Engine/Transmission (1998.5 - 2002) VP44 SO vs. HO

[AFoulk]

Hey all! I bought an 02 H. O. a couple months ago with 76000miles on it and think my pump might be showing early signs of going out. I have a dead spot in the power curve from 2000-2300rpms and when I'm cruising at 60mph or faster on the highway, it has kind of a surge to it... I can hear it, but you don't feel it or see the rpm's fluctuate. It hasn't thrown any codes yet (I checked them) and I've got 8-9psi of fuel pressure at WOT. I had someone on another site tell me that the HO pump actually pushes less fuel than the SO's. Is that true? What other differences are there between the pumps, and is there a higher flow factory pump I can change to without going to a hotrod pump? I'm planning on getting an edge juice w/attitude, fass fuel system and some higher flow injectors soon, maybe even a turbo if I have enough left over and just wanted to make sure my injection pumps straightened out before I spend all that money on the "fun stuff. "

 

[blacksheepdiesel]

AFoulk,

HO truck = HO pump. SO truck = SO pump. You can put a HRVP on either HO or SO. Rumor has it there will be some extreme high output VP's before too long.

Your "dead spot" sounds more like it might be the APPS. Find a buddy with an HO truck like yours and swap his APPS that acts normally on his truck to your truck and see if the dead spot and surge disappear, if so you have found the problem. You do not have to remove the APPS from the aluminum mounting block to make the switch.

I would recommend AirDog over FASS. PM me for dealer contact.

Godspeed,
Trent

 

[AFoulk]

I don't think its the APPS as it seems to have the dead spot no matter what my throttle position... it just seems that as long as I'm on the throttle enough to get the rpms to 2000 and higher it has that dead spot. doesn't matter if I'm at 1/2, 3/4, or full throttle. don't know if that makes any sense or not. And the surging occurs whether I'm using the throttle or if I have the cruise control set. Unfortunately, I don't have any buddies with an HO that I could swap sensors with to see if that is the problem. I have a buddy that has a SO, but all my other friends have 12valves. I'm beginning to think they're the smart ones

 

[BLively]

i have an HO pump on my SO truck. i didnt dyno it before the swap, so i dont know if there is any power difference. but i was told the same thing about the HO pump pushing less fuel??

 

[mhenon]

Any difference in failure rates of HO vs SO? Is the SO VP a more reliable pump?

Mike

 

[blacksheepdiesel]

AFoulk,

OK, your second post makes the dead spot sound more like a VP44 issue, and it doesn't always throw codes when it starts dying, mine never threw codes. The surging could be VP44 or APPS.

BLively,

Yes, if you add extreme fueling mods to both the HO and SO the SO will ultimately push more fuel. The new "mega-super-duper" VP that is rumored coming out may or may not change that, don't know.

mhenon,

I have never heard anyone say anything about difference in failure rates. My original HO lasted 400,000 miles, to me pretty darn reliable!

Godspeed,
Trent

 

[JFlagg]

AFoulk, were do you live, I have a 02 HO if you are anywhere close to St Louis.

 

[SBall]

AFoulk,
The surging you describe is almost exactly what I had been experiencing with my truck. Like you said, you could hear it, but you couldn't feel it. With my truck (6-sp and 3. 54:1), the surging was most obvious around 50MPH in 5th gear, (2000 RPM), and cycled about once/second or so. Above and below that RPM range it didn't surge.

When cycling the key 3x I had the P1693 code and when the dealer plugged in their fancy code reader it revealed a P0216 code too. To make a long story short, I ended up swapping out the VP44 with a Blue Chip pump and it runs very smooth now, no more codes.

 

[AFoulk]

yup, thats exactly how mine acts, but I checked for codes with my buddy's Matco scan tool, and all I had in there was a code for the fuel tank sending unit (I think because I really over filled it the night before). Will my cummins warranty cover the injection pump if that is indeed on its way out? My warranty is good till July 8th and its going in soon to have the oilpan gasket replaced. Will they even replace it if its not throwing any codes?



JFlagg, sorry, I'm in PA... wouldn't wanna risk driving that far if my pump is on its way out

 

[SBall]

AFoulk,

Where in Pa. are you? If you can get your truck to the Boyertown area we could see what my scan tool reveals. However if your truck is still under warranty and due to go into the shop, they could also investigate it for you.

Steve

 

[AFoulk]

I'm about 20-30min. east of Hershey (depending on the traffic). I'm gonna see if the dealer will take a look at it since its gonna be there anyways. Thanks though.

 

[PC12Driver]

A quick way to tell if it's the APPS...

... is to engage the cruise control and see if the surging goes away. The 02 ETH's cruise is all electronic and bypasses the APPS when it's on (there's no vacuum servo - the ECM takes care of the speed control directly). If the surging goes away, it's time for a new APPS.

 

[AFoulk]

Nope, it does it whether my cruise control is engaged or not. Thats why i was thinking it wasn't the APPS.

 

[PAckley]

Regarding the SHO VP44 reliability, Industrial actually claims they do more precise building of this pump over the HO pump. I had to focus on fuel pressures with the edge/juice monitoring pressures. First was the large banjo kit with Vulcan big line reloation kit and stock fuel pump. I would have 13 psi but wot would drop to 7-9 psi. I changed to Glacial system with Walbro pump and idle pressure is 19-20 psi never getting below 13 psi at wot. Solved that problem!

The SHO VP44 is great power producer, I rarely use more than stock settings on Edge, although I will use "mileage" setting when towing. No need to use other settings as they just produce too much smoke, even though I have set fuel settings to minimum smoke. When engine is warm, the idle hunts a bit which I am told may happen to an engine with the SHO VP44. Some feel it sounds like engine has a cam in it, but I would prefer a less obtrusive idle as the engine is loud enough to almost break windows!