Hesitation under load..fuel starvation?? - Dodge Cummins Diesel Forum
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post #1 of 23 (permalink) Old 01-02-2019, 11:21 PM Thread Starter
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Hesitation under load..fuel starvation??

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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post #2 of 23 (permalink) Old 01-03-2019, 08:06 AM
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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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P pump swapped

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post #3 of 23 (permalink) Old 01-03-2019, 08:07 AM
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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

2000 4x4
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phatshaft 62 over s475
DOR steering+suspension
P pump swapped

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post #4 of 23 (permalink) Old 01-03-2019, 08:49 AM
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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?

02' 2500 5.9L 24v ext cab sb 4x4
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post #5 of 23 (permalink) Old 01-03-2019, 12:07 PM Thread Starter
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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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post #6 of 23 (permalink) Old 01-03-2019, 03:42 PM
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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?

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post #7 of 23 (permalink) Old 01-03-2019, 04:42 PM Thread Starter
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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-m...CABEgJqo_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!!

2500 5.9 24v 5spd ext. cab 4x4
Raptor RP-150
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post #8 of 23 (permalink) Old 01-04-2019, 01:28 AM
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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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post #9 of 23 (permalink) Old 01-06-2019, 03:27 PM Thread Starter
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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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post #10 of 23 (permalink) Old 01-06-2019, 06:45 PM
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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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post #11 of 23 (permalink) Old 01-06-2019, 07:15 PM
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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.

2000 4x4
Built Auto
phatshaft 62 over s475
DOR steering+suspension
P pump swapped

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post #12 of 23 (permalink) Old 01-06-2019, 07:42 PM
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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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