Injector Failure, a rare and horrific tale of woe

[MattaClark]

My 257k 2007 xc70 suffered a uniquely stupid form of engine failure last week.
TL;DR injector failure caused misfires, a smoking tailpipe, a flooded cylinder, and compression failure in three cylinders.


Backstory
Fuel economy suddenly dropping in the last month (down to sub 14mpg in city driving from usual 18mpg), followed by an ECM- 121B code with CEL, and ECM-121D a day later. My MAF was reading slightly low, around 9 g/s at idle. MAF readings while driving seemed to indicate some sort of air leak,
My PCV was done in July, but I rechecked it, and found a crimp clamp slightly loose. Vacuum leak solved? Code is gone but MAF is low and fuel economy is still down, fuel trim increases a bit when throttle is open. I rednecked together a smoke tester, didn’t find any leaks in the intake. There is a little fluctuation in fuel pressure. Fuel pump is 44.9% duty cycle at idle.

Figuring this is a high mileage vehicle, I start with the control variables, and begin replacing sensors. MAF, MAP, and Fuel Pressure Sensor get swapped, and I cleaned the gears of my throttle body. Cleaning the MAF gears seemed to solve low/ fluctuating MAF readings but fuel economy is still poor. I buy an injector rebuild kit from The Injector Shop and add a bottle of LiquiMoly fuel additive.

I removed the old extremely filthy filter baskets in my injectors, and after some googling, decided to flush my injectors with a syringe filled with solvent and a spare wiring pigtail attached to a battery to trigger the solenoid. I was cautious of burning out the solenoids and only connected the circuit for an instant while pushing fluid through. Backflush first to remove any debris from old filter baskets, then forwards. 1-4 have no issues but Injector 5 sticks and leaks— I keep flushing, and it operates normally. At this point I wasn't totally happy with the spray patterns, so after seeing injector 5 stick, I went ahead and ordered a new set. In the meantime I replaced the filter baskets and O-rings, and put my rebuilt set back in...

Vehicle took two short trips (maybe 3 miles total) with rebuilt injectors, but fuel economy seems mostly the same, maybe slightly better (we're doing about 10.2 mpg city driving). At this point I’m suspecting a bad fuel pump, PEM, or possibly an O2 sensor. Fuel trim still increases very slightly under throttle, nothing dramatic. At this point the vehicle hasn’t been driven hard, and I also have it in the back of my mind that there may in fact be an air leak that’s exacerbated under boost.


The Incident
Started the car and gave it the usual few minutes to warm up in the 40ºF winter morning. No issues.
Got about 5 minutes down the road and noticed a slight stutter at an uphill stop light. Within the next two minutes (about .7 miles) of city driving the stutter had escalated to bogging and almost stalling at stops. No dash lights, temp normal.
While crossing a bridge at about 35mph the engine started misfiring heavily, and by the time I had crossed and pulled into a parking lot there was a large cloud of grey smoke from the tail pipe, and the check engine light was flashing.

Shut off the car and popped the hood. Coolant was clear and at normal level, oil was maybe a touch low but looked fine. Found soot in the tail pipe, smells a bit like gas.
Let it sit for a while. Attempted restart, cranks but misfires on attempted restart. Second try gave two cranks before stopping mid crank. Yikes.
At this point, I’m suspecting a fuel system failure. The cheap bluetooth OBD2 reader I have is useless, showing no DSTCs and a P0000 freeze frame (unreadable code). I have some tools and a spare coil with me, but after visually inspecting the fuel rail and coils I determined there’s not much I can do without codes.

tailpipe soot immediately after the incident

tailpipe soot.jpeg (49.61 KiB) Viewed 2882 times

Diagnosis
Left the vehicle for the night, came back the next day with ViDA.

