Newbie Fuel System Issues

[AtlantaSBR]

After driving my rig for a few months I recently started having some issues.

I replaced all the glow plugs due to the inability to start In cold weather and things we good for a while.

Replaced the fuel filter and separator after consulting the TM and then the issues began. It ran great for a few weeks afterwards and felt like it had more power than ever and then it began just shutting off at idle or while driving.

Currently no fuel will ever come out of the fuel separator drain when “idling” and I tested the output of the fuel filter and it doesn’t meet the spec of 1 pint while cranking for 30 seconds from the TM.

I have bled the system multiple times and if I unscrew an injector fuel does come out so hoping it isn’t the injection pump.

TL/DR; should I replace the fuel pump or drop the fuel tank and check for debris there? Worth changing fuel filter again after only 20-30miles? Any idea why my separator drain isn’t working?

Been scouring the TMs and the fuel pump seems to be the culprit but not sure if I am missing something on these old rigs. Also, the drain throws me off

 

[Coug]

If fuel won't come out of the drain when cranking then I'd say you're looking at either a bad fuel pump, or a blockage in the fuel lines.

Fuel not coming out the drain of the filter sort of indicates the lift pump isn't working, but not 100% sure.

From what others have said there are some check valves in the fuel lines that are notorious for becoming plugged up. I don't know exactly where they are located though.

Dropping the fuel tank to check it out is also a good idea, as whatever would be plugging up the check valves had to come from somewhere. Since you have one fuel system issue, you might as well go through the rest of the system so you don't have the "I fixed one thing, it worked good for a little while, now something else failed"

 

[AtlantaSBR]

If fuel won't come out of the drain when cranking then I'd say you're looking at either a bad fuel pump, or a blockage in the fuel lines.

Fuel not coming out the drain of the filter sort of indicates the lift pump isn't working, but not 100% sure.

From what others have said there are some check valves in the fuel lines that are notorious for becoming plugged up. I don't know exactly where they are located though.

Dropping the fuel tank to check it out is also a good idea, as whatever would be plugging up the check valves had to come from somewhere. Since you have one fuel system issue, you might as well go through the rest of the system so you don't have the "I fixed one thing, it worked good for a little while, now something else failed"

Just did some more searching in the forums and am going to test the check valves today. There are times i think the fuel system is pulling a vacuum and the drain line sucks in air. Starting at IP check valve then headed to the tank. Hopefully it is something simple.


Sent from my iPhone using Tapatalk

 

[Retiredwarhorses]

Start at the fuel tank, look into the tank by removing the access panal and remove the fuel sender.
Next, remove the anti-flow back valves and delete them all together.
Next, pul the hose into the fuel filter from the pump, crank the truck and see if you get a good low of fuel, if no fuel...bad fuel pump.
Next, check and change filter, test output flow from the outlet of the filter canister into a jar.
This now leaves you with an injection pump issue that can range from a gummed up pump due to algae, a bad fuel cutoff switch etc.

 

[AtlantaSBR]

Start at the fuel tank, look into the tank by removing the access panal and remove the fuel sender.
Next, remove the anti-flow back valves and delete them all together.
Next, pul the hose into the fuel filter from the pump, crank the truck and see if you get a good low of fuel, if no fuel...bad fuel pump.
Next, check and change filter, test output flow from the outlet of the filter canister into a jar.
This now leaves you with an injection pump issue that can range from a gummed up pump due to algae, a bad fuel cutoff switch etc.

Delete the check valves permanently or just to test?

I have cranked from the fuel tank into the filter and it comes out about at the same speed as the filter does. Filled up about 1/2 pint in 30 seconds of cranking.


Sent from my iPhone using Tapatalk

 

[Action]

Delete the check valves permanently or just to test?

I have cranked from the fuel tank into the filter and it comes out about at the same speed as the filter does. Filled up about 1/2 pint in 30 seconds of cranking.


Sent from my iPhone using Tapatalk

some folks delete the check valves permanently. The drain petcock by the washer bottle is pre-filter.

 

[AtlantaSBR]

some folks delete the check valves permanently. The drain petcock by the washer bottle is pre-filter.

I meant I have removed the rearmost fuel line (into filter/separator) and cranked that into a container and also cranked from the fuel separator into a container and they flow at similar rates.


