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Hey Everybody,

I picked up my first cummins a few months ago and this is my first diesel I have every owned. The pickup is a 2001 ext cab 2500 5spd with 140k miles. It has a Raptor RP-150 lift pump and the rest of the motor is just about stock.

Anyway on to the problem..every now and then I haul a big tex 14lx dump bed trailer with a good sized load of dirt/gravel which ends up being about 10-12000lbs or so. On any incline going 50-60mph down the highway, there would be a very quick and very abrupt cut out from the motor (it happens in the blink of an eye but it shakes the whole truck). There is no loss in fuel pressure, it remains steady at 14-15psi. After this hiccup the truck keeps on chugging like nothing happened. This would happen once a month or so. However, last weekend, I drove about 4 hrs towing my cherokee in the dump bed trailer and 3 hrs in, the truck started up again on the hiccuping problem. The most common it occured was within a 3-6 minute window and it is all dependent on pedal position and load on the motor. I pulled over, took the jeep off thinking that a lighter load would help and it did not. I then ditched the trailer at a friends house, drove the truck around the block and now even with no trailer, going up a hill winding her up in the top of 2nd she'll slam me with a hiccup.

It seems like anytime under high fuel consumption/load there is a problem. However, I just took the truck out, warmed it up, ran through the gears at WOT and it was fine. Some hills are fine and others are not. It seems to be fairly random, yet consistent when the truck is under load. There is no white or black smoke either and the truck never has a hard time starting or a rough time running. It also does not matter if the truck is fully warmed up or just pulling out of the driveway, if I really beat on it up a hill it will most likely happen (sometimes not though). I have changed the fuel filter, TPS, re-calibrated the TPS and still nothing seems to help. I also hooked up my scanner and there are no current or past codes showing up and no check engine light.

I am thinking its either the VP Pump or ECM...what do you guys think?? Any insight would be greatly appreciated!!
 

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You need a fuel pressure gauge to see if the injection pump is losing pressure.

Also check for air leaks on the fuel lines and even the return line from the head to the injection pump.
Look for wet fittings, and snug them up. If keep leaking replace sealing washer on banjo bolt.
 

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Also you need to check for codes with a scanner, it’s been awhile since I had a vp44 but they should throw codes if they are acting up
 

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Pureface, the op stated he has a steady psi of 14-15, (assuming thats with in cab gauge). Also he stated has found no codes with his scanner. I sort of have a similiar thing happening with my truck when it shifts into 3rd gear direct (i think). Are you sure its not trans related?
 

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I do have a gauge in the cab and I have seen no sudden loses in fuel pressure. To reiterate I have checked the codes and there was no current or stored codes. I just checked the truck and there isnt any leaking fuel or wets spots that I can see. I am fairly sure that it is not transmission related because it has happened in just about every gear when I am hammering on it. Also its a manual 5spd
 

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How is the fuel pump installed in relation to fuel filters and where is the fuel pressure gauge reading from? And what brand and type of fuel pressure gauge and how its installed?

You said "just about stock", so what does that mean? Is there ANY type of electronic device on the engine? Anything changed from stock?

What about other gauges? Do you have the ability to see boost and EGT's? :thumbup:
 

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Discussion Starter #7
The lift pump is located under the pickup beneath the drivers seat on the frame rail upstream of the fuel filter. It goes fuel tank, lift pump, fuel filter, then vp pump. The fuel pressure sending unit is installed with a banjo bolt on the inlet of the vp pump. It's a maxtow gauge like this one here: https://www.maxtow.com/black-green-maxtow-30-psi-fuel-pressure-gauge/?gclid=EAIaIQobChMI1NThhsjS3wIVRR-tBh2vfgBGEAQYBCABEgJqo_D_BwE

It's installed on the pillar along with boost and egt gauge. The gauges have been installed for about a year with no problems. I purchased the truck at auction so I'm not too keen on the previous owners details but there is a jumper wire on the top of the vp pump which I assume means the guy had electronics hooked up. The wire is cut and I have always ran the truck stock. "Just about stock" means there is no other tuning programmers just a cold air intake and 4in exhaust all the way back

I really appreciate all the help!!
 

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Is your WTS light staying on for a longer than normal period of time before going off? That is an indication of ECM problems. You could double check your scan tool as well by checking the system with a different one. Typically these sorts of issues do throw codes, but not always picked up by some scan tools.

However since you do have a wire tapped onto the VP44 from the previous owner I would recommend checking that connection for sure as that can quite easily create an issue if it is not done properly. Moisture can penetrate the connection thus causing corrosion. Perhaps not your particular issue but worth checking out. Also check your ground connections to the frame and engine block and back to your battery cables as those can cause a lot of issues as well.
 

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Discussion Starter #9
It does not seem like the WTS light is staying on longer than normal. It is getting a little colder in Oregon so its hard to tell if its the ECM or the cold weather. I have a cheaper scanner that I initially hooked up to the truck and it did not show any codes either. I checked the tapped wire and it seems all good. I have never used a wire tap like the one on the vp pump and I was wondering if anyone has had any problems with these. I have a attached a pic to show you what it looks like. It looks kind of like a screw type wire tap.

I also checked all the ground connectors to the battery, block and frame. I am thinking about just replacing the ECM since it is my main suspect and it is fairly easy to change and cheaper than a vp pump.
 