Codes:

• ECM-2470 Front heater oxygen sensor (HO2S), bank 1 - faulty signal
• ECM-310C Misfire, at least one cylinder - Catalyst damage
• ECM-311D Misfire cylinder 1 - Emission agitation
• ECM-313D Misfire cylinder 3 - Emission agitation
• ECM-315C Misfire cylinder 5 - Catalyst damage
• CEM-3F90 Fuel pump (FP) relay Open circuit or shorted to ground

CEM-3F90 is the only code that stands out to me, others are more indicators of misfire and improper fuel conditions than of component failure.
With ViDA connected, turned KeyII and read fuel pressure stored fuel trim. Long term fuel trim is at -0.14%, fuel pressure is at… 97kpa? I prime the pump a few more times watching the fuel pressure: it starts around 240kpa and drops precipitously within seconds. That’s not good.
Unfortunately, this isn't going to be as simple as a bad coil. My suspects at this point were fuel pump sender, injectors, and since there is no relay on these cars, the PEM.
Wagon gets towed home.


At a Netizen's suggestion I peaked in the downpipe and checked the turbo. Still there, evidence of some oil burn off, but turbine passes the wiggle test with flying colors. O2 sensor is a bit dirty. We can rule out turbo failure.

The new set of injectors (GB Remanufacturing via FCP) arrive the next day. After swapping out all injectors, the fuel rail is holding pressure again! Well, mostly… ViDA reads 301.51kPa at the rail in Key II, then drops to 293.98kPa over 54 seconds. 0.14kPa per second loss is negligible, I’ll blame it on the old sender. I had considered swapping back to the original fuel pressure sensor, but stopped here since the injectors had solved it.
At this point I attempt a start and got three cranks followed by a partial crank and sudden stop. There's some sort of interference. Could fuel conditions have burnt and then bent a valve?

Pulled plugs:

• Cyl 1-3 are mostly fine, dirtier than they should be given they were replaced in July and have less than 4000 miles on them. Cyl 4 has some depositing on it. Cyl 5 is damp with fuel.

Depositing on plug 4

plug4 Medium.jpeg (79.82 KiB) Viewed 2882 times

After renting a Borescope from Autozone, I discovered that Cylinder 5 was flooded. How flooded? I siphoned out 80ml of raw fuel. That explains the partial-crank condition.
After getting a second bore scope that could check the valves (cheap one off amazon), it's not looking good. There is significant coke build up, and all five cylinders are absolutely nasty. The valve damage looks more like a slight chipping around the edge than burning to my untrained eye.

Borescope shows: (link to all photos)

• Cyl 1: Extremely heavy carbon depositing, piston head is entirely black. Edges of exhaust valve heads have some damage.
• Cyl 2: Some depositing on piston. Slight damage on exhaust valves.
• Cyl 3: Heavy and odd depositing, almost looks like the cylinder head was melted. Valves are fairly clean, maybe some slight damage l.
• Cyl 4: Some depositing but honestly not bad at all. Exhaust valves have depositing.
• Cyl 5: Flooded. Valves aren't pretty but they're not obviously burnt up or bent.

cylinder 1 piston

cyl 1 piston.jpeg (74.57 KiB) Viewed 2882 times

cylinder 3 piston

cyl 3 piston.jpeg (48.33 KiB) Viewed 2882 times

60 of the 80ml of raw fuel removed from cylinder 5

fuel removed from cyl 5.jpeg (78.01 KiB) Viewed 2882 times

At this point I have a fair picture of what has happened. The coking and deposits are extremely heavy and will obviously have to be dealt with, but we still have a crank no start. Compression tester on order.


Compression test
(First test was done at 24°F ambient temp, subsequent tests done the next day at 29°F. Comma indicates a re-test. Wet test performed with a few ml of engine oil. All tests done to 6 rotations.)

• Cyl 1: 0psi, 40psi | 0psi, 0psi | 42psi, 0psi
• Cyl 2: 100 psi | 115psi | 38psi, 35psi
• Cyl 3: 0psi, 0psi | 0psi | 38psi
• Cyl 4: 95psi | 125psi | 60psi
• Cyl 5: 0psi | 52 psi | 50psi
  Cylinder: First test | Second test | Wet test

I’m not totally confident that my compression tests are accurate, especially the wet tests which were done as the battery was losing charge, but i think it still gives enough of an indication to be useful.
Little or no compression in cylinders 1 and 5, zero compression in cylinder 3. Firing sequence is 1-2-4-5-3, so seeing the worst damage on Cylinders 5, 3, 1 is logical given cylinder 5 failure, and consistent with apparent valve damage in the borescope images. Wet test indicates possible ring damage in cylinder 3 and possibly 1 and 5.
The fact that the dead cylinders aren't adjacent and that the coolant and oil are still looking good means that the head gasket is unlikely to be the failure point, although it was old and wasn't done any favors.

