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New VP44 & FASS / Low Fuel Pressure

4231 Views 20 Replies 7 Participants Last post by  groundHog
Well, after spending the better part of two weeks trying to absorb all I can from this site, I have a question.

Last week, my VP44 died. I replaced it and at the same time changed the stock lift pump to a FASS DDRP and put in a new filter. I did about 145 highway miles the next day and it ran incredibly well.

Then the day after that, I went to work in heavy start/stop traffic. About 17 miles into my trip, it started running rough and missing. It got progressively worse and barely got me to work (total 25 miles). I had codes P0122, P0251 and P0252.

To make a long story short, I pulled the connectors off the VP44 and the APPS, hosed them down with contact cleaner, blew them out, reconnected, reset the APPS and cleared the codes.

That seemed to fix everything until I was on my way home. About 17 miles into the trip, again in start/stop traffic, it did the same thing. This time, I had P0251,
P0216 and P0252. By this time, the VP44 & FASS have a total of 162 miles on them. I pulled the connector again, reconnected without doing anything to it and started the truck. Again, it worked fine. Unfortunately, this was more than an hour after it stopped, so I don't know if it got better because it cooled off or because I pulled the connector.

Anyway, I put a gauge package in today (ISSPRO EGT, boost & electric fuel pressure) and took a test drive. Fuel pressure was initially 14 - 15 psi at idle and dropped to 5 - 6 on normal acceleration. On heavy accel, it was dropping to as low as 2 psi and very slow to come back up :doh:. My test drive was about 8 miles total and toward the end, the pressure wouldn't come back above 10. Idling in my driveway, it was about 9. Outside temp, for what it's worth is about 56°.

Any ideas? I'm wondering if I have a problem in the power supply to the FASS now.
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Hey Burner, I just replaced my stock pump with the FASS DDRP last thursday and had kinda the same problem with my truck. After the initial test run of about 30 minutes it ran great for about 25 of them then I was about 4 miles from home and lost fuel pressure. made it home very gingerly. Long story short I tried many things the rest of the day gave up at midnight got back on it saturday took the pump off and noticed at the pump head one of the screws didn't look right, wasn't seated down and looked cockeyed just a little bit. I took the 4 screws out and the end plate off to check the o-ring seal, it looked fine then I put it back together making sure to tighten them down like you would a tire on your truck. Put it back on and now have 17 psi at idle, drops to 8 psi full throttle 0 to 70mpg but jumps back up to 17/18 psi now every time. Normal driving it doesn't drop below 12 psi. My psi's were about the same as yours on my first test run, I believe the pump was sucking air at the pump head causing my low fuel pressure. Now I can just flat out run it like a dog and it just keeps on going. Hope this helps!!!

Talked to my supplier (the diesel store.com) they talked to FASS, FASS is supposed to call me back, waiting on FASS to call me to give them the good news
 

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Discussion Starter · #4 · (Edited)
Wow, that gives me hope! I spent the night wracking my brain (both shriveled up little cells) trying to think of things to check. I'll get busy and report back later. Thanks!

cmns2500: As a platinum member of the Murphy's Law Alumni Association, I have a mortal fear of tapping the pump wire. :)
 

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Wow, that gives me hope! I spent the night wracking my brain (both shriveled up little cells) trying to think of things to check. I'll get busy and report back later. Thanks!

cmns2500: As a platinum member of the Murphy's Law Alumni Association, I have a mortal fear of tapping the pump wire. :)
i hear ya there man:thumbsup::doh::lol4:
 

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sounds like that will fix it:thumbsup:

i just hope you don't plan on usin a tuner that taps the pump wire with the DDRP though..
I agree, It's my understanding that this is not a good ideal with the DDRP
 

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Discussion Starter · #7 ·
Well, after a long day of tinkering, I'm no better off. I pulled the FASS DDRP, made sure it was clean on the outside and carefully removed the cover plate. The 4 screws seemed OK and the O-ring was in good shape. I reassembled it, paying attention to the sequence & torque of the screws, then put it back on the truck.

Getting back out on the road, things started out OK like last night. I get about 21 psi when I bump the starter and it was idling at 14 - 15 psi.

