Partial dead pedal???

[Beepbeep24v]

Hey guys looking for some answers on my 99 24 valve 3500 auto. It has bhaf/industrial injection vp44/and fass 150 with big hose lines and in tank sump all installed at same time about two years ago. Fuel pressure gauge is installed about a foot from ip with shrader valve cracked idk if it’s to close and giving an erratic reading but it will idle steady at about 14 then jump up to 18 while driving then all the way down to 10 then back up so basically it fluctuates up and down while driving between 18-10. Another thing that’s going on. sometimes it has a long start when hot sometimes not. And every day when cruising above 65 it will stop accelerating and only give me 30% throttle. boost drops to 4% apps shows to be working right with throttle response when This happens engine or rpms don’t shut down I can still run 60-70 just with only limited throttle and fuel pressure will stay at about 12-14 when it happens. Until it feels like kicking back in boost will jump up and engine will take off depending on where my throttle pos at time.showing no codes from autozone scanner. Recently did apps reset and didn’t work then installed new apps still nothing did reset on new apps and nothing. disconnected Grid heaters still nothing. Did alternator wire re route and still no change. Crank pos sensor went out. Was giving me code/ no crank/long cranks. Replaced with Cummins sensor. Code went away and still having the issues. Checked grounds and terminals/pcm connections all seem ok so idk what else to do really don’t wanna start throwing vp or new lift pump at it if it’s something electrical or ac noise! Pls help. Also grid heaters were throwing a code before I unhooked idk what was wrong with them but I just un plugged them. Right now I have exhaust manifold leak at back of manifold toward pass side and a little oil or residue on bottom of turbo I guess where it bolts up at bottom? Can still push 28 psi boost when it doesn’t lose throttle she runs like a top 80-90 idles and city drives fine till throttle drops on highway 

Edited July 30, 2020 by Beepbeep24v
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[Haggar]

Keep looking.

 

It sounds suspiciously like a dying VP with no codes.  But that is an expensive jump to just throw a part at it.  It is very hard to confirm though.  is the problem wiring, ECM or VP?

 

You just have to check everything else to death, then decide to replace one of the two components (vp or ecm)  if the ECM is booting properly, my money is on the VP. 

 

Good luck

HTH

 

Hag

[dripley]

I have had a failing MAP sensor do that same thing. Sometimes I would get a 236 or 237 code with it some times not. If the ECM sees little to no boost it will defuel the engine. But in that line of thought when my OE VP was dying it would do same thing except it blew blue smoke when it would happen and it never set a code. And like @Haggar said, lack of codes makes even more fun to diagnose. 

Edited July 31, 2020 by dripley

[Beepbeep24v]

Thanks from the reply @Haggar ecm seems to be booting properly cel lights up when key is turned over and goes away I think that’s how we know it’s working? Im also leaning towards the vp considering the hard starts when hot. But also thinking it’s electrical or something else causing defuel. I’ll look over everything again and see if I can find something 

Thanks for your reply @dripley I would hope it’s just a failing map sensor! I’ll pull it and take a look at it see if it needs cleaning or replacement and see what happens. If the map sensor was on its way out would it be showing boost pressure? I’m getting 0-3 in town and 4-5 normal highway speeds if I accelerate it will go up with acceleration fine but when the dead pedal starts it will drop to 4psi and remain there until dead pedal stops. Also I’m not getting any smoke at all I used to get black smoke residue on rear fender but now even with chip turned up it’s all clean....

[Royal Squire]

Could be your tuner acting up

[Great work!]

Try the cold water trick on the Vp next time there is a long hot crank. If it fires right up thats usually a sign of electronics on pump failing. 

[Tractorman]

2 hours ago, Beepbeep24v said:

I’m getting 0-3 in town and 4-5 normal highway speeds if I accelerate it will go up with acceleration fine but when the dead pedal starts it will drop to 4psi and remain there until dead pedal stops.

