Injector Balance Test?

[99 2dr]

Alright guys, I'm still trying to figure out my detonation/ pinging issue. Justin @ BB told me to do an