23 Gal Tank Efi in tank fuel pump issues

[Broncostang]

i have about 6 month run time on new build and about 1000 miles, throttle body fuel injection system with 23 gal efi tank with in tank fuel pump. Everything was fine until I tried to start last week and notice I couldn't hear the pump kick on. I tested volts at the wire and getting 12 plus volts to the fuel pump at start until it cycles off. At first I was thinking issue with the ecu in the throttle body, but if I'm showing voltage at the fuel pump wire; seems that its either issue with pump or wiring in the tank? Also, is there a replacement part number for the pump to get a local parts store for these?

Can you test a fuel pump with wire directly from battery to pump wire to see if it powers on?

Any suggestions would be appreciated before i drop the tank...

 

[904Bronco]

Random thoughts here...

You haven't shared what 23 gal tank you have? That might narrow it down to a pump replacement, also need to know how many LPH your system needs, plus pressure. (guessing 60 psi?)
How is the ground for the pump? For giggles, can you replace the fuel pump relay as a test? Guessing it is probably internal to your TB system.
There might be an issue with the ECU, can you have someone listen after the pump cycles, then you attempt to start it, to see if the ECU turns the FP back on?
Parts these days, well there are no guarantees it seems on how long they will last
Yes, you could briefly apply direct Batt voltage to the pump, but you have already stated that you have power to it. And you have heard it cycle on to pressurize the system.
ECU in TB, so aftermarket fuel injection... I am sure the manufacturer could provide you with a FP part# and then you could cross it over. Not all fuel pumps are equal though

 

[rocknhorse76]

Start by putting in a ground wire from the tank body to the frame. Don’t rely on the mounting strap or channel for a pump ground. One of the screws that secure the pump cover to the tank will do. Try turning the key on to see if the pump cycles. If it doesn’t, run a jumper wire from the battery to the pump. If it still doesn’t come on, you have a bad pump or faulty wiring in the tank. Let me know what your results are before you go any further.

 

[jamesroney]

Start by putting in a ground wire from the tank body to the frame. Don’t rely on the mounting strap or channel for a pump ground. One of the screws that secure the pump cover to the tank will do. Try turning the key on to see if the pump cycles. If it doesn’t, run a jumper wire from the battery to the pump. If it still doesn’t come on, you have a bad pump or faulty wiring in the tank. Let me know what your results are before you go any further.

Everything @rocknhorse76 said...except don't trust the ground wire to the frame. Ground it to the body. (or ground your frame to the engine block / body.) The frame on an early bronco is not connected electrically to the battery ground, except thru the steering column shaft bearings, and the gas tank where it touches the body and strap. I will never understand why the fuel gauge ground is attached to the frame.

As @904Bronco said, you need to know if you have a PWM pump, or a regular 12V high pressure pump. No problem jumping a normal fuel pump and letting it run. I usually jump it at the fuel pump relay to avoid endless cycling of the key.

Step 1, jump power at fuel pump rely.
Step 2, measure fuel pressure at the rail.
Step 3, check the pump power.
Step 4, check the pump ground.
Step 5, replace the pump.

 

[Broncostang]

Thank you sir! The braided ground strap had come loose inside the pigtail mount.

 

[rocknhorse76]

Everything @rocknhorse76 said...except don't trust the ground wire to the frame. Ground it to the body. (or ground your frame to the engine block / body.) The frame on an early bronco is not connected electrically to the battery ground, except thru the steering column shaft bearings, and the gas tank where it touches the body and strap. I will never understand why the fuel gauge ground is attached to the frame.

As @904Bronco said, you need to know if you have a PWM pump, or a regular 12V high pressure pump. No problem jumping a normal fuel pump and letting it run. I usually jump it at the fuel pump relay to avoid endless cycling of the key.

Step 1, jump power at fuel pump rely.
Step 2, measure fuel pressure at the rail.
Step 3, check the pump power.
Step 4, check the pump ground.
Step 5, replace the pump.

Don’t listen to anything I say.

 

[Broncostang]

Don’t listen to anything I say.

 

[Broncostang]

Well I thought I had this solved until I went to try and start this morning, no fuel pumping. Yesterday I drained the tank, lowered enough to put another ground strap on then filled up with a few gallons of gas and the pump came on and started. Tested this morning; Still getting 12 volts when key is cycled on for 5 sec l, also ran a jump wire to the pump and didn’t hear anything. Ran an additional ground strap to double check grounds. I have smelled and could hear enormous amount of pressure built up in tank when releasing the gas cap since I’ve been using the bronco. Could this be causing an issue with the fuel pump causing it to lock up? I’ll drain the tank again and see if that frees up any pressure in fuel pump.

23 gallon Tom’s in tank fuel pump gas tank

 

[DirtDonk]

You really shouldn’t ever have pressure buildup in the tank.
Whether that’s causing your problem or not, it’s hard to say. But it shouldn’t be there.

What exact tank is this, and how old is it?
Not how long is it been installed necessarily, but how long ago did you buy it. And was it brand new from a vendor at the time, or used from someone else?

At one point there was a rash of pick up tubes, falling off and out into the tank from of bad clamp, or bad hose, or something. I don’t really remember anymore.
There was also a batch of tanks that came out with a weld spatter in the pick up tube.
But no matter what, how are you venting the tank?

 

[Broncostang]

Vented through gas cap only, I just drained it and re tested, the pump still will not cycle .

I had drilled a small hole in the gas cap for venting, and the 3/4” hose that comes up to filler neck area. No other venting system is being used.

Purchased 11/2020 Brand New
Tom’s Bronco 23 gal efi w/in tank pump Part #6199

 

[Speedrdr]

Don’t listen to anything I say.

It’s too late; I done already listened!! Lol

Randy

 

[rocknhorse76]

It’s too late; I done already listened!! Lol

Randy

 

[Broncostang]

The ground wire that attaches to the pump inside the tank want’t crimped properly causing insufficient/inconsistent grounding.

 

[DirtDonk]

Great find. Glad you figured it out.
And thanks for coming back around to let us know.

Paul

 

[rocknhorse76]

Glad you got it sorted out.

 

[nvrstuk]

Glad you figured it out BUT... you STILL have to fix the "enormous amount of pressure" in the tank you were talking about.