injectors ... valve cover?!?

I've looked into a service that tests fuel injectors for flow rate and spray pattern, then ultrasonically cleans them and returns them reconditioned with new O-rings and screens and before/after test results, less than $20 per.

I don't know whether there's an issue with my injectors (my engine only began to run less than perfectly at around 200,000 and the cause isn't found yet), but considering the mileage I wouldn't mind spending that money as the test results would allay my curiosity and the cleaning couldn't hurt.

Only I was checking in the manual for the injector removal procedure and read that the first step is to remove the valve cover.

Seriously? The valve cover needs out for the injectors?

Gee, I'm generally one for doing things by the book, but I was in there last fall and still remember the time it took to dig that cover out. Granted the first time takes the longest, but still....

So my question is for anybody who has worked on injectors for these cars: is that really the only way to get them out, or has anyone worked out a less laborious way?

If it has to be the valve cover I'm going to have to reschedule with the injector service, because I'm not going to have that much time to spend this week.

Thanks,
-Chap

 

Yeah, I'd thought of that, or at least the in-tank injector cleaning additives (techron, etc.).

One thing that especially appeals to me about the injector service is the idea of getting them back with before/after test documentation. I could glug something into the tank and after that think the engine seemed improved or it didn't, and if it did I'd be happy, but I'd have missed an opportunity to see whether my subjective experience correlates with something else measured.

-Chap

 

No, thank goodness, it doesn't. The fuel rail does pass under a sort of semicircular hook-shaped portion of the valve cover that juts forward from the inboard end - and this hook-shaped bit doesn't look like it could have any purpose at all except to be in the way when you want to move the fuel rail. But it gives about a half inch of clearance for the rail to move around, and that turns out to be plenty for access to the injectors. The rail doesn't have to be disconnected from the fuel hose, but only to have the three bolts removed that hold it in place. The two in front are easy access. The one in back, down roughly beneath the PCV valve, is easier to get to after moving the wire harness, park cable, and PCV hoses out of the way, but still a PITA. By unplugging the cam sensor I got my only viable wrench angle on it. (Somebody remind me to plug the cam sensor back in.)

That bolt is right next to another one so it's hard to tell which is which. The right one is the more rearward of the two; the one in front is a ground connection there's no need to disturb.

Anyway, there was no need to disturb the valve cover itself, or the wipers or cowl. Hooray.

-Chap

 

Well, when you send Rich at Cruzin Performance a set of injectors, he records a bunch of flow and spray-pattern tests before cleaning, then ultrasonically cleans the injectors in solvent, records after-results for the same tests, and replaces O-rings, screens, and grommets.
(click for full size)
The grommets on the third row there were my originals; on the bottom are the ones Rich supplied. The originals had a more elaborate shape: the bottom of the injector is sort of cupped in the wider top, and the narrow 'neck' at the bottom surrounds the injector nozzle where it enters the head. The replacements are plain flat grommets that just sit between the injectors and head. Out of curiosity I ordered the official Toyota ones, 23291-41010 at the dealer, and got the same plain flat things Rich supplied. I don't know why the old ones were different. Maybe a design change, or maybe they really were plain to begin with, and years of heat and pressure smushed them into that shape.

At the end of the process you get your injectors back with the before and after test results:


You can see that these at 204,000 miles were still performing so well that there was scarcely any room for Rich's magic to improve anything! Technically then I had no need to spend the money, but I'm glad to have learned this.

I've owned the car for about the last 80,000 and never bothered putting anything but the cheapest nearby gas in it. I had never even heard of "Top Tier detergent gas" until a month or two ago, and I've certainly never sought it out. Likewise I've never run any fuel system cleaner. I don't know what the previous owners did. But it looks like these injectors hold up really well in the long haul, even under conditions of benign neglect.

Edit: to see what qualifies as bad results, see this post where the injectors really were causing intolerably rough running.

-Chap

 

I didn't ask him to explain that in any more detail than I could read on his site. Clearly the static tests involve applying a constant 12V to the injector for 20 seconds, or until the first one reaches 100mL, respectively, and the other tests involve pulsing it at some rate and duty cycle (which I don't know, but I guess the duty cycle could be estimated from seeing that a 90 second pulsed test delivers roughly the same volume as 20 seconds static).

