Gear hunting, Fuel pressure, and a random rare occurence fuel cutoff

[smelonas]

New here, but not new to dodges. Some of you will probably know me from CF.

 

My grandpas truck, 2001 Cummins 47RE and completely stock, spent all day working on it, various things, but I did some diagnostics and thats why I am here.

 

Ill start with the gear hunting issue first.

I tested AC noise. has about 0.03V, which is 'acceptable' apparently. Okay.

Had no real way to log the truck while driving, I dont have a snap on scanner or similar to watch APPS and other parameters that might effect TCC operation. This diagnosis was kind of a dead end. Mostly I wanted to identify AC noise and go from there, which I did.

Issue seems to become more prevalent as you drive the truck. For the first 15 minutes of operation, it runs fine. No hunting, perfect. Once you settle between 32 and 37mph with light throttle she hunts, same between 47 and 55. randomly kicks in and out of TCC.

Any pointers or help here would be great.

 

Fuel pressure. LOL

8psi at idle and a very lazy pump that struggled to bring gauge needle up when I bumped the starter. Pressure dropped to 2-3psi at WOT, or less maybe.. Obviously the pump is the OEM in tank pump, which is useless.

Is there a good aftermarket drop in pump for in tank pump conversion that was done? FASS and airdog come to mind. I read about the FASS DDRP for the block mount replacement and was hoping I could get input on that. A conversion back to that would probably suit him just fine as the truck is lucky to see 5k miles a year. But Im not even sure if thats wise or stupid or what, you tell me.

 

The random occuring fuel cutoff..

This is a tough one because I dont know how to describe it because I have never been in the truck when it happens. Ill explain it the way grandpa did.

Cruising down the road, pedaling(cruise never gets used ever), doing between 70 and 80 and for no reason it just cuts off. Almost like the FSS or whatever the VP44 has, gets turned to the fuel off position. Hold pedal in same position and truck just coasts, give a juice of throttle and she comes back to life and then goes down the road just fine. Only happens randomly and fuel filtration is no real issue because I have a BF7977 in the stock canister.

 

Ive searched for a couple years about the fuel cutoff issue(been happening since 2016), and I have never found anything similar. No codes in the dash either. Truck runs really strong, italian tune up didnt really make it run better, so the truck is healthy but it just has some random issue with it.

 

First time posting to M1973M, looking forward to joining this engaging forum. CF was/is getting... yeah.

Edited April 3, 2020 by smelonas

[Royal Squire]

What you call fuel cut off sounds like APPS to me 

[Tractorman]

@smelonas, I didn't see anywhere in your post with information regarding year of your truck.  Your signature shows 2007, but you mention VP44 in your post, so I assume your truck is a '98.5-'02 second generation.

 

If your truck is a second generation with a VP44 injection pump, then your fuel pressure is normal for an OEM in-tank lift pump.  With a stock engine, you will not harm the fuel pump.  There is an internal vane pump inside the VP44 that supplies fuel flow to internal controls and to the 14 psi overflow valve.  Just as long as you always have a positive VP44 inlet pressure, the VP44 will be adequately cooled.

 

1 hour ago, smelonas said:

The random occuring fuel cutoff..

This is a tough one because I dont know how to describe it because I have never been in the truck when it happens. Ill explain it the way grandpa did.

 

You need to talk to Grandpa again.  I don't think the fuel is being shut off.  I think he is experiencing the "dead pedal" symptom in which the engine goes directly to idle.  It will feel like the engine died because all fueling stops except for idle.  The dead pedal will usually last for about 5 to 20 seconds and then clear up on its own.   If the engine truly does die, then the tachometer will go to zero. 

 

Not all VP44 trucks will read engine codes using the ignition key.  I would try to get access to a quality code reader and check for codes again.  A failing APPS will likely trigger a "dead pedal", but other things can cause this also.  A failing APPS could also be related the TCC hunting, as well.

 

- John

 

 

[dave110]

WELCOME! I do recognize you from over there. I just visited the new 'improvement' What a mess! Lots of upset members. Maybe they'll jump over too.

You'll get lots of good advise here. I'll just say quickly for now that it sounds like AC noise is in check. Also make sure your battery connections are good, grounds are good and clean, and batteries are in good shape. These trucks are very finnicky in the electronics dept. and bad connection/grounds have caused me issues over the years. More helps on the way............... like right now. I see @Tractorman beat me to it!

[smelonas]

8 minutes ago, Tractorman said:

@smelonas, I didn't see anywhere in your post with information regarding year of your truck.  Your signature shows 2007, but you mention VP44 in your post, so I assume your truck is a '98.5-'02 second generation.

