SalsaBoy

Can someone just tell me if a HO(high output) pump will work on my 99 automatic that came with the SO (standard output) pump. I've read about the differences and ability to upgrade etc. I ordered a replacement SO from a junkyard and they sent me a HO pump. Will it work on my stock truck or do I need to send it back? I can tell that the fuel inlet and return are higher on the pump and the support bracket on the back is different. Everything else looks the same.

AggieJustin

Actually, all the brackets and connections should be the same. The SO pump is a direct replacement for the HO pump, so you should be able to reverse with no issues.

It would work, but considering that most people go to the SO pump even if they have HO, I would try to get the right one on there. If you're planning to stay stock, it might not be an issue. But if you want to do any upgrades, you'll get better returns on the SO pump.

SalsaBoy

I'm planning on staying stock. I don't want to spend another day putting it on and it not working but if it will work, I'll use it to avoid having to wait another week until I can get another replacement.

AggieJustin

Actually, it should work. I just remembered that someone had swapped pumps between an HO and SO trucks and both ran fine after the swap. You may actually notice a little bit better low-end response with the HO pump over the SO, it just doesn't work as hard on top with additional fueling boxes added on.

Nomad

Not sure if an HO pump will work on an SO truck, but a buddy just did a pump on his '01.5HO and was given an SO pump by mistake--and no worky! Timing is an issue with the pump from what i understand.

pind

in my experience, which doesn't count for a heck of a bunch. We have installed SO pumps on HO engines, and they work, but the HO pumps don't work on the SO engines.

Timing is only an issue if you mix up the keys. If you have a "29" pump, it needs a "29" key, etc.

still not sure on why the HO pump doesn't play with the SO engine though. or not entirely sure anyway, have some ideas, but not enough time to play those ideas through.

mini14

smaller plungers on the ho pump and its 027 for an so and 028 for an ho, and the keyway is timed to each individual pump determined on the test stand. no such thing as 1 key for an 027 or 028, they all vary. when in doubt get an so pump they work on both.

pind

there are actually 45 different keys for the vp pumps. There is a number on the side of the pump, that tells you what key you need. That is what I was referring to

rattlerbob5.9

Please explain this further about the # on the side of the pump = key.

I am sure some others would like to know as well.

pind

See that machined face on the side of the pump.

Toward the front of the pump, there will be a three digit number.

If you get hold of a bosch authorized rebuilder, give them the model number of the pump, and then that three digit number, they should be able to provide the proper key for that pump.

rattlerbob5.9

Thanks Pind ,

So we cannot get a direct read off of it they would need to decode the info for us to come up with the proper key # would this be correct ?

pind

no man, its a direct read. But chances are, you don't have all the different keys in your back pocket.

On that little hump, at the front of the machined surface, is a three digit number. the numbers are larger than the rest of the numbers on that surface. if the number is 044. you need a 44 key, if it is 017 you need a 17 key, etc.

rattlerbob5.9

OK - Direct read i got you. Thanks for the education.

SalsaBoy

thanks for the info guys. Since there was doubt I sent the pump back. Another week down but at least I didn't spend another day in the NC heat putting it on and taking it back off.

PIND-that is a pic of the HO pump right? That is what my latest pump looked like. THe fuel intake and return on my stock pump is lower on the housing.

pind

that is a picture of a vp44 pump from some application, but not the dodge application. Just used for reference.

The dodge/cummins vp pumps all have the inlet and return at the same location, or at least all of the 100+ pumps I have changed have been that way. I have an HO pump here, and an SO pump, and other than model number 028 vs 027, they look the same.