Notices
86-95 Trucks & 4Runners 2nd/3rd gen pickups, and 1st/2nd gen 4Runners with IFS

How to test fuel pressure on a 3.0 vz-e truck

Old 05-10-2019, 01:25 PM
  #1  
Registered User
Thread Starter
 
Join Date: May 2019
Posts: 13
Received 0 Likes on 0 Posts
How to test fuel pressure on a 3.0 vz-e truck

I'm not exactly sure how to test and what I'm testing for if anyone has a link or something info that will help that would be nice.
Maeson Yosick is offline  
Old 05-10-2019, 01:52 PM
  #2  
Registered User
 
Join Date: Sep 2007
Location: San Francisco East Bay
Posts: 6,605
Likes: 0
Received 103 Likes on 93 Posts
2. You'll need a gauge and a way to connect it. The easiest way is a gauge built for that purpose, like
Amazon Amazon
This one comes with the banjo-schraeder adapter that you will need. You'll want to leave the adapter in place; if you remove it and replace the original bolt, you'll need new crush washers.
3. Here's a picture of one installed: https://www.yotatech.com/forums/f116.../#post52330847
4. What should the pressure be? All answers are found in The Good Book: http://web.archive.org/web/201003261...87fuelpump.pdf

(for completeness, several on this forum have "rolled their own" pressure gauge, and permanently installed it. You can find their writeups by searching. On the 22re, it is probably more common to attach your gauge through the CSI rather than the FPR; that takes a 10mm banjo rather than the 12mm on the FPR.)

1. Why are you testing fuel pressure?
scope103 is online now  
Old 05-10-2019, 02:53 PM
  #3  
Registered User
Thread Starter
 
Join Date: May 2019
Posts: 13
Received 0 Likes on 0 Posts
Originally Posted by scope103 View Post
2. You'll need a gauge and a way to connect it. The easiest way is a gauge built for that purpose, like https://www.amazon.com/Actron-CP7838.../dp/B0009XQUKC This one comes with the banjo-schraeder adapter that you will need. You'll want to leave the adapter in place; if you remove it and replace the original bolt, you'll need new crush washers.
3. Here's a picture of one installed: https://www.yotatech.com/forums/f116.../#post52330847
4. What should the pressure be? All answers are found in The Good Book: http://web.archive.org/web/201003261...87fuelpump.pdf

(for completeness, several on this forum have "rolled their own" pressure gauge, and permanently installed it. You can find their writeups by searching. On the 22re, it is probably more common to attach your gauge through the CSI rather than the FPR; that takes a 10mm banjo rather than the 12mm on the FPR.)

1. Why are you testing fuel pressure?
I'm testing fuel pressure because my truck doesn't run and I think that could be a problem, the fuel pump work and I just replaced the filter and the AFM unit, checked all fuses they're good, replaced COR that should be good, I'm just kinda lost on what to do to fix it ha.
Maeson Yosick is offline  
Old 05-10-2019, 03:07 PM
  #4  
Registered User
 
Join Date: Sep 2007
Location: San Francisco East Bay
Posts: 6,605
Likes: 0
Received 103 Likes on 93 Posts
Doesn't run at all?
Before you go to the effort of testing the fuel pressure, you could check flow. Replace the fuel return line from the FPR with a piece of clear vinyl 6mm (1/4") tubing to a suitable container. Run the pump by jumpering FP to B+. Then do it again at idle. On my '94, I got about 1/2 liter/minute at idle.

If your pump isn't running, or produces less pressure than required in the FSM, or if your filter is blocked, you won't get any flow out. But if the FPR has failed (so that it doesn't "back up" enough pressure in the rail), you'll get plenty of flow out anyway. So adequate flow is only 1/2 of the equation, but it's the more important part.
scope103 is online now  
The following users liked this post:
Maeson Yosick (05-10-2019)
Old 05-10-2019, 03:23 PM
  #5  
Registered User
Thread Starter
 
Join Date: May 2019
Posts: 13
Received 0 Likes on 0 Posts
Originally Posted by scope103 View Post
Doesn't run at all?
Before you go to the effort of testing the fuel pressure, you could check flow. Replace the fuel return line from the FPR with a piece of clear vinyl 6mm (1/4") tubing to a suitable container. Run the pump by jumpering FP to B+. Then do it again at idle. On my '94, I got about 1/2 liter/minute at idle.

If your pump isn't running, or produces less pressure than required in the FSM, or if your filter is blocked, you won't get any flow out. But if the FPR has failed (so that it doesn't "back up" enough pressure in the rail), you'll get plenty of flow out anyway. So adequate flow is only 1/2 of the equation, but it's the more important part.
Correct, doesn't run at all I passed the relays and such so I know the fuel pump is working I hear it work but then the truck won't turn over.
Maeson Yosick is offline  
Old 05-10-2019, 05:04 PM
  #6  
Registered User
 
Join Date: Sep 2007
Location: San Francisco East Bay
Posts: 6,605
Likes: 0
Received 103 Likes on 93 Posts
"won't turn over." To me (and most people) that means it Won't. Turn. Over. I'm guessing it DOES turn over, with gusto, when you turn the key to start. It just doesn't FIRE or RUN.

Just because you passed the relays doesn't mean fuel is getting anywhere. (Which is why you want to check fuel pressure -- which is smart diagnosing.) Checking the fuel pressure is the acid test for, well, fuel pressure. But you can save a few bucks by checking for flow first. If you're not getting flow out of the FPR, it's pointless to check the fuel pressure until that's fixed. Something else is wrong.

