help diagnosis

T

thomas_guerra

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help starting problem diagnosis

hey guys, looking for some help on my wife's 2.7l 98 4runner AT.
I did a quick search but didn't see anything quite related on the first few pages. If i missed something, I apologize in advance. Feel free to point me in the right direction if there is already a thread on this.

My wife truck has recently (starting about 2 weeks ago, happening daily) had a starting issue. It would crank over extremely well, but start after an amount of time. (First a few cranks, then progressively more and more.) The longest I've been at it is maybe 15 minutes. Once it starts it runs just fine. There is a CEL but my Bluetooth OBD doesn't read any codes, nor does the service at Autozone. BTW Starting fluid would start the car for a second or two, then die...

I used to hear the fuel pump whenever I stopped cranking, but today the vehicle would not start, and I couldnt hear the fuel pump.

I guess what I'm looking for is the fuel pump schematic/pinout to try to jump the pump and diagnose that.

Sorry to be long winded, but has anybody else had similar problems?

Also, not sure if it is related, but the ignition cylinder locked up on us. The key would not turn past the locked position, but I somehow got it loose and the key now works.

Thanks for any and all help-
thomas
 
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Fuel pump circuit opening relay is under the dash right next to the hood release handle.

To jump it you'll connect the two horizontal terminals which is kinda tricky due to the angle. With the jumper in place, turn the key to "on" and the pump will run.

You'll want to jump the two bronze/copper terminals in this picture... On the plug side, obviously.

images




For future reference, try to be a bit more concise in your title... It'll draw more attention.
 
Jumping the fuel pump is a good place to start, but the ECU won't fire the pump if it doesn't sense the engine cranking, so it could be a sensor. I believe the crank position sensor triggers that, but I'm not sure.

It's strange that you have a CEL and aren't seeing any codes. I'd dig into that a little further. Maybe try another reader. What happens when you send it a reset signal?
 
[MENTION=63487]A.Wilson013[/MENTION]: Yeah I saw that my title wasn't all too descriptive but was unable to edit it.
Thanks though for the pin out. I'll try it when I get off of work.
[MENTION=116745]jeremyc74[/MENTION]: the crank position sensor? You wouldn't happen to have the voltage those are supposed to be at for me to test it? And my Bluetooth obd claims to see the ECU, says there's no pending codes, no stored codes. But if I tell it to reset the CEL, it goes away...
 
I just got home from work. The last time the truck started was about 3 am this morning. This morning (745a-8a) is when I couldn't hear the fuel pump. Now at 845pm, the truck started up no hesitations, first try. I don't know if the time of day has anything to do with it, or the duration of time that has passed since the last start up.

I'm beginning to think ignition switch could be the culprit.

Any thoughts?
 
thomas_guerra said:
I just got home from work. The last time the truck started was about 3 am this morning. This morning (745a-8a) is when I couldn't hear the fuel pump. Now at 845pm, the truck started up no hesitations, first try. I don't know if the time of day has anything to do with it, or the duration of time that has passed since the last start up.

I'm beginning to think ignition switch could be the culprit.

Any thoughts?
Click to expand...

Why?

There are only 3 reasons why an engine won't run. Fuel, spark, and compression. Check the easiest of these first, for me that is spark, then fuel, then compression.
 
IBallEngineer said:
Why?

There are only 3 reasons why an engine won't run. Fuel, spark, and compression. Check the easiest of these first, for me that is spark, then fuel, then compression.
Click to expand...

Right, i understand the basics of it. But i was thinking the switch is sending intermittent signals for the fuel.

I see the tach move, but i do have new plugs that i don't necessarily want to possibly foul out.

This morning I could not hear the fuel pump prime or purge out fuel as i was trying to start it. Most times I can.

Granted I haven't tested/replaced the maf, but once started it runs as it should.
 
thomas_guerra said:
Right, i understand the basics of it. But i was thinking the switch is sending intermittent signals for the fuel.

I see the tach move, but i do have new plugs that i don't necessarily want to possibly foul out.

This morning I could not hear the fuel pump prime or purge out fuel as i was trying to start it. Most times I can.

Granted I haven't tested/replaced the maf, but once started it runs as it should.
Click to expand...

My point is this.

Even if you have no spark, the ignitions switch is only one of MANY potential failures. Why not test the fuel pump, that is easy!

:cheer2:
 
thomas_guerra said:
Other than my initial question of jumping the wiring, what is the best method to test it?
Click to expand...

Well, depends what part of it you want to test. I'd start with the easy part, measuring the resistance at the pump. If that's within spec I'd start thinking about checking fuel pressure at the rail...

v9JqJnB.png
 
A.Wilson013 said:
Well, depends what part of it you want to test. I'd start with the easy part, measuring the resistance at the pump. If that's within spec I'd start thinking about checking fuel pressure at the rail...

v9JqJnB.png
Click to expand...



So I measured resistance, but have a couple of questions. What increments is used to measure this? and what would the value be in 100 degree weather?

I am using the smallest increment (20), and am getting a reading of 2.3 ohms in 100 degree weather. Oddly enough, today it started like a champ. Even though it is still having this weird starting problem.
 
thomas_guerra said:
So I measured resistance, but have a couple of questions. What increments is used to measure this? and what would the value be in 100 degree weather?

I am using the smallest increment (20), and am getting a reading of 2.3 ohms in 100 degree weather. Oddly enough, today it started like a champ. Even though it is still having this weird starting problem.
Click to expand...

Touch your test leads together. What are you reading then?
 
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