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What would cause an 01 HO 6spd to de-fuel in hot weather?

GM Guy

GM Guy

Manual Trans. 2WD Enthusiast
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Location
NW Kansas and SC Idaho
hey guys, my boss is looking at another dodge cummins. it is an 01 reg cab, 11 ft bed capable chassis cab, HO cummins 6 speed 2wd. 11ft aluminum flatbed, overall a clean truck, but it has a problem they have yet to trace down. It will de-fuel in hot weather. they have changed the IP, and numerous other things, all work was done by the local dodge dealer, and they are pretty knowledgeable, but they are stumped.

The farm equipment dealer who owned it and the dodge dealer both are sick of it, and sick of working on it, and want it gone, but the price doesnt reflect that, they want over 10 grand, and the a/c still needs charged, and the tires suck.

does anyone know what the issue could be?

thanks!
 
What is the lift pump pressure under load? As for the A/C, evaps in them are fairly troublesome so it may not be a cheap fix. $10K is WAY to high for it from your description.
 
the problem has been ongoing for 5 years, it will run great all winter long, and spring and fall, but summer, you stand a good chance of it de-fueling if you go out.

due to the consistency, can it still be the LP? I would think it would have failed eventually in those 5 years, but maybe not.

I think if he wants the truck, he might offer to take it IF they fix the a/c and put new tires on. I keep telling him to trade in the lone dodge cummins with the automatic, but he wont. :)
 
De-fuel could be from high IAT's. Summer weather would force the issue.

Aftermarket hot air intake?

Bad electrical connector affected by heat including a sensor?
Maybe plugged intercooler internally or externally?
Bad turbo?
Plugged exhaust?
Bad fan clutch - and if it has an EV clutch it may set a code.

You would have to look at the scanner and see if something is tripping a de-fuel.

Why are you even thinking about getting a Lemon?
 
Cummins don't defuel from hi iat. I would check the wastegate an make sure it's working. Those years will defuel from overboost and they did have significant trouble with the wastegates sticking. Also check fuel pressure!!!!!
 
TRUE Cummins engines with the CM550 ECM will defuel (at least for temperature reasons) for some of the following:
-Air Fuel Control Derate - The engine fueling is being limited due to lack of oxygen (boost pressure). This state can also be active for excessive boost pressure.
-Coolant Derate - The engine torque output is being limited to reduce the coolant temperature.
-Turbocharger Fuel Control - The engine torque output is being limited to reduce turbocharger turbine inlet temperature.

However, since the ECM and wiring harness are Dodge Supplied its hard to say whether or not the derates will operate the same. I'm betting not. And I'm looking at the Cummins / OEM wiring diagram right now for the 01 Dodge, no sign of a Turbo inlet temp. sensor. Could be the EGR valve sticking open, or like stated above the wastegate. High outside temperature could be just enough to make a CAC rubber boot leak. Or the rubber sensing line that controls the wastegate can actuation.

Any codes?
 
new info: over the years, both the injection pump and the lift pump had been changed in an attempt to locate the issue.

not much has been asked, as my boss doesnt want to get in a brainstorming session with them and help solve the problem. :) so he just remembered a few key parts mentioned in conversation.
 
Smart man. Personally? I'd tell your boss to keep looking. Its just not worth getting a truck (especially for what they are asking for it) that as soon as you get needs immediate work. Been there, done that, and even have the T-shirt.
 
he offered them 9 and they took it.

he will be getting a list of everything they have touched, parts lists, etc.

he does like a challenge, and he loves chassis cabs with 11 ft beds, and realizes that a NV5600 is a little stouter for his needs after the last round of fuel plated 98 12V and 30+ K loads VS NV4500. Plus, he finally agreed to my theory of a 2wd! :D

I will have to see it, but he says that it is quite a bit nicer than his 98 12V, and it is still a 7-7.5 on the 1-10 scale, so I imagine it is a 9 or so.
 
Don't assume that just because the dealer replaced something that it works! I would start with fuel pressure even if they replaced the pump.
 
