Hard Start Issues

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Jan 17, 2019
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Hey all,

I've been wrenching on the FJ80 a bit doing some PM/chasing a hard start problem. The problem I have is when I crank the engine, it will turn for what seems like a long time(~5 seconds), and then when it turns over, it will sometimes act as if choked. Like you put carb cleaner in the intake. It will then rev up to normal idle rpm. I have not seen a pattern of when it stumbles.

I have changed out fuel pump, damper, regulator, fuel filter, cleaned injectors and cold start injector, ran some carb cleaner to clean the TB, checked and charged the battery, and all the normal maintenance items (minus a valve adjustment, kickdown cable adjust, and accelerator cable adjust). The truck runs great otherwise.

In my limited knowledge, have narrowed it down to 4 possible parts:
  • Cold start injector (leaky or doesn't open)
  • Cold start injector time switch (won't tell CSI to open)
  • VSV
  • Starter Motor (not enough power behind the crank)
Which part do you suspect is causing me the issue?
 
Joined
Nov 9, 2012
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Year?

Do you have a CEL with engine off, key in "RUN" position?

Have you removed the two screws on the AFM by the air cleaner and pulled on the harness? If not, don't.
 
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1992 FJ80, 3FE.

I measured the fuel pressure before replacing the fuel line parts (pump, regulator, damper). Pressure was good but I replaced anyway as PM.
 
Joined
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Year?

Do you have a CEL with engine off, key in "RUN" position?

Have you removed the two screws on the AFM by the air cleaner and pulled on the harness? If not, don't.
1992, 3FE
I have removed the screws on AFM, but then remembered the stories and did not pull and re-inserted screws. Removed via the metal clip.

CEL is on when key is at "ON" position.
 
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all the normal maintenance items (minus a valve adjustment, kickdown cable adjust, and accelerator cable adjust). The truck runs great otherwise.
Please elaborate on, "all the normal maintenance items".

All mechanicals must be adjusted FIRST.
If the throttle cable is too tight (very common error) and it is not allowing the throttle plate to fully close, The TPS will give false information to the ECU. The ISC valve will not function properly.
This also includes a valve adjustment which should be done every 15K miles according to the FSM. If yours haven't been adjusted in 30 years, it might be time.

The 3FE is a fuel injected tractor motor from 1986. Don't overcomplicate it.
 
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I've replaced cap, rotor, plugs, wires, PCV valve, EGR modulator, valve cover gasket, and Air Filter. Cleaned tuna can and EGR Valve.

Copy all. So I should adjust my cables and get a valve adjustment done before tackling any other item, such as the cold start injector?

Update: I checked the CSI to see if it shot fuel and if it leaked. CSI looks perfectly fine. Strong flow and no leak.

Started when cold with the same issue, as if choked. Drove for about 10 mins. Engine at temp. Turned off and cranked. Started flawlessly. Tried again and it started up perfectly again. Perhaps its only when cold or when off for a while?
 
Last edited:
Joined
Jul 23, 2014
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Location
Lahore - Pakistan
 
attach the fuel pressure gauge, run the engine,
shut off and observe the behaviour

if it loses pressure in a matter of a few seconds then either the fuel pump is leaking or the injectors, because of it was an external leak you would've known

it should maintain about 20 psi for at least 5 mins before it starts to go lower
even after 30 mins, when you crank it should be able to prime / go full pressure within one or two seconds
 

flintknapper

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attach the fuel pressure gauge, run the engine,
shut off and observe the behaviour

if it loses pressure in a matter of a few seconds then either the fuel pump is leaking or the injectors, because of it was an external leak you would've known

it should maintain about 20 psi for at least 5 mins before it starts to go lower
even after 30 mins, when you crank it should be able to prime / go full pressure within one or two seconds

^^^^^

This
 
Joined
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attach the fuel pressure gauge, run the engine,
shut off and observe the behaviour

if it loses pressure in a matter of a few seconds then either the fuel pump is leaking or the injectors, because of it was an external leak you would've known

it should maintain about 20 psi for at least 5 mins before it starts to go lower
even after 30 mins, when you crank it should be able to prime / go full pressure within one or two seconds
Will do that when I have a chance. I place the gauge at the cold start injector port. Is that valid?
 
