2000 LTD not starting. Fuel pump brainbuster

[zoombyu86]

When i bought the truck a few months ago it had a P0171 code. Gave it the full tune-up and cleaned the MAF and changed O2 sensor. code was gone. A few weeks ago, code came back, cleaned MAF, no luck. after a few days the truck had random moments where there was no acceleration for a second when you tried to roll from a stop. it still ran fine.

A few days go by and i decide to get a MAF from the junk yard to see if it went away. on my way to the yard, I felt lucky to even make it as the truck did not want to stay running. Not typical signs of a bad MAF. I tried two MAFs they had and it would run REALLY rough and not even get rolling. I got towed home and started to troubleshoot. I tested the pump through the hole, resistance checked good. checked for voltage while cranking and i got about 9.8. I thought i read you should get close to what the battery puts out which mine was at about 12.4. i used my motorcycle battery and the pump would run although it was VERY quiet compared to how loud it normally seems, even with the tank drained.

hooked back up. Wouldnt start. I swapped the EFI relay with the one next to it (Im just seeing what sticks here) and it works! let it run for a few seconds and shut it off. Get everything hooked back up and wont start now. WHAT THE HELL. So i tested again. 9.x volts to the connection, now ohms read open and wont run on a battery. Suspect pump.

I dropped tank and put it on a bench and check ohms...1.2 (WTF). it ran on a battery. I already have a denso on the way so the pump is getting changed regardless. Is it possible to have an intermittent connection inside of the pump? Should I be testing anywhere else. After the pump its really just testing for pressure which still leads back to the pump correct? Should i be seeing more than 9.x volts at the connection? maybe someone could pop their hatch under the rear seat and test for me real quick.

*Note* when truck originally died, upon turning the key to start position, I could NOT hear the pump priming.

 

[cbr900boy]

When i bought the truck a few months ago it had a P0171 code. Gave it the full tune-up and cleaned the MAF and changed O2 sensor. code was gone. A few weeks ago, code came back, cleaned MAF, no luck. after a few days the truck had random moments where there was no acceleration for a second when you tried to roll from a stop. it still ran fine.

A few days go by and i decide to get a MAF from the junk yard to see if it went away. on my way to the yard, I felt lucky to even make it as the truck did not want to stay running. Not typical signs of a bad MAF. I tried two MAFs they had and it would run REALLY rough and not even get rolling. I got towed home and started to troubleshoot. I tested the pump through the hole, resistance checked good. checked for voltage while cranking and i got about 9.8. I thought i read you should get close to what the battery puts out which mine was at about 12.4. i used my motorcycle battery and the pump would run although it was VERY quiet compared to how loud it normally seems, even with the tank drained.

hooked back up. Wouldnt start. I swapped the EFI relay with the one next to it (Im just seeing what sticks here) and it works! let it run for a few seconds and shut it off. Get everything hooked back up and wont start now. WHAT THE HELL. So i tested again. 9.x volts to the connection, now ohms read open and wont run on a battery. Suspect pump.

I dropped tank and put it on a bench and check ohms...1.2 (WTF). it ran on a battery. I already have a denso on the way so the pump is getting changed regardless. Is it possible to have an intermittent connection inside of the pump? Should I be testing anywhere else. After the pump its really just testing for pressure which still leads back to the pump correct? Should i be seeing more than 9.x volts at the connection? maybe someone could pop their hatch under the rear seat and test for me real quick.

*Note* when truck originally died, upon turning the key to start position, I could NOT hear the pump priming.

Have you checked the Circuit Opening Relay? It directly controls the fuel pump and it is located directly under the interior fuse block on the driver's side.

 

[zoombyu86]

Have you checked the Circuit Opening Relay? It directly controls the fuel pump and it is located directly under the interior fuse block on the driver's side.

I saw you had a similar thread. Did you ever get it resolved? I have yet to check the COR. I couldn't find anything on how to test it before I had to be somewhere.

 

[IBallEngineer]

When i bought the truck a few months ago it had a P0171 code. Gave it the full tune-up and cleaned the MAF and changed O2 sensor. code was gone. A few weeks ago, code came back, cleaned MAF, no luck. after a few days the truck had random moments where there was no acceleration for a second when you tried to roll from a stop. it still ran fine.

A few days go by and i decide to get a MAF from the junk yard to see if it went away. on my way to the yard, I felt lucky to even make it as the truck did not want to stay running. Not typical signs of a bad MAF. I tried two MAFs they had and it would run REALLY rough and not even get rolling. I got towed home and started to troubleshoot. I tested the pump through the hole, resistance checked good. checked for voltage while cranking and i got about 9.8. I thought i read you should get close to what the battery puts out which mine was at about 12.4. i used my motorcycle battery and the pump would run although it was VERY quiet compared to how loud it normally seems, even with the tank drained.

hooked back up. Wouldnt start. I swapped the EFI relay with the one next to it (Im just seeing what sticks here) and it works! let it run for a few seconds and shut it off. Get everything hooked back up and wont start now. WHAT THE HELL. So i tested again. 9.x volts to the connection, now ohms read open and wont run on a battery. Suspect pump.

I dropped tank and put it on a bench and check ohms...1.2 (WTF). it ran on a battery. I already have a denso on the way so the pump is getting changed regardless. Is it possible to have an intermittent connection inside of the pump? Should I be testing anywhere else. After the pump its really just testing for pressure which still leads back to the pump correct? Should i be seeing more than 9.x volts at the connection? maybe someone could pop their hatch under the rear seat and test for me real quick.

*Note* when truck originally died, upon turning the key to start position, I could NOT hear the pump priming.

