LPFP not cycling

[MT_Diesel]

I started my truck yesterday morning and it started just fine. I let it warm up 10 min or so and when I went out to go the truck wasn't running. It was -3* outside but truck was plugged in and LE winter fuel additive in the fuel. I tried to start it and it cranked for 15 seconds and wasn't building rail pressure. I also noticed the LPFP didn't cycle.

Today I waited til it was 17* in case the fuel was gelling yesterday. Turned the key on several times and no LPFP. I didn't bother trying to start it. It is a FASS titanium 125. Truck also has diesel Dr dual fueller.

Thoughts on troubleshooting ideas? I'll check the fuse but that'd be too easy. Any other procedures? If it needs replacement, should I avoid the FASS? I'm aware of the troubles people have had with FASS and air dog. Would the fuel lab pump be a better replacement, and if so any chance it would work with the FASS filter and separator?

Finally, knowing the HP fuel system is made of glass in the 6.4, are there any precautions I need to take with fuel pump replacement? Definitely want to avoid HP issues. Any help is appreciated!!

 

[powerstroked08]

Make sure your fuel shut off switch isn't tripped

 

[DEEZUZ]

go back to a stock supply pump and stop rolling the dice with these fuel pumps. IF you need more fuel than stock can put out, put a 6.0 or 6.7 lift pump... I would never ever run any of these aftermarket pumps. Have seen and heard nothing but trouble across the board

 

[MT_Diesel]

Reset fuel shut off, no change. I'll test the fuel pump relay when I get chance.

This pump was on the truck when I bought it so I don't have the stock pump.

Also forgot to mention no codes were thrown when I went out and truck wasn't running.

 

[powerstroked08]

I would start at the basics then. check the fuse, then go from there. Check for voltage at the pump etc. Also I have been running a fuelab pump for awhile now and its been awesome. Easy install and it works flawlessly. Its a digital brushless motor and is quiet. I have no complaints.

 

[White_monster]

go back to a stock supply pump and stop rolling the dice with these fuel pumps. IF you need more fuel than stock can put out, put a 6.0 or 6.7 lift pump... I would never ever run any of these aftermarket pumps. Have seen and heard nothing but trouble across the board

This is not a good idea. The fuel pressure used on the 6.0 and 6.7 is way higher than the 6.4 should ude. The k16 injection pump already has seals that tend to leak when pressure is cranked over 14psi so why would putting 60psi be a good idea. You could use a regulator and dump pressure that way but then you are heating fuel up, via the pressure, for no reason.

OP I'd start with the basics and go from there. The motor may have failed but before jumping to conclusions test everything. I've had great luck with my Aeromotive a1000 pump. Going on 6 years with it and about 100,000miles on it.

 

[MT_Diesel]

Thanks for the reality check white monster. I was thinking the same think about stock pump pressures.

I'll check the basics as soon as it warms up a little (-2* now) and report back.

 

[DEEZUZ]

This is not a good idea. The fuel pressure used on the 6.0 and 6.7 is way higher than the 6.4 should ude. The k16 injection pump already has seals that tend to leak when pressure is cranked over 14psi so why would putting 60psi be a good idea. You could use a regulator and dump pressure that way but then you are heating fuel up, via the pressure, for no reason.

OP I'd start with the basics and go from there. The motor may have failed but before jumping to conclusions test everything. I've had great luck with my Aeromotive a1000 pump. Going on 6 years with it and about 100,000miles on it.

Yes, the use of those pumps and regulator is what I was referring. I wouldnt worry about what, maybe an extra 15-20 degrees that the fuel would see being at that pressure?

 

[MT_Diesel]

Had a chance to troubleshoot it yesterday with warmer weather. Tested voltage at the pump and it doesn't appear be getting power (small female terminals made it tricky with my multitester probes). The fuse appears good and I swapped the relay for a known good one. I removed the fuel shutoff switch, continuity is good through it in the on position and jumping across the plug terminals didn't change anything. Also, it has voltage when the pump should be on.

Next steps are to use an extra battery I have to put power directly to the pump to check function, then test the high amp side of the relay. I'm cautiously optimistic that it's not the pump.

Any other suggestions? Thanks!

 

[Jonnydime]

go back to a stock supply pump and stop rolling the dice with these fuel pumps. IF you need more fuel than stock can put out, put a 6.0 or 6.7 lift pump... I would never ever run any of these aftermarket pumps. Have seen and heard nothing but trouble across the board

Do 6.0 or 6.7 fuel pumps flow more than a 6.4?

 

[MT_Diesel]

I direct connected a battery to the pump and the pump works fine. Replaced the fuse even though it looked good and took the relay out and actually tested it. Relay functions as it should. So now it looks like a harness problem. Anyone know of a problematic spot in the harness that would cause no voltage to the pump? If not, I'll just start tracing and testing the circuit.

I'm thinking it was fortunate the truck died while idling instead of while running down the highway since it essentially ran itself dry. Am I going to need to purge air bubbles out of the high pressure system in addition to the low pressure system? Is it possible (or even likely) that I did damage to the injection pumps? Thanks for any input.

 

[MT_Diesel]

Well, I figured it out. Whoever installed the FASS pump left the wiring harness loose in the engine bay and the wiring loom (and presumably the wires) was melted by the exhaust manifold. When I peeled off the melted loom, there was no visible exposed wire or melted insulation but I cut out the suspect section anyway. The fuse for the FASS (wired directly off the battery with a relay) was blown so I replaced that. Fuel pump works now.

Now for my question. Since I didn't technically run the system dry and suck air up in the tank, do I need to purge air out of the low (and/or high) pressure system? I didn't try to start it since I was an ice cube when I finished. Bleeding the low pressure system is easy enough but I don't have the tool to replace the banjo bolt and bleed the high pressure system.

I would appreciate any advice. Thanks!

 

[powerstroked08]

I would cycle the key a few times and listen for the air to purge in the fuel tank. Then start it

 

[MT_Diesel]

You don't think I'll need to open the schrader valve on the fuel cooler?

ETA - Does the fact the fuel bowl has been removed change the process any?

 

[MT_Diesel]

It's never easy. :fustrate: I cycled the pump on 10 times for the full 30 sec each time. Then tried to start it. Its not building rail pressure and no start. Any suggestions? Thanks!

 

[powerstroked08]

How many times did you try to start it?

 

[powerstroked08]

I have had them air lock up and need to be bled with the low pressure pump on, while cranking it over with the jumper wire by the passenger battery, with the back banjo bolt out of the fuel cooler. Not hard to do but you need a double banjo bolt, and an eyelet with a hose on it(to a bucket) to purge the air out. At least that works good for me.

 

[MT_Diesel]

I only tried once. Probably should have tried more.

Where do you get a double banjo bolt and an eyelet? Do you have to get them from ford or can you get them at any automotive store? Now the temp has dropped back below zero so think I'm going to take it in to the local diesel performance shop and have them do it this time. But I'd like to get the equipment the next time it happens.

Thanks for your help.

 

[Lipka101]

Man. You give up easily. Turn the key on, Crack the rear bolt on the fuel cooler, cycle it a few more time and start it up. Worked great with a completely empty fuel system.

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