Also being an 01 HO engine, make sure it has the correct injection pump on it. it is quite common for them to put on the wrong pump as the 01-02 HO pump was a special pump and used only on the 01-02 HO engines with 6 speed manual trans. Surprisingly it is actually a lower output pump than the regular pump so it would feel like a defuel going to it.
 
more info:

it has the little light on the dash installed for fuel pressure, and it works. IDK who makes it, but I assume the pressure parameters are designed for this motor and its requirements?

He said there are two temp sensors, ambient and charge air. he still needs to get the paperwork, but in the meantime, he is diving right into replacement without diagnosis, and is trying the ambient IAT sensor.

how does the circuits work on the IAT sensors? I am starting to suspect a wiring issue, since the dodge boys likely followed the service manual to a T and changed everything, but who knows. do these suffer from ground issues like a 6.5L? if so, where are the common grounds?

all input has been useful and is appreciated, keep it coming!
 
Ambient air temp is for the PCM and the overhead display only. It has no input to the ECM at all whatsoever. Teh intake air temp on the engine goes straight to the ECM. You REALLY need to get it to defuel and see what it is doing when it happens. Like I posted earlier, I have heard of more than 1 instance of the wrong pump getting put on em. Or the wastegate actuators failing in salt belt states. i believe it uses the HX 40 hybrid on the HO engine, it is an HX35 center section with larger housings and impellers. A decent turbo, but had more than it's fair share of failures. Throwing parts at it is like burning 100 dollar bills. It normally won't do anything except leave you lighter in the wallet.
 
forgot to mention, apparently it had started doing it, did it for a year or two, then got the IP changed, no change in symptoms. I could have him get the number off the pump, but if it behaved exactly the same with the OEM pump, and the replacement, could it be the pump still?

so on a manual truck, the PCM will only utilize the ambient sensor for the compass/temp display? also, I assume if it has electric fans it will factor ambient into fan operation with the a/c?

also, since no one paid attention to the intake, is there any specific intakes that everyone would recommend for a heavy towing dually? dirt roads are constant, so priorities from most improtant to least important are:

1) dust filtering
2) Cold air suction
3) filter area and ducting (wants enough flow for a towing motor, but without sacraficing filtering ability for flow)
4) Price
5) ease of install
6) emphasis on least improtant, performance.

factory is plenty acceptable, and affordable, so if that is the best, feel free to reccommend it.
 
another question: how many computers are on this truck? PCM and ECM? I assume in a manual truck, the PCM is more of a body and chassis control module? a vehicle control module if you will.
 
01 has an ECM mounted on the side of the block, a PCM mounted passenger side firewall, air bag controller inside, ABS controller, and also the cluster has a control module in it. There is also a central timer module in it as well I believe which was a early but crude BCM set-up(I don't think DODGE offerreed a BCm until 02 in the full size trucks). The PCK pretty much only controls the cruise control, A/C, and alternator as well as serving as a communicator for the ECM to the cluster. It's a pretty screwy system if your not accustomed to working on CHRYSLER products. Get it on a scanner and see WHY it is defueling first. ECM's in that year range did some screwy things as well as crank sensors would give intermittent problems as well.
 
I assume the scanner will be like a tech II? I assume the cheapy harbor freight code reader we have wont do crap other than give us any codes that pop up?

if that is correct, IDK where we would get a scanner. I doubt dodge would willing loan one of theirs out for diagnosis. there is a Cummins Shop in town that he gets along with, could they have even better computer equipment that might pinpoint the issue?

Is any of the computer software used by folks on the 6.5L also able to work well with dodge cummins? This might push me over the edge on finally getting some software. make recoomendations on 6.5L compatability first, since I will be buying for 6.5L use first and foremost, but if it can help with this dodge issue that would be great.
 
I'm not sure which scanners will work with the CUMMINS as most generic scanners will only read the PCM. I would think autoengenuity would work though, but don't if it would for a fact or not. I'm sure the CUMMINS dealer has a quality scanner that could read it.
 
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