I have a 2004 Cummins with the 305 engine. What fuel pressure should this truck have at the CP3 pump? I just put in a pressure guage and don't know what kind of pressure I should have or what is needed for safe operation of the truck. The truck is stock with a auto. and I have put 4 inch exhaust on it but nothing else. thanks Keith

 

I have the quad FP gauge and see 7 PSI at idle (with race removed for upgrade to X2). I can pull it down to 3 PSI at wot. Stock lift pump but I've got my eye on the Glacier Walbro 392 setup.

 

My stock lift pump put out 9 psi at idle

 

A good new pump should put out 10psi at idle and go NO LOWER then 6 or 7 at WOT. If you get lower then that you can starve the injection pump and damage it. The injection pumps are a double edged sword because they are capible of sucking, or pulling fuel to them selves, all the way from the tank...BUT they need pressure or they will fail. Your injection pump should put out about 6,000 psi, at idle and in netrual. Max at WOT with about 30psi boost, you should have about 26,000psi rail pressure

 

Bfluri I have 6psi. at a idle and about 3 to 4 psi WOT. It looks like better get a new pump before it does some damage to the cp3. Thanks for the help Keith

 

Yeah, that is waaay low. My buddy is in the same boat as you. You should fill out your signature so we know what you have and what mods you have done. Also, do you know if you have the stock lift pump on there or do you have the mod that put the pump in the tank, where it belongs! If you go to dodge and get a new lift pump they will give you a mod kit that will remove the lift pump from the filter housing and install it in the fuel tank. Its a pain in the *** and if your not to savy with trucks and stuff you may want to either have them install it, or get a traditional lift pump, they are really easy to replace. The pump in the tank is suposed to last longer.. Installing it requires you to drop the tank to install it. You also have to remove the driver front wheel well and install a new relay and a few wires. Its not too bad just a pain in the butt to drop the tank.

 

I'm suspecting my lift pump may be on its way to failure. A recent test indicated it was fluctuating between 7-9 psi at idle. Could low pressure cause a temporary starvation of the injector pump which could ultimately lead to an intantaneous, temporary, power interruption? Question #2: If my non-dealer auto repair shop replaces the lift pump with an in-tank pump, does the computer need to be reflashed?

 

Question 1, I dont think low pressure would cause a power interuption.. that injection pump will suck its own fuel, its not good for it though. How are you getting your pressure readings? Do you have a fuel gauge? I didnt have a gauge and my lift pump went out and I had no idea becuase the truck still ran. I ran it like that for a week until it finally died. Thank god the injection pump is ok though.

Qusetion 2,
You can have someone else, or do it yourself. Dodge recommends reflashing the ECU. The truck will run fine without it though so I dont know why you need to. I did it and it cost 1 hour of labor at the dealer. They told me it was so the ECU knows it running a different pump and has an extra relay on it. I guess its better safe then sorry.

I think you sound mechanical enough that you can do the install yourself. Its self explanitory for the most part. The new relay taps into an exsisting harness that runs back to the tank already. The harness is the same as on a gass truck so the pins and wires are already there, just unused for a Diesel. Other then that all you have to do it apply power to the relay, from the battery, remove the lift pump and install and normal banjo bolt to attach the fuel line coming from the fuel tank. Make sure you have an empty tank of fuel to make it easier. The kit for a 34 gallon tank it about $315.00 but for a 35 gallon tank its about $550.00 I dont know why either. Dont forget, you can always just buy an aftermarket lift pump and install that in the normal location. That is a very easy job to do.

 

The readings are coming from a local auto repair shop that's quite reputable. I have the truck in there for another issue and asked them to test the lift pump while it's there. They've estimated the cost of replacement at around $600, including labor. I didn't realize there is a difference in tank size, let alone the lift pump, and they may not, either. The procedure you related sounds pretty straight forward; I may try it. I think I'll do a little research on an after market for the original location as well. It may prove to be cost effective.

 

$600!!!!! geez...where are you located, I will come do it for $500..lol I dont recall any names of aftermarket lift pumps but you can do a search on here for then and find a thread with talk of them. Getting a replacment lift pump would be cheaper for sure but there is a reason Dodge moved it to the tank. Lift pumps are stupid. Its easier to push fluid then to pull it. Thats why cars have them in the tank...duh! lol If you have any sort of mechanical ability you will be able to install the mod. Its just a pain it the butt to drop the tank is all. It comes with new fuel lines and some other stuff too but you dont really need to use them. It requires a special tool to remove the fuel line fittings and I didnt have it so I just pulled the line off the fitting and stuck it on the new on..easy. If you have a floor jack, and piece of wood, long enough to support the fuel tank, then you are good to go. You dont even need to take it out from under the truck, just drop it, pull the sending unit from the tank. Its a big white plastic thing with a big plastic nut that hold it in which it threaded to the tank itself. Pull that out, and drop the new one in. That has the pump and new level sensor in it. The wires that run the pump are already in the harness that is attached to the sending unit, just not used. I would sugest you try that, unless you have a 35 gallon tank, then its gonna be pricy! If you do it, send me a private message and I will send you my phone number, in case you run into trouble while installing it.

 

I'll appologize now to wyobigk for hijacking his thread, but this is getting very interesting. From reading my owner's manual, I've been under the impression I have a 35 gallon tank; didn't even know there were two sizes. What's the best way to determine which tank I have? If it's the real pricey one, it may be more cost effective to go for the replacement lift pump. It sounds as if I can do this in my garage using my motorcycle floor jack, or I have access to a hoist if that would be easier. Thanks for the info.

 

I think it says it inside your glove box. I also believe if you have a long bed, you have a 35 gallon tank and vice versa for a short bed. You can also call your dealer and ask for the parts department and give them the VIN, they will tell you.

I used a motorcycle lift to lower my tank actually. My lift is full size though. If you have one that just lifts from the center of the engine area it may work, you may just have to watch out for it tipping then sliding off. To my surprise, it was dead easy to get the tank straps off and out. Another option is to unbolt the bed and slide it back enough to get to the fuel tank sender. I was going to do that but I have a stupid bed liner in there and I didnt want to deal with trying to pull that out, plus I had a few people with me to help drop the tank.

I was looking around on the web for a lift pump for you and I found one on www.extremediesel.com for about $260.00.

 

Wow! Thanks!! I'll check that out right away. BTW, I do have the long bed, so I probably have the 35 gallon tank. You just gave me another option, too. I have a Handy Lift motorcycle lift as well as the motorcycle jack, so that, too, may work well to support the tank; probably have to remove the wheel vise, though. I'll check out the website and see what my options are since I have the larger tank. Thanks again.

 

So whats the verdict?

 

I'm going to get the in-tank pump listed on the web site you provided; priced at $278. They list pumps for both the 34 gal. and 35 gal. tanks and they're priced the same. It'll have to wait until next month (budget reasons), but I'm going to tackle this myself. If you hear of a near nuclear explosion, or a sighting of blue flames, in southeast Iowa you'll know I'm having difficulties. From what you describe, though, it sounds pretty straight forward. I do have a couple of friends who work for independent shops and I can get help from them if necessary. Thanks for the all the info and help.