demasters

22re 23lbs. book says I should have 38-44. Could this be why my truck has been throwiing codes? 24,25,31,41? Alot of you have help me check different things this past week, like the AFM TPS Timing. Could it been that it wasn't getting enough fuel? I took the filter off and blew throuh it and it wasn't plugged. just to be sure I got a new one and blew through it and it was the same. So now I guess it's down to the fuel pump right?

mt_goat

There is also a pre-filter inside the tank before the pump but could also be the pump or low voltage to the pump. The wires going to my stock pump were very small and it wouldn't take much corrosion to effect the voltage. I hear the fuel pump is very voltage sensitive.

demasters

So being that the pump is pumping could it be the filter in the tank? What shouldt the voltage be going to the pump?

mt_goat

That's a good question and I don't know. I guess ideally it would be pretty close to the alternator output. I'd say if it's not at least close to 12V that may be a problem.

mt_goat

Where did you test the fuel pressure, before or after the fuel pressure regulator?

demasters

I tested after the regulator ant the cold start injector. With the truck running it reads 25psi. not running 23psi. I was going to check the psi befor or after the fuel filter but I don't know what the pump should be putting out.

demasters

Another thing is that it is not holding pressure when the truck is shut off. Testing at the rail the FSM says it should hold at least 21psi for 5 min. Goes right to 0.

mt_goat

Oh! well it could be the regulator then.

mt_goat

Hummm....that should be a good clue too, but I'm not sure what it is.

mt_goat

I would study this diagram carefully:
http://personal.utulsa.edu/~nathan-b...23descript.pdf

It kind of looks like to me the cold start injector is up line of the regulator, but I'm not sure.

demasters

just did the psi check at the fuel filter. Still 23psi. I think I'm going to install a new pump. Fockers are pricy

Yoda

You could MOMENTARILY pinch the return line and see if the pump is capable of higher presure (return line is at rear of manifold, towards the charcoal canister)

If it does get higher, may be bad pressure regulator.

Also clamp off return, then shut off truck. If it then holds pressure the regulator is bad. If it does not hold pressure, could be the pump (checkvalve inside)

dcg9381

That's odd.. Mine reads 44psi while running.
I've got a spare reg if you decide you need one... But I'd replace the inline filter and maybe the sock filter first.

timebandit

If the psi cans like that pinch, the return line if it holds the reg is bad. If not the check valve in the pump is bad.

Targetnut

YODA is very right to check your pressure regulator. The way it works is to restrict the fuel flow enough to maintain the proper pressure. If it's bad in a manner to cause low pressure it is likley to cause the bleed down of pressure as well.

Crimp off the return line while measuring the pressure at the cold start injector. The pump should be able to get 80 - 100 psi. if it does not increase look at the pump. If it does increase you'll be needing a pressure regulator.

Proper testing is the way..........

Grasshopper

P.S. leaky injectors can also cause bleed down

Yoda

Leaky injectors will give you a gradual bleed down. The pump or pressure reg can be immediate

Yoda

What book are you using, and what year is your truck?

The 85 factory manual says 33-38 PSI with vac line disconnected, and 27-31 PSI with it connected. ( Other years may be different)

demasters

Hey hey figured it out. I put a pressure tester on the line before the filter. Still 23psi. So I bought a new fuel pump. Droped the tank and pulled the pump up. Wala the hose that connects the pump to the hard line had pulled off on one end. I thought hell why I'm in here should I replace the pump or take my chances? For $230 I took my chances. Now I have 38psi without the truck running and 44 when running.

I'm thinking that this has been all of my problems. Like the AFM signals and bad TPS signals. I think the computer was telling it to adjust for the fuel that it was'nt getting.

Thanks everyone for the help. I'll drive it tomarrow and see how she does.

dcg9381

I think it's performance engineering that offers walbro pumps for the toyota truck/4runner for around $100..... Second thing is that my truck doesn't hold pressure for 5 minutes either. It drops fairly quickly after the pump is shut off.

mt_goat

I'm running a Walbro pump now. It's a lot noiser than the stock pump but so far works great.