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How to test fuel pressure regulator?

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Old 05-03-2011, 05:06 AM   #1
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How to test fuel pressure regulator?

Im looking for the best or easiest way to test the FPR on my 85 Pickup. I know there is a way to do it with a pressure gauge but not really sure how to do it or if there is a certain type I need. The truck is also not running right now. When it was running it was really rich so i want to check this before i try and mess with the TPS. Any help on this would be appreciated.

Thank you, Reid.
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Old 05-03-2011, 07:14 AM   #2
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Make sure the vacuum line is connected to the FPR:
http://www.4crawler.com/4x4/CheapTri...ine_Pix/8.html

If not, you'll be running too rich at low engine loads.

You can use that vacuum line, connected to a hand vacuum pump to vary the fuel pressure and listen for a change in pitch in the sound of the FPR with the fuel pump is running:
- http://www.4crawler.com/4x4/CheapTri...shtml#FuelPump

I have heard you can rig up a temp. test point by modifying the banjo bolt fitting for the cold start injector with parts from NAPA. Or I installed a permanent pressure sender on my fuel rail:
- http://www.4crawler.com/4x4/CheapTri...rPressureGauge
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Old 05-03-2011, 02:31 PM   #3
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All my vacuum lines should be in the right places. The dealership gave me a print up of the vacuum hoses, although my 85 has a few more lines then what is showing. I went through the whole intake, had my injectors cleaned, new filter and fuel pump. Ive checked my AFM and TPS with an ohm meter. Not sure if the TPS is set correctly though. I was just told if the vacuum line port off the FPR holds at 10psi it should be good. Have you heard of this? Not sure what to get to test that out though.
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Old 09-23-2011, 11:26 AM   #4
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I am also trying to find out how to test the FPR. Or at least the fuel pressure making it to the FPR. If I got the M12 x 1.25 banjo bolt adapter, would I just screw it where the FPR goes and unplug the VSV?
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Old 09-23-2011, 11:58 AM   #5
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Cold start injector would be one place to try.
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Old 09-23-2011, 01:12 PM   #6
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Where could I find a M8x1.0 banjo bolt adapter?
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Old 09-24-2011, 04:06 PM   #7
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Ok, so I couldn't find a M8x1.0 banjo bolt for the CSI, but I did find an adapter to fit where the FPR is on the fuel rail. I tested the pressure and it was at a steady 20psi. Shouldn't the pressure be somewhere around 33psi or so with the FPR removed?
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Old 09-24-2011, 05:53 PM   #8
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The operating pressure is a little under 40 psi with the regulator in place, so likely something over that without a regulator (and no return line for the fuel).
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Old 09-24-2011, 06:06 PM   #9
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Ok, so I definitely have a fuel pressure problem! What should the psi be coming straight from the fuel pump?
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Old 09-24-2011, 06:45 PM   #10
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Not sure the exact spec, it is not listed in my FSM. But if the regulated pressure is up to 38 psi or so, one would assume the unregulated pressure is more than that, maybe 40-50 psi. Make sure the pump is getting full voltage.
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Old 09-24-2011, 08:11 PM   #11
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Would I just put a multimeter on the + & - terminals at the top of the pump? Or would I actually have to take the pump out the tank and test it? And would you happen to know the specs for that?
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Old 09-24-2011, 08:17 PM   #12
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You of course want to test the pump under load, so that is it pulling the full current through the circuit. So test the terminals on the top of the pump or if that is hard to get to, someplace along the wiring close to the pump. General rule of thumb in the Toyota test procedures for such things is that the voltage at the load should be within 1/2 volt of the battery at the same time. So if the engine is off and you have the pump jumpered on, and you have 12.5 volts at the battery, you should have something like 12 volts at the pump. If you see something like 6 or 9 volts, then that is probably telling you that there is a voltage drop someplace in the circuit, trace back and find it. Why do that test? Well, if you do have a drop someplace in the wiring, and you pop $100 or whatever on a new pump and put it in, guess what? You'll still have low fuel pressure and you'll be out $100 to boot!
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Old 09-25-2011, 06:50 AM   #13
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Now I believe my PS pump/pulley is bad! The belt on the PS pulley is screaming! I've heard you can get a shorter belt and bypass it or get a free spinning PS pulley. Does anyone know how to do this?
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Old 09-25-2011, 07:07 AM   #14
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Probably the idler/tensioner pulley. If so, easy enough to pop the bearing out and if it is not too far gone, clean and grease it. If shot, new bearing is not terribly expensive, we carry some of the common sizes for that pulley.
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Old 09-25-2011, 07:39 AM   #15
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Ok, so even though the sound is coming from the p/s pulley, you believe it is my idler/tensioner pulley?
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Old 09-25-2011, 07:52 AM   #16
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Easy enough to check, pull the belt and give the idler pulley a spin. If it feels gritty, tight or wobbly, then it is likely that bearing. If it feels normal, then it may be the pulley on the p/s pump, but in that case the pump probably needs to be rebuilt.
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Old 09-25-2011, 08:12 AM   #17
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So you are saying there is no way to bypass the p/s pulley? Maybe get a shorter belt? I have heard of this, but not exactly 100%
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Old 09-25-2011, 08:18 AM   #18
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Sure, just take the p/s belt off. If typically only drives only the p/s pump.
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Old 09-25-2011, 12:30 PM   #19
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So, I took my p/s belt off and replaced my idler pulley... When I started it, it had a bad lag/hesitation when turning over, finally caught and started (cold), ran pretty rough for about 30 secs and then died and wouldn't start again like it has been doing... Example: Previous time I had it running and took a test drive, I drove about .5 mile, stopped at the stop sign and wouldn't start! Do you have any idea what is goin on or where I could start? I know I need to test the voltage on my fuel pump since I only have 20psi coming from the pump... I have to borrow my buddies multimeter tomorrow and will get that done. But what is the lag when starting? Could it be my timing? Which I adjusted earlier before I started it! Please help! This truck is turning into my worst nightmare!
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Old 09-25-2011, 03:48 PM   #20
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Was the fuel pump test jumper installed when you has starting issues? If not, try leaving that jumper in place.
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4runner, 94, 98, check, damper, fuel, pickup, port, pressure, presure, regulator, sr5, test, testing, toyota

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