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Help. Fuel pressure loss on 85 22re

Old 05-07-2019, 02:11 PM
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Help. Fuel pressure loss on 85 22re

So this is my first post, after roughly 6 months of research and hundreds of dollars in parts and and time and lots of hair loss. So I ask the best place for answers.

Lets get to it.

I have an 85 4Runner 22rec 4x4.
I rebuilt the motor this winter during a lay off and stabbed it back in the truck and when trying to get back going it wouldnít start.

I have since got it to idle. With a truck load of new parts.
NEW:
4 fuel pumps
injectors
fuel pressure regulator
filter
afm with a known good one
coil
plugs and wires
distributor cap
Injector plugs
Coolant temp sensor
cold start injector with known good one

The problem is the truck will idle fine and will rev up to about 2000 rpms and then just fall on its face. I hook a fuel pressure gauge up it will bring it up about 38 psi with a jumper and key on. With the truck running at idle, smooth as silk, with a little bit of throttle the fuel pressure bottoms. I have covered the main feed line on the pump housing with a rubber fuel hose so I know itís not bleeding by there. No visible fuel leaks at all. Truck is dry as a bone. All grounds and connections seemed to be spot on. 12v at the pump at all times.

No codes

I am lost on this, any suggestions on this would be awesome. Thank you guys.

Iíll try to get some videos up to show whatís going on.

Last edited by 934runnerdeluxe; 05-07-2019 at 02:34 PM.
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Old 05-08-2019, 08:02 AM
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Probably a crushed or clogged fuel supply line
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Old 05-08-2019, 09:20 AM
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Have you checked the throttle position sensor? That could be a culprit if it falls off after a certain amount of throttle
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Old 05-08-2019, 10:47 AM
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Originally Posted by trevor1985 View Post
Have you checked the throttle position sensor? That could be a culprit if it falls off after a certain amount of throttle
Doesn't work like that. The pump should be supplying enough volume for the regulator to maintain the designed pressure with the injectors essentially wide open (near saturation).

You can pull the return line off the regulator and plumb it into a catch container. Run the pump via the diagnostics jumper for one minute. Then measure the fuel, it should be very close to 500cc.

The scenario with a fuel line clog will show less volume due to the restriction. It is similar to having a fuel pressure regulator up steam of the injectors, the pressure behind the clog will be maintained by the pump's internal pressure release. Think of a garden hose, you can slightly open the tap and pinch the hose to build up pressure but what comes out the end of your wide open spray nozzle is just a trickle. Close the spray nozzle to a point that matches the tap opening and you have a good spray not a trickle.

This clog could be a physical kink, it could be rust, it could be sludge, and even any combination of these things.
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Old 05-08-2019, 01:44 PM
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Originally Posted by Co_94_PU View Post
Doesn't work like that. The pump should be supplying enough volume for the regulator to maintain the designed pressure with the injectors essentially wide open (near saturation).

You can pull the return line off the regulator and plumb it into a catch container. Run the pump via the diagnostics jumper for one minute. Then measure the fuel, it should be very close to 500cc.

The scenario with a fuel line clog will show less volume due to the restriction. It is similar to having a fuel pressure regulator up steam of the injectors, the pressure behind the clog will be maintained by the pump's internal pressure release. Think of a garden hose, you can slightly open the tap and pinch the hose to build up pressure but what comes out the end of your wide open spray nozzle is just a trickle. Close the spray nozzle to a point that matches the tap opening and you have a good spray not a trickle.

This clog could be a physical kink, it could be rust, it could be sludge, and even any combination of these things.
I took the line loose from the pump, and loose from the filter. I then hooked about 90psi of air through the main feed line for about 45-60 seconds. (Whatever was left in the tank) Granted that doesnít exactly tell us anything. Now I have visually inspected the lines and it doesnít look like thereís any rust or kinks down the body that you can see. But sludge and rust on the inside, is there anything you can put in the lines to eat this stuff out?

As far the tps I have adjusted and triple checked it to make sure itís good. It checks out good on all accounts.
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Old 05-14-2019, 05:25 PM
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Bump*
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Old 05-14-2019, 08:48 PM
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Originally Posted by 934runnerdeluxe View Post
Bump*
Look thru Terry's threads, i couldn't find it but I'm not as motivated as I expect you will be, I don't recall if he uses solvent of any kind to clear fuel lines.

BUT! You didn't say anything about the test results just jumped right to blowing a little bit of air through it. This means you don't know if it was actually a flow problem or have any baseline to compare any possible progress to.
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Old 05-15-2019, 10:26 AM
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Here is one of Terry's posts. He just used compressed air to clean out the lines. I thought he put something in the lines on when of his trucks to soak for a while.

Here is his post on his 1988 4Runner: https://www.yotatech.com/forums/f199.../#post51633022

I found a thread where Terrys87 replies on how he cleans out his lines. He says on really dirty fuel lines, you can use Marvel Mystery Oil or PB Blaster and let it soak for a while.

https://www.yotatech.com/forums/f116...em-too-266872/

If you have the fuel system apart, it doesn't hurt to clean out the lines at the age of these vehicles, even if dirty fuel lines isn't what is causing your problem.

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