How to test spider injectors

Random misfires are 99% of the time fuel pressure related. Check the pressure KOEO then with the engine running. Also check the pressure drop with the engine running, you rev the engine and watch the pressure. You want a minimum of 60 psi KOEO, Should hold that for 10 seconds or more when you turn off the key.

Next check for vacuum leaks. High trim on one bank only, could also be related to a bad O2 sensor.

pump with a delphi unit from NAPA. It did not fix the problem. I tested the fuel pressure. I will say I am getting 58 psi when I checked it the other day but becasue it had the problem with the old fuel pump I am thinking it is not that.

I have no codes for the o2 sensor. On my scanner they both seem to be switc hing normally.

Actually, I am trying to make a smoke machine to check for vacuum leaks. (t rying to figure out what I can use to produce smoke". I did spray brake cle aner and found one leak.

The problem is the cutting out is only under certain conditions at part thr ottle. I have checked pretty much every sensor and replaced the plugs and w ires and cap last year.

58 psi when? Post - Key on Engine off - Engine Idle - Engine at 2000 rpm - How long it holds pressure when turned off.

When was the last fuel filter change?

MUCH easier way - Take a cheap propane torch, Turn it on but don't light it. Trace the lines and around the gaskets. When you get near a leak the engine will rev up a bit.

Smoke works very well BUT if you put certain chemicals in there it can really screw things up.

What are the short term and long term fuel trims?

What conditions and approx what throttle position?

You said you replaced the pump, plugs, wires and such last year. Were the ignition parts before or after the problem?

Truck stock? Any performance stuff?

What scan tool are you using? Might be able to give you some things to look for if I know what the tool can do.

am having an intermittenant radom multiple cylinder misfire code. This truck has

359,000 but other than that runs good. I am getting a higher than normal fuel trim on bank one.

pressure drop to see if I could locate a bad one. I dont have a machine to pulse it but would a 9 volt batter or something similar work?

plugs and pump were replaced after the problem. Fuel pressure KOEO. Help pressure with keu off over 10 minutes. Truck bone stock. Scan tool most expensive one at harbor freight.

Mainly wanted to build a smoker for fun but also for this project.

Fuel trims varry. Long term on bank one goes as high as 13. Usually 6-7. Other bank usually 3 less than bank one.

LT fuel trim normally doesn't go much over +5 normally. What are the average voltages shown by the O2 sensors?

How about compression numbers?

One of my plans is to do a compression test this weekend. o2 sensors switch quickly from a low of .100 to a high of .800. Hard to tell but it seems li ke the bank I am having toruble with goes a little higher than that and sta ys at .800 a second longer. I believe I replaced one of the sensors last ye ar but it did not change anything.

By the way the hesitation or miss seems to be at slight throttle over level ground. No problem when giving gas to pass or at idle.

I am curious though back to my origional question, is it possible to pulse these injectors at home without special equipment to read the fuel pressure drop?

only one? ?

anyway, swap them and see if it changes the bank that's "misfiring".

why do you keep coming back with this vehicle and its same old problem? you ask for help, then ignore it, and then wonder why you don't fix anything.

Nope. Even with a tech 2 the only testing available is shutting off the injectors one cylinder at a time. This design is not the common design of an injector. A common injector will spray fuel when opened. The SCPI unit will not spray fuel unless there is engine vacuum at the poppet valve on the end of the tube at the same time the injector pulses.

The thing is that you are seeing one bank lean and misfiring. The SCPI system won't do that. It can cause an overall lean or overall rich but not single bank problems. Being that the FP held I don't believe you have a leaking fuel pressure regulator in the intake (which can cause one side to run rich) You could swap the O2s side/side and see if anything changes. It is possible you just have a lazy sensor or one that is marginal.

WOuld a vacuum leak cause these symptoms?

Anything that allows air in after the MAF can cause a lean misfire. Vacuum leak, bad intake gasket, cracked intake.

I have aa almost dead miss at times on a 99 suburban, 5.7 with the vortec. The genesys scanner showed over 10k misfired on 1 cylinder, I suspect injec tor, being that plug, and wire made no change, 2 of the other cylinders sho wed 60 to 70 misfires in same cycle while the other 5 cylinders show no mis fires, is it possible to check this injection package before a 300 dollar v isit to parts store