 

If your truck is a second generation with a VP44 injection pump, then your fuel pressure is normal for an OEM in-tank lift pump.  With a stock engine, you will not harm the fuel pump.  There is an internal vane pump inside the VP44 that supplies fuel flow to internal controls and to the 14 psi overflow valve.  Just as long as you always have a positive VP44 inlet pressure, the VP44 will be adequately cooled.

 

 

You need to talk to Grandpa again.  I don't think the fuel is being shut off.  I think he is experiencing the "dead pedal" symptom in which the engine goes directly to idle.  It will feel like the engine died because all fueling stops except for idle.  The dead pedal will usually last for about 5 to 20 seconds and then clear up on its own.   If the engine truly does die, then the tachometer will go to zero. 

 

Not all VP44 trucks will read engine codes using the ignition key.  I would try to get access to a quality code reader and check for codes again.  A failing APPS will likely trigger a "dead pedal", but other things can cause this also.  A failing APPS could also be related the TCC hunting, as well.

 

- John

 

 

Sorry for not posting more info about truck. Im used to mine being the only one that ever needs help.. Perks of owning a dodge. HEHEHE

 

ANYWAY, Ill edit first post to show the info on the truck. I will also state it here.

Truck is a 2001 dodge ram 2500 4x4 Cummins, 47RE, Stocker than the share market. 

 

I understand that the APPS is an extremely critical piece to this mystery. It was one thought I had when I was pondering the TCC issues after a false assumption of excessive AC noise.

 

My guess is that he is experiencing dead pedal. Moving the pedal position would move the sensor to a different potentiometer position(i think thats how these work?..?) which would trigger it to 'wake' up. And of course if the truck receiving a hazy APPS signal it will bounce back and forth between TCC lock and unlock.

 

Ill look into the fuel pump thing. Ive heard that in stock applications that 8psi is the target number. Thankfully it doesnt drop to zero, but it sure gets real close.. 

Problem with all this is that i am moving away, so his free, honest, knowledgeable diagnostics are also leaving. 

 

Thanks everyone so far. I have been stalking this place for about a year or more, with CF the way it is, Its dumb. Im looking forward to poking around in the third gen section!

[dave110]

Have a live data tool like a Scangage2, OBDlink, etc you can drive with and see what the APPS is doing voltage wise?

Edit: I see you said you don't have a Snap On scanner. One of the ones I listed will read it as well. An OBDlink MX is like $80.

Edited April 3, 2020 by dave110

[smelonas]

Well, my only thing is, I am in a drag race to get packed and moved in the next few days, so unfortunately I wont be able to trouble shoot this thing further. I simply dont have the time to. Which sucks. But thankfully I narrowed down some of the other things that just about any shop would overlook.

 

Thankfully money isnt a BIG issue, he just wants it to run right, so Im probably just going to tell him to take it to a shop and have them replace the APPS. He cant do it, or wouldnt want to at least(83 years old), so it ends up being his only option. After that, Ill have to just work with him to diagnose it further if it doesnt fix it. 

[dave110]

Hmmm. How about trying an APPS reset? Not saying it'll fix but it's free, and easy enough you could print out the procedure here and give it to him or talk him through it over the phone.

Many here like the Timbo APPS ( sold in the forum store) much better than an OEM that a shop will want to install. It's a simple mechanical design that's proven and a whoooolle lot cheaper, like $170 I think. Just some options.....

[smelonas]

I was just looking at APPS prices. Yeah, timbo, definitely the way to go it seems. I dont think grandpa needs a whole new bracket and sensor and everything else haha.

 

Im going to weigh the options tonight/tomorrow and figure out a game plan for the old boy.

 

Thanks so much for the help guys, Ill try and keep this updated and let yall know the results!

[dripley]

Back 13 years ago l was fighting dead pedal issues also. I took it to a local shop in Maryland and they hooked up to their scanner and took it for a drive. The only thing they could find was low fuel pressure. I to had the Dodge in tank fuel pump. That was Dodge's answer to the crappy block mounted OE pump. I had 5 psi at idle and near 0 at WOT. So I added a booster pump from BD on the frame rail near the fuel tank. This got my pressure up to about 12 and 8 psi. The dead pedal was gone until about 4 or 5 years ago

Then I had surging and dead pedal issues and was fighting electrical gremlins. I did find a bad splice in my 5v supply to the sensors. I fixxed the splice, replaced all of my battery cables and cleaned the grounds. And the problem was finally gone again.

Out any surging or dead pedal issues I have experienced it has never been the APPS.

[JAG1]

Fellow Dodge owners you know that Mike Nelson says any fuel pressure lower than 14 psi causes slow death to the vp? Remember that the overflow valve does not open until it sees pressures at 14 and above. Mike also taught us that at idle we need to see 19 psi to allow for WOT draw down as this keeps the overflow open when the VP is most likely to start overheating. Especially when going up grades and hauling heavy, that VP needs to see maximum flow of return fuel to remove the heat. So important.

