, I would not point fingers at VP just yet. Have you checked your AC noise from alternator and just in general. That could be the cause failing ECM in the first place. Hopefully it's just some ground wires or wires in general. After you do your AC noise check highly recommended to do the ground mod.

[Mopar1973Man]

9 hours ago, my99ram said:

I bought a code reader and it says P1689.

 

Try replacing the fuel pump relay in the PDC.

[Me78569]

the lift pump going on and off randomly makes me think you have a wiring issue or an ecm that is giving up the ghost.

[my99ram]

13 hours ago, Dieselfuture said:

I find it hard to believe original VP same problem another new VP same problem, I would not point fingers at VP just yet. Have you checked your AC noise from alternator and just in general. That could be the cause failing ECM in the first place. Hopefully it's just some ground wires or wires in general. After you do your AC noise check highly recommended to do the ground mod.

Thanks, I have done the ground mod. I did it on Sept 26th 2018. My readings before - 037.6mv and after - 017.5 mv.

14 hours ago, Marcus2000monster said:

I would go through your wiring and make sure everything looks good first. It is possible that you got a bad VP44. 

Thanks,

Will check the wiring.

13 hours ago, Mopar1973Man said:

 

Try replacing the fuel pump relay in the PDC.

That is the first thing I am going to try, then wiring next per the article DTC P1689.

[int3man]

14 hours ago, Mopar1973Man said:

 

Try replacing the fuel pump relay in the PDC.

I chased intermittent Engine shutting off.  It was the relay.  Cheap fix!!

 

Michael

[my99ram]

Thanks Michael, I hope my fix is easy too!

[my99ram]

I'll replace the relay first and report back if it works or not.  Might take awhile as I don't drive the truck that much in the winter.

[dripley]

You can just swap a relay from the horn or such to test.

[my99ram]

Swapped it with the horn relay.  Went for a 10 mile test.  No problems, ran fine.  However, it started and ran fine for about 100 miles after the first time it quit before it quit the second time.

I hate intermittent problems.

Edited December 6, 2018 by my99ram

[dripley]

Did the horn work?

[my99ram]

Yup, horn worked.

On 11/26/2018 at 10:56 PM, IBMobile said:

@Mopar1973Man

 

 

 

I have a question concerning this article.  Does this mod replace the original fuel pump relay or an addition too?

I printed it out and read it but can't quite wrap the old grey matter around it, yet.  More thinking needed.....

[dripley]

6 hours ago, my99ram said:

Yup, horn worked.

I have a question concerning this article.  Does this mod replace the original fuel pump relay or an addition too?

I printed it out and read it but can't quite wrap the old grey matter around it, yet.  More thinking needed.....

This is for an after market electfic lift pump. The oe pump had no relay and got its power thru the ECM. I slso see you have fuel boss so you would have no need for this anyway.

[IBMobile]

12 hours ago, my99ram said:

I have a question concerning this article.  Does this mod replace the original fuel pump relay or an addition too?

The relay is needed if there is an electric lift pump used.  The stock system has the  ECM powering the lift pump directly.  With this mod the power for the pump is drawn from the PDC and not the ECM.

 

I too have a Fuel Boss lift pump and have the electric lift pump disconnected.   I only run the electric lift pump to prime the system.