Sent from my iPhone using Tapatalk

 

[Retiredwarhorses]

Sounds like it’s good up to the Injection pump

 

[papakb]

Take a voltmeter and check for 24 volts on the #54 wire on the top of the injector pump with the ignition switch turned on. There should also be an audible click from the IP when the switch iis turned on. This is what opens and allows fuel into the IP when the switch is turned on. The solenoids have a habit of failing and not allowing fuel to flow. Easy enough to test and replace if necessary only a couple of screws to hold it on and no fuel fittings to take apart.

When you replaced the fuel filter and seperator did you install a new O-ring in the housing? They often get overlooked and will crack over time and allow air into the housing. You can also install a pressure guage in the top of the filter housing where the pressure traansducer is to monitor pressure with the engine running. It should be at leave 3-5 psi.

 

[AtlantaSBR]

Take a voltmeter and check for 24 volts on the #54 wire on the top of the injector pump with the ignition switch turned on. There should also be an audible click from the IP when the switch iis turned on. This is what opens and allows fuel into the IP when the switch is turned on. The solenoids have a habit of failing and not allowing fuel to flow. Easy enough to test and replace if necessary only a couple of screws to hold it on and no fuel fittings to take apart.

When you replaced the fuel filter and seperator did you install a new O-ring in the housing? They often get overlooked and will crack over time and allow air into the housing. You can also install a pressure guage in the top of the filter housing where the pressure traansducer is to monitor pressure with the engine running. It should be at leave 3-5 psi.

Yes, I did install a new O-ring during the fuel filter/separator.

I will bust out the volt meter and check this week when I find some time. When I reconnect 54A to the IP I hear a click if the ignition is turned on when trying to remove air from the filter.

[mention]Retiredwarhorses [/mention]

The part that makes me lean towards fuel pump is the flow rate in the TM of 1 pint per 30 seconds and when the engine stalls out I have to remove air from the separator again.

Could it be pulling a vacuum somehow and that is why the flow rate is low and I can hear air sucking in the drain.


Sent from my iPhone using Tapatalk

 

[Action]

Yes, I did install a new O-ring during the fuel filter/separator.

I will bust out the volt meter and check this week when I find some time. When I reconnect 54A to the IP I hear a click if the ignition is turned on when trying to remove air from the filter.

[mention]Retiredwarhorses [/mention]

The part that makes me lean towards fuel pump is the flow rate in the TM of 1 pint per 30 seconds and when the engine stalls out I have to remove air from the separator again.

Could it be pulling a vacuum somehow and that is why the flow rate is low and I can hear air sucking in the drain.


Sent from my iPhone using Tapatalk

Why do you keep opening the drain? That is to let water out of the can.
You stated earlier that you get the same flow from the drain as you do to the IP. But then you say you here a sucking sound from the drain. The water drain cannot push liquid out and suck at the same time. the drain does not let air out. The bleed screw on top of the can does.
Open the bleed screw and crank until fuel cones out. Close screw. (With power wire pulledout of IP.

 

[AtlantaSBR]

Why do you keep opening the drain? That is to let water out of the can.
You stated earlier that you get the same flow from the drain as you do to the IP. But then you say you here a sucking sound from the drain. The water drain cannot push liquid out and suck at the same time. the drain does not let air out. The bleed screw on top of the can does.
Open the bleed screw and crank until fuel cones out. Close screw. (With power wire pulledout of IP.

I get the same flow into the separator (rear fuel line into the canister) as I do to the IP (front outlet).

Nothing ever comes out the drain.

I have to use the bleed screw at the top of the fuel separator housing every time the truck stops running. It runs dry every time it starts up and I have to re-bleed.


Sent from my iPhone using Tapatalk

 

[AtlantaSBR]

Take a voltmeter and check for 24 volts on the #54 wire on the top of the injector pump with the ignition switch turned on. There should also be an audible click from the IP when the switch iis turned on. This is what opens and allows fuel into the IP when the switch is turned on. The solenoids have a habit of failing and not allowing fuel to flow. Easy enough to test and replace if necessary only a couple of screws to hold it on and no fuel fittings to take apart.

