piñon&juniper

Thanks for the thoughtful reply. Can you recommend a good vacuum gauge setup, and for that matter, a reputable and not too costly fuel pressure gauge I could consider? More soon-

I just found the article on that valve, so I'll pursue all that good info.

Ok, if anyone is still paying attention... I got it all back together, and it runs, but something ain't right. Summary of current state of affairs: Problem 1 (Solved): ECU control of fuel pump is bypassed using @IBMobile's ASD relay technique. Works great. Problem 2 (soon to be solved): The ASD is controlling an Airtex style inline lift pump in the stock location, not Airtex brand. Seems to work, but only pumps about half the expected volume of fuel when tested. This pump is brand new (Standard Ignition STD FTP5 from O'Reilly). With all my recent experience with the unreliability of these pumps, I have ordered an AirDog FP 100 upgrade to mount on the frame rail. I't not here yet. Problem 3 (sort of solved): In messing with the fuel tank basket to replace the fuel sender and resolve a blockage of some kind, I replaced the original damaged fuel screen and another original fuel screen with my own made up draw tube in which I included a check valve. That valve now seems unnecessary, but it made sense at the time. The blockage issue is fixed, but the check valve probably adds a little unnecessary restriction to the line. Problem 4 (not yet addressed): I have a pretty janky looking fuel pressure sender and gauge setup, and I'm not too confident in its accuracy. There have been wild variations in its readings. It's range is 0-15 psi, and to be useful, it should be more like 0-30. Historically it mostly stayed pegged and only dropped a little under heavy load. More recently it's at 12 or so at idle, 5-9 on light load driving, and plummets under heavier loads down to 1 or 2. Observing this behavior for the first time is what started me off on my lift pump quest. Even since getting things kind of working again, the gauge has behaved in both ways (reading mostly pegged and now, consistently, the more alarming low pressure readings). Putting in a more reputable pump system will eliminate one of my variables. Getting a reliable fuel pressure gauge will eliminate another. My Question for now is: Is there any known possibility of an issue in an otherwise functional VP44 that would cause intermittent fluctuations in the return fuel volume and/or the pressure set point for that return? As I assembled things the most recent time, I observed the return flow, which was steady at idle but which increased dramatically with RPM. Perhaps that's normal with the VP44's internal vane pump? I'll update again after the AirDog installation. Thanks

What pump setup did you use?

Truck running again. The modification of the pickup in the tank worked. In the process, I found that there is no check valve in the tank. The part of the fuel canister that I though must be a check valve was in fact another fuel strainer, coarser than the one fuel had to pass through first. Go figure. I have no explanation for why I couldn't pull fuel through, but now I can. The 8 month old Airtex style lift pump was indeed bad. Maybe it went bad sooner due to the blockage? I don't know. Im ready to shop for a better lift pump set up now... seems cheaper than a week of lost labor and mysteries. Nothing like three problems at once to make for good troubleshooting. Thanks for all the help-

Yeah, but that’s still several paychecks away. And this in-tank stuff would not have been solved by that anyway. Still, I’m going to do it some time soon.

Here's the update: Truck runs basically right with a dip tube from the pump inlet directly into. diesel can. Transfer pump (I'm using my other Airtex pump that is 8 months old connected to the line in the engine bay) cannot pull fuel through the stock fuel lines to empty the tank. I dropped the tank and disconnected the supply line there, and it blows clear. There is some kind of obstruction in the pickup cannister- I couldn't pull any fuel through at the tank. Once I pull the canister out and it drains, I can both pull and push air through. Am I correct that part of the canister is a check valve to prevent supply line fuel flowing back to the tank and help maintain prime? I think I see where that would be (a D-Cell sized inner part on the bottom half of the canister that the fuel pickup line connects to the top of. If that is malfunctioning, it could explain some of the difficult priming and intermittent fuel pressure behavior. I'm attaching a picture of the alternative pickup I installed a couple of days ago, in case it illuminates anything, but my next move is going to be bypassing that inner check valve deal altogether, dropping a new line to the bottom with a stainless mesh strainer and an aftermarket check valve that I just ordered from NAPA, which I should get today. More soon! 392C049F-4379-4A3E-9D7C-399236995ED8_1_201_a.heic I tried to listen for it but way too much engine and exhaust noise, even with a listening tube stuck down through the tank filler. Safe to say that stream was dried up on running.

Yes, that makes sense. I'll try a free-flow test of the lift pump as well. I've read that it should pump about 45 oz of fuel during its normal 25 second priming period. Does that sound right? The weird thing is that this is happening with the eight month old pump and with the brand new pump exactly the same, and I can hear pretty healthy fuel return stream in the tank. I'll do my tests tomorrow morning- thanks to all of you-

I was getting toward that conclusion. I’ll try it ASAP and let you know. Thanks.