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I’m currently having a similar issue and I believe my is related to the APPS sensor. I saw you said you replaced the tps, but was that with a quality tps? I ordered mine from timbos
 

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The wire tap you posted is the exact same one I got with my edge juice programmer. You should remove it and make sure there isn’t any corrosion.

I still think it’s Fuel related since it only happens when you hammer on it... can you adjust your fuel pressure so that at idle it’s at 20psi? ( I believe too high is bad for the vp44)

Also try another scanner, I don’t know if you know anyone who works at a shop but my buddy has a snap on that can read more codes then my cheap one.

I’m not sure I’d go replacing the ecm, maybe if you can find a used one for cheap. I have never seen an ecm fail and I know a few people with vp trucks

Could always just P pump it.
 

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just to be clear...the WTS stays on longer ? that is normal for cooler temps.

what you want to verify is....the WTS ILLUMINATES IMMEDIATELY when the key is cycled on. if it hesitates to illuminate, that is the sign of a problem.
 

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the 20 psi at idle wont hurt....i idle at 21-22, and see 25 at WOT.

HIGH PSI AT CRANKING can cause issues.

i prefer the WELLS APPS from autozone undr the duralast name.


all this said, does the tack ever drop out for a sec ? or possibly a speed sensor....
 

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Discussion Starter #14
I forget where I got the TPS, I put it on a few months ago. It was not from timbos, but I just checked out their website and I am going to hook up my voltmeter tomorrow just to make sure I dont have any erratic voltage.

I just took off the wiretap to check for corrosion and I see no signs. Just a normal bare wire. I can adjust my fuel pressure, but what is the reasoning behind cranking it up to 20psi?? If it was a fuel problem, wouldn't higher pressure just cover it up? Ill try to kick it up tomorrow after work and let ya know.

Ill ask a few buddies for a different scanner, I have the Genesis Evo 5.0. Some day a P Pump, but not now, this is my work truck and its hurting me having it out of commission.

There is no delay for the WTS, when the ignition is on, all the dash lights come on along with the WTS and it stays on until its ready. There is no delay at all and it illuminates as soon as the key is turned on.

Back before this was a huge problem I would come up to stop lights/signs and the tack would have the slightest drop, something that the average person would never notice or if they weren't paying attention/music was too loud. It was almost like a/c compressor kicked on..maybe a drop of just a 100-200 rpm. If I had the music down and was paying attention I could hear/feel it but something that was not very noticeable which is why I never thought much of it. Maybe it was just the preliminary signs of what this all escalated too...
 

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personally i dont know why the 20 psi question was asked.
i am.just commenting that 20 wont hurt while running.

it can at cranking, but that is not an issue here.

how does the tach act when idleing ?

it maybe a crank/cam sensor issue, even as far as a speed aensor....scan tool and drive, log or view all data. have aome else drive while you watch.
 

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It just sounds electronic to me... I'm no fan of Glowshift gauges but nonetheless I'm going to guess that its not lying to you whereby you're not reading much much lower fuel pressures than you think simply because I'm going to guess the Raptor is fine and running correctly and through all the normal cycle procedures too.

So that said, I know you've changed the APPS but it still sounds like a flat spot in the rheostat, or a connection to/from the APPS. The only way to know is to hook a scope to it or test the voltage swing of the APPS.

The only other electronic device I say could be causing a problem is the alternator. If the alternator is weak and/or the diodes are bad then the AC voltage noise can get very high and create electronic interference with other sensitive electronic devices on the engine. And these engines are very sensitive to such electronic anomalies too. Test for AC is very easy too if you have a volt tester with both DC and AC readings. :thumbup:
 

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Ill take the truck for a whip around in the morning and watch the tach a little closer. From what I recall, there is no sudden drop in the tach but I will take a video to make sure. If there was a drop, that would mean crank sensor..right?

I didn't have time today to check the APPS but I will do that in the morning before I go drive it. I will also check out the alternatorl. I was also flipping through some youtube videos looking for similar problems and from what I can tell, this guy has the exact same problem as me. Pay close attention to around 26 and 40 sec. I know its a 2004 but he's got the same motor..right? 5.9 24v? Check out the vid:
 

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The similarities between the 2nd gen and 3rd gen are very limited. Yes, they have the same engine block but there were way too many changes throughout the entire truck which would suggest that if your truck is doing exactly what you see in that video, and thats a 3rd gen, then whatever similar symptoms you guys are experiencing is electronic. Either bad connections/grounds, or connection issues somewhere.

If you know anyone with a scope, that would help you understand whats going on during those moments in real time data. :thumbup:
 

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That makes sense..I never really thought of it like that. Ill do a once over on all the connections in the morning and call some buddies to see if anyone can help out with the scope. I really appreciate all the help!
 

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Finally got home from work at a decent hour today and tested the AC voltage on the truck and it was at 0.2 volts at the battery, that is acceptable, isnt it? However, when I fired up the truck tonight, the tach was not working and did not budge. So I shut the truck off after about a minute of running and then turned it back on. The tach still never moved until about 30 seconds after I started it the second time. When it moved it slowly went up to about 900rpms bounced around for a bit there before it settled in steady at 900 (there was no hesitation or stuttering in the motor). Would the crank sensor or engine speed sensor be the cause of this? Also is it possible that a faulty signal from either of these sensor be the cause of the hesitation while under load?
 
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