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Lift Pump Not Working, Where to Start

Alright pull the plug to the optic sensor and cranked the engine for 20 seconds...no fuel at the injector lines. Did the same with the CPS which is brand new and same thing...no fuel at the injector lines. Replaced the return line to the IP a with clear hose and....no fuel. At best there was gurgle of fuel at the IP inlet side when I replaced the old hose.

I will buy and install a fuel pressure gauge before the IP, but this had a recent Feed The Beast install, albeit with the rubber hose. That hose is in good condition. Don’t know about the hose from Lift Pump to FFM.

Getting down to the final strokes here. I will try the other IP. Failing that, it’s either a rebuilt IP or I’m harvesting the good stuff off this truck and then selling it to the scrap yard. I need it out of my backyard due to upcoming landscaping project and I need to finish my boat after getting a repower done pre-Covid. I don’t need to be working on my son’s truck while he’s out playing.
 
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Will L. said:
Clear line is 1/4” return line coming out ip. The only time you put clear line between the FFM and IP is when you have air bubbles out the IP, but cannot find where the leak is. If no bubbles go into the IP, but bubbles come out, then the IP is leaking and sucking air or is causing cavitation inside the IP must be repaired.

Pressure gauge is after rubber line from ffm before metal inlet line of ip. The most common place of rubber fuel line failure is that piece just before the ip. Over the years I have had 3 people from this site send me pics of how that line failed and they replaced an ip mistakenly because of it. I have had 1 guy and 1 gal on hummer forum do the same. I did it 2 times in the fleet. 2 other guys 1 fleet and 1 dealership did it. CRAZY COMMON error. I know I sound dumb hammering this point but figure out why I have been saying it since I joined this forum. $100 gauge set up that stops early ip death and often stops replacing a good ip.

if you were getting tons of fuel coming out where the solenoid was removed when testing then the fuel pressure gauge waits for now.
But you still work should take the time andthe three dollars to put on the clear return.

Double check all the pins are not bent inside the connectors. Then get the scanner on there. The removed ip from crash should be fine. Never seen a crash damage an ip unless it got smacked which would have visible damage. This indicates the original ip wasn’t the cause to me.

yes optic/crank sensor test is good idea. Something electrical or electronic goin on here.
Does ecm work on both? Did you remove and clean the grounds? Have to scrub em- looking ok on outside doesn’t mean anything.
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What will scanner tell me when the damn thing is not running?
 
Big T said:
The return line to the IP is dry and will remain dry because the IP is pumping nothing
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This statement is confusing.

The Injection pump returns fuel when it's turning no matter what the fuel demand is. If the fuel stop solenoid drops on key off it may quit returning fuel. The IP uses fuel for cooling and lube so it returns an insane amount of fuel vs. what it sends to the injectors.

If you are saying the return is dry when cranking ... you have a big problem. I am assuming you are saying this.

I would dump the return line into a bucket and try one more crank session just in case the return is plugged solid somewhere. Still no fuel from the return line: pop off the oil fill and use a mirror to make sure the IP is actually turning.

It's looking like the pump is locked up with a sheared driveshaft.

Vehicles are too valuable to sell to a scrap yard at this time. They got no chips and ain't making new vehicles at the moment!

@Will L. I hate flappy and kinky rubber hoses esp before the IP.

hose_flapper.jpg


Hose_flapper1.jpg
 
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WarWagon said:
This statement is confusing.

The Injection pump returns fuel when it's turning no matter what the fuel demand is. If the fuel stop solenoid drops on key off it may quit returning fuel. The IP uses fuel for cooling and lube so it returns an insane amount of fuel vs. what it sends to the injectors.

If you are saying the return is dry when cranking ... you have a big problem. I am assuming you are saying this.

I would dump the return line into a bucket and try one more crank session just in case the return is plugged solid somewhere. Still no fuel from the return line: pop off the oil fill and use a mirror to make sure the IP is actually turning.

It's looking like the pump is locked up with a sheared driveshaft.

Vehicles are too valuable to sell to a scrap yard at this time. They got no chips and ain't making new vehicles at the moment!

@Will L. I hate flappy and kinky rubber hoses esp before the IP.

View attachment 65013


View attachment 65014
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Click to expand...

The return line is getting fuel from the injectors. The injectors are not getting fuel. The drivers side injectors do not have the injector lines connected so there is no way the return lines can return fuel.

Is that fuel pressure acceptable?

The oil fill spout is off so I will check that is turning, but I checked that before installing. The IP is fully seated and tightened down so it is in the gear.
 
Are you getting fuel coming out the ip return line?
Forget everything else- this is mega crucial.
Don’t have the clear- fine: take the rubber line off and have someone crank engine and make sure fuel is coming out the nipple. Its like 99% of the fuel from the lift pump goes through the ip ANY TIME it is turning.
No fuel coming out is huge problem
 
Will L. said:
Are you getting fuel coming out the ip return line?
Forget everything else- this is mega crucial.
Don’t have the clear- fine: take the rubber line off and have someone crank engine and make sure fuel is coming out the nipple. Its like 99% of the fuel from the lift pump goes through the ip ANY TIME it is turning.
No fuel coming out is huge problem
Click to expand...

Clear line installed. No fuel.

Injector lines not connected on driver's side, thus return lines cannot return anything from that side.
 
I think you need to understand the return system better. All the return lines connect together, including the return coming out of the IP. Then the fuel gets returned to the tank. So you should have fuel coming out of the IP return, if you don't then there is an issue in the IP. Someone can correct me if I'm wrong but I believe you should have fuel coming out even when not turning as long as there's fuel pressure. Also your blow by is coming from the EGR passage and is normal.
 
ak diesel driver said:
I think you need to understand the return system better. All the return lines connect together, including the return coming out of the IP. Then the fuel gets returned to the tank. So you should have fuel coming out of the IP return, if you don't then there is an issue in the IP. Someone can correct me if I'm wrong but I believe you should have fuel coming out even when not turning as long as there's fuel pressure. Also your blow by is coming from the EGR passage and is normal.
Click to expand...

My understanding of the return lines is that they return excess fuel from the injectors back to the IP. The return line to the IP flows in, not out.

I have done every test requested, save for hooking up the Tech II to a non-running engine. I will now install the old IP to see if I get any fuel.
 
I swapped fuel solenoid shut offs and some fuel came out of IP into clear line. Still nothing at injector lines. Assuming the pump can only slide one way into timing gear, photo also shows pump fully seated.
0EF74849-1AA5-45FB-8022-1905F066C998.jpeg
 
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