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low fuel pressure after Lift and Injection Pumps Install


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Hello All,

I'm new to the forum, but have used this sites detailed articles quite extensively to learn more about my truck, and to troubleshoot my issues. (A quick thank you to any and all who have contributed to the site, as it is very well put together.) Having said all that, I seem to have run out of road on my own, and need to ask a question for the sake of clarity and specificity to my problem.

The truck is an '01 2500 automatic with about 250,00 on the odometer.

To go all the way back to my initial issue, I started getting dead pedal symptoms with a P0216 code, and fluctuating fuel pressure (sometimes 15PSI, sometimes about 7PSI depending on time of day and significant drop in pressure even on light acceleration) So decided to replace the VP44 and lift pump. I got a new one from BlueChip Diesel and replaced it this weekend along with a new Airdog FRRP-100 lift pump. I test ran the truck around the block, maybe a five minute drive and everything seemed great. I started with 15 PSI and it dropped maybe 1-2 PSI with hard acceleration. The next morning, jumped in to run errands and started at 10 PSI. I was concerned, but thought maybe it takes a minute to warm up (possibly a very dumb way to look at it, feel free to correct me.) I went about two miles to the hardware store and was very slowly losing pressure. I came out of the store, started and had 5 PSI that dropped a little more. I thought maybe I had a leak, but none were found, I jiggled wire harnesses just for good measure with no increase. I decided to re-prime the filter bowl and when I went to bump the starter, I did not hear the lift pump start at all. I unplugged the wire harness and cleaned it and seated it firmly, and got it to run again. The bowl primed and I started the truck again with 5 PSI, so I limped it the 2 miles home.

I have checked voltage to the lift pump (red wire going into lift pump) and get just under 12 volts when I just bump the starter. However, when I start the truck, it starts at about 10 volts and within a few seconds there is no voltage at that wire. Is that normal? I read there is no relay to the lift pump, so that wire should stay at 12 volts the entire time, Correct? The truck does not die, it stays at about 4 PSI, so its getting power from somewhere. 

I will also mention that there is a bit of a wiring nightmare under the hood. The previous owner added all the gauges himself and it isn't pretty, as well as several aftermarket stereo upgrades that he roughly stripped before he sold it to me. I've already lost the EGT gauge since taking ownership, so I'm somewhat suspect of the gauge itself. It's also in a location that I haven't seen. When looking at other owners pictures of their injection pumps, I've noticed no one has the gauge setup like mine. He added a fitting to the banjo fitting of the pressure line going into the injection pump with a hose running up to a sensor. Is this a typical setup?

The only thing I did not change was the filter, because the plastic cap to the bowl is stripped badly. I was able to get it off once when I first bought the truck about six months ago, and thought I didn't tighten it down very much for this reason, but am struggling mightily getting it off. I did take the line loose after the filter bowl to see if it was plugged up, and I had significant flow but that is just an eye judgement. I feel like it is enough to say it's not plugged but I could be wrong.

Any and all thoughts and guidance is very much appreciated!

Thank you!

Austin

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With the raptor it does have a adjustment screw for the pressure  have you tried turning it up. The pressure gauge sounds like the same way I put mine in and never has problems with it.not 100% sure but I thought I read somewhere on here that someone makes a metal cap 

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It sounds to me that your problem is in the power to the lift pump. When my grid heaters cycle my fuel pressure drops a little due to the voltage drop. You should have 12v to the pump on the oe harness. You could try hot wiring the pump to the battery just to see if that solves the pressure problem. Could be something in the ECM going out since the 12v comes from there. 

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It may be a good idea to check your fuel pressure with a second source.  There plenty of stories of people thinking their pressure is low so the adjust their pump to increase pressure.  Many of these people find they are adding too much pressure and their gauge was off the whole time. 

There are several ways to set up a fuel pressure guage, the big thing is to protect against water hammering.  I use a needle valve , others have a snubber.  Which guage do you have? Electric or mechanical?

Just want to make sure that you are chasing the correct problem.

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It may be a good idea to check your fuel pressure with a second source.  There plenty of stories of people thinking their pressure is low so the adjust their pump to increase pressure.  Many of these people find they are adding too much pressure and their gauge was off the whole time. 

There are several ways to set up a fuel pressure guage, the big thing is to protect against water hammering.  I use a needle valve , others have a snubber.  Which guage do you have? Electric or mechanical?

Just want to make sure that you are chasing the correct problem.

That's a good point but if he has no power to the wire that power on fuel pump then it's something electrical. 

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  • 4 weeks later...

Hey all,

I apologize for the slow response, and truly appreciate the responses. I submitted this during the site upgrade, and had issues logging on for a few days, so I chased down the problem and forgot to update you all ( very sorry.) I took a deep breath, took a fresh take on the problem, and started simply with the issue. I cleaned the connections to the lift pump, and managed to get my gauge to show in the cab "properly." I don't doubt that it is beginning to fail, but for the time being it is showing good pressure there. I believe it is an intermittent problem with the gauge. (it is mechanical.) I also took my time checking voltage to the lift pump, and the 12V returns after about 30 seconds and stays there. I guess I would get nervous when I saw zero and pulled the voltmeter and shut down the truck too quickly to see that. Thank you all for your help and advice!!

Austin

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5 hours ago, Austin said:

Hey all,

I apologize for the slow response, and truly appreciate the responses. I submitted this during the site upgrade, and had issues logging on for a few days, so I chased down the problem and forgot to update you all ( very sorry.) I took a deep breath, took a fresh take on the problem, and started simply with the issue. I cleaned the connections to the lift pump, and managed to get my gauge to show in the cab "properly." I don't doubt that it is beginning to fail, but for the time being it is showing good pressure there. I believe it is an intermittent problem with the gauge. (it is mechanical.) I also took my time checking voltage to the lift pump, and the 12V returns after about 30 seconds and stays there. I guess I would get nervous when I saw zero and pulled the voltmeter and shut down the truck too quickly to see that. Thank you all for your help and advice!!

Austin

Put a needle valve before your fuel pressure gauge and crank it down shut and back off just a hair so fuel can get through. It will prolong life of your gauge ,and eliminate any unstable pressure spikes. 

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