My speculation about why the pulse test might improve more than the static one is that if there's any slight gumming of the parts at all, it might show up first in a slowing of the pintle motion in response to pulsing, but I haven't even asked him whether that's what he thinks is going on.

There's another mystery I haven't asked him about, and that's about the flow rate. There is a specified range in section SF of the manual for volume to be delivered in a 15 second static test - I don't have the number in front of me, but if you scale it up to 20 seconds to match Rich's test, it's still a substantially lower rate than he reports. I don't think that means my injectors flow too much (the OBD reported fuel trim is pretty near zero), so I'm not sure what it does mean. I see that he tests with a 0.705 specific gravity fluid, where other figures I've seen for auto gas are around 0.739, and I wonder if that's enough to explain the difference.

There's an interesting article here about the cleaning process, that includes example data from some RX-7 injectors that really were bad enough to benefit from the work. In that case, the tech said that even those injectors "would be passable in most cases, for everyday driving". Numbers as closely matched as mine were before cleaning, amazingly enough, would I think meet his standards for "high-performance builds" ... at 204,000 miles!

-Chap

 

Somehow I came up with a complicated speculative answer while the simple one eluded me: the 6% increase you noticed was in volume delivered, in both of the tests that measure volume delivered in a set time. In the two tests that stop and compare volumes as soon as the first injector has reached 100 mL, probably there would have been a corresponding reduction of the time needed to deliver 100 mL, had the time been shown in the report.

I think the 100 mL tests mostly serve as an easy way to assess the rate balance among the four injectors by deemphasizing the absolute flow rates, and the timed tests are the ones where changes in delivery rate will show up.

I've read that the balance among injectors may be the more important property (or more important than a six percent absolute flow rate effect, maybe?). The table on page DI-12 suggests that the ECM is able to learn a fuel trim of ±20% or so.

As to the absolute flow rates, the range given on page SF-13 is 36 to 46 mL in 15 seconds, which for a 20-second test would be 48 to 61, way lower than the 76 or 77 reported by Rich. He is using a 0.705 specific gravity fluid but then I also think he's using a lower test pressure than that of the Prius fuel supply (43.5 psi, where page SF-50 says 44 to 50), so I don't know why he sees such large flow rates.

Hmm, page SF-13 also says a difference between injectors of up to 10 mL is acceptable ... in a 15-second test a 10 mL difference is about 25%. So maybe even the balance is not so very critical. So the 1 or 2 percent differences among these injectors on the 100 mL tests would represent a very well-balanced set.

-Chap

 

My notes from when I had the plugs out only say "light tan deposits considered normal." I didn't make any note of differences between plugs.

Looking again at the pic, hmm, there is a little extra black fluff on 3, isn't there?


-Chap

 

I meant to mention that after putting the injectors back in, I got the same dread Engine Cranks And Never Starts puzzler that so many others have reported here, mostly after doing engine swaps. I'm sorry to say I did not get to the bottom of it. I really wanted to go methodically and pin down just what was going on, but I had ignored my own advice to do a force charge before taking things apart, so I didn't have juice in the traction battery for a lot of test starts. When it went below 30% I punted and reset everything by unplugging the aux battery for a minute, and after reconnecting it started right up (and of course I'd lost my chance to learn any more about what it wasn't doing at first).

I did at least do a little troubleshooting. I had the advantage of not having done a complete engine swap, so there were far fewer things that could be messed up. I started by testing the fuel pump and injectors manually. Not having the proprietary scantool to command the pump ON, I looked at applying 12 V at the pump terminals under the rear seat, and gave up after finding how hard they are to reach even after pulling the rear seat and the grommet. Decided it's much easier to test the pump by just pulling the circuit-opening relay and jumpering terminals 3 to 5 of its socket with the ignition on. Right there under the hood and you can do it standing up. Can just hear (barely) the pump start, back in the tank.

After running the pump to build up some pressure, I could just unplug each injector and put 12 V across its terminals and hear it click. With a stethoscope it's easy to hear each one spit some air and then quietly flow fuel. Confirms the injector works and the pump built up pressure, and gets a little extra shot of fuel into the ports in case that helps starting. But my next starting attempt after that still cranked with no other signs of life.

