P0087 - low fuel pressure (very unhappy GS!)

Ziggy1024 · July 30, 2019

This doesn't appear to be a common problem, so I've not found much out there by way of guidance - any ideas appreciated!

My car: 2010 GS450h.

The problem: Over the weekend I noticed a 'hiccup' (momentary loss of power, no fault codes) twice (on two different days), but then the car ran fine afterwards. Yesterday however, the dreaded engine warning light appeared on my way to work - code p0087. Didn't find much out through a quick google in the day, but when I set off to get home it transpired that all was definitely not well. It was a bit hesitant to start with, but very quickly got worse - now it runs fine as long as you don't give it more than a tiny bit of throttle - if you do, it cuts out completely and reverts to Battery power until restarted. If driven very gently, it switches between engine and electric power just fine. I tried clearing the code (shown as 'pending' btw) but it comes straight back and there's no change to the symptoms. I got the car home ok (not on the motorway though!), but now I'm stuck with what to do!

Everything is pointing at this being a fuel issue and nothing to do with the hybrid system. The fuel setup is (I believe) very similar to that on any number of 6-cyl GS/ISs, but I've not seen much mention of this problem anywhere.

The potential faults as I see them:

High pressure fuel pump - would it run at all if this had failed? Would I expect to see any other fault codes?
Low pressure fuel pump - same questions as for the HP pump! I can command it to run in techstream and it seems ok from there, but that's a pretty limited test.
Fuel pressure regulator/piping/filter - I don't even know what the setup looks like but I guess it feels more like something has 'stopped' from an electrical point of view rather than a leak/blockage?
Fuel rail pressure sensor - the only reference I've found to these failing sees other fault codes thrown too...

Anyone else got any genius ideas, or seen something similar??

Farqui · July 30, 2019

Hi Jon, sorry to hear that you have trouble...normally the fuel filter would be a good starting point but I believe it's buried within the fuel tank so will not be easy to access.

Isn't there a recall on the fuel pipes fracturing at the front of the engine? Yours is an '10 so could well have the later pipes fitted that aren't prone to leaking.

Just out of interest, how old is your 12v Battery? - I just read some threads with similar issues to you that were resolved by replacing the aux Battery. There was also an issue with an engine temperature sensor reading very low, maybe you can read those via an OBD reader?

Good luck getting to the bottom of the mystery and do keep us updated on your progress.

Fingers crossed.

Ziggy1024 · July 30, 2019

Thanks for joining in - the moral support is appreciated!

The simple answer on fuel pipes is that I don't know. Worth asking Lexus though, I guess... thanks for that. Fuel filter is in theory not a service part - I had the same thought! Could be worth a check though - I believe there's an inspection hatch to get at it relatively easily.

Temperature sensor appears ok - all of the readings look normal in the freeze frame data against the fault code in techstream.

I don't know how old the Battery is, so that had crossed my mind too, however I've not had any issues with it apart from this, and it seems unlikely that it would start going wrong ~30 mins into a journey when up to temperature (and charge). Again the freeze-frame data says a solid 14.2V... Short of just buying a new one though, it's hard to be sure!

Ziggy1024 · July 30, 2019

Looking at the freeze frame data in techstream against the fault code - can anyone sanity-check my logic?

Fuel pressure (kPag)
-3: 180
-2: 180
-1: 100
0: 180
1: 200

Fuel pressure target value (MPa)
-3: 6.22
-2: 9.54
-1: 12.00
0: 10.59
1: 6.75

Given that MPa= kPag x 1000, these two say to me that it certainly isn't making (seeing?) as much fuel pressure as it wants!

HP FP discharge rate:
-3: 280
-2: 280
-1: 280
0: 280
1: 0

Is that it turning the high pressure pump off as the code is set?

Injection way:
-3: Direct
-2: Either
-1: Either
0: Either
1: Direct

I don't know what the terminology is here! Anyone shed any light?

Hangie · July 30, 2019

Hi,

Filter is in a tank and even if not officially serviceable can get contaminated and can be replaced.

There is also relief vale present to avoid too high preasure. Maybe it is faulty and is leaking which leads to too low preasure.

Car have dual injectors which mean it can be directly or in-directly injected. As you got issues with both injectors types I would start with a pump in tank and filter.

Ziggy1024 · July 30, 2019

12 minutes ago, Hangie said:

Hi,

Filter is in a tank and even if not officially serviceable can get contaminated and can be replaced.

