weird starting issue that I can't figure out

2000 tacoma 3.4 5 speed trd

This issue initially only happened once a month but now it happens evertime I go to start the truck.

Truck will only start with starting fluid.
Once it is running it will stay running, and runs perfect.
If I shut the truck off and try starting it again, it will just crank and crank, until I spray more starting fluid.

what I know:
Fuel pump is good, and working.
Fuel is getting to the rail on startup, I have not checked the pressure though.
recently replaced plugs, wires.
no check engine light

any ideas?

 

Check the fuel pressure (need special adapters, from what I've read). You could have a bad pressure regulator.

Did this problem suddenly get worse when you 'recently replaced plugs, wires' ?

 

No, its actually been about 10k miles since I replaced plugs and wires, I just wanted to point out that they're fairly new.

I will try this and see if it works.
What tells the ecu that the engine is in start up? crank sensor? or ignition switch?
Because its like the start up enrichment isn't working. So the injectors are not firing on start up, which would explain why it starts up on starting fluid, but runs perfect once its running. And would a bad crank sensor throw a code?

 

I clamped the return hose for the fuel regulator and it didn't help.

going to switch ECU's with a buddies truck to see if that's the problem

 

The ECU does monitor a signal from the starter for starting fuel management, the injectors will fire with or without it. Toyota calls it the "STA" signal and it is a direct input to the ECU. The engine should start without it, just not as well. Sick crank sensors don't always set a code.

Just a thought here. The ECU will not allow the fuel pump until it sees a signal from the crank position sensor "EN" (V6) and/or the "STA" signal. The CPS signal is required to keep the pump running and is sufficient in itself for the ECU to allow the pump. The STA signal itself is not is not a requirement for the pump to run but it "may" override the CPS signal.

Here's the thought. While cranking, voltage is lower. A geriatric fuel pump might not run until it gets full power (after cranking). Do you know for sure the pump is running while the engine is being cranked?

 

Just tested the pump while cranking.
I disconnected the main fuel line and fed it into a Jug, then cranked the engine and fuel came out of the hose. so the pump is working while the engine is being cranked. And it looked like a good amount too.

The pump I have installed is a 190lph pump from URD with about 12k miles on it.

 

Well, it was a shot.
Injectors firing while cranking or at least getting firing voltage?

It's a long shot but on this table you can see the "STA" signal and the 6v you should see and where to see it, eighth line down.
I say its a long shot because manual trans folks can push start without using the starter at all.

 

Have you checked your MAS? I was having a starting issue that was solved with a new MAS.

 

well, still no luck with my truck.
Here's what's happening, The injectors are not firing on start up.

I've replaced the crank sensor, which didn't fix the problem. I had a buddy come over with one of those fancy snapon diagnostic systems and he got the truck to start, and im not entirely sure how those snapon things work, but i'm guessing they can override the ecu in some ways. Because with the machine hooked up the injectors fired on start up and the truck started no problem. but with the machine disconnected the injectors don't fire on start up and the engine does not start.

So whatever tells the ecu that the engine is starting and that is should fire the injectors, is faulty, or the ecu is faulty.

The snapon system also showed that the crank sensor and MAF are good and reading properly.

so what should I do? Buy a used ECU? or keep digging?

thanks in advanced

 

bump for desperation!

 

Swap Ecu with a local?

 

that's probably the best idea.
I don't know anyone with the same truck as me unfortunately. I guess i'll ask around

 

I'd take a quick peek behind the dash and see how the plugs are on your key cylinder, only my left rear window didn't roll up, but rolled down, the plug next to the kick panel was just barely, BARELY, not pushed in enough, so check it just in case, or a wire got sheared or something, good luck!

 

Don't know if it would not start the truck but I hear knock sensors wear out. I don't know but good luck

 

not a bad idea. thanks man.

i'll look into this. thanks

 

We know it has Air and Spark for Starting and running. I think you answered your own question. It's lacking"choke" for starting. That's all I got. Dirty fuel filter ?

 

Longshot, but did you get this figured out? Im having the same issues.

 

OP has not been active for last 6 mo.

 

Figured. Didn’t pull up his profile go check that.