07 Toyota Sienna, fuel delivery problem

Just an observation...Paul spends a lot of time making sure he understands the circuit involved in this vehicle related to the fuel pump. It was a bit complicated at first but after he understands it, we understand it because Paul is good at explaining what is taking place. I loved the visual that is made possible by his colored pencils. He follows the path of the power side and before long I have that "Ah ha" moment. I was a bit surprised that the new pump required more amperage needed to run it, but Paul gave a few examples of why that happened (in a response to my comment). It was a long video but I'm glad I stuck with it because it was a learning moment for me. I follow a lot of other automotive repair channels that show you how to replace parts...I'm past that. This is what I need! Well done.

(Thanks for the shout out!)
Quite the fuel pump circuit!
:blink:
I'm glad Paul took the time to go over it in it's entirety.
I'm also enjoying the transparent scope overlays, great stuff.

I do have a question about the amperage test at the pump resistor.

The old pump was pulling around 4 amps at idle in the low speed mode.
That turns out to be around half the amperage that the replacement pump was pulling.
This is exactly where I get tripped up using my amp clamp in this kind of diagnosis.

Ok, there's some current draw on the system. This presumably indicates the condition of the power and ground.
But even if we knew for a fact that the pump should be pulling 8 amps, how can we use the 4 amp measurement to point us toward a faulty pump?

I could see second guessing myself and the measurement, wondering if the low current is a symptom of maybe a bad ground or some other voltage drop.

Like I said, I get tripped up with the amp clamp like this all the time. I just can't see the smoking gun and end up loading the circuit myself or volt drop testing at the component.

Any tips, pointers or experiences are welcomed​ from everyone!

Shoot! Sorry Wyatt, I didn't see this here or I would have just responded to this post instead of making a new one!

I hope you don't mind if I merge the two.

Noah wrote:

(Thanks for the shout out!)
Quite the fuel pump circuit!
:blink:
I'm glad Paul took the time to go over it in it's entirety.
I'm also enjoying the transparent scope overlays, great stuff.

I do have a question about the amperage test at the pump resistor.

The old pump was pulling around 4 amps at idle in the low speed mode.
That turns out to be around half the amperage that the replacement pump was pulling.
This is exactly where I get tripped up using my amp clamp in this kind of diagnosis.

Ok, there's some current draw on the system. This presumably indicates the condition of the power and ground.
But even if we knew for a fact that the pump should be pulling 8 amps, how can we use the 4 amp measurement to point us toward a faulty pump?

I could see second guessing myself and the measurement, wondering if the low current is a symptom of maybe a bad ground or some other voltage drop.

Like I said, I get tripped up with the amp clamp like this all the time. I just can't see the smoking gun and end up loading the circuit myself or volt drop testing at the component.

Any tips, pointers or experiences are welcomed​ from everyone!

I totally understand what you're saying Noah.
This is why I was trying to show the initial turn on of the pump but could not because of the high speed mode activation during initial start up.
I actually could have but chose not to and here is one of the main reasons why:
If there was say resistance on the feed or ground side of the pump, when the high speed mode activated, I would have had a pressure rise and once I saw the psi dropping even in the high speed mode, I made the call.
I think my logic here is correct. Thoughts?

Ok, I think I see what you're getting at with the initial turn on spike.
It would certainly take a good power and ground to support the high current when the motor turns on. This is something I'll have to pay more attention to the next time I break out the amp clamp.

So you're saying that even with a poor ground for the pump that there definitely would have still been a pressure change when the circuit switched between high and low pressure modes?

Thanks for coming over and joining the conversation, we all know how busy you are. I appreciate you taking the time to help me wrap my head around it, lol.

No problem Noah. Combine away!

Noah wrote: So you're saying that even with a poor ground for the pump that there definitely would have still been a pressure change when the circuit switched between high and low pressure modes?

Thanks for coming over and joining the conversation, we all know how busy you are. I appreciate you taking the time to help me wrap my head around it, lol.

Yes, though you could argue the volume was also changing because of the snap throttle test.
But think about it. Difference in potential is what is important. 12v on feed, bad ground reading 4v.
14v on the feed will still raise your current flow even though ground voltage may rise a bit from additional current.
I'm rambling...

Thanks Noah

Not rambling at all, thank you for explaining it to me!

Did that make sense?
Also 4 amps was plenty of current to produce more psi than what we had at idle. I think.

Just filmed an 07 Navigator 5.4 with low psi today. Initial turn on amperage was 21 amps. No crawling on the ground for this old man today

ScannerDanner wrote: Just filmed an 07 Navigator 5.4 with low psi today. Initial turn on amperage was 21 amps. No crawling on the ground for this old man today

lol, that's awesome!

I think that's where I have the most trouble, is knowing how much amperage any particular component should be running at.
With voltage it's pretty cut and dry, but with the current measurements, I guess you need the experience to tell. I just don't have the confidence with that tool yet to GET that experience.

It would be great if manufacturers started publishing amps draw numbers for pumps and all motors and solenoids but pigs will fly first.
I recently bought some right angled quick release adaptors for my fuel pressure gauge so I can do most euro boxes without faffing. They are especially good for connecting at the in-tank fillter outlet on Valeo systems I would post a link but the ebay seller has disapeared.

Hi guys, thought this video was a really good one. Just a day earlier i was looking at a buddys Mercades C220 that has an engine vibration at 1500rpm and above and will sometimes fall on its face. It feels like fuel starvation, plus it was giving me a P062A fuel pump output plausability code. I carried out an amperage test with the low amp probe and the pump at tickover was drawing 4 amps. I attached a fuel pressure gauge and i had 3 bar at idle and then on a snap the pressure dropped slightly. Paul stated that on a snap fuel pressure should not be dipping, is this true on a diesel engine as well as a gasoline motor? As the Mercades i was looking at is a diesel. Basically im trying to determin if this pump is well on its way out as the amps reading was too inconclusive for me to call a pump confidently.
Long winded and maybe well off topic but thought i would bring it up anyway ☺
Thanks guys