 

Just for clarification,  I don't think you are experiencing a "dead pedal" (engine dropping to idle and staying there).  I believe the engine is going into "limp mode" because the ECM or PCM is detecting some abnormality somewhere and therefore de-rates engine power for damage control.  I know that you probably already know this, but I just wanted to clarify the terminology.

 

Maybe your code reader is not picking up a code that could help to diagnose.  I don't have much experience in this area, but others have said that different code readers can give different results. 

 

- John

 

 

[Beepbeep24v]

@Royal Squire I don’t think that’s the issue it was doing this before quadzilla was installed 

1 hour ago, Great work! said:

Try the cold water trick on the Vp next time there is a long hot crank. If it fires right up thats usually a sign of electronics on pump failing. 

Never heard of this trick? I’m willing to try though I’m guessing pouring cold water over top of vp then crank? 

@Tractorman that’s what I’m thinking it’s going in and out of limp mode for some odd reason and not telling me. I’ll get a better scanner and see if I can get anything to come up 

Edited July 31, 2020 by Beepbeep24v

[Mopar1973Man]

If you have the Quadzilla tuner you can check the PSG temperature. The aluminum cover doesn't count. The PSG module has all the electronics mounted on the aluminum plate facing the fuel side. So the fuel temp is directly related to the temperature of the PSG. Like a few here that were told only need 3/8" fuel line are the very same people now reporting 150°F fuel temps and higher. I'm still with 1/2" lines and AirDog 150 that is keeping fuel temps way down like 120 to 130°F typically. Huge difference in protecting the VP44 from heat when you have a constant fuel pressure of 15 PSI (WOT) to 17 PSI (Idle). I'm able to keep the overflow open and keep flushing cool fuel through the PSG area. 

 

Yes typically my IAT temp and Fuel Temp will match as seen below. When I shut down my fuel temp does not rise only cools off from that point. There is no heat soak from the block that raises fuel temp. This below was 3 hours of driving in 103 to 105°F temp day and in city traffic and highway both. NOTE: Engine oil temp is the trans temp.

[Beepbeep24v]

Thanks @Mopar1973Man for your reply I’ll see what my numbers read today. Just curious I’m running stock trans with quad I see your quad shows you’re in 5th gear. But mine will only show an L for 1st gear and will only show up to 3rd when it’s in od  is that normal? And I see your TC lockup is in green does it usually stay solid green or go away? Mine will pop up green then go away?

Edited August 1, 2020 by Beepbeep24v

[dripley]

30 minutes ago, Beepbeep24v said:

Thanks @Mopar1973Man for your reply I’ll see what my numbers read today. Just curious I’m running stock trans with quad I see your quad shows you’re in 5th gear. But mine will only show an L for 1st gear and will only show up to 3rd when it’s in od  is that normal? And I see your TC lockup is in green does it usually stay solid green or go away? Mine will pop up green then go away?

Mike has a 5 speed not an auto. Not sure how the Quad knows what gear he is in however. I am sure @Mopar1973Man can tell us.

[Beepbeep24v]

@Mopar1972Man this is what my iat and fuel temp shows after driving a bit after n hour I got iat up to 156 and fuel temp remained around 120? Is iat temp to high?

This is when it decides to give me partial engine load as you can see I'm almost 80% throttle. It  says 3rd gear but it's in od and no green tc lockup light till you let off gas then it says 4th gear until you press gas again goes back to 3 and light goes off 

 

Edited August 3, 2020 by Beepbeep24v

[Mopar1973Man]

Gear number is based on the gear and tire info in the settings of the iQuad. Pan to the right one for more gauges like what ive got. You can run IAT 145°F no problem. Won't hurt it. I built my MPG fooler to set 143°F IAT Temp. Cold IAT below 80°F will cause MPG loss from the sudden jump of about 4° jump in timing. Hence why most loose MPG in the winter where I only maybe loose -1 MPG at most. Cold air is not the answer being ugnition needs heat to make fuel go from liquid to vapor to BANG!.