 

Add to this the poor design of the sediment screen at the bottom of the in tank lift pump, where you cannot get too and you got dirt and sediment that can slow down flow rates. 

 

A common solution is to go with the big line kit and a fass or AirDog lift pump on the frame, removing screens and in tank lift pump and replace with the 1/2'' draw straw. This comes in a kit from Vulcan performance. This kit will include the proper wire harness so the lift pump cannot damage the ECM when it starts to go out and causes excessive power draw on the ECM. The wire harness allows the ECM to control the lift pump, but with power being taken from the batteries and has further diode protection for the ECM.

 

I have seen lots of sediment on my intank screen and lift pump at the bottom of the tank. It was 2/3rds blocked and was glad to get that out and now have an accessible filter that is now outside the tank at it should. These trucks need flow or you choke them to death, that's the correct philosophy, good flow and not having anything to do with the factory's skinney little set up. Sorry about the rant. 

Edited April 4, 2020 by JAG1

[wil440]

Before I fitted a FP gauge I had a sort of engine off moment which would happen at very light throttle accelerating, like a very long cough, fitted a FP gauge and while it was no where near as low as yours it was low, so I did some quick work to remove the PO rubbish which was the smallest inline filter you could possibly get, I had fitted Cat filters and filter head prior to this ,  this removed the cough, then fitted a FP gauge, once I could see what was going on mechanical pump ordered straight away from DAP, FP now is just fine and tops out at well over 20 psi, idle is 12 to 14 due to the cat filters I think being 2 micron.... and I removed another electrical item from my truck.... win win

Your fuel pressure is way too low

BTW my truck had a Fass block mounted stock replacement..... and the basket in the tank was spotless so no excuse there

Edited April 4, 2020 by wil440

[jag]

For gear hunting & TC lock & unlock, I would figure out which one it is first. They are not the same. Gear hunting would be related to the TV cable or the throttle valve in the valve body or a combination of both. For sure check the alternator as per Mikes instruction & do the W-T ground setup before you go any further, that way you can take that out of the equation. For gear hunting what I did was set the TV cable per Dynamics instructions & installed a Sonnax Throttle Valve kit, Part number 22771-03k. The stock valve body is aluminum & the valve is steel which wears out the valve bore & this kit repairs that, no more gear hunting! Now for the TC cycling, I installed a TC unlock switch so it can't cycle & when I get up to speed, I switch it back to factory. There you go, & they will never haunt you again. I did mine last fall when I installed a new engine & have not had a hiccup since. The switch I used was a 3 pole, that way you can command the TC to lock to if you like to also. Forced lockup will break stock shafts, so keep that in mind.  The switch hookup diagram I got from CF back in 2008.

This is how you do it.

TC-Lockup-diagram.bmp

Edited April 5, 2020 by jag
update

[smelonas]

So, to wrap this thread up..

 

Grandpa got the timbo apps and installed it. Took it for a shortish drive, but nonetheless a drive and when it downshifted it stayed in that gear. He knows technical but sometimes he doesnt talk in it, hard to say exactly what it did. But he seems happy and is truck apparently back to 'normal'.

 

Still pondering the fuel pump upgrade but hes going to run it and keep an eye on it for now.

 

Will update if anything else comes up.

 

Thank you again for your help guys. And a big shootout to MM1973 himself for allowing us to convene in this microcosm and talk about these silly trucks.

[Mopar1973Man]

Your welcome...

 

Hanging in gear could be output speed sensor on the tailshaft of the transmission. It can be excessive AC noise. Maybe the TV cable mis adjusted.

[smelonas]

1 minute ago, Mopar1973Man said:

Your welcome...

 

Hanging in gear could be output speed sensor on the tailshaft of the transmission. It can be excessive AC noise. Maybe the TV cable mis adjusted.

I have nothing that's points to a misadjusted TV cable. AC noise was within spec. I dont think its hanging in gear, I'd have to drive it to know. But by his account it wasnt doing anything unordinary and he seemed to be thrilled about it not constantly burping in and out of lockup.

 

I consider this case closed until he drives it more. He maybe goes through 3 or 4 tanks a year. Cant really says it's fixed until it gets more miles, but for now, it's how I'm calling it. Trust me when I say I will certainly be the first person to know if it starts any odd symptoms again.

 

If anything does come up, I will consider the OD housing OSS. At least pull it and clean it.. Truck only has 96k original miles. But again, they weren't built very well to begin with. Even though the 47s seems to stand up electronic wise better than the 48s. There might not be any truth to that statement just see a ton of 48s with electrical issues.

 

Thanks again!