Issues with Upgraded Fuel System

I recently had the full Prospeed fuel system upgrade installed on my truck and then tuned with HP tuners. It’s a nice kit and it made great power, but I am trying to figure out how to handle an intermittent issue with long cranking cycle on startup.

After I got the truck back, I noticed that it would take noticeably longer to crank the truck in the mornings or if the truck had sat for a few hours. Im not sure what the correct metric to use here, but normally the truck would take about 3 “revolutions” of the starter to crank. On the long crank cycles, it is now taking 10-15 “revolutions” of the starter to crank.

The stock FPR and fuel system is designed to hold pressure in the fuel system after shut down. The Aeromotive FPR in this system holds no pressure on shutdown and the gauge instantly drops to 0. Per the Aeromotive website, this is normal and they are designed that way to maximize flow.

What I suspect is happening, is that over time the fuel is draining back to the tank after shut down. Note that the tundra does not have a “priming” cycle like other cars that turn the fuel pump on with the key in the “on” position. The fuel pump does not get turned on until the vehicle is actually cranked. Since there is no residual pressure in the system, then the pump is effectively priming the lines each time it is started. Sometimes it starts right up like normal, others it take a bit longer.

I am in no way stating anything negative about Prospeed or their kit, but I need to figure out how to fix this. They have been responsive in this issue, however they said they could not replicate the issue over 3 days that they had they truck. I even went over there one morning and it cranked right up with no issue. That said, the issue has persisted since i received the truck back and continues to do so.

 

This is a low rent schematic of the fuel system:

 

Can you take a video of it and send it to the company since they say they couldn't reproduce it over 3 days? Seems like you know when it will happen and can replicate the issue easily. Maybe get them to look in to it more. You might have gotten a faulty part.

 

I did send them a video, but have not heard back from them.

 

Doesn't sound like there's an issue? You said the system doesn't hold pressure, which matches everything you're saying. I think there's a few options to "fix" it, ie keep fuel in the lines--probably easiest would be to install a check valve somewhere on the pressure side. Then when the pump turns off there's still fuel on the non-return side. The second idea, which probably would work better in conjunction with the first, is tap into the fuel pump wiring and hot wire it to the ignition so when the key goes in it starts priming. I think that'll reduce cranking time, but not a lot. If you can get the check valve, then when the pump starts priming early it's to build line pressure and not try to fill all 12ft of empty line, then you could get in and turn it on and not have to wait a few seconds to prime the whole system every time.

EDIT: I just saw a post on instagram actually where they run a check valve straight off the fuel pump, presumably for the exact reason you're experiencing.

 

The TI 267 is supposed to have an internal check valve to prevent backflow. But if it is not holding any pressure at the FPR (considered normal per Aeromotive) then i could see fuel draining back on the return side.

Either there is a hardware issue or a systematic issue that was potentially not discovered during R&D of this kit. I am taking it back to Prospeed monday.

A couple options for systematic repair are exactly like you say, either trigger the fuel pump with a relay or put a CV in the system. I posed the question about the CV to Aeromotive, but they are recommending triggering the fuel pump to prime with the key on and a momentary switch (so its not running constantly). Personally i like the idea of a check valve, but they feel it could impede flow if placed downstream of the FPR.

 

https://www.youtube.com/embed/X5ES7VUC5v4

 

Here is a video that is likely more helpful in figuring out the issue. I’ve been recording startups over the last several weeks. Since the issue is intermittent, I never know when it’s going to happen at this point.
One thing that is notable in this video, is that when it is starting correctly(first two starts), the pressure on the gauge spikes immediately. When it has issues(last 2 clips) the pressure does not spike until after the truck actually starts running. Any thoughts on this?
https://youtu.be/t62OYw5-pag

 

Well guys, it's back at prospeed. Ill keep you updated.

 

I did receive the truck back today. Since i hate threads like these that never seem to have resolution, i believe my issue has been fixed.

Prospeed replaced the Aeromotive FPR. Disassembly of the old one showed some defect(s) that were not made readily available to me, but observed by the shop. A new unit went in its place. Secondly, a check valve (believed to be flapper style) was added near the external fuel filter.

Truck has been cranking like a champ. Where the pressure used to instantly fall to 0, it now holds pressure over a period of time (TBD).

Lastly Prospeed is a first rate shop to deal with. its no wonder people ship their vehicles here from all over the world. My truck made almost 600hp and 540 tq on the dyno and it feels like it. That coupled with their customer service is a solid testament to their product and service.

 

Long(er) term update. The Check Valve slowly faded out and i was back to where i was with the long cranks. I finally posted about this on SM and found out others were having this issue with the integration to the Tundra. This led me down the electric avenue and i found what seems to be a solution. If someone is interested, i can go in to all the details, but basically i came up with a plug and play harness that works on 2007-2011 trucks that isolates the FP ground from the control module and allows priming of the pump on the second key position. Have had zero issues in the last month with this setup.

 

im having a issue with a transfer flow 48 gallon tank that I had installed..after it sits overnight or for a few hours it does the same as yours.
my solution I did was I hooked up my reader and it has a actuator test and I can turn on the fuel pump..it works it'll start right up but its a pain in the butt to boot up the reader every morning or after its been sitting a while. I would like to hook up something like your talking about. can you help me out?
thanks

 

I would get in touch with @ViktorG the SME could probably assist.....?