OK, a couple of ideas. Mostly just clarifying because it sounds from your diagnostics that you have a bad pump. But... You said at first you tested the resistance and it was good, what is good? Then you said it tested open, which we all know is not good. Then it tested 1.2? The FSM says it should be .2 to .3 Ohms, so 1.2 would NOT be good either.

Now, it's too late for this now, but fuel pressure is actually tested FIRST. Even the FSM steers you in that direction first. And know it isn't automatically the pump if pressure is low. There is a Fuel Pressure regulator and a fuel filter that could be at fault too. And then there are a few hoses to consider as well. The resistance readings that you DID give are all bad, so let's hope that was the only problem.

 

[zoombyu86]

OK, a couple of ideas. Mostly just clarifying because it sounds from your diagnostics that you have a bad pump. But... You said at first you tested the resistance and it was good, what is good? Then you said it tested open, which we all know is not good. Then it tested 1.2? The FSM says it should be .2 to .3 Ohms, so 1.2 would NOT be good either.

Now, it's too late for this now, but fuel pressure is actually tested FIRST. Even the FSM steers you in that direction first. And know it isn't automatically the pump if pressure is low. There is a Fuel Pressure regulator and a fuel filter that could be at fault too. And then there are a few hoses to consider as well. The resistance readings that you DID give are all bad, so let's hope that was the only problem.

I skipped the fuel pressure just because I wasn't even hearing the pump come on with the key. i just checked the FSM and it says .2-3.0 ohm, not .3, so it was within limits there. There is a month old fuel filter in there.

I plan to test the COR tomorrow and replace my pump anyways when it comes in Wednesday. I get the feeling that the pump was just on its last leg. It got the P0171 code which means "lean" (thinking the pump was getting weak) then the way it was sputtering and wouldnt even accelerate and now wont even start. With the battery connected it sounded so quiet. So, if not a pump, then possisbly a regulator.

Thanks for the extra insight. always good to hear other opinions.

 

[cbr900boy]

I saw you had a similar thread. Did you ever get it resolved? I have yet to check the COR. I couldn't find anything on how to test it before I had to be somewhere.

Still haven't resolved my issue but I feel like I'm getting close. Keep us updated.

-Danny

 

[alico268]

Perhaps try cleaning the throttle body and the Idle Air Control unit connected to the bottom of the throttle body. A while ago I had a 4Runner that wouldn't start and feared that I would be dropping the tank. Did some research and decided to replace the throttle body and IAC (throttle body had some questionable corrosion where the coolant flows through that I noticed from a previous cleaning.) That did the trick and vehicle started right up. Just another area to consider if it helps.

 

[zoombyu86]

Perhaps try cleaning the throttle body and the Idle Air Control unit connected to the bottom of the throttle body. A while ago I had a 4Runner that wouldn't start and feared that I would be dropping the tank. Did some research and decided to replace the throttle body and IAC (throttle body had some questionable corrosion where the coolant flows through that I noticed from a previous cleaning.) That did the trick and vehicle started right up. Just another area to consider if it helps.

I cleaned that up a few weeks ago and has run smoothly since. New filter, new/cleaned MAF, new fuel filter, cleaned TB and IAC, new plugs and wires.

 

[zoombyu86]

She lives!!!

Still haven't resolved my issue but I feel like I'm getting close. Keep us updated.

-Danny

UPDATE: I got my Denso fuel pump from Rockauto.com today, immediately put it in my tank that i already had pulled and sitting on my bench in my unheated garage (it's been below freezing all day). The swap took minutes, then I was able to install the tank within an hour. She fired right up on the first crank and stayed idling for 30 minutes.

To keep everyone informed. She got power to the connection at the plug. Good resistance on the pump. Pump ran when a 12v motorcycle battery applied and appeared to be good flow from the outlet tube (it wasn't after I saw the new pump spew fuel with 12v applied) but would NOT start the truck. Assuming she was just old and weak. Main sign pointing me to the pump was it not priming when the key was turned over. As of now, I'm saying the pump is the culprit unless otherwise noted.

Thanks for everyone's input here.

 

[kball]

Just throwing this out there to try and help you diag. The fuel pump is only activated when cranking the engine or the engine is running. Turning the key to the start position will do nothing.

 

[zoombyu86]

Just throwing this out there to try and help you diag. The fuel pump is only activated when cranking the engine or the engine is running. Turning the key to the start position will do nothing.

Thanks. Yea I figured this out the hard way. But she is running now

 

[Drcoffee]

Imagine a wire in the pump with a break in it. While cold, the the wire ends touch and the electricity flows but at a reduced voltage. As it heats up, the end separate and the pump stops running.

Thats what you were probably experiencing.

 

[IBallEngineer]

Just throwing this out there to try and help you diag. The fuel pump is only activated when cranking the engine or the engine is running. Turning the key to the start position will do nothing.

While I haven't actually tested my 4runner. Virtually all modern fuel injection systems pressurize when you turn the key to the ON position by energizing the pump for a few seconds, usually only 2. When you turn to the START position, you are cranking the engine and there is already fuel pressure to fire the engine but the fuel pump is NOT energized.

 

[kball]

While I haven't actually tested my 4runner. Virtually all modern fuel injection systems pressurize when you turn the key to the ON position by energizing the pump for a few seconds, usually only 2. When you turn to the START position, you are cranking the engine and there is already fuel pressure to fire the engine but the fuel pump is NOT energized.

Oops I picked the wrong word, should have used ON not Start... I'm pretty sure when I installed my kill switch I put a meter on the power wire and did not see anything until cranking. If it was only for a second or two maybe I missed it.

 

[zoombyu86]

I probably worded it wrong too...I was not hearing the pump prime(pressurize) when key in the "ON" position. With a meter attached, there isn't power applied to the pump at this time (how does it prime then?) but read voltage when turned to the "start" (cranking)position.