93 3.0 4Runner

Trying to diagnose a hard starting problem.

Should the fuel rail hold pressure after you shut the motor off ?

I have replaced the Fuel Pump, Fuel Pressure Regulator, Fuel Pressure Damper, Injectors and all of the Rubber Seals around them, and a host of other items.
I get 38-40 psi when running but immediately drops to zero when shut off.

Any ideas on where to look next ?

 

Should hold some pressure. Looking back at my last fuel pressure test results, I see that mine dropped form 42 to 32 after five minutes of being left off. That was taken with at least three bad injectors. I don't think there was anything else wrong with it at that point., Consult the FSM for specs. I think checking after five minutes shut off is one of the numbers it looks for.

Oh, where did you tap into your fuel system to get your readings? That will make a difference. Mine was actually at the rail fitting.

 

Tapped in at the rail fitting just below the fuel Pressure regulator.

The hard starting problem occurred before I replaced the injectors. The injectors are re manufactured.

Is there anything else that could cause sudden pressure drop ? I know that's an open ended question but I'm looking for anything and everything.

Thanks for the reply thus far.

 

check 4crawlers cheap tricks page. hes got an writeup for what hes done with his lack of fuel pressure.

 

Found his website and will try some more troubleshooting tomorrow.
Thanks

 

Found the AFM not testing to spec. Got one coming in the mail.

Jumped the the fuel pump and have 44 psi when key is turned on. Pressure still drops to zero almost immediately after turning key off.

 

immediate drop can be a couple things. it may be the residual valve in the fuel pump itself, allowing fuel in the rail/pressure line to backflow. you can "defeat" some of the hard semi-warm starts by turning the key to the "start" position without putting the clutch pedal down, and then after one or two seconds put the pedal down and the truck should start (don't release the key from the "start" position, just push the clutch pedal. this might work with an automatic, but you'd have to do it differently. perhaps put the truck in "D", foot on brake, turn to "start" which might activate the pump, but not the starter. then. release key, put in "P", and then start normally.

 

Ok I need to ask are you smelling fuel at all ??

If not I am thinking it is either the fuel pump or a crack or leak in the fuel pressure line on the fuel pump bracket

I read the specs on the fuel pressure holding since it was not a issue at the time I don`t recall them

 

[QUOTE=wyoming9;52358327]Ok I need to ask are you smelling fuel at all ??

If not I am thinking it is either the fuel pump or a crack or leak in the fuel pressure line on the fuel pump bracket

I read the specs on the fuel pressure holding since it was not a issue at the time I don`t recall them[/QUOTE

No gas smell and no signs of an external leak.
When I replaced the injectors, I jumped the fuel pump to pressurize the fuel rail and everything checked out fine.
The Pressure dampener was replaced due to leakage.

When I replaced the fuel pump, I remember replacing a small rubber hose at the pump but didn't pay much attention to the other components around the pump area.
I guess that's my next project is to pull the tank and check the pump.

Thanks for the reply

 

Does jumping the fuel pump do the same thing since once jumped, it turns on instantly providing pressure to the rail.

The hard starting could be the AFM that I found to be out of spec when I tested it.
I have a replacement coming later this week.

Thanks for the reply..

 

Jumping FP to B+ bypasses all the switches and relays

Allowing the fuel pump to be turned on.

 

right, does the same, but allows you to drive without the fuel pump jumpered, IF rail pressure is the problem.

wally

 

Thanks Wally. I appreciate the input/advice.

I have been been chasing this hard start problem for several months now. With all of the advice and information given on this website, I feel like I'm finally gaining ground..