How do you know if one of your injectors is not closing?

[Lextreme II]

Like the title stated. How would differential diagnose this and what are some of the symptoms we might expect?

 

[cribbj]

I'd think a rough idle, rich AFR, fuel pressure dropping off rapidly after you turn the key off, perhaps hard to start, all might be some of the symptoms. Diagnosing it completely would probably involve removing all the injectors and having them flow tested but with back pressure on the pintels to see if any are slow or weak to close, or are leaking.

A good tech with a digital oscilloscope (and really knows how to use it) could be a handy thing to have around.

I've been drooling over these Pico Scopes for the last 3-4 years, and they're just about down to the price I want to pay:

http://www.picotech.com/auto/automotive_oscilloscope.html

Here's an article on diagnosing injector problems with one:

http://www.picotech.com/auto/articles/electronic-fuel-injection.html

Note, it's pretty easy to diagnose a dead injector, but one that's sticking, or leaking, isn't nearly as straightforward. Still I think these scopes are way cool, and nearly every time I'm diagnosing something on the car I wish I had one.

 

[Lextreme II]

I'd think a rough idle, rich AFR, fuel pressure dropping off rapidly after you turn the key off, perhaps hard to start, all might be some of the symptoms. Diagnosing it completely would probably involve removing all the injectors and having them flow tested but with back pressure on the pintels to see if any are slow or weak to close, or are leaking.

John,

You are too wise.... that was exactly what I had. The above symptoms as I was complainting for the past few months.

 

[cribbj]

Hehehe, I don't know about the wise part David, but these are pretty common symptoms for many fuel system related problems. You just have to isolate the problem now.

IIRC, you said your fuel pressure was dropping off fast after the key was turned off, and you'd already changed the regulator, so IMO it could still be the check valve in the fuel pump, a leaky injector, or a leaky o-ring somewhere in the system before the regulator.

If the fuel pressure wasn't dropping off fast after key shutoff, then nearly all the symptoms mentioned in my first post could be ignition related too.....

 

[Lextreme II]

We used a mighty vac and the pressure drop very fast. I changed the FPR and little later I also changed the fuel pump with possible leaky valve. However, with two above changes it didnt help at all. All those symptoms were killing me. I was so frustrated. Finally I just change to a set of stock injectors and reprogram the split second and they car started right away.

 

[cribbj]

So it seems it was a sticking or leaky injector all along?

Glad you got it sorted; are you going to have these injectors tested to confirm the problem? Be sure to mention there's a leaky one in the bunch, else they may just flow test them under static conditions, and that won't find the bad one.

 

[Lextreme II]

Jim from The Injector Prefector has been helping me out along. I am waiting for few other injectors so i can send it all to him to test.

 

[stevechumo]

David,
I've been to this place and the owner was very helpful. He can help you out with all of the injector problems. He's in Lakewood, Ca. Here: http://www.fiveomotorsport.com/Injector_SetsTOY.asp. Or you may go to RC Injectors at: http://www.rceng.com. This manufacturer is also local. The technicians here were very helpful to me. Ross (the owner) at RC can basically customize many things related to the injectors.