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I will perform the pressure test tonight. After doing more research, I think the injectors might be leaking. I had a shop clean them about 2 months ago, but they told me today they pressure cleaned them instead of taking them out and taking them through an ultrasonic bath. The pressure clean method can leave debris in the opening causing them to leak.

If the test does say that I have a leak, can those injectors be salvaged and cleaned properly? Or are they too far gone?

Now my concern. If the injectors have been leaking, how much damage has this already caused to the engine? (Cylinder walls, oil dilution, stripping oil from bearings) I know the 3FE is a tough engine, but still.

Also, if I change the oil, since the gasoline is less dense, will it remain up above the oil and act as a degreaser as I drain? If I am overthinking this, just tell me to stop :). Just trying to minimize damage, to engine and wallet.
 
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I will perform the pressure test tonight. After doing more research, I think the injectors might be leaking. I had a shop clean them about 2 months ago, but they told me today they pressure cleaned them instead of taking them out and taking them through an ultrasonic bath. The pressure clean method can leave debris in the opening causing them to leak.

If the test does say that I have a leak, can those injectors be salvaged and cleaned properly? Or are they too far gone?

Now my concern. If the injectors have been leaking, how much damage has this already caused to the engine? (Cylinder walls, oil dilution, stripping oil from bearings) I know the 3FE is a tough engine, but still.

Also, if I change the oil, since the gasoline is less dense, will it remain up above the oil and act as a degreaser as I drain? If I am overthinking this, just tell me to stop :). Just trying to minimize damage, to engine and wallet.

get replacement injectors, toyota doesnt recommend ultrasonic cleaning anyways.

and once you sort things out just change the engine oil.
 
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I've read good things about Witch Hunter Performance on this forum for injector cleaning. If I did get new ones, do you have a recommendation?
 
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Alright, I did the pressure test today. Yesterday I broke the banjo adapter :doh:.

Results: At steady state with the engine running, the gauge shows ~35 psi. When I turn off the engine, the pressure spikes to about ~42 psi, the shoots down. It reaches 10 psi in about 4 seconds. I then tried to pinch the return line to see if there was any change. When a helper turned it off, I pinched the line and the pressure decrease slowed down, but still reached 10 psi in a matter of seconds. Side note: I heard a clicking sound when I pinched the line. Sound went away when I released the return line.

I suspect leaky injectors now more than before. I don't think its the pump because it is a brand new Denso pump installed 2 weeks ago.

Thoughts?
 
Joined
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Alright, I did the pressure test today. Yesterday I broke the banjo adapter :doh:.

Results: At steady state with the engine running, the gauge shows ~35 psi. When I turn off the engine, the pressure spikes to about ~42 psi, the shoots down. It reaches 10 psi in about 4 seconds. I then tried to pinch the return line to see if there was any change. When a helper turned it off, I pinched the line and the pressure decrease slowed down, but still reached 10 psi in a matter of seconds. Side note: I heard a clicking sound when I pinched the line. Sound went away when I released the return line.

I suspect leaky injectors now more than before. I don't think its the pump because it is a brand new Denso pump installed 2 weeks ago.

Thoughts?
Where is the fuel line check valve in the system? I it part of the pump or is it between the pump and the injectors? Otherwise the fuel after shut down could be bleeding back to the tank.
 
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Where is the fuel line check valve in the system? I it part of the pump or is it between the pump and the injectors? Otherwise the fuel after shut down could be bleeding back to the tank.
Great question. I have no idea. According to this website, its internal to the pump: Products | Fuel Pumps

By chance, do you mean the regulator? That would be after the injectors on the return line.
 
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Great question. I have no idea. According to this website, its internal to the pump: Products | Fuel Pumps

By chance, do you mean the regulator? That would be after the injectors on the return line.
Nope, I was referring to the check valve. I have not had reason to dig into the fuel system as you are.

I thought it was in the pump, but that confirms it. Since you installed a NEW pump, we will assume it is now good.

That said, then yes, it could be either the pressure regulator or the injectors, as the unused fuel recirculates back to the tank and if during operation the pressure is too low, it could be because the regulator is not holding pressure back. so the fact that your fuel pressure drops off in a few seconds, it is the injectors or the regulator. Keep narrowing it down.
 
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