Here are two videos. First, I jumper the lift pump so it is simply always running. Fuel pressure on my gage is pegged, so above 15 or 16 psi. Once I start the truck, fuel pressure drops slowly, though I know the pump is running. Second, without the jumper. In this scenario, the new relay I installed actuated by the ASD relay 87, is starting the pump briefly on ignition, and continuously on running, as expected. I keyd over to ignition 3 times, each time raising the pressure a little, but after start, fuel pressure drops slowly again. I have no hard start issues (except as described earlier, on hot days with a hot engine, end even then only 2-5 seconds of cranking and then starts fine). 01DodgeFP - 1.mov 01DodgeFP - 2.mov

Mine is what seems to be called 'airtek' style. it mounts in the same location but the body is horizontal, with output toward the front, and inlet toward the back with an elbow on the inlet to accommodate the factory flex-line/quick connect.

Still having problems... I did the ECU lift pump control bypass following IBMobile's second method (using the ASD relay output terminal 87 to trigger a new relay for the lift pump). I now have the lift pump powered during starting and running, which is an improvement over what I had before (it ran during starting and intermittently or not at all when running). But I still have the same fuel pressure issue: fuel pressure goes up briefly when the key is turned on, and will go up and stay up if I run the pump with a jumper, but as soon as the engine starts, the pressure drops steadily to zero. The truck can still idle but will starve under any load or higher rpm. I took the trouble to break out a junction in my new lift pump wiring so I can attach a trouble light and see that the pump is powered when it should be (though of course I can't hear whether it's running when the engine is idling). More potentially pertinent information: This round of troubleshooting began when the truck ran low in fuel and would not re-prime. I took the opportunity to drop the tank, replace the broken fuel sender, and check things down there. The short flexible fuel lines between the hard lines at the frame and the fuel tank fittings were kinked during the tank removal (I don't see how that could be avoided) so I replaced them with good quality 3/8" and 5/16" fuel lines and hose clamps with a generous loop to ease fuel tank servicing. While replacing the sender, I tried to clean the screen elements at the bottom of the housing, and in opening it, I tore the screen, of course. Since those are very expensive as far as I can tell, I replaced the part with a different style strainer that had the right size fitting (7/16 ID) and a lug that I could use to fasten it in place. That seemed to work well enough. Getting the lift pump to prime and bleed the air was very difficult, as it had been when I installed it last October. I assumed it was another lift pump failure, but that would be strange with an 8 month old pump. Still, because of the bad reputation on the (inline style) basic lift pump, I had a spare handy. But it also made me wonder whether there could be some kind of issue with the tank-to-lift pump plumbing. In fact that possibility has been in the back of my mind for a long time, and that's one reason I went ahead and replaced the stock flex lines at the tank with new rubber. Is it possible that there is a leak in the suction line into the lift pump that would allow the pump to develop full pressure without the engine running, and then let in enough air to break the pump vacuum once the injection pump starts to pull? I don't have any wet leaks that I can see. Are there any good ways to check this that I can do without a lot of special tools? I'm pretty confident in my recently installed rubber lines and their connections, but could there be such a leak inside the tank's pickup tubing, or at the engine end? One more detail- this truck has had slightly hard starting when hot and when the weather is hot (only under those conditions) for as long as I have had it). Someone somewhere suggested that could have to do with air in the fuel. Does that make sense to any of you? Thanks for any ideas.

It comes on as it should, and all other engine and sensor functions seem fine. The history of erratic lift pump pressure and function seem to indicate just the run circuit for the lift pump is bad.

Thanks to both of you. I did mess with relays in the PDC before further research told me I was in the wrong track. I have tested the leads at the harness to the lift pump. I presume those are directly connected to the pins you mention on the ECM connector? If they are, then there is certainly a failure in the run circuit on the ECM but full voltage on prime/start. And I understand how that happened. I do indeed have a stock setup. I feel good about the relay approach and I appreciate the guidance. Just about to tip over 400K on this workhorse.

I've got my 2001 2500 5-speed 4x4 down with a lift pump problem. Currently the newly replaced (in-line style, original location on engine) pump is primed and working during starting and maintains over 15 psi (that's the my of my gage). If the truck has sat for a few minutes, it will turn on briefly when the ignition is turned on, and it responds to blipping the starter by turning on for 25 seconds. I can hear good fuel flow returning to the tank (which I just cleaned up when replacing the fuel sender). Once I got the fuel circuit bled of air, it started just fine, but as soon as the engine starts, the lift pump shuts off. The injection pump is apparently able to pull enough fuel to keep idling, but can't rev up much- obviously it's starving for fuel. Gage slowly drops to zero. I've swapped relays around for the fuel system and the ASD, with no improvement. I replaced the earlier lift pump with a fresh one, though the earlier one wasn't very old. There are no codes showing. My search of the forums suggests that the ECM might have a burnt out circuit that runs the lift pump while the engine is running as opposed to starting. If that's so, I don't know why it would be, and I'd like to positively diagnose it before embarking on that repair. I have had strange lift pump behavior, including drops in pressure that vary with load but also come and go intermittently. I did replace the lift pump that came with the truck from the previous owner after I had is pressure drop to zero at times, and at this moment I have just replaced the one I put in, because I thought it was causing the problem... not so, apparently, so I guess I have a working spare. Can anyone point me to any discussions that address this, or provide any further troubleshooting guidance? If my ECM is the problem, I'm more tempted to set up a new relay off some other signal source to turn the pump on, in hopes that I can retain the shut-down function that would trigger in case of a wreck. I'm guessing a new or repaired ecm isn't in my budget. Thanks for any ideas.