When you replaced the fuel filter and seperator did you install a new O-ring in the housing? They often get overlooked and will crack over time and allow air into the housing. You can also install a pressure guage in the top of the filter housing where the pressure traansducer is to monitor pressure with the engine running. It should be at leave 3-5 psi.

Kids were distracted for a few minutes when I got home from the office so I busted out the multimeter.

Getting 24.4 bolts on 54 at the IP.

Maybe related but I noticed two vacuum/vent lines dangling near the separator.

One starts between the air filter/exhaust and tees off below the middle of the windshield and then connects to nothing.

The other tees off of the line running off the fuel pump behind the right right front tire and then crosses over to the drivers side and connects to nothing.

About to dig into the TMs to see where these are supposed to go but thought someone might be able to point me in the right direction I don’t see anything obviously missing a line.

 

[AtlantaSBR]

Just looked at the TM and my vent line #2 isn’t connected to the fuel pump vent line at all. It runs across the engine then tees off to the power steering pump then nothing. The other orphan vent that runs across the engine and isn’t connected to anything connects at the location where #2 does in the TM.

 

[Daves86]

Look like the lines that go to the deep water fording kit got cut. Do you have something like this near you fuel filter?

 

[AtlantaSBR]

Look like the lines that go to the deep water fording kit got cut. Do you have something like this near you fuel filter?
View attachment 828573

No i do not.

If those lines caused the problem It seems odd that the truck ran fine for a couple months then started doing this.

I guess I will go ahead and reroute the lines according to the TM since I don’t have the deep fording kit.

 

[Action]

Look like the lines that go to the deep water fording kit got cut. Do you have something like this near you fuel filter?
View attachment 828573

That is the back side of the fording swich. The hole below guage cluster is left open and the lines cut when they remove the fording switch for demil.

 

[Daves86]

No i do not.

If those lines caused the problem It seems odd that the truck ran fine for a couple months then started doing this.

I guess I will go ahead and reroute the lines according to the TM since I don’t have the deep fording kit.

Not saying those are the cause of your problem, just trying to help you identify what they are to assist in the troubleshooting process. I do not believe those lines are the cause of your issue. From what you have described you are thinking there could be debris in the tank, that could cause the truck to stall, and when the engine stops the suction from the lift pump stops and the debris fall free from the fuel sock. Plausible, only way to prove or disprove is to pull the fuel tank and check.
Hope that helps.

 

[AtlantaSBR]

Not saying those are the cause of your problem, just trying to help you identify what they are to assist in the troubleshooting process. I do not believe those lines are the cause of your issue. From what you have described you are thinking there could be debris in the tank, that could cause the truck to stall, and when the engine stops the suction from the lift pump stops and the debris fall free from the fuel sock. Plausible, only way to prove or disprove is to pull the fuel tank and check.
Hope that helps.

I appreciate all the help. If the kids/wife let me I will try to drop the tank and check all the fuel lines this weekend. If that doesn’t do it, new fuel pump is next it would seem based on the TMs and the expected flow rate.

 

[Milcommoguy]

Another "Cat it the Hat" story. HMMWV that's FAT... clean out that crap.

Not to rag on one's new to you HmwV... knowing it's old and ??? abused. Why wouldn't one not want to go thur the fuel system when first getting one. We ?? check the fluids, check the hub's ?, tighten loose nuts and bolts, mess with start system, floppy fan, spray some touch up paint... looking good.

Sure the poly thanks are a lot more forgiving than an old steel one. (M38A1, M37 & some CUCV's as an old school rusty tank guy) Once a load of crap gets sucked up it's becomes a bigger headache.

It's just me... but I couldn't wait to drop the tank. Drained, it was easy (could have been easier, but it's a HumV) disconnect driveline, fumble with lines and wrestle it out. Good time to cut in the service plate, make all like new, check U-joints and ditch the old brake disk, slip on new hoses, etc. OK, started out easy... ended up two day cuss fest. LOL

New style tanks more or less cheap, shipping not so much do to size. I was lucky. One was local. Either way it's coming out or getting inspected and cleaned.

Guess what I am saying is "it's a good feeling knowing what 's lurking in the old tank" Better new.

Whats in your tank? CAMO

Nobody was insulted in this post.