Walbro pressures

[HighSierra86]

Ok so i need someone to compare notes with....Ive been seeing some low pressures with my new fuel system set up. Im running a new walbro FRB-5 LP with a 30 micron racor pre-filter and the stock filter in the engine valley. I have my pressure tap right before the IP and have verified the pressures with a second guage at the t-valve. All filters are new.

I am seeing about 4-5psi at idle and about the same while driving. Lowest pressure i saw was just under 3psi but never above 6psi. Guage seems to spend alot of time in the 3-4 range. Now what I am wondering is if these are normal numbers, or a bit on the low side. The pump is advertised as a 10psi pump, now I didnt expect that but maybe more along the lines of 6-8psi.

My stock LP was running at about 6-9psi, now that is obviously with the smaller lines/less volume, and no pre-filter. I would be much happier with some higher numbers especially considering the truck is running a stock PCM. Im hoping to reflash in the very near future but Im not gonna do it until I know I am supplying the IP with enough fuel.

If anyone could share their findings I would appreciate it. My next step is dropping the tank again and remove the sock...

-Nick

 

[racedaymechanic]

where are you getting the pressure from for the gauge? mine rarely drops below 10 psi even at wot, idles at 13-15

 

[buddy]

He has the FRB-5, not the FRC-10

I was getting about the same as you with my FRB-5. Are you getting the same pressures out of the T-valve as at the IP?

I contacted Walbro, and they sent me a stiffer spring to install into the unit and it rased the pressure a few psi. There was a thread about this a couple years ago from Matt, who eventually put his stock unit in series with the FRB-5.

If you read the pressure right out of the unit it is probably 10psi, but you lose a few psi through the FFM, which is why we really need 12-15psi units. The FRC-10 is a 16psi unit from Leroy.

 

[StoonTurboTahoe]

I see the same results as raceday with my FRC-10, except it drops to about 6psi at WOT.

 

[dka99burb]

Mine acts very strangly so I am thinking it may be my sending unit for my gauge. When cold I have 13-15 with pump on, engine off. 10-12 at idle and 5-6 driving. All when cold/cool. Once the truck is good and warm, ~195, the pressure drops by about 5psi or more. I don't see more than 8 psi at idle and heavy acceleration will drop gauge to 0. If it did it all the time I would assume my 28micron pre filter is clogged or the tank sock but it changes after running for a while????

 

[buddy]

It could be the return fitting on the IP, sometimes if they arent regulating the housing pressure high enough too much gets sent back to the tank and you cant hold LP pressure. Could still be a clogged something, with IP demand the LP needs to flow more fuel to maintain higher pressure but if its sucking a lot of vacuum from the tank it might not be able too. So could try without fuel cap on. Or sock could be clogged.

 

[HighSierra86]

Correct on the FRB-5. Guage is before the IP.

I remember matts problems from a while back and read through his thread again. Almost the exact same issues Im having, but now even lower pressures.

I put on about 200 miles in the last two days and tried some different diagnostics.....Aside from my earlier posted numbers, I noticed the more I drove the more the drop in pressure. After driving for a while the pressure started dropping until the guage was bouncing from 0-3psi. I also verified the guage pressure with a mechanical guage at the t-valve again. At this time I was figuring the sock was clogged, so I blew about 120psi of air thru the feed line into the tank. Same crap for pressure. No change.

I also bypassed the racor filter assembly with near identical pressures. I saw only an increase of about .5-1psi, so that wasnt of concern. I decided to eliminate the possability of the sock, so I dropped the tank this morning and took it out. I am still seeing low pressures. 3psi at idle. I checked all my fuel lines again for kinks or any other odd issues. So at this point in time my finger is pointing at the brand new pump.

Im not gonna bother changing the spring as I need this thing on the road now. Ill eventualy change it and keep the pump as a spare, but at this time im sick of screwing around with it. Gonna order an FRC-10 from leroy right now and hopefully be done with this. A bit upset that I wasted $100 on the FRB-5, dont know if it is a lack of factory testing/quality control or what. Kinda dont want to buy another, but im not paying $400 for the raptor settup. Way too much overkill in my book.

Thanks for the help so far guys and ill let you know how I make out with the new pump.

-Nick

 

[Matt Bachand]

Yep, I have stock one inline before my racor 10 then the stiffer spring one after. Most times at idle im around 5psi and 2-3 WOT. .... Unsure where my restrictions come from, used to have 10psi..... Fuel pressure is t-d after factory fuel filter.... I just accepted it as my truck runs fantastic.

 

[bison]

Yep, I have stock one inline before my racor 10 then the stiffer spring one after. Most times at idle im around 5psi and 2-3 WOT. .... Unsure where my restrictions come from, used to have 10psi..... Fuel pressure is t-d after factory fuel filter.... I just accepted it as my truck runs fantastic.

I get that with the stock LP and FTB mod on my 98
The 95(bone stock)has better pressure all around than my 98 ( same 93 LP)

 

[WarWagon]

There is new information on the return line fitting out of the IP having a pressure regulator in it as Buddy pointed out above.

