Fuel pressure at VP44 inlet?
10-04-2011, 03:31 PM
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Fuel pressure at VP44 inlet?
02 Dodge 3500, 5.9L diesel...I have lost performance in my diesel most notably when turbo boost should kick in. Truck will accelerate but gradually, whereas before it was very evident I had turbo input. I get no codes in the odometer window . I have checked the fuel pressure at the injector inlet and it is 8 PSI. What should it be ? Doc
10-04-2011, 03:43 PM
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Is that 8psi at idle? Or 8psi under load?
Generally, you should keep fuel pressure above 10psi at all times since fuel is used to cool the pump in addition to being pushed to the injectors.
Generally, you should keep fuel pressure above 10psi at all times since fuel is used to cool the pump in addition to being pushed to the injectors.
10-04-2011, 04:41 PM
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10-05-2011, 02:29 AM
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I bought a Raptor 100 today to replace my intake junk that Dodge uses...it is preset at 15-17 PSI and adjustable if you desire. Bosch specs say the pressure at the inlet should never drop below 10 PSI.
10-05-2011, 09:49 AM
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10-05-2011, 06:44 PM
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Your loss in HP could have been because the fuel temperature sensor in the VP was reading overly hot fuel from running such low fuel pressure and thus caused the VP to defuel. The question should be is, how long did you run with such low FP because 8 psi at idle more than likely meant zero psi while driving? Very bad for the VP in more than one way. This is why its so important to have a fuel pressure gauge.
10-05-2011, 08:15 PM
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Your loss in HP could have been because the fuel temperature sensor in the VP was reading overly hot fuel from running such low fuel pressure and thus caused the VP to defuel. The question should be is, how long did you run with such low FP because 8 psi at idle more than likely meant zero psi while driving? Very bad for the VP in more than one way. This is why its so important to have a fuel pressure gauge.
10-06-2011, 12:07 AM
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No.....more like zero psi. Thats because you will find that your new Raptor will have a 4 psi drop from idle to WOT. Meaning that your 18 psi idle will be around 16 psi cruising and around 14-15 psi at WOT. The more HP you make the bigger that difference will get too. So comparing the output capabilities of the OEM lift pump to the Raptors ability, you were probably around zero. And I'm glad to read that you have an understanding of what damage that low fuel pressure could have done. At least you're being realistic. Also, yea, $500 to install a gauge is a little pricey. Its not hard if you have any auto mechanical knowledge. We'd be more than happy to walk you through the process.
10-06-2011, 06:39 AM
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No.....more like zero psi. Thats because you will find that your new Raptor will have a 4 psi drop from idle to WOT. Meaning that your 18 psi idle will be around 16 psi cruising and around 14-15 psi at WOT. The more HP you make the bigger that difference will get too. So comparing the output capabilities of the OEM lift pump to the Raptors ability, you were probably around zero. And I'm glad to read that you have an understanding of what damage that low fuel pressure could have done. At least you're being realistic. Also, yea, $500 to install a gauge is a little pricey. Its not hard if you have any auto mechanical knowledge. We'd be more than happy to walk you through the process.
10-06-2011, 07:56 AM
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a mechanical gauge and some line with a needle valve can be done for 80-100 dollars, electric gauges are way more, a low pressure idiot lite can be done for about 25$ (cummins sells a sender for around 20$ or a sender and lite for around 60-80)
10-06-2011, 08:09 AM
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Where would you put the mechanical guage? At the FP ? I will go this morning and see about a warning light type setup...seems the best way to go...I just want to know when it is low..not check it every driving moment. Thanks for your comments....Doc
10-06-2011, 02:08 PM
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Finding a VP without having a core charge simply would mean you could have the VP just incase it ever fails. You're then only saving a couple days of down time while you wait for the replacement but you're still out the money for something that potentially may never fail. I'd wait.
There also may never be any codes indicating a problem. VP codes are generally created when there is a mechanical problem. Matter of fact the VP can fail completely electronically and never throw a code.
As for gauges, mechanical can be cheaper than electric but also know that you will have to deal with the fuel lines running in the cab or the fuel isolator line running in the cab to eliminate fuel to the gauge. Personally I dont care for either so I chose electric, but thats just me. Hooking up the gauge isnt all that hard as long as you know exactly what to do. The hardest part is figuring where and how you want to mount the gauge in the cab. Yes, you could simply hook a mechanical somewhere under the hood for reference when you want to open the hood and look but really, what good will that do you except to know what idle psi is.
Lastly, as mentioned, you can opt for a low pressure indicator light but I'm not sure if they're adjustable or not and most guys state that they come on at around 2-5 psi, which is far far to low. General consensus is never less than 10 with more people coming to the conclusion that never less than 14-15 is best. So sorry if I'm confusing you any more.
There also may never be any codes indicating a problem. VP codes are generally created when there is a mechanical problem. Matter of fact the VP can fail completely electronically and never throw a code.
As for gauges, mechanical can be cheaper than electric but also know that you will have to deal with the fuel lines running in the cab or the fuel isolator line running in the cab to eliminate fuel to the gauge. Personally I dont care for either so I chose electric, but thats just me. Hooking up the gauge isnt all that hard as long as you know exactly what to do. The hardest part is figuring where and how you want to mount the gauge in the cab. Yes, you could simply hook a mechanical somewhere under the hood for reference when you want to open the hood and look but really, what good will that do you except to know what idle psi is.
Lastly, as mentioned, you can opt for a low pressure indicator light but I'm not sure if they're adjustable or not and most guys state that they come on at around 2-5 psi, which is far far to low. General consensus is never less than 10 with more people coming to the conclusion that never less than 14-15 is best. So sorry if I'm confusing you any more.
10-12-2011, 08:14 PM
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Look to "streamline" your fuel system. Get rid of banjo bolts. Use Vulcan Performance's kit that has a fuel pressure port right where it connects to the VP44 - connect a grease gun hose (12") - then a "T" at the end - install a pressure sensor for your Fuel Pressure Gauge on one side, and install a 5 psi switch that will close if pressure drops down to 5 - 7 psig.
Note that many trucks might still have the aluminum block where the original lift pump was mounted, and that piece should be removed and the fuel line connected directly to the fuel filter (without using one of those suck banjo bolts!!)
Note that many trucks might still have the aluminum block where the original lift pump was mounted, and that piece should be removed and the fuel line connected directly to the fuel filter (without using one of those suck banjo bolts!!)