Conclusions:
Injector 5 stuck open, flooding cylinder 5 and allowing raw fuel into exhaust, causing other cylinders to operate in lean condition. Compression loss in multiple cylinders due to valves, possible ring damage, and likely premature bearing wear. I haven't assessed the O2 sensor and catalytic converter for damage yet.
Without sending the old injectors for testing, I can’t be 100% certain of injector 5 failure, but all signs point to it.

Could injector failure be a symptom of different root cause? Were my declining fuel economy and ECM-121B/D codes related? Let me know your thoughts.
A plugged Catalytic converter caused excessive back pressure this does a better job of explaining the poor fuel economy leading up to the failure but causing injector failure like that seems less likely. Electrical short in the injector harness, ECM failure, or other electrical issue could also have kept injector 5 open. I find it unlikely that the fuel additive would contribute to this but it may have exacerbated the condition.
I spoke to an independent Volvo tech who said he’s only seen one failed injector in 15 years. A dealership service manager also said injector failures are incredibly rare, but it would be consistent with the symptoms.

I want to be very clear that injector failure was almost certainly caused by my own fault when improperly testing/ cleaning the injectors, either due to debris or over-heating the solenoid, and not due to age or poor maintenance (although that probably contributed. If you are reading this thread looking for answers to your own issues, look elsewhere, injector failure is exceptionally rare. That said, I hope this is a useful case study of how catastrophic a failed injector can be. Please learn from my mistake, get your injectors serviced professionally or just replace them.


Here's a link to a google drive folder with more photos and data for those interested.

[MattaClark]

What to do about it?

I have pretty limited options right now. While I have tools and don’t mind doing work myself, I don’t have garage space so any work I do has to be done curb side, and it’s December. My wallet is drier than dad’s thanksgiving turkey, and while I can make do for a month or two without a vehicle, this is a pretty painful lesson.

A) Attempt a rebuild with a head/ valve job and hope the bottom half is still okay (iffy at best). Either DIY for $1500 or pay ~$7000 for a shop to do it. A full engine rebuild doesn't seem worth the investment.
B) Engine swap. Looking at a low milage engine from ErieVovo for $1850. Looking at $8000 ballpark at a shop, or $2500 DIY.
C) Cut losses, part out what is easy and get a new vehicle.

I purchased the car this summer for $2500 USD and have invested about $8k in service parts since (extended timing job including VVT components, PCV, all fluids and transmission flush, haldex overhaul, new front suspension, wheel hubs, some coolant system pieces, and other small things. All DIY). I also have $750 worth of brake parts waiting to be installed. That said, the interior is worn, and the body is showing age and neglect. Napkin math says I should expect to invest another few thousand into the car in the next year or so for transmission, suspension, and steering rack work.

Health check for "Moxie" after some hard driving in the Allegheny National Forest this past summer.

[vtl]

"C" if your pockets are light.

"B" otherwise. Also before installing "B" - do "A" on it (a rebuild). At least need to replace valve stem seals, because for that to be done properly you need to degrease valve stem guides to bone dry. And correct the valve lash. Without hydraulic lifters and no regular valve adjustment performed these engines commonly die at around 220-250k miles. No one does it, of course, because it is a royal and expensive PIA on these engines, so they all burn exhaust valve.

My engine rebuild cost me $3k in 2020. In parts and some precision tools that I didn't have. Another $3k for the transmission. The car is still chugging around.

[jonesg]

I'd look for another , same yr and scavenge all the good parts off the dead one.
i've seen rebuilt heads for less than $1k.

I paid $2K 8 yrs ago for a salvage title 04 v70 and its been very good.

[MattaClark]

I'd look for another , same yr and scavenge all the good parts off the dead one.
i've seen rebuilt heads for less than $1k.

I've been looking around for a match but slim pickings in my area so far.