On my 3 mile drive to the highway, everything looked good. My first run up the entrance ramp at WOT showed 6 psi. Then I exited and got back on. This time, it hit 1 psi. I had to coast and let the engine idle to get it back to 12. After that, it cruised at 70 mph with 7 psi and 55 mph with 8 psi.

Back on the surface streets going home, it never got over 12 and on the final stretch of about 1/2 mile up a very slight grade at a steady 30 mph, it would gradually tick down to near zero. By coasting & idling, I could get it back up a little, but I was nursing it home. Just like yesterday.

Ugh. Bad DDRP? Sucking air before the pump? If I'm sucking air, I'm inclined to get a relocation kit & put the DDRP near the tank. If that's it, hopefully the problem point would be in the supply line and not in the tank.

I'm also tempted to abandon the the DDRP and go with an Airdog. Money is starting to become a problem, but I really don't want to buy another VP44.

:S:
 

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Are you running a Mech. fuel press. gauge? I was having a lot of trouble with getting consistant readings from mine. I removed the isolater and installed a needle valve. The gauge soon took a crap for good. I put a new gauge in and all is great. In fact it never worked that good... EVER. Just my .02
 

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Discussion Starter · #10 ·
I'm running the ISSPRO EV2 30 psi electric fuel pressure gauge. It's a stepper motor gauge with a 3-wire sender. I have the sender mounted to a banjo bolt 1/8" NPT adapter on the bottom of the fuel filter housing.
 

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Read the Newbie post that Clunk put together...
It sounds like you might have one of two issues here; 1. if the pump is louder than normal when the pressure drops you are sucking air or have a clogged inlet screen... 2. The overflow valve could be getting stuck open. This is the nut on the banjo bolt return fuel line at the front of the VP These are designed to pop at anything over 16psi. If you are running 18 to 21 like you post, it could be getting stuck open and fuel is bypassing the VP alltogether. A new one is about $35 at any Dodge Dealer that is still in business..... Chris
 

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my ddrp is not getting above 13psi idling. it says that it pumps 33% more than the oem but how can that be with only 1 more psi.
 

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Discussion Starter · #14 ·
Thanks for all the replies and info, guys. :yourock: I had read Clunk's post before.

Interesting comment about the overflow valve; I'm using the new one that Midwest Fuel Injection supplied with the rebuilt VP44, but that's not to say it's not a possibility. It's something I hadn't considered anyway.

I couldn't tell any difference in sound level from the pump between pre-drive when pressure was good and post-drive when it was low, but the way the gauge is reading, I'm guessing the most likely culprit is air coming in through the supply line from the tank.

Paul at MFI suggested Thursday that I run clear fuel line from the filter, up out of the hood and back down to the injector pump so I could see foaming or bubbles if air was being sucked in. I had that setup for a day, but it made me very nervous because that clear line is pretty flimsy. I did protect it with split loom tubing, but it was a bit leaky at the pump end. I drove about 50 miles like that and never saw bubbles, but who knows? Maybe if the weather cooperates tomorrow, I might try it again now that I have the fuel pressure gauge and can see what that's doing.
 

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Well, after a long day of tinkering, I'm no better off. I pulled the FASS DDRP, made sure it was clean on the outside and carefully removed the cover plate. The 4 screws seemed OK and the O-ring was in good shape. I reassembled it, paying attention to the sequence & torque of the screws, then put it back on the truck.

Getting back out on the road, things started out OK like last night. I get about 21 psi when I bump the starter and it was idling at 14 - 15 psi.

On my 3 mile drive to the highway, everything looked good. My first run up the entrance ramp at WOT showed 6 psi. Then I exited and got back on. This time, it hit 1 psi. I had to coast and let the engine idle to get it back to 12. After that, it cruised at 70 mph with 7 psi and 55 mph with 8 psi.

Back on the surface streets going home, it never got over 12 and on the final stretch of about 1/2 mile up a very slight grade at a steady 30 mph, it would gradually tick down to near zero. By coasting & idling, I could get it back up a little, but I was nursing it home. Just like yesterday.

Ugh. Bad DDRP? Sucking air before the pump? If I'm sucking air, I'm inclined to get a relocation kit & put the DDRP near the tank. If that's it, hopefully the problem point would be in the supply line and not in the tank.