There is also relief vale present to avoid too high preasure. Maybe it is faulty and is leaking which leads to too low preasure.

Car have dual injectors which mean it can be directly or in-directly injected. As you got issues with both injectors types I would start with a pump in tank and filter.

Thanks for the input Hangie!

I'll have a look at the filter.

The relief valve hasn't been triggered (it's OFF in the freeze frame data), but is there a way of testing it? Do you know where it is physically located?

Something I'm not sure of is how the car would be expected to react if either of the fuel pumps was inoperable - could it run (in the limited way I'm seeing) on one of the pumps alone?

Hangie · July 30, 2019

Hi,

If it is faulty it can leak while in OFF hecne dropping the pressure.

As far I'm aware there is only single pump in a tank. Then it is all plumbing 🙂

Ziggy1024 · July 30, 2019

9 minutes ago, Hangie said:

Hi,

If it is faulty it can leak while in OFF hecne dropping the pressure.

As far I'm aware there is only single pump in a tank. Then it is all plumbing 🙂

Yes, I appreciated that's what you meant - I just don't know how to go about testing it!

Does anyone have any reference fuel pressures? What should I be seeing?

WRT the number of pumps, there's also the high pressure pump (you might call it something else?) in the engine bay - I think (correct me, anyone?!) the engine can run on direct or port injection depending on circumstances, and wondered whether the problem could therefore be with whichever of those systems isn't used under light load. E.G: is the high pressure pump only used for the direct injectors?

Ziggy1024 · July 30, 2019

Well if nothing else, I've ascertained that changing the in-tank pump would take about 10 minutes! Popped it out for a look - hard to tell without dismantling it completely, but what I can see of the filter in the bottom looks fine, and the inside of the tank certainly looks clean. No great surprise given that the car's only done 60,000 miles, mind...

Farqui · July 30, 2019

Well that is good news, that the filter is just under the rear seat.

Ziggy1024 · July 30, 2019

5 minutes ago, Farqui said:

Well that is good news, that the filter is just under the rear seat.

The pump's under the seat - the filter is buried inside the pump assembly...

Farqui · July 30, 2019

Yup, all in one and soaking wet...

Ziggy1024 · July 30, 2019

So who knows anything about what I should expect to see in the way of fuel pressure?

According to techstream, "Fuel Press" (kPag) is <200 when running, but when the engine (and fuel pump) shut itself off (after the hybrid Battery charged sufficiently), the value started gradually climbing. It went as far as 5200 after about 6 minutes, then started dropping again...

Is this increase normal, explained by e.g. heat soak into the now-stationary fuel at the rail, or is it potentially a sign that the sensor is playing up?

What should fuel pressure be with the engine running? Anyone else who could take a look at what their car (any 6-cyl GS/IS I guess) would be a hero!

Mihanicos · July 31, 2019

The DTC occurs when the fuel pressure on the high pressure side is too low. Fuel pressure is achieved by a mechanical pump driven by a camshaft and is regulated by the spill control valve. A fuel pressure sensor monitors the pressure and is regulated between 4 and 13 MPa.

If the pressure is lower, the ECU closes the spill control valve. If the pressure continues to drop, the ECU blocks the power to the spill control valve so it remains open and regulates the engine to a max of 2000 rpm.

Check for fuel leaks on all pipes of the fuel system after the high pressure pump. [ Fuel pipes to direct and indirect injection injectors. Fuel injectors leaking.] ]

Fuel pressure relief valve.

Fuel relief valve relay.

Fuel pressure sensor.

Fuel pump for high pressure.

To carry out some tests you will need the techstream.

Kindest regards,

Chris.

Edited July 31, 2019 by Mihanicos
Missed to include the possibility ofleaking injectors

Ziggy1024 · July 31, 2019

1 hour ago, Mihanicos said:

The DTC occurs when the fuel pressure on the high pressure side is too low. Fuel pressure is achieved by a mechanical pump driven by a camshaft and is regulated by the spill control valve. A fuel pressure sensor monitors the pressure and is regulated between 4 and 13 MPa.

If the pressure is lower, the ECU closes the spill control valve. If the pressure continues to drop, the ECU blocks the power to the spill control valve so it remains open and regulates the engine to a max of 2000 rpm.

Check for fuel leaks on all pipes of the fuel system after the high pressure pump. [ Fuel pipes to direct and indirect injection injectors. Fuel injectors leaking.] ]

Fuel pressure relief valve.

Fuel relief valve relay.

