Hello all. Trucks a 2001 5spd/4x4. I had what seemed to be a failing lift pump so I installed a new FASS 150 and straw kit. My pump barely makes noise when I turn the key, sometimes my gauge goes to 2 or 3 psi other times 6 or 7. It seems like the pump is not getting the power it requires. I was told my ECM could be problematic. Truck seems to run fine I occasionally get a spike in my volt meter  triggering "check gauges" but wouldn't that be a PCM issue? Any direction is greatly appreciated, I have searched but am nervous to shell out for am ECM if it's something else.

Clean EVERY ground on the truck.

 

Check for Voltage to the lift pump from the ecm when running.  I would't worry so much about cranking psi at htis point.   I would guess you just have a bad ground or something causing your issues.  

 

Check your alternator for AC noise. 

 

Lube every plug with Dielectric grease.

Good advice above. When you first turn the key you only get a little blip, 1/2 second or so, hence the low pressure. bump the starter with no engine start and it should run for 25 seconds or so. Your idle and WOT pressures are the ones to watch.

Edited December 30, 20168 yr by dripley

ECM is supposed to control a relay that switches on the pump to run off the batteries. Getting power to run the pump from the ECM is not good as the amount of lift pump load can increase over time, especially as it wears, can slowly burn up the ECM circuit board. Remember the ECM isn't to be used as a fuse cause it's too expensive.

 

Fist thing is to do 1/2 inch lines all the way so the pump doesn't work as hard and raise the pumps full potential. It has to maintain above 14 psi at all times to get max cooling flow to the injection pump.

Install a rely for the fuel pump.  The relay will reduce the load on the ECU giving it a longer life along with giving the fuel pump full battery/alternator voltage and amperage it requires.

 

Doesn't the fass already use a relay?

Edited December 30, 20168 yr by Me78569

Only if it's installed.  It's not mentioned in the original post, only the ECU and the FASS.  So, was the relay installed with the FASS? 

His symptoms indicate that the lift pump is powered only by the ECU. Plus the OPs' way of describing what he did for his install says the same thing. I hope he gets back to say he changed it and got it right.

 

Thanks for the diagram IBM.

 

 

I agree. IBM diagram is the cats meow. Did it for my truck, fuel pressure is very steady.

 

I did a little looking at Fass install instructions and would seem they come with the relay and wiring harness though I did find one set for a 150 that did not have the relay just a harness to connect straight to the factory plug. The seemed old but could not tell for sure.

 I guess when i read the OP's post I just thought he was confused on what the pump does at key on. Thought he was expecting full pressure at key on.

 I am sure the OP will respond and straighten us all out.  

2 hours ago, klcammie said:

I agree. IBM diagram is the cats meow.

 

He does that at camp too...

Tmi

So to answer a few things mentioned above. I installed the wiring harness with the FASS and 1/2" lines. Replaced all the fittings, added a draw straw to my tank. I recently cleaned every ground when I had my manifold and turbo off ~6 months ago. If I key bump my LP runs but doesn't power up (whine) like it should, it sounds very underpowered if you will, gauge doesn't raise up above 7-8 psi regardless of key on/key bump, sometimes less. If I start the truck it idles/holds fast in the same psi region it primed too. (I have a new gauge as well as I thought it could be the gauge originally). The FASS 150 replaced my old FASS HPFP 95 that was on there for about 9 years. It was steadily producing less and less fuel psi so I bought a new one because I like the Titanium series filtration better then Wix inline filters lol and thought it had given up. New pump installed got cavatation, thought I was sucking air even after LP prime per FASS directions. Added draw straw to address that as I had a broken return line in my tank. Now, no cavitation, no bouncing in my guage, just low fuel psi. Even had FASS send me a new check ball and spring for the return side. Old FASS 95 used same 1/2" line and the same FASS wiring harness (FASS pn WH-1002) but I used the new ones provided anyway. 

Well that did answer a lot questions. Have you checked the voltage going to the pump?

Agree check to see what Voltage you are getting at the pump when running.  

Thanks gents, I'll check and report back