slow to fire up
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TorqueOfTheDevil
Member
Hard to go "blind" as such.. but +1 for fuel pressure.
I have a cheap and nasty fuel pressure regulator and the fuel system loses pressure overnight. it takes a few seconds to build up on the first start of the day.
That's fine by me, it means oil pressure gets a head start with the cranking.
I have a cheap and nasty fuel pressure regulator and the fuel system loses pressure overnight. it takes a few seconds to build up on the first start of the day.
That's fine by me, it means oil pressure gets a head start with the cranking.
This could be many things. Remember, to crank instantly -- you need 3 things -- fuel, air, and spark. You have to troubleshoot/do maintenance on each sub-system as you try to filter down to the problem.
[MENTION=10169]TheDurk[/MENTION], I'm thinking this technically could also be starter contacts on the way out, right? Long turnover attempt and an eventual start.
[MENTION=10169]TheDurk[/MENTION], I'm thinking this technically could also be starter contacts on the way out, right? Long turnover attempt and an eventual start.
TorqueOfTheDevil
Member
I'd say that's unlikely as the OP said its cranking.
I agree it's unlikely, just saying to keep it in mind in case he exhausts all the other areas.
If you read enough T4R, you'll see some cases of long cranking ending up as contacts or battery connections even with an eventual start.
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JRZEE2000TR4LTD
Senior Member
I don't see how this can be. If the starter is engaging and turning the engine over then the contacts and the battery terminals are handling the electrical load and doing their job. That is assuming that a "slow start" doesn't mean the starter is struggling to turn the engine over instead of longer cranking times, which it sounds like the OP is talking about. That being the case, focus on fuel delivery and ignition.
Take a long look at the IAC valve.
The starter rolls the engine over real good. Had the IAC apart and cleaned it when I did the engine swap last year.After that it took what seemed to be too long of cranking on a cold engine but the cold idle was at 1250 rpm and warm idle was at 650 rpm with good throttle response. Throttle response is still good. In the past month the slow fire up on a warm engine surfaced.
JRZEE2000TR4LTD
Senior Member
Those idle rpms are fine. The IAC is more in control of letting air in when first starting and during idle. Some have reported success cleaning it but more have reported the opposite. Sounds like you said that the problem started after you cleaned the IAC. Also, could check the engine temp sensor.
TheDurk
Elite Member
I'd agree it's unlikely. Several cases on here where it has been the fuel regulator or fuel pump.
Seems like the fuel pressure is bleeding back. If I turn the warm engine off and immediately restart it fires right up. Does the FPR keep the fuel from bleeding back or is there a check valve in the fuel supply system? Spark plugs only have about 6,000 miles on them. Also I believe there is a relay for the pump so it only pumps when cranking or motor running. The air intake plenum has to be removed to check fuel pressure, correct?
cbr900boy
New member
My vote would also be for the fuel pump, especially if the fuel is bleeding back. My understanding is if you have a bad FPR you would have TOO much fuel pressure (I could be wrong though). I would definitely look into replacing the pump based on the amount of miles you have. I replaced mine at around 265K. I bought the Denso kit on Amazon for $90 and it was identical to the original in every way. The kit came with everything including the strainer.
Dropping the tank was pretty straight forward and it took me about 5 hours because I like to take my sweet ass time and inspect everything. Also, if you replace the pump, you should also replace the EFI relay and Circuit Opening relay since they control the pump, might as well since they go bad also. Good luck.
-Danny
You might be rite. The FPR is closed until the engine fires up creating vacumn which opens up the FPR to bypass fuel back to the tank. Appling throttle reduces the vacumn closing FPR bypass. I could remove the return line from the FPR with engine off and blow into it to see if it is stuck open a bit, if it takes air bad FPR. Thanks
St Runner
Member
I know everybody rolls their eyes every time I say it, but upgrade your ground. If it cranks a long time both hot and cold it could be lacking in sufficient ground. Here is my theory, your starter takes the most amps of anything in your truck. If the ground is borderline sufficient all the other sensors and electronics your truck needs to start and run will not be getting enough ground to function properly when starting. Works perfectly when not starting. Remember this is a closed loop system, the ground is equally as important as the positive voltage. I upgraded the ground in my Tacoma and cut down on the cranking time both hot and cold.
JRZEE2000TR4LTD
Senior Member
FPR doesn't use vacuum on our trucks. The hose coming off of it goes to the airbox. If there's fuel in that hose, that's bad.
TheDurk
Elite Member
He's right. That hose to the airbox is the vacuum-sensing hose, that tells the FPR when the engine wants fuel, or doesn't.
From the FSM:
Disconnect the vacuum sensing hose from the fuel pressure
regulator, and plug the hose end.
(o) Measure the fuel pressure at idle.
Fuel pressure:
265 - 304 kPa (2.7 - 3.1 kgf/cm2, 38 - 44 psi)
(p) Reconnect the vacuum sensing hose to the fuel pressure
regulator.
(q) Measure the fuel pressure at idle.
Fuel pressure:
226 - 265 kPa (2.3 - 2.7 kgf/cm2, 33 - 38 psi)
If pressure is not as specified, check the vacuum sensing hose
and fuel pressure regulator.
(r) Stop the engine.
(s) Check that the fuel pressure remains as specified for 5
minutes after the engine has stopped.
Fuel pressure: 147 kPa (1.5 kgf/cm2, 21 psi) or more
If pressure is not as specified, check the fuel pump, pressure
regulator and/or injectors.
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