fuel pressure prob

STORM TROOPER

STORM TROOPER

New member
hello and thanks in advance for any help. recently got my ty back on the road and noticed a problem w/fuel pres, it is set @ 50lbs w/no vac,when i start driving it and get into the boost the pres will go up close to 60lbs but then back down to arround 45lbs,bought new afpr and ran a single vac line straight to it same results:rant:
 
The Devils Own Chariot

The Devils Own Chariot

Active member
Re: fuel pressure prob

STORM TROOPER said:
hello and thanks in advance for any help. recently got my ty back on the road and noticed a problem w/fuel pres, it is set @ 50lbs w/no vac,when i start driving it and get into the boost the pres will go up close to 60lbs but then back down to arround 45lbs,bought new afpr and ran a single vac line straight to it same results:rant:
Click to expand...

When you pull vacuum to the FPR that simulates WOT. The reading you get at that point should be all the greater pressure reaches. Im sure Im just stating the obvious to you but some times it helps to go back to the basics.
 
STORM TROOPER

STORM TROOPER

New member
Re: fuel pressure prob

nope straight pres from fuel rail fitting, regulator said it was lb for lb,if fuel is set @50 and run 20lbs of boost should result in 70lbs of fuel i cant figure out wtf is wrong
 
Don W.

Don W.

Stab it and steer it
Re: fuel pressure prob

Rookie said:
When you pull vacuum to the FPR that simulates WOT. The reading you get at that point should be all the greater pressure reaches. Im sure Im just stating the obvious to you but some times it helps to go back to the basics.
Click to expand...

Pulling the vac line at the FPR only simulates atmospheric pressure, not boost. In this case FP should go to about 38# and stay there. Now if we didn't have turbos your statement would be correct. :tup:

HTH

When "on boost" 1 lb of boost should add 1 lb of fuel pressure. Base of 50 + 10lbs of boost should equal 60lbs of FP for example.
 
STORM TROOPER

STORM TROOPER

New member
Re: fuel pressure prob

HTH

When "on boost" 1 lb of boost should add 1 lb of fuel pressure. Base of 50 + 10lbs of boost should equal 60lbs of FP for example.[/QUOTE]

this is correct but i cant get over 60lbs it is set for 50 and running 16lbs boost:rant:
 
Don W.

Don W.

Stab it and steer it
Re: fuel pressure prob

Well in that case, IMHO, you have a fuel pump issue not necessarily a regulator issue. With the motor off and the fuel pump hot wired so its running squeeze the return line and see if FP will go over 60 or 70 or whatever number you want within reason. (There is a FP test connector at the firewall near the dist. in case you didn't know.)
 
SY2932

SY2932

Administrator
Re: fuel pressure prob

Don W. said:
Well in that case, IMHO, you have a fuel pump issue not necessarily a regulator issue. With the motor off and the fuel pump hot wired so its running squeeze the return line and see if FP will go over 60 or 70 or whatever number you want within reason. (There is a FP test connector at the firewall near the dist. in case you didn't know.)
Click to expand...

Yep:
IMG_0846.sized.jpg

"Applying 12 volts to fuel pump test connector to troubleshoot fuel pump or set fuel pressure with vacuum line still connected and motor off (note fuse for safety)."

My $ is on the fuel pump too.
 
STORM TROOPER

STORM TROOPER

New member
Re: fuel pressure prob

unable to get to the return line but i turned the afpr all the way in and got 70lbs fp. my fuel pump is a newer wbro255.any ideas
 
Don W.

Don W.

Stab it and steer it
Re: fuel pressure prob

Don't know how to test beyond suspicion. However it just occurred to me that there may be a problem with the intake screen on the bottom of the pump pulling shut and causing what you're seeing. :2cents: Pulling the pump is the only way to look at it that I know of.
 
STORM TROOPER

STORM TROOPER

New member
Re: fuel pressure prob

Don W. said:
Don't know how to test beyond suspicion. However it just occurred to me that there may be a problem with the intake screen on the bottom of the pump pulling shut and causing what you're seeing. :2cents: Pulling the pump is the only way to look at it that I know of.
Click to expand...

what will i be looking for?
 
Don W.

Don W.

Stab it and steer it
Re: fuel pressure prob

There is a small filter, I think GM calls it a screen, on the bottom of the filter.
 
STORM TROOPER

STORM TROOPER

New member
Re: fuel pressure prob

NecroWolf said:
put the feed line from the fuel rail in a bucket and measure the volume over a specific time. i don't remember the specs for our trucks though. what size of injectors are you running?
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50lb inj,guess i will be dropping the tank again:( thanks again for all the help
 
J

jpalmer

New member
Re: fuel pressure prob

i have not read all of this.........would a voltage drop cause this with a load on the electrical. I know the boost-a-pump is suggested at levels above stock:dunno:
 
STORM TROOPER

STORM TROOPER

New member
Re: fuel pressure prob

jpalmer said:
i have not read all of this.........would a voltage drop cause this with a load on the electrical. I know the boost-a-pump is suggested at levels above stock:dunno:
Click to expand...

i was kinda thinking about that but how would i test for that while driving?
 
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