Hard to start when weather and vehicle are hot- SOLVED (1 Viewer)

[ColoradoBoy]

Hooked up the pressure tester today (July 4) - system now holds pressure when shut off, (new FPR 23280-74100) but no change in the hard-to-start-when-hot symptom. Idle speed fuel pressure holds at 37 psi. When key is turned off, pressure rises to 42 psi, and holds pressure slowly ending at 27 psi @ the 30 minute mark by my recorded observations.

I noticed a small clicking sound coming from the direction of the FPD after the ignition was shut down. Repeated about the same every time I started it up and shut down again. Is this normal, & I never noticed it before, or is it an indicator of needing a new FPD? EDIT: FSM says the ISC should be making a clicking sound immediately after stopping the engine... moving on!

I would love any insight you all may have at this point in the diagnostic details that I have posted so far... I'm still stumped.

Cheers!

 

[jonheld]

The FPD is a small expansion tank with a spring loaded diaphragm. Its job is to even out the fuel pressure fluctuations as the 2 sets of injectors fire.
There is a set screw under the plastic cap that should be preset from the factory, however many folks have reported that the screw falls out after 30 years.
The set screw can be reinstalled, but I have no clue as to the proper setting.

This OEM part is still available, but the part number has been superseded twice.
23207-74010 original part#
23207-46010 first update
23207-20011 what is currently available from Toyota
All that being said, I don't think this would cause your symptoms, but it's worth looking into if the set screw is rattling around inside the cap.

 

[jonheld]

Idle speed fuel pressure holds at 37 psi. When key is turned off, pressure rises to 42 psi, and holds pressure slowly ending at 27 psi @ the 30 minute mark by my recorded observations.

What is the fuel pressure during the hard to start scenario as compared to a cold start?

 

[ColoradoBoy]

Good morning, Mr. @jonheld thanks for following along. That is a good question that I had not thought of- I'll need to check & see what (if any) differences exist in pressure and report back. My testing yesterday was all on a fairly warmed-up motor. I knew I should have left the gauge port installed on the fuel rail... Oh, well. I'm pretty sure you already have an idea by suggesting the pressure test under the different temperature conditions; would you mind sharing?

Your explanation of the FPD is my understanding as well; I think I'll go ahead and get a new one (30 years) as well as order up a new gas cap and work on the Charcoal can rebuild (mine is definately plugged up!) referenced in this forum while I wait for parts to arrive. Other than those last items, I really don't know what else to chase down. (now that I think about it, temperature & fuel tank pressure must be part of this equation.)

Thanks again to everyone here on MUD, it really is nice to have a resource to keep motivation up and soak up the knowledge base while chasing these types of things down.

Cheers!

 

[ColoradoBoy]

Been a little while- still need to get time and $$ to finish this diagnostic!

Pulled the charcoal canister last night; not completely blocked, but certainly restricted. Will have it refreshed and reinstalled today. (if you are contemplating this, go for it! It truly is a job. Thanks to all who traveled that road and posted for the rest of us.) Took a short drive to get the engine hot and no change in the hot start issue. With any luck, I will test fuel pressure cold vs hot today (although it is already pushing up into the 80s), per @jonheld 's prompting.
I have not had the spare change to order the new FPD- I will get my wife to help me with some more in-depth under-hood investigation & see what we find.

I suppose it is getting narrowed down to the fuel pump and/or injectors at this point? Pressure in the fuel rail holds, so does that positively eliminate the pump check valve?

GRRRRR....

 

[ColoradoBoy]

Referring back to post #21...
After installing the referenced FPR, I have noticed a bit of top end 'oomph' being absent while traveling the highway and at high elevation during steep sections of trails. By 'oomph', I mean that the engine feels tight and constricted instead of spinning up to higher revs smoothly. My wife has noticed it, as well. I was wondering before I ordered it, and wondered what the operating pressures of the original part vs. the replacement part are. Any input from the group?
Cheers!

 

[ColoradoBoy]

... My thought being that the new FPR is OEM for 1996-99 Toyota Celica 1.8 & 2.2 liter motors. Maybe I jumped the gun... (?)

 

[jonheld]

Referring back to post #21...
After installing the referenced FPR, I have noticed a bit of top end 'oomph' being absent while traveling the highway and at high elevation during steep sections of trails. By 'oomph', I mean that the engine feels tight and constricted instead of spinning up to higher revs smoothly. My wife has noticed it, as well. I was wondering before I ordered it, and wondered what the operating pressures of the original part vs. the replacement part are. Any input from the group?
Cheers!