"C" if your pockets are light.
"B" otherwise. Also before installing "B" - do "A" on it (a rebuild). At least need to replace valve stem seals, because for that to be done properly you need to degrease valve stem guides to bone dry. And correct the valve lash. Without hydraulic lifters and no regular valve adjustment performed these engines commonly die at around 220-250k miles. No one does it, of course, because it is a royal and expensive PIA on these engines, so they all burn exhaust valve.

I don't have any experience doing internal engine work more involved than a head gasket, but I can learn. What's your threshold for a rebuild before install? Is a healthy 84k mile engine still worth rebuilding? Should I plan to rebuild the upper half no matter what to save future grief?
Anything else that I should try to service at the same time to for massive labor savings such as the transmission? Obviously I would be silly not to do the engine mounts while I'm there.

It looks like an engine swap is the more expensive option (vs buying a new beater) but it's could be a good way to get more bang for the buck in the long term. If I engine swap, and go the extra mile of rebuilding a donor, is it worth looking at other engines such as a B5254T4 with an ECU swap (saw an R block for sale not too far away)? I've heard that lower displacement t5 engines like the B5244T5 aren't a good match for low range torque needs of heavy xc70s.

Thanks for the advice

[josefloretovar]

An Ultrasonic Cleaner for Injectors can be used to clean and test fuel injectors, but this equipment is typically needed by repair shops, and is rarely used by individuals.

[vtl]

I don't have any experience doing internal engine work more involved than a head gasket, but I can learn. What's your threshold for a rebuild before install? Is a healthy 84k mile engine still worth rebuilding? Should I plan to rebuild the upper half no matter what to save future grief?
Anything else that I should try to service at the same time to for massive labor savings such as the transmission? Obviously I would be silly not to do the engine mounts while I'm there.

It looks like an engine swap is the more expensive option (vs buying a new beater) but it's could be a good way to get more bang for the buck in the long term. If I engine swap, and go the extra mile of rebuilding a donor, is it worth looking at other engines such as a B5254T4 with an ECU swap (saw an R block for sale not too far away)? I've heard that lower displacement t5 engines like the B5244T5 aren't a good match for low range torque needs of heavy xc70s.

Thanks for the advice

Me neither have had any experience rebuilding engines, not even head. Read the Tim Gilles' engines rebuild book and followed common engineering sense.

84k should need nothing beyond PCV overhaul. Unless it was in a traffic light to traffic light car. Inspect the cylinders with borescope for exhaust valve steam seals leak. If they leak, yeah, it is easier to replace them with the engine out. Real good degrease is needed to seat the new seals properly. No oil residue, no glue, no nothing. Also Volvo seals on exhaust, others don't last.

Replace the rear main seal while it is easily accessible. Dropping transmission to fix the leak a few months later is no fun.

Everything else you can do with the engine in place.

It is not easy to swap ECU from different model, you would need to mate it with the rest of the car's electronics. T2 is very torquey, especially with a modest stage 1 ECU tune and 3" downpipe (in case your stock 2.5" downpipe needs a replacement). I have a Hillton stage 1 and catted Snabb downpipe.

[cn90]

This is why I never buy cars with >150K miles. It is just headache and costly to bring to stage 0.

I usually buy at 100K. If you look hard enough, you will find 100K cars for $4k-$5k.

Fuel Injector lifespan is about 150K-200K. After that, it is guess work.

[erikv11]

Let's see: I've been through 9 Volvos @ 5 injectors each, mileage on them between 160k and 300k, so that's 45 fuel injectors reaching or well past end of lifespan but I haven't run across a single bad one yet?

And why is no one posting to the forum about all these injectors that crapped out between 150k and 200k? Come on people, fess up!

Fuel injectors can of course go bad (see this thread!), but failure is extremely uncommon and it certainly doesn't happen on a clock. Main issue is they get dirty and that can lead to failure - sending them for a cleaning (like OP tried to DIY) is probably a good idea as the car gets up to 200k, but most of us don't even do that unless for performance purposes when planning to push the engine. Probably contaminated or bad gas could kill them prematurely, too.

[vtl]

I cleaned 5 of mine once, they were clean enough at like 170k miles. Gas sold in US is lot better than in other parts of the world, and it has a lot of detergents.

Also 20 injectors 50 ranging 270k miles, half of them are far past 200k miles, also no failure. These injectors are pretty good, actually. They do fail, but very rare.