Myself I removed the FRC-10 as it was ruined from no prefilters and went with a 140 GPH alcohol rated Mallory gerotor pump. (Overkill! But I was sick of constant fuel starvation the 1995 has given me. Bad fuel aside.) A prefilter caused a vacuum in the fuel system and the engine was stalling out before I changed the pump. My engine more or less quits without a lift pump anyway so this pump is not a disadvantage. The Mallory pumps holds 10 PSI at the water drain at redline bliping the throttle. The chart says 100 GPH at that pressure although I have a prefilter and am pumping B99 to skew the numbers over gasoline/alcohol. B99 is the reason for the alcohol choice. Initial results are that the fishbite I have been chasing is finally gone on the 1995. Overkill works sometimes. Yes, I used a relay for the OPS as this is a 5 Amp pump.

Again the Walbro's are impressive and Leroy sells a gerotor pump (100 GPH) as well that has 2x the flow of the FRC-10 (50 GPH).

The FRB-5 is rebuild-able and could be sold for a 1993 and older 6.2/6.5.

 

[HighSierra86]

Well its about damn time that problem is solved. Brand new FRC-10 from Leroy and my guage is where it should be. Needless to say the FRB-5 could not put out the pressures that the truck needed, not even close. In fact, when I took it out I was seeing from 0-3psi at idle. No more. Same results with two different pumps. Dont know what the problem was there, as this is lower than what most people have encountered.

Anyways, very happy with the new pump so far. Idle pressures are beyond expected between 11-14psi. A few WOT runs brought it down to 5psi for only a second, and it quickly recovered. A big thanks to leroy at pmdcable.com for the quick and professional help as usual.

Time to order my re-flash from Heath now that I have enough fuel for the pump :thumbsup:

-Nick

 

[bison]

nice pressure

 

[DieselCash]

Mine sits at around 12 at idle.

The lowest I have seen is around 3.

It averages between 5 to 9.

I like my FRC-10! :thumbsup:

 

[dka99burb]

Does everyone run a 'snubber' on their fuel pressure sensor? I am wondering if they may have something to do with my low readings?? I can't even think about pushing to WOT right now.

 

[bison]

A snubber only prevents needle flutter.
I have snubbers on al my diesels with a pressure gauge

 

[Burning oil]

View attachment 33042

Well its about damn time that problem is solved. Brand new FRC-10 from Leroy and my guage is where it should be. Needless to say the FRB-5 could not put out the pressures that the truck needed, not even close. In fact, when I took it out I was seeing from 0-3psi at idle. No more. Same results with two different pumps. Dont know what the problem was there, as this is lower than what most people have encountered.

Anyways, very happy with the new pump so far. Idle pressures are beyond expected between 11-14psi. A few WOT runs brought it down to 5psi for only a second, and it quickly recovered. A big thanks to leroy at pmdcable.com for the quick and professional help as usual.

Time to order my re-flash from Heath now that I have enough fuel for the pump :thumbsup:

-Nick

Thank you! Great pressue.

Does everyone run a 'snubber' on their fuel pressure sensor? I am wondering if they may have something to do with my low readings?? I can't even think about pushing to WOT right now.

Wish I knew what to advise. You did blow out the hard lines? Maybe check or replace the rubbers? Running a pre LP filter?

A snubber only prevents needle flutter.
I have snubbers on al my diesels with a pressure gauge

I need a snubber for my boost gauge. What are ya'll doing buy them or making one. If buying where?

 

[Burning oil]

View attachment 33042

Well its about damn time that problem is solved. Brand new FRC-10 from Leroy and my guage is where it should be. Needless to say the FRB-5 could not put out the pressures that the truck needed, not even close. In fact, when I took it out I was seeing from 0-3psi at idle. No more. Same results with two different pumps. Dont know what the problem was there, as this is lower than what most people have encountered.

Anyways, very happy with the new pump so far. Idle pressures are beyond expected between 11-14psi. A few WOT runs brought it down to 5psi for only a second, and it quickly recovered. A big thanks to leroy at pmdcable.com for the quick and professional help as usual.

Time to order my re-flash from Heath now that I have enough fuel for the pump :thumbsup:

-Nick

Thank you! Great pressue.

Does everyone run a 'snubber' on their fuel pressure sensor? I am wondering if they may have something to do with my low readings?? I can't even think about pushing to WOT right now.

Wish I knew what to advise. You did blow out the hard lines? Maybe check or replace the rubbers? Running a pre LP filter?

A snubber only prevents needle flutter.
I have snubbers on al my diesels with a pressure gauge

I need a snubber for my boost gauge. What are ya'll doing buy them or making one. If buying where?

 

[bison]

Thank you! Great pressue.

Wish I knew what to advise. You did blow out the hard lines? Maybe check or replace the rubbers? Running a pre LP filter?


I need a snubber for my boost gauge. What are ya'll doing buy them or making one. If buying where?

Leroy, you should not need a snubber for a boost gauge.if your gauge flutters i would suspect your waste gate flutters(vac problem)

i have made snubbers by soldering a hose barb or fitting shut shut and drilling a very tiny hole in it.
One can also use a small needle valve in the line,that way one can adjust it.

Wiki makes a universal brass snubber 1/4 pipe tread both sides,i got mine via my local Bumper to Bumper( they had to order it in).About $14

 

[Burning oil]

Definately for my boost, the needle just sits there and vibrates. Disconected it as it would destroy itself like that. The gauge itself has a very small orfice. I'll look at the waste gate soon too.

 

[Matt Bachand]

nice pressure

Shit yeah thats nice PSI!