Fuel Pump Fuse blows

Can't find the same issue anywhere, feel free to link it if you find it.

2010 5.7L 2wd tundra Harrop Supercharged tune from D3
DW 340 LPH fuel pump

The truck was supercharged and the fuel pump replaced about 20k miles ago, it had no issues for about 18k miles but recently it started having an issue where at or near redline the fuel would get too lean and cause the knock sensor to go off and cause a misfire so I'd have to pull over and restart the truck, I thought it was just because I was using 91 instead of 93 and tried keeping it off red line, then it blew a fuel pump fuse at redline one time, then it would blow the fuel pump fuse every 3-4 days, then every day, and now it makes it between 100 feet and 5 miles before the fuse blows.

I have already replaced the fuel pump, and I had the wiring checked by the dealership, they only checked the front half of the car not to the tank since they wanted 3 hours labor to drop the tank and diagnose, at this point i'm thinking maybe its a bad fuel pump control module and it progressively getting worse was due to corrosion getting worse over time? any input is welcome!

The wires from the pump to the hat are not shorting
the wires from the hat to the output fuel pump control module are not shorting
I am unsure how to test the wires from the fuel pump control module input to the relay for shorts.
In the picture the 3 highlighted pins all had continuity, but only some of the time? should they? The highlighted pins are all on the input side of the fuel pump control module

 

Is it a stock or aftermarket FP? And are we talking about a 15A fuse?

My guess is you have a restriction along the way. If it were on the suction side, its less likely to draw a load a its cavitating the pump.

A restriction limiting flow could be partially cause this but I suspect something else. You need to get an amp meter in line with the pump and see what its actually drawing for current. Again, OEM pump or aftermarket?

Most hand held DMM's cap at 20 amps and may not be able to handle this.

Put eyes on the entire run of fuel pipe from tank to injectors and make sure there are no kinks. Also, swap out the fuel pump relay as bad contacts could play a role here too.

GL

 

New thought. The Fuel Pump Control ECU, if damaged could be suspect as it has to pass 25A to that ECU. It's at the back of the truck, left side. I'd replace it and the two relays.
EFI and C/OPN...

 

Replaced the fuel pump control ECU, the fuel pump, and had the wiring inspected by a dealership who assures me there is nothing wrong with the system from the battery to pump... Any ideas are greatly appreciated.

 

Maybe try using a pump hardwire kit: High-current Universal Kit to Hardwire Fuel Pump to Battery – DeatschWerks

What size fuse is it that blows? Flex Fuel or Non-Flex Fuel truck?

 

maybe add some dielectic grease on associated connectors?
https://www.acehardware.com/departm...vmzZGhxhf6V9g3Yro2BoCKFkQAvD_BwE&gclsrc=aw.ds

 

Gonna throw a guess in as a bad fuel pressure regulator. The first Harrop kits had a janky setup where they had you crush the original regulator with a tool to increase the fuel pressure. The later kits like mine would just ship out with a higher pressure FPR. If it failed and jacked the pressure up it could cause major load on the fuel pump and jack the amp draw and blow fuses and kill the pump. You will have to get a replacement from Harrop since it’s not a normal fuel pressure FPR. Id then due some data logging after replacing it and make sure the fuel trims and AFRs look good. Just a guess, but makes sense to me if you checked everything else.

 

I have the newer kit, the kit is only 6 months old and came with the instructions to crush my FPR but also came with a pre-assembled one, what would a normal fuel trim and AFR be? I have a way to test it but Im not sure what im looking for.

i might try running a separate run like the DW one for the pump but i feel like thats not an actual fix, since the truck ran fine for 15k miles then slowly started getting worse like something getting corroded/rusted/clogged

It is a 15a fuse that blows, I have gone up to a 25a and it still blows and I dont want to go higher, it is a Non-Flex Fuel vehicle.

Next I'm going to try disconnecting the return line and ensure theres nothing clogging the line, then Ill go grab a pressure tester and ensure the regulator is holding the correct pressure in the rails.

Will update here.

 

For kicks you might try swapping relays around too. It seemed like it took 3 of them to complete the path.

That said, if the contacts were burned, the resistance would go up until the burned. Still worth a shot. Remove and exchange or remove, power them on and zero your ohm meter and measure across contacts. Should get 0.1ohms or so.

Did you ever swap out the pump ECU at the back of the truck?

 

You would probably want to see the LTFTs +\- 15-20%. AFR at WOT should be 10-11.5ish but you would need a wideband gauge to read that rich. Swap in the stock Fuel pressure regulator and see if it keeps blowing the fuse with regular driving. Just don’t go WOT as it will be lower pressure and run leaner unless you got it tuned with the lower pressure.

 

I have tried swapping out the pump ECU and i have tried swapping around relays, installing a standalone circuit from DW now as somebody else suggested^ i will measure resistance across relays if it continues to have issues with the new circuit

 

Update : i ran the DW hardwire kit from battery to pump and used the old positive 12v signal for the fuel pump for the new relay, the new fused line did not blow but the factory fuel pump fuse did blow, the one thats only job is as a signal wire for the relay????? Going to find a new signal wire source and try again tomorrow

 

The downside as I'm guessing you know is that in the event of violent crash and fuel line rupture, bypassing the OEM configuration would allow fuel to be pumped and a fire to continue.

I was wondering if it would march up the food chain and take out the next fuse.

 

Solved the fuel pump fuse blowing, one of the bolts from the fuel rail had slowly backed out and the fuel rail was just, loose. Not sure how it caused the fuse to blow but it did.

 

I’m guessing there was some type of ground issue

 

But i ran a hardwire kit to power the fuel pump completely separately from the factory circuit, and the original fuel pump fuse still blew, a short at the rail would cause injectors to stop working (is my assumption) which should be the EFI fuse instead of the fuel pump fuse? I hope? And one bolt was still tight so only half the rail could move, very strange and makes very little sense logically.

 

Nothing grounds to the fuel rail. The bolt being loose shouldn't have affected anything pressure-wise, unless the injector closest to it was coming loose as a result, but there would be fuel spray to indicate that.

Can you post how you connected the wiring?
--Which wire from source to relay pin, grounds, etc.
Relay location?
Pump Ground location?
Relay Trigger-on?
--I think you said you intercepted fuel pump positive for this?
Relay Ground location?

 

The fuse no longer blows after tightening the bolt. That was the cause of the issue.

couldn't tell you why.