It's been a while, and I can't find a good # with the search. If I measure the resistance of each injector, across the two injector pins, what's the magic # of "clogged injector"? Over 20 ohms?

Diagnosis so far... car runs like crap when it first starts up- it starts, runs for a second, stalls. Start it back up, runs fpr a second, stalls. This happens over and over again until I've had enough, and put my foot on it to raise the rpms. And until the car warms up, it'll run strong for a bit, then act like it wants to stall... then run strong for a bit, acts like it wants to stall, etc. Also, I always smell gas.

Threw a pressure gauge on it one day. Key off, attach gauge, key on, pressure rose to 42 PSI, then dropped like a stone to zero. I tried it again, same thing. Panic set in- I saw myself replacing the pump for a THIRD time. So I got out the GM book... after crimping return lines and feed lines and etc, the book points me towards a leaking injector.

So I'd like to Find the injector. I picked up a set of Multec injectors from a junkyard for $10, and want to send them to Rich @ Cruzin Performance (like I did with my current set, 3 years ago), but I'd hate like hell for it to be my cold start injector, and not one of the regular injectors.

Oh yeah; I can measure resistance of the cold start injector just like a regular injector, right? Or is there a different procedure for that one?

Thanks! This problem is driving me nuts; hasn't been prevailent over the summer, but now that it's getting cold overnight again, it takes forever for the car to warm up enough to act normal.

 

I'm not for sure, but my understanding was that an injector will stick open due to some sort of mechanical failure, not electrical. Meaning, the resistance won't tell you which is stuck open. Once the fuel pressure drops, you might try pulling out all the spark plugs and seeing if a particular cylinder is drenched in fuel.

 

You can always do it the difficult way and pull the fuel rail with the injectors out of the intake and prime the pump and clamp the return to watch for leaks. You're going to have to take the fuel rail out a bit anyway if you're replacing injectors.

 

Or the easier but less definitive way of monitoring fuel pressure after shutdown. If you have a leaking injector, the pressure will fall off pretty quickly, and not maintain for fifteen + minutes as it should. If you have a leaker, you'll have to pull the fuel rail to isolate it (yuk). If not, you've saved yourself a bunch of time.

Electrically, a leaking, stuck, or clogged injector will look identical to a good one.

 

Thanks! And Vader, didn't I already do that? (see my third paragraph above) Or is there a different procedure you're talking about?

ViciousZ, thanks for that idea! I'll give it a check this weekend. Like I said, the fuel pressure falls right away, so a couple of cycles of "key off, wait, key on, prime, lose pressure" should really soak a spark plug! (And probably fill the crankcase with fuel, but I think I need an oil change soon anyway, might as well do one.) So I won't be able to tell anything from a meter... hm, that sucks. Well if I gotta pull the rail anyway, I guess I'll just send that spare set of injectors to Rich... I can't help but feel these injectors clogging is my own fault. I sent them to Rich about 3 years ago, and never ran ANY kind of cleaner through them since!!! Not even a bottle of dry gas! Oops.

This spare set of mine are the Multec injectors; any truth to what I hear about off-the-shelf injector cleaner ruining them?? Sounds strange, I don't see how it's possible, but who knows...

Thanks!

 

Tom,

Sorry. I wasn't reading carefully enough (not enough caffine). You've already isolated the problem to a rail/injector. About all you can do at this point is to pull the rail and pressurize the system while watching the injectors.

Incidentally, talk to Rich about those Multecs. Depending upon what type you have they may be O.K. and they may be junk. The earlier Multecs were prone to failure.

As for periodic maintenance on your injectors, I don't have a lot of faith in injector cleaner additives. The best thing I can suggest is to run clean fuel and change your fuel filter at regular intervals (no cheap filters!).

 

Back when I bought my 89 T/A, gas stations were still selling pure gas. Then they switched to gasohol in my area and I soon needed 8 new injectors. The shop told me the alcohol was dissolving the insulation on the internal wiring and the new generation of injectors didn't have that problem.

The best cleaner I've heard about, but never used, is called BK44 or something like that. It's not sold to the public, only repair shops. Never heard anyone complain about it.

 

You're gonna need a nice DVOM with the Injector duty cycle capability.

Last I checked those DVOM's were rather expensive ($400). Sounds like the injector is stuck open though, you have all the symptoms. Nasty idle, etc.....

Brian P

 

Okay, cool, thanks Vader, I thought there might've been a second procedure that I missed. Didn't know the Multec's had some early problems, I gotta get the part #'s off those injectors, they're still sitting in the garage on a shop towel. I'll post what I find out. Are the bosch pintle-type injectors still "king" of fuel injection, or is the hot ticket the Multecs now?

Sciguyjim, ya know, I have no idea what kind of gas they sell around here. I know they add some stupid additive in the winter that causes me to use twice as much gas to go the same distance.. don't see how that decreases emissions, but hey, what do I know.

Sena, I do have a fuel injector tester- and not those silly little noid lights, it's the one that hooks to each injector, for doing a balance test, along with a fuel pressure gauge. Think that'll help me at all? I don't see how; it pulses the injectors, and if my injector's stuck open, what's the point?

What I'd like to do is find out which injector is screwed up, without pulling the rail. I'm worried that the bad injector is the cold-start-injector at the back of the intake manifold. I'd hate like hell to pull everything off and switch 'em, and then find out I still have the same problem. That cold start injector's still the original 241,000 mile unit!

Can Rich clean a cold start injector? Doesn't look like a regular injector to me; never pulled it out.

Oh and also, I've seen those multimeters that test for duty cycle. How would I check the injector using it? I've got a Fluke III meter, but it doesn't have anything about duty cycle. Maybe I'll pop the coin for one.