I think I also did another start attempt keeping a meter probe on the circuit-opening relay terminal to be sure the ECM was energizing it. And I think I saw that it was, but I don't have the clearest notes from that part.

There was such a complete lack of any sign of combustion that I was starting to think the ECM was just boycotting either injection or spark signals for some reason. (As goofy as that is - if it's decided not to start for some reason, why even crank then? Unless the cranking is the HV ECU's decision, and the ECM dissents....) I wanted to watch the injection signals during the next start attempt, but that was where I looked at my SoC and did the power-cycle reset of desperation. I did have the stethoscope on an injector for the next attempt after that, to possibly learn whether it was injection signals being withheld. But of course that was the attempt that started up just fine, so I didn't learn much.

I didn't really look at OBD readings during all this. I have since wondered this: because before removing the injectors, I depressurized the fuel rail by pulling the circuit-opening relay while the engine was running, letting the engine die of lean mix, maybe at that time the ECM learned a very rich fuel trim, causing flooded start attempts later? If I had checked the fuel trim on the scantool I might have seen that. (In that case, adding more fuel by doing injector tests would only add to the problem.)

There were two conditions I know of that could have contributed to my issue. One was the aux battery voltage. It had been sitting without charging the whole week, closer to two, that the car was apart, and then was under key-ON load for quite a while as I messed with fuel pump and injector tests, and I hadn't even thought to check its voltage. In the middle of all this I glanced at the scangauge and saw < 8V under load. Oops. For the remainder of my attempts there was a charger connected to the aux battery. I know this can't have been great for the battery (already 7 years old), but it still recharged ok and is back to reasonable voltages and not giving trouble.

Also, after finally getting a successful start, I relaxed and finally did pull codes, and one of them was P0340, because you know, I did say

and none of y'all did. Of course it was after the successful start that I discovered this, so we know that doesn't completely prevent starting (it just uses fixed, default valve timing and runs strangely) - at least, not after an aux-power reset.

With the engine finally running, I didn't let it stop until I'd force-charged back to 80% SoC. Then I shut it down and plugged the cam sensor back in, and it's been running well ever since. (The force-charge from under 30% back to 80% gave me the first chance I think I've ever had to hear the battery fan actually run.)

So anyway, yes, I too have now experienced the dread startless start syndrome, enough to gather some small amount more information about it, but hardly enough to explain it. Still puzzling.

-Chap

 

Exactly.

And yet a common one, if you try to go back and count the threads that have started in just the last year alone by people who have done engine swaps (usually) and then post about crank-but-no-start issues ... which they usually describe as starts-then-dies-after-several-seconds because that's what it sounds like.

After experiencing it I think it can only be (one or more of):

• ECM isn't energizing the circuit-opening relay (fuel pump)
• ECM sending no, or incorrect, pulses to the ignitors
• ECM sending no, or incorrect, pulses to the injectors (it's possible to have a no-start because of a too-rich mixture, so maybe the problem could be these pulses are absent, or maybe way too wide)

as the three needed ingredients are compression, fuel, and spark, the compression is pretty much mechanically determined, and the engine otherwise had all the conditions it needed to start as soon as the ECM was reset from whatever state it was in. The two questions I still wish I had answered are:

• What is that state exactly? What's different about those signals from the ECM?
• What exactly gets it into that state?

The next person it happens to who is able to stick a datalogger on one of the ignitor wires, one of the injector wires, and the circuit-opening relay will probably nail down the first answer.

As to the second question, I think there were three possibilities in my case:

• Engine died on a too-lean condition last time it ran (I depressurized the fuel rail by pulling the circuit-opening relay and letting the engine die)
• Aux-battery voltage got low (my fault, forgot to put a maintainer on it during two-week downtime)
• P0340 (my fault, forgetting to plug cam sensor back in). Note I didn't correct this until after the engine started, so the P0340 by itself won't prevent starting, at least after the ECM is reset.

-Chap

 

No, I didn't, sorry. Been a few years now since I last had that car.

 

That, of course, would be an entirely different problem from anything described in this thread.