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Walbro Lift Pump Fail

1994ch

1994ch

Well-Known Member
Messages
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Location
South Carolina
Well my lift pump on my truck is starting to go out. When it fails it still makes noise like it is pumping but it does not even allow the IP to suck fuel from the tank. I made it home by taking the fuel line loose and relieving the suction that the IP had put on the system, whacking the LP like you would an old mule, bled the air out of the system and got it started. I made it about 1/4 mile and saw the fuel pressure drop to 0 again. This time I shut off the engine before it quit, flipped my OPS bypass switch and as I coasted down the road the pressure started coming back up. After restarting, the pressure stayed low for 10 miles or so before slowly climbing back to 6-8 PSI. It has done this several times now. Once several years ago, once about a month ago, and now twice on Sunday. I don't trust it so am shopping for a new LP. Has anyone ever tried one of these?
https://www.napaonline.com/en/p/BK_6101016?partTypeName=Fuel+Pump&keywordInput=facet+fuel+pump
P/N BK 6101016 from NAPA
 
That one is rated 8psi At 45 gpm free flow Even the ac delco is rated 9.5 at 35 gpm free flow.
So maybe is as good as the Delco, but definitely wont out perform it to speak of- have to break out the Boyles slide rule...

If yours is not flowing while failing- there is an obstruction there. Maybe something getting sucked up in the tank or line-

Depending what kind of warranty it has it might be worth the price, if standard then I would pass.
 
If my memory serves though it seems that the stock one only ever held about 4 PSI and would drop to 1-2 on acceleration.

As for the Walbro, I think I have heard that they do not free flow when they fail. That was a down side of switching to that type of pump, although when I bought it I thought it was supposed to be long lasting, so worth the price (I guess it lasted maybe 4 years or so.... and 15,000-20,000 miles.........................but not really what I would like to think of as long lasting.
 
Yeah, the fact that the rating of the delco is 9.5 and almost no one ever gets it- it’s because of the way they do the inflated ratings. They being the entire industry, not just delco.

No flow on fail pumps can be used, just add a tee on ether side of the pump with a one way check valve joining them. The one way will stop the pump from pumping back to the tank, and when the lift pump is off, the ip can suck past the one way valve.
 
Facet pumps seem to work okay. there was a square looking facet on My truck when I bought the truck. It would cut to 0 PSI when the temps got cold, about 10 above. Driving on the highway at about 65, on the hills, the pressure on this facet pump would cut to about two PSI.
The one thing I dont like about the facet is the 1/4" NPT thread for the fittings. It is too bad that they dont come with the 3/8ths NPT so that step up fittings would not be needed. I often wonder if it is the 1/4" NPT that caused the pressure to dip to 0 when it got cold and then such low pressure on the hills. Even on the flats at those speeds the pressure would seldom hit 4 PSI on a warm day.
just a little food for thought. LOL
 
MrMarty51 said:
Facet pumps seem to work okay. there was a square looking facet on My truck when I bought the truck. It would cut to 0 PSI when the temps got cold, about 10 above. Driving on the highway at about 65, on the hills, the pressure on this facet pump would cut to about two PSI.
The one thing I dont like about the facet is the 1/4" NPT thread for the fittings. It is too bad that they dont come with the 3/8ths NPT so that step up fittings would not be needed. I often wonder if it is the 1/4" NPT that caused the pressure to dip to 0 when it got cold and then such low pressure on the hills. Even on the flats at those speeds the pressure would seldom hit 4 PSI on a warm day.
just a little food for thought. LOL
Click to expand...


If you have the old dead one, cut it open and see if you can enlarge the ports.
 
1994ch said:
If my memory serves though it seems that the stock one only ever held about 4 PSI and would drop to 1-2 on acceleration.

As for the Walbro, I think I have heard that they do not free flow when they fail. That was a down side of switching to that type of pump, although when I bought it I thought it was supposed to be long lasting, so worth the price (I guess it lasted maybe 4 years or so.... and 15,000-20,000 miles.........................but not really what I would like to think of as long lasting.
Click to expand...

Walbro's are a plunger pump. Two one way valves that will flow on fail. If the pump is clicking it's working. I suggest you start looking for a restriction like the screen in the walbro bowl plugged, tank sock plugged, kinked hose, etc. Have you loosened the fuel cap? Also drain some fuel from the FFM into a clear container and look for water. Does your fuel small like gasoline? Bad batch of fuel plugging the filter or gasoline vapor locking...

I put a racing 110GPH pump in at one time and that wouldn't overcome a biodiesel softened hose that was kinking shut. Diesels will vapor lock if you plug the fuel inlet due to the rotary pump in the IP pulling enough of a vacuum to vaporize diesel.
 
Yep Walbro design is flow on fail, and they did have a run of quality issues for awhile. Seems the FRC series was more problematic.

