Another bad VP?

[QuadRunnerJake]

I will get intermittent dead pedal when driving above say 60mph with light pedal pressure.. I also get this weird hanging up when revving the truck in neutral it will rev up just fine then hang up at say 2000rpm then come back down..all of the issues show up after some amount of highway driving.

 

   Drives fine on short trips, long trips it's constantly cutting out at some point. The hanging up thing worries me that something mechanical is ****** up. How often does the control unit fail vs mechanical on newer units that have been fuel starved at some point?

 

   I have a new fass 150 pump motor and so VP44 installed less than 10,000 miles ago. I did blow up the fass 8000 miles ago leaving me stranded and forcing me to limp the truck 30 miles. No real issues until the last 1000 miles or so.

Edited August 24 by QuadRunnerJake
Add info

[Tractorman]

Have you checked for trouble codes?  If so, what are they?  Most of the time (not always) codes will show up when a VP44 injection pump begins to fail.

 

- John

[QuadRunnerJake]

Not yet. No CEL like last time, but I'll go flutter the key a few times and check. Last time my VP took a **** it did some real weird stuff. I would have no pedal control at idle unless I mashed it. Then it would shoot to 1500 to 2000 stick there for 3 secs, smoking like crazy without touching the pedal, then depending on if I touched the pedal or not it would either drop back down to idle or if I kept it above that hang point of 1500 I could drive normally until It dipped below. .

 

   I was smoking out every stop light when this happened. Didn't matter if it was cold or hot.

This will be my third dead VP and I am not thrilled. Bought from Taylor Diesel a Bosch Refurb shop.

Edited August 24 by QuadRunnerJake

[QuadRunnerJake]

So I got a P0122 and the companion code so gotta scan for the rest. P0122 is apps I thought but idk the pump hanging when hot makes me think the VP is done. I just bought a s472 and 150hp nozzles for my compound aspirations so this will be an expensive month lol.

[Tractorman]

 

P0122 (M) Throttle Position Sensor Voltage Low Throttle position sensor input below the acceptable voltage
range.

 

The "M" (Malfunction Indicator Lamp) may or may not light dependent on EPA requirements. 

 

15 hours ago, QuadRunnerJake said:

I will get intermittent dead pedal when driving above say 60mph with light pedal pressure.

 

This definitely falls in-line with a dead pedal symptom when cruising at a common road speed under a light throttle - worth checking out.  The OEM style APPS can get a worn spot on the potentiometer when driving at repeated highway speeds over long periods of time.

 

15 hours ago, QuadRunnerJake said:

I have a new fass 150 pump motor and so VP44 installed less than 10,000 miles ago. I did blow up the fass 8000 miles ago leaving me stranded and forcing me to limp the truck 30 miles.

 

How well did the engine run on your 30 mile "limp"?  The VP44 internal vane pump (called "feed" pump by Bosch) would still bring in plenty of fuel through the dead lift pump as long as there was not a severe restriction inside the dead lift pump.  If the engine performed normally on the 30 mile trip, then there may be no harm done to the VP44.

 

Can't really offer any help with the hanging injectors.  What injectors are you currently using and how many miles on them? 

 

- John

 

Edited August 24 by Tractorman

[QuadRunnerJake]

It didn't run the best not gonna lie. Realized at the same time the fuel filter wasn't flowing very well either. The whole reason I noticed the LP died was because of the fuel starving.

 

Fast forward to today the truck makes more power than it ever did before. It runs great on short trips around town. Especially running it hard. Never acts up other than on the highway or after being on the highway for hours I can get it to do that Throttle hang up issue.

 

  Has anyone ever had their truck just hang up during free revving? I can rev it hard up to 3k then it will drop down to 2k hang there sounding kinda like its missing then come down.

 

I haven't replaced the apps or injectors before and it's got 200000. I have some 7x10 nozzles in my garage. Nozzles I just bought for $100. I was planning on pop testing them at home and reshimming as necessary with a little homemade pop tester using a cheap bottle jack and pressure gauge.

[Great work!]

Do you have a delayed wait to start light. The high idle and delayed WTS is how my ECM started it's death.

[QuadRunnerJake]

3 hours ago, Great work! said:

Do you have a delayed wait to start light. The high idle and delayed WTS is how my ECM started it's death.

Have had neither of those symptoms. My rpm gauge also likes to bounce around 100rpm+- if that is relevant. It's done that for a very long time though. Before my first VP

 

Edited August 25 by QuadRunnerJake

[Tractorman]

On 8/24/2024 at 7:09 AM, QuadRunnerJake said:

This will be my third dead VP and I am not thrilled. Bought from Taylor Diesel a Bosch Refurb shop.

 

Do you know if your VP44 pumps were refurbished - as in a new PSG vs. refurbished PSG, and was the pump run and the PSG calibrated to the pump on the Bosch 815 test stand?

 

- John

[QuadRunnerJake]

Thank you all for the help. The issues I was experiencing were a result of poor connection at driver side battery terminals. I have no idea why the issues only happened at highway speeds and when hot. Nonetheless, I got the cables right and all issues resolved.