Fuel pressure sensor.

Fuel pump for high pressure.

To carry out some tests you will need the techstream.

Kindest regards,

Chris.

Thank you Chris! I can stop looking at the low pressure side at least, and looking for leaks is something I can manage! I do have techstream, although I'm definitely not an expert at using it yet... Are there some specific tests you'd run?

Ziggy1024 · July 31, 2019

Is the 'fuel press' (kPag) that I've seen in techstream actually the low side reading?

Mihanicos · July 31, 2019

Hi,

The freeze data gives you three sets of readings before the DTC, one set of readings when the DTC was set and one set of readings after the DTC was set. These data are given in 0.5 seconds intervals.

Since the DTC refers to the fuel pressure high side, the readings you have refer to the fuel pressure high side.

Using the Techstream, alter the fuel target pressure and observe that the fuel pressure fluctuates. you can lower the target pressure by 12.5% and increase it by 25%. If the pressure changes by the exact amount, then you may have a faulty ECM.

If there is no change, then you must check the fuel relief valve and its relay.

During these tests you have to put the engine on inspection mode. Put the gearbox on P. Press twice the accelerator fully. Move lever to N and press accelerator fully twice. Move the lever to P and press the brake pedal and the start button simultaneously. The engine should start and you can vary the engine rpm up to 2500.

Always start with the easy tests and with the cheap replacements. Good luck.

Chris.

Ziggy1024 · July 31, 2019

Thanks again Chris!

I've actually just left the car with Lexus for a pre-arranged appointment (on another issue that they've been trying to resolve since the car was covered by the extended warranty!) - having a courtesy car for tomorrow will save me a lot of hassle, so I didn't want to cancel that. Clearly they'll have a look at this issue too, but if/when they want to start randomly replacing expensive parts, I'll get stuck back into your suggestions...

Cheers,

Jon

Ziggy1024 · August 1, 2019

@Mihanicos Chris, Lexus have come back as saying it's the HP fuel pump. I've not got their reasoning yet (and I'll do whatever I can to confirm it as per your recommendations above), but my initial thought is that I'll source a used one - they don't seem a common failure so at least they should be available and relatively affordable... Any thoughts?

Next task is to research compatibility between years, or even other models.

Ziggy1024 · August 1, 2019

Oi, @Farqui ! Whatya doing, 'liking' my misfortune?! 🤣

Farqui · August 1, 2019

I was pleased that you had a direction to follow.

I just hope that the dealer has a good reason and isn't asking you to play 'parts darts'.

I reckon I'd start by first checking the filter in the tank, ensuring the pickup and pipework is okay tickety boo.

Good luck anyhoo's.

Ziggy1024 · August 2, 2019

I was only joking @Farqui !

I'm pretty sure that the issue is with the HP side. Dealer had identified the same candidates as Chris @Mihanicos above, but as far as I can tell concluded that the pump was more likely than the valve/relay based on previous experience.

Swapping the pump doesn't look too difficult (quoted at 1.3h labour) so given that I should be able to get a used one easily enough, I'm tempted to give that a go...

Ziggy1024 · August 8, 2019

So without wanting to count too many chickens just yet...

The HP fuel pump is easy to replace. Lexus quoted 1.3 hours which I guess is fair enough as everyone needs a tea break at some point (I don't actually have any complaint about their estimate - I understand what they need to cover!).

Remove the air hose from the throttle body, or you can't get at some of the below - 10mm for the jubilee clip
2x 12mm nuts (pump flange to top end of engine) - no access problems for those, but you'll need a deep socket and an extension.
2x E8 studs - there is other pipework in the way if you try to remove the pump without taking the studs out
19mm spanner for the fuel connection closest to the back of the engine. You can get a spanner on there with enough clearance to turn it - persevere!
Spring clip on the small fuel hose, quick (squeeze!) release on the remaining one and one electrical connector

Total about an hour including getting tools out, 'help' from a 7-year old and tidying up afterwards.

And yes, it seems to be working so far. 😎

Farqui · August 8, 2019

Well done :thumbs_up: and fingers crossed that it's a long term fix.

Did you source a used pump in the end?

Ziggy1024 · August 8, 2019

Proof that the spanner fits:

@Farqui Yes, I decided that as it seems nobody else has ever seen one go wrong, a used one would be a safe enough bet! I believe a lot of GR-engined cars (is250, gs300 etc.) use the same pump, but as I didn't find definitive proof on that, mine came from another 450h!