Have 2 FRB-5 pumps, one the older design and the other is the updated higher flow/pressure design. The updated one is working well for my 6.5 for the last 12,000 miles (basically since I bought the truck last november). The old one was on my 6.2, now it's going to be used as the transfer pump between the tanks when the new bed gets built next week.

Also have a Raptor pump that's been sitting for about 6 years I'd be willing to sell.
 
Ok thanks for the info........... since it has happened a couple times, I had convinced myself that it was the pump, but it looks like I need to do some more trouble shooting.

Thanks again.
 
So my first trouble shooting step was to open the fuel cap. (no suction)
Next I opened the bleed valve at the engine and relieved a vacuum..................
There was also another vacuum on the inlet to the Walbro which I mistakenly took to mean that the problem was in the pump, but I see now that was just the check valves preventing reverse flow.

So whatever the restriction was it moved out of the way when I relieved the suction.

My excuse for my miss diagnosis............. it was dark, raining, and I was on a gravel/dirt road................. yea I know excuses excuses..... thanks again for setting me straight.
 
Sounds like between the fuel pump and tank pickup including the tank screen. Hoses are suspect. Seen any silver streaks of junk in the fuel filter lately? That's the tank lining coming off and plugging the sock and bypass valve. Remove fuel cap and blow air into the pickup, suction, line and that can buy time: unclog the sock.
 
1994ch said:
So my first trouble shooting step was to open the fuel cap. (no suction)
Next I opened the bleed valve at the engine and relieved a vacuum..................
There was also another vacuum on the inlet to the Walbro which I mistakenly took to mean that the problem was in the pump, but I see now that was just the check valves preventing reverse flow.

So whatever the restriction was it moved out of the way when I relieved the suction.

My excuse for my miss diagnosis............. it was dark, raining, and I was on a gravel/dirt road................. yea I know excuses excuses..... thanks again for setting me straight.
Click to expand...
In thos kinds of circumstances, the only thing a person is wanting is to get home. No excuses necessary.
Just hope You can get it figured out without too many complications.
 
Here is a thought for you to consider and what I have in my rig, dual lift pumps plumbed in parallel, Walbro FRB5, and stock lift pump since it was already there no extra plumbing required to leave it there.

Both powered by independent 25A relays on firewall under hood to provide the hi-current power, with the low draw current control side of the relay maintaining the OPS no engine running shut off protection in event of crash.

Individual switch for each pump so I can run 1 or other pump, or both lift pumps if needed ,or neither if diagnosing a flow restriction issue from tank sock plugging.

As part of my "bulletproofing of fuel delivery system, I also have frame rail mounted pre lift pump 30 micron Racor filter with vac switch to let me know when filter is clogging, same as I have on the FFM's 10 micron filter element and pressure gauge in cab to monitor IP supply pressure, and (1) green LEDs for lift pwr available to each pump indication, and (1) red Led to alert for each filter clogging.

Dual pumps gives extra gpm if needed but also maintains some fuel always to the IP should a pump crap out completely or start going to wimpy flow from wear and tear, important redundancy feature IMO, as if you have ever tried to haul a load or move fast with IP xfer pump only pulling fuel you are having a bad 6.5 day :)
 
Having a pressure sensor at the ip inlet in metal, and one pre filter wired to a switch then to a single gauge so you can always see pressure while driving, then hit a button when you see it a little low can tell you instantly if LP is loosing ground or the filter is getting plugged. Will also save nickels And time on when to change fuel filter.
 
Thanks for all the ideas.

I have previously installed a pre lift pump filter, and removed the in tank sock. Also have a pressure gauge after the engine filter, but I will have to look into adding something to indicate a plugged lift pump filter. It seems though that the pickup tube in the tank may be sucking up a chunk of tank lining or something.............. it has not happened again for a while... I dread having to drain / drop the tank but that may be what it takes.

If it is lining in the tank, do I just clean it out? Or is it time to find a new tank?
 
1994ch said:
Thanks for all the ideas.

I have previously installed a pre lift pump filter, and removed the in tank sock. Also have a pressure gauge after the engine filter, but I will have to look into adding something to indicate a plugged lift pump filter. It seems though that the pickup tube in the tank may be sucking up a chunk of tank lining or something.............. it has not happened again for a while... I dread having to drain / drop the tank but that may be what it takes.

If it is lining in the tank, do I just clean it out? Or is it time to find a new tank?
Click to expand...
There would not be a lining unless someone coated it in the past however; there is a baffle that is held in place by push on clips washer combo they are known to pop off then drifting around the tank could occasionally get pulled to the pickup by the pulling of the lift pump and the baffle moves around too.
 
This is the silver strips of the GM OEM tank lining coming off on a 1993 and 1995. An uncoated steel tank would rust through quick. If you see this in any fuel filter - this is where it's from. The clogged bypass valve on the tank sock stopped the engine. Time for a new tank - they are cheap.


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