I'm also tempted to abandon the the DDRP and go with an Airdog. Money is starting to become a problem, but I really don't want to buy another VP44.

:S:
Have you tried the DDRP without the mesh screen? if not try it and test it out, I did and liked the results
 

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Thanks for all the replies and info, guys. :yourock: I had read Clunk's post before.

Interesting comment about the overflow valve; I'm using the new one that Midwest Fuel Injection supplied with the rebuilt VP44, but that's not to say it's not a possibility. It's something I hadn't considered anyway.

I couldn't tell any difference in sound level from the pump between pre-drive when pressure was good and post-drive when it was low, but the way the gauge is reading, I'm guessing the most likely culprit is air coming in through the supply line from the tank.

Paul at MFI suggested Thursday that I run clear fuel line from the filter, up out of the hood and back down to the injector pump so I could see foaming or bubbles if air was being sucked in. I had that setup for a day, but it made me very nervous because that clear line is pretty flimsy. I did protect it with split loom tubing, but it was a bit leaky at the pump end. I drove about 50 miles like that and never saw bubbles, but who knows? Maybe if the weather cooperates tomorrow, I might try it again now that I have the fuel pressure gauge and can see what that's doing.
you drove 50 miles today? with what kind of pressure? I couldn't go over 3 miles without having to bleed the air out.
 

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Discussion Starter · #17 ·
Sorry for the confusion. I drove 50 miles Thursday night after putting the clear fuel line in with a loop so I could watch it through the windshield. That was before I had the FP gauge installed (which was yesterday), so I don't know what was going on with the pressure then.

Then I drove 3 miles Friday and the clear line started leaking, so I removed it and put the stock hose section back between the filter and the VP44.
 

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Discussion Starter · #18 · (Edited)
Problem solved! :woot: And -- thank God -- without having to drop the tank! Tonight I decided to do what I should have done days ago -- replace the supply line from the tank to the lift pump. Also, Eric at Midwest Fuel Injection said the intake prescreen on the FASS DDRP is sometimes a problem, so I removed that too.

Well, I cranked 'er up and behold! Fuel pressure! :headbang: Yessir, I got 20 psi at idle. I took it out on the highway and ran the accelerator pedal all the way up to "11".

The lowest pressure I could get was 18 psi!!! At one point, the gauge appeared to flirt with 17 psi, then thought better of it. ;)

This weekend's project (after replacing the front rotors & pads on my wife's car) will be to weld up a relo bracket and move the DDRP back on the frame. Now I need to decide whether to cut the connector off the engine harness and solder an extension to the relay or cut the one off the FASS and work forward from there.

Thank you all for your help. This forum rocks!


Edited to add: Quick release fuel fittings are the work of THE DEBIL!!! That is all. :SMART:
 

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710Burner said:
Problem solved...replace the supply line from the tank to the lift pump. Also, Eric at Midwest Fuel Injection said the intake prescreen on the FASS DDRP is sometimes a problem, so I removed that too...
I think the fuel systems on these trucks have more issues than just the lift pump. Like fuel lines, fuel gauge floats, ...

Back in January when I installed a DDRP, it delivered 18-20 psi at idle and 12 or so at WOT, but only after I installed a DrawStraw II and a 3/8" fuel line. I had some serious fuel tank issues: the float had disintegrated and caked up on the stock fuel draw/bucket system. That's why I installed the DSII (and 3/8" fuel line), and that's when the DDRP provided much better fuel pressure. After the DSII install, I couldn't get the pressure down to 10 psi.

I also have an inline filter installed on the fuel supply line to the DDRP. I added it for two reasons: (1) I dint think the little screen in the DDRP inlet line would last long with all the pieces of the disintegrated float that were caked on the stock draw system, and (2) the DDRP was difficult for me to reach, and I hated the idea of having to take off the inlet fuel line to check and/or clean the inlet screen.

So...it sounds like a larger fuel line and an inline fuel screen should be included with a DDRP install.

- djb
 

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that's why people who ain't gonna make huge power should go ahead and get a Raptor 100, it comes standard with the 1/2 inch lines, and all else needed to install...:thumbsup:
 
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