How do you find a bad injector?

[BuffaloGuy]

I have a suspicion that I might have a bad injector but don't know how to find it. The motor runs fine when warm but on cold start I think an injector or two may not be working that good. Also, I don't get as good of mileage as before and at night loaded I can see a definte cloud in the headlights behind me. (More than usual)

Short of pulling them all and taking them to a shop is there a way to diagnos if they are working 100%? Then, I can rule out the injectors and eaze my mind or replace and be done with it.
Thanks!

[Jim P]

An old trick on tractors, is to start the engine when it is cold and feel the exhaust manifold where it attaches to the head. The coldest spot on the manifold is where the bad injector is.

[charliepeterson]

If you have 100K then pull them all. They don't owe you anything. I pulled mine at 75K.

Sure some people will get 200K, but the cold starts and performance/mileage will decrease.

[BuffaloGuy]

Thanks Guys. It's a new motor (20K) and supposedly new injectors but I have my doubts. I've done new glow plugs, tested the wiring to them and had to replace the glow controller so I kind have it narrowed down.

It's either a bad injector or the IP is getting tired. It has 120K on it so that's possible.

I'll try the manifold trick this am.
Ken

[Scooby]

You can also use an infared gun to read manifold temps when first started- if you know anyone that has one. They dont cost much either, and come in real handy for electrical work- finding loose connections in power distribution panels !!

[Shad]

Hey Buffalo guy, does your truck miss a little at start up? mine misses a little for about 10-20 seconds when cold sometimes. I have been thinking along the same lines....Our electrical guys at work have a infered gun at work I'll have to check that out.

[britannic]

Here's a sure way to find a bad injector:

1. Get a rag
2. Idle engine
3. With a 3/4" crowfoot wrench, loosen the #1 injector nozzle nut, until fuel weeps/sprays (use rag to absorb and prevent a mess).
4. Check for change in idle rpm and misfire
5. Repeat steps 3 and 4 for each injector

A loosened injector nozzle that has little or no effect on the idle speed indicates a suspect injector.

[BuffaloGuy]

Thanks Brittanic. I'm familiar with this method but the trick here is that it runs rough when cold. By the time I loosened injectors and such it would have smoothed out.

I tried the feel the manifold trick yesterday but the way the manifolds are laid out it is too hard to tell what was going on. I'm going to give it another try today (it's 0F). The infarred tool would make a big difference since it is much more sensitive than my hand.

Ken

[Barry Nave]

When GM R&R my Eng. 4years ago it was a long block and all injectors were reused.
I think when bad injectors won't hold there POP psi they blead down?

[britannic]

Originally posted by The Buffalo Guy:
Thanks Brittanic. I'm familiar with this method but the trick here is that it runs rough when cold. By the time I loosened injectors and such it would have smoothed out.

I tried the feel the manifold trick yesterday but the way the manifolds are laid out it is too hard to tell what was going on. I'm going to give it another try today (it's 0F). The infarred tool would make a big difference since it is much more sensitive than my hand.

Ken Bad injectors are usually bad all of the time, so you may want to start looking at glowplugs, HPCA (assuming you have the mech. inj. pump in your '93), excessive cylinder/piston ring wear, etc.

[kowsoc]

Try adding a good dose of injector cleaner...it might clear the bad nozzle. I use PowerService (grey bottle) at the 6 cetane dose and the extra cetane helps starting. The engine doesn't rattle so hard on startup either.