Piston Slap: Finding fuel in a thirsty Toyota

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1989 Toyota Tacoma front three-quarter piston slap thumb
Toyota

Michael writes:

I have an ’89 Toyota pickup, I have replaced every component in the injection system and even sent the computer away to be serviced. The problem is I have no ground pulse to injectors: I do have power but not the ground pulse.

Any ideas? I suspect the wiring harness but have not checked it yet. I have a rebuilt engine, and it ran great for three days then quit.

Sajeev replies:

Hi, Michael. So the rebuilt computer didn’t fix the ground pulse issue? Just want to verify that before proceeding. And thank you for your question! (By the way, we need more people like Michael emailing me at pistonslap@hagerty.com.)

Michael answers:

No, it did not. However I am not certain that the computer is working as it should. At this point I’m not sure how I can determine this.

Sajeev concludes:

For the sake of all of our readers, let’s take a few steps back. Always check for spark in a no-start condition, either with an inline tester or a long screwdriver (if you can be trusted not to electrocute yourself). Once you are sure it’s a fuel issue, check for fuel pressure; this video might help.

Once you’ve verified that spark exists and the fuel system is pressurized to factory spec (supposedly between 38–44 psi), it’s now time to test the injectors. Since the truck is (shockingly) not firing any injector enough to start the engine, test the signal going to the injectors by connecting your digital voltmeter to the positive side of the injector plug, and then connect the other end of the volt meter to an unpainted metal part on the engine.  You should see a voltage reading of 12 volts at this time, but if the number is lower it might still be fine; check to see what voltage Toyota EFI systems give to their injectors. This is also the time to check each individual fuel injector’s resistance (i.e. use the ohm scale on your voltmeter) and make sure they aren’t dead. The internet says you need to be within 13.4–14.2 ohms on each injector, but that could be for a different application; always ensure you have the factory specs before proceeding.

If you get the right voltage at the fuel injector wiring and they ohm correctly, either the injectors are physically clogged or the engine computer’s internal ground has failed. I’m not smart enough to wager a guess as to which one is more likely, but what if all those injectors are indeed dead?

You might be in more trouble, as this seemingly-credible vendor suggests new replacements are either unavailable or not to be trusted.  You should then yank your injectors and have a third party rebuilding service fix the ones you have.  You can find these services anywhere from Google, eBay, and even Facebook groups dedicated to Toyota’s 22RE engine.

Good luck with your diagnostics, and tell us how it pans out!

Have a question you’d like answered on Piston Slap? Send your queries to pistonslap@hagerty.com, give us as much detail as possible so we can help! If you need an expedited resolution, make a post on the Hagerty Community!

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