But if you have fuel flow out, checking for pressure will confirm the FPR is good.
scope103 is online now  
Old 05-10-2019, 06:39 PM
  #7  
Registered User
Thread Starter
 
Join Date: May 2019
Posts: 13
Received 0 Likes on 0 Posts
Originally Posted by scope103 View Post
"won't turn over." To me (and most people) that means it Won't. Turn. Over. I'm guessing it DOES turn over, with gusto, when you turn the key to start. It just doesn't FIRE or RUN.

Just because you passed the relays doesn't mean fuel is getting anywhere. (Which is why you want to check fuel pressure -- which is smart diagnosing.) Checking the fuel pressure is the acid test for, well, fuel pressure. But you can save a few bucks by checking for flow first. If you're not getting flow out of the FPR, it's pointless to check the fuel pressure until that's fixed. Something else is wrong.

But if you have fuel flow out, checking for pressure will confirm the FPR is good.
OK I will get some clear vinyl tube and test the fpr return line for flow, from my understanding if there's no flow the fpr is broken if there is flow it works and something else is wrong with my truck. There for I would continue on and buy a gauge and check the pressure?
Maeson Yosick is offline  
Old 05-10-2019, 07:12 PM
  #8  
Registered User
 
Join Date: Sep 2007
Location: San Francisco East Bay
Posts: 6,605
Likes: 0
Received 103 Likes on 93 Posts
Well, I imagine there might be a failure mode of the FPR where it blocked all flow, but that would be unusual.

The way it works is the pump runs at full blast all the time. The FPR measures the pressure in the rail, and "returns" whatever flow would make the pressure higher than needed. With engine off, it's returning all the flow. At idle, returning most of the flow. At WOT, the injectors are taking a lot of fuel, and much less can be returned by the FPR.

If your pump isn't running, or if the filter is blocked, or if the pump is just so weak that it can't reach 33psi in the rail, then nothing would come out of the FPR. No flow from the return of the FPR usually indicates a problem toward the pump, not in the FPR.
scope103 is online now  
Old 05-11-2019, 02:05 PM
  #9  
Registered User
Thread Starter
 
Join Date: May 2019
Posts: 13
Received 0 Likes on 0 Posts
My truck doesn't run so I turned it to the "on" position so the pump runs, I put a clear piece of tubing on the return line then let the pump run and nothing, but when i took off the return line some fuel still leaked out the line and on my hand.
Maeson Yosick is offline  
Old 05-11-2019, 04:33 PM
  #10  
Registered User
 
Join Date: Sep 2007
Location: San Francisco East Bay
Posts: 6,605
Likes: 0
Received 103 Likes on 93 Posts
Time to RTFM. The fuel pump is NOT supposed to run with just key-on. (It runs with the key to start, then once air flow starts the FC switch in the VAF takes over.) To run the pump for testing you just use the procedure in the Manual page I cited to. (The SST is the same one you use to check for codes.)
scope103 is online now  
Old 05-11-2019, 05:16 PM
  #11  
Registered User
Thread Starter
 
Join Date: May 2019
Posts: 13
Received 0 Likes on 0 Posts
Originally Posted by scope103 View Post
Time to RTFM. The fuel pump is NOT supposed to run with just key-on. (It runs with the key to start, then once air flow starts the FC switch in the VAF takes over.) To run the pump for testing you just use the procedure in the Manual page I cited to. (The SST is the same one you use to check for codes.)
I jumped the diagnostics box with a jumper from Fc-B+ turn the key one click(nothing) turn the key to start(I hear the pump running). Let pump run for a minute or so and nothing came out of FPR. Next step replace FPR? Or any other tests I can do to narrow down the problem?
Maeson Yosick is offline  
Old 05-11-2019, 06:28 PM
  #12  
Registered User
 
Join Date: Sep 2007
Location: San Francisco East Bay
Posts: 6,605
Likes: 0
Received 103 Likes on 93 Posts
First, I'd find out why the pump is not running with the jumper. Fp to B+ just bypasses the COR. It's actually fairly easy to get the wrong hole in the diagnostic connector. Use your multimeter; you should have battery voltage on B+ with key-on. With key off, check resistance to ground at Fp (the resistance is single-digit ohms, so it will look a lot like a dead short). If Fp was REALLY shorted to ground, you'd get fireworks connecting battery voltage to it.

I can't hear my pump with key to start; the starter makes too much noise. But I suppose you could move to the back and put your ear close to the tank and hear it. I think it's VERY unlikely to be a bad FPR; if it was stuck closed you'd have too MUCH pressure in the rail. The truck would start, but run like poop.

So I think your pump is not pumping. Fuel pressure test is next, but if you want to defer the $50 for the tool, you can take one more step. You can loosen the banjo bolt below the FPR, start the pump (CAREFUL!) and look for a vigorous spray of fuel. I usually advise against loosening any pressurized fuel connections, because that pair of crush washers MUST be replaced every time. But since your plan it to attach a fuel pressure gauge there, you were headed in that direction anyway. (I always got my crush washers from the dealer. They're not expensive online, but shipping will get you. Or, see this discussion: https://www.yotatech.com/forums/f116...s-made-307567/)
scope103 is online now  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
mason1982
Post Your Tests Here
3
07-30-2017 06:17 PM
Waterfreek
Post Your Tests Here
1
07-23-2017 07:59 PM
MUD-LIGHT
Post Your Tests Here
0
08-13-2012 05:50 AM
NeverSatisfied
84-85 Trucks & 4Runners
1
02-13-2009 10:34 AM
ThomasJ
99+ Tundra, 00+ Sequoia, 98+ Land Cruiser/LX470
1
08-27-2005 05:38 PM


Thread Tools
Search this Thread
Quick Reply: How to test fuel pressure on a 3.0 vz-e truck


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: