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Discussion Starter #21
Today I was able to test the fuel pressure. The connector is located right under the drivers seat. It did not look good at 33 psig. Steady at 33psig 5 minutes after shutdown. Pressure should be at least 40 psi so my conclusion is to replace the fuel pump & Filter assembly. The tank does not look impossible to drop just need to get the van high of the ground. Any other advice would be appreciated.
 

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06 Sienna FWD, 08 Sienna AWD
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I've never dropped any of our Siennas' fuel tanks, but a trick I've heard elsewhere is to find out the thread size of the tank strap bolts, buy one or two sets of progressively longer ones, and install those a bolt at a time to lower the tank down (a jack is still useful). Sometimes that lowers it enough to provide access to the pump / sender assembly without having to put the tank on a jack or bring it all the way down to the garage floor.

An empty-ish tank makes this a lot easier of course. :) Gasoline weighs about 6 lbs / gallon = 120 ~ 126 lbs of gasoline for a full tank. Of course all of the standard cautions apply when working with a gasoline tank! Leave the van's battery disconnected until everything is reassembled. I'd recommend reviewing the factory service manual's procedure for the pump replacement.

My recommendation is to go OE (Denso, I believe) with the pump. I don't think there's an inline filter on these vans other than the pickup sock on the pump. Install a new regulator and pickup sock while you're at it (if they don't come already installed on the pump assembly - sometimes one or both are included).

- G
 

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Discussion Starter #23
Today I was able to run the fuel pressure test and the pressure was only 33 psig. After shutting the engine off the pressure held steady at 33 psig for 10 minutes. After 20 minutes it dropped to 31 psig. looks like I will be replacing the fuel pump but not sure if I need to replace the pressure regulator while I am at it. One problem the black plastic coating on the fuel line is deteriorating. About 1/2 inch got pealed off before I could get the connector to seal. Not sure if this will be of concern as the connector is not leaking at pressure.
 

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Discussion Starter #25
Thanks for the write-up. One problem I am not able to find the location of the fuel pressure regulator on the fuel tank. Opened the smaller port with a ring but could not remove the assembly. I can lift it an inch or two but something is holding it. I did not want to break it so I gave up on that. Nowhere else do I see a spot for the fuel pressure regulator. Can someone please point me in the right direction.
 

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Discussion Starter #26
Found it it is part of the fuel assembly so no need to replace it since I replaced the whole fuel pump module.
 

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06 Sienna FWD, 08 Sienna AWD
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Awesome, vinder1! Have your fuel trim numbers improved? :)

Any tips for us on dropping the fuel tank?

- G
 

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Your Fuel Trims are so high , they are off the charts .. basically the car is starved for fuel. Your AF sensors and Misfires - I would not have even gone looking into - the first thing I check is Fuel Pressure! There is a fuel pressure damper on the fuel rail (probable cheap and easy culprit - $15 to $60 part depending) . Then the other possibility is Fuel pump and pressure regulator .. they are in the tank. I do not see an easy way to access them on your model year. I think the 04's and before you could remove 2nd row seat behind the driver and pull up carpet for an access panel to the Fuel Tank.

Check the pressure at the banjo bolt on the fuel rail - there is an adapter kit you can use - A-Zone has a kit you can borrow to check the pressure . My first guess though is the damper at the rail.
 

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My car would run smoothly sometimes at idle and at other times not so much. My symptoms where the ever present check engine light and misfire-air/fuel codes. My van would run rough at higher speeds and had no power at high end. Flooring the gas pedal the van would have trouble making it up to 55 mph.

If someone had told me before this the Fuel Pulsation Damper Assembly could cause this I would have told them they were crazy. I learned a lot troubleshooting this problem not the least was how to eat humble pie and realize I was lost and needed help.
I could have told you and I would have told you. That damper maintains the pressure at an even Kiel so you don't get pulsations from the varying engine draw. / fuel pump oscillations.

Before people go replacing all kinds of parts and fuel pumps for conditions like yours .I do try to tell them that they should verify the damper is good .. well people look at me funny with that yeah what an idiot look ..
ok Elmer go spend the $1000 on parts and service / fuel pump replacement ..Sincerely yours that screwy rabbit.
 

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I replaced my fuel pump assembly about 6 weeks ago, and of course had to autopsy the failed unit. I noticed a bunch of black ooze coming out of the filter, but I am not sure if that was the root cause of my particular problems.

So I am curious: has anyone pinpointed the exact failure mode for these fuel assemblies? The thing consists of the pump, the pressure regulator, fuel level gauge, and fuel filter. The pump, regulator, gauge, and the o-rings are all available individually. But not the fuel filter. Could this be coincidence? The conspiracy theorist in me thinks this may be a sinister plot by Toyota.
 

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I could have told you and I would have told you. That damper maintains the pressure at an even Kiel so you don't get pulsations from the varying engine draw. / fuel pump oscillations.

Before people go replacing all kinds of parts and fuel pumps for conditions like yours .I do try to tell them that they should verify the damper is good .. well people look at me funny with that yeah what an idiot look ..
ok Elmer go spend the $1000 on parts and service / fuel pump replacement ..Sincerely yours that screwy rabbit.
I am an experienced competent mechanic who has fixed everything on this van for 16 years myself.
I took it to a shop with three experience certified mechanics who were also unable to pinpoint the problem.
We then elected to call Toyota Technical repair assistance and while they were helpful they also could not pinpoint the problem. We found the damper was the culprit by accident.

It is comforting to know that someone can pinpoint this problem after the fact without proper troubleshooting..

The damper is mainly to smooth the pulsations from the injectors slamming shut and popping open that set up pulsating waves in the fuel rails. The fuel pump sends out a pretty consistent flow of fuel but the pulsation damper can also smooth out any ripples. It is next to impossible to actually monitor the fuel pressure in the fuel rails. You can see the pressure to the rails but not inside them.

The faults you get with this component failure are intermittent type that trigger miss fires codes and in some cases air/fuel mixture faults.
When you get these codes the proper procedure is to first troubleshoot the misfire code checking the spark ignition coil and injectors. Even these can be intermittent and have a failure at high temps or certain conditions. The air fuel sensor can also affect the condition but by monitoring you can sometimes pick up an intermittent sensor with a scope

It is indeed a rare individual who can completely bypass proper troubleshooting prototypical and jump right to the problem
 

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I’ve got a recurring P0174 and P2197 but only on bank two. Been chasing this for several thousand miles. I thought I had it after a couple vacuum line repairs, fuel trims are near perfect now, MOST of the time. It's almost always fine around town (which I think is because I’m varying throttle inputs enough to keep the trims from throwing a code) but a decent highway trip will trigger lean codes. I can watch the bank two trims go from good (meaning +/- 3%) to plus 20 without warning after several miles of highway driving.
Its always just one bank though, which eliminates a lot in my mind.
Could the damper cause an intermittent fault on only one bank?
 

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I am an experienced competent mechanic who has fixed everything on this van for 16 years myself.
I took it to a shop with three experience certified mechanics who were also unable to pinpoint the problem.
We then elected to call Toyota Technical repair assistance and while they were helpful they also could not pinpoint the problem. We found the damper was the culprit by accident.

It is comforting to know that someone can pinpoint this problem after the fact without proper troubleshooting..

The damper is mainly to smooth the pulsations from the injectors slamming shut and popping open that set up pulsating waves in the fuel rails. The fuel pump sends out a pretty consistent flow of fuel but the pulsation damper can also smooth out any ripples. It is next to impossible to actually monitor the fuel pressure in the fuel rails. You can see the pressure to the rails but not inside them.

The faults you get with this component failure are intermittent type that trigger miss fires codes and in some cases air/fuel mixture faults.
When you get these codes the proper procedure is to first troubleshoot the misfire code checking the spark ignition coil and injectors. Even these can be intermittent and have a failure at high temps or certain conditions. The air fuel sensor can also affect the condition but by monitoring you can sometimes pick up an intermittent sensor with a scope

It is indeed a rare individual who can completely bypass proper troubleshooting prototypical and jump right to the problem
Just for GP: I could have done it before the fact - but I wasn't there - would have loved to help you save some cash :). Experience ..
Misfires - only 2 reasons for that - Cylinder has no fuel, or cylinder has no spark. (could be no air but extremely unlikely).
Misfires in one cylinder (coil pack or injector) misfires across the board - multiple cylinders is more likely a fuel issue like fuel pump, fuel regulator, fuel damper) as you have coil packs.
Your right about the rails - seeing that pressure is pretty difficult - it shows up in pulsations of how much fuel your injector feeds to the cylinders - the computer starts asking for more fuel, then might get too much .. depending on the damper condition. Think of the damper as an arrester like on your water pipes in your house. ever hear the term water hammer where the pipes bang when water is shutoff. Well that is what happens in your fuel line as the injectors open and close.
 

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I'm keeping my fingers crossed for the fix that solved my p0174 code. There was one hose that had a crack and it was the one from the resonator to the valve cover ( this hose has a heat rubber/foam like shroud around it). The other hose was the pcv hose as it was very hard and brittle. The next components I changed were the two post cat oxy sensors and since then my fuel trims are much better ( I was also getting an intermittent p0420 for cat efficiency Bank 1). These sensors have been on the car for 14 years now , 176k miles. My long term fuel trim hovers around 7 ish on long runs. Like I said , keeping fingers crossed
 

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New fuel damper, and a new crossover line because the original bent during damper removal...plus three new injectors on problem bank number two.
Runs even better than it did, and initially had negative fuel trims on bank two (which I anticipated since delivery was much more efficient than with older injectors).
Within two miles of highway RPMs, bank two went lean again and the P2197/P0174 came back. Can drive for twenty miles around town with codes or issues.
Extended highway driving eventually yields 5.000 volts on Bank 2 Sensor 1. Pull over, shut it off, and it goes back to normal upon restart, at least for a bit.

So far, I’ve done the sensor, bank two injectors, pressure damper, MAF and repaired five separate vacuum leaks. Every repair other than the MAF seems to have yielded a better running condition, but I’m running out of ideas.
 
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