The operating fuel pressure of the original part is outlined in the FSM. I have no idea about the replacement.

 

[jonheld]

Pressure in the fuel rail holds, so does that positively eliminate the pump check valve?

That eliminates the injectors leaking.
If the pressure in the fuel rail is higher than normal for an extended period of time due to a failed FPR, then the check valve in the fuel pump can become sticky.

 

[ColoradoBoy]

That eliminates the injectors leaking.
If the pressure in the fuel rail is higher than normal for an extended period of time due to a failed FPR, then the check valve in the fuel pump can become sticky.

Thanks, Jon. I want to see if I am understanding this relationship between pump and FPR (simple explanation): the fuel pump check valve is to keep fuel from draining back into the tank when shut off, and keep pressure in the rest of the system. The pressure created by the pump is greater than the pressure required by the rest of the system, which is where the FPR's job comes in to regulate the system pressure. Correct?
Sorry if I am so slow- I am truly more of a visual learner when diving into my abstract/unknown theories.

 

[jonheld]

Thanks, Jon. I want to see if I am understanding this relationship between pump and FPR (simple explanation): the fuel pump check valve is to keep fuel from draining back into the tank when shut off, and keep pressure in the rest of the system. The pressure created by the pump is greater than the pressure required by the rest of the system, which is where the FPR's job comes in to regulate the system pressure. Correct?
Sorry if I am so slow- I am truly more of a visual learner when diving into my abstract/unknown theories.

Essentially correct. The fuel pump runs at a constant speed regardless of engine load. The ECU controls a VSV to the diaphragm of the FPR that basically dumps excess fuel back to the tank. Again, 1986 technology 1st generation fuel injection.
The check valve lives inside the pump just before the outlet port. The pump fires, the spring is compressed and the valve opens. The pump stops, the valve closes to maintain pressure.
In some cases with the 3FE and a failed FPR, the check valve can get stuck in the closed position due to constant overpressurization of the fuel rail. It is not a guaranteed outcome, but it has happened to several folks.

 

[ColoradoBoy]

Essentially correct. The fuel pump runs at a constant speed regardless of engine load. The ECU controls a VSV to the diaphragm of the FPR that basically dumps excess fuel back to the tank. Again, 1986 technology 1st generation fuel injection.
The check valve lives inside the pump just before the outlet port. The pump fires, the spring is compressed and the valve opens. The pump stops, the valve closes to maintain pressure.
In some cases with the 3FE and a failed FPR, the check valve can get stuck in the closed position due to constant overpressurization of the fuel rail. It is not a guaranteed outcome, but it has happened to several folks.

Doh! OK, that clears things up a bit in my (feeble) mind. Thank you- I’ll keep chipping away at this! I was assuming the pump check valve worked opposite of this explanation.

 

[jonheld]

Doh! OK, that clears things up a bit in my (feeble) mind. Thank you- I’ll keep chipping away at this! I was assuming the pump check valve worked opposite of this explanation.

If you look at the diagram on page FI-46 of your FSM it is clear.

 

[ColoradoBoy]

OK... got a new Denso fuel pump on the way to me. Re-tested fuel pressure today and was back to square one. Pressure @ idle 42psi, no change when vac port is disconnected, & rail pressure dropped to zero immediately after shutting the motor off. Still need to check the pressure on hot-hard-start vs. cold start. I left the test port connected this time, so I'll do it before next post.

EDIT:

Installed new fuel pump (old was non-OEM) ran a few start sequences and plugged in the fuel pressure tester. All is well again. The fuel pressure stays in range for time after shut-off, and it appears from various running sequences that the hard to start when hot issue is done. The starting is no longer beating the heck out of the starter with long crank times. I believe in my chasing this around, I have learned the relationship of the fuel system a little bit better, so another lesson learned moving forward. I believe the combination of worn-out FPR and stuck valve in the fuel pump was the root cause of the hot start issues. I did notice during my prior tests, that I was getting mixed results on my pressure tests, but didn't put together the picture fully together in my own mind yet. (finger-gun to head; pull trigger)

I'll resrve the right to hold full judgement on this until the end of the weekend to be sure- Going over to meet some friends at a yurt! Plenty of time to test out in the mountains!

EDIT: Problem solved!! Fuel pressure is consistent and new fuel pump/FPR seem to have corrected the issue. Ran around the mountains this past weekend and under all conditions started right up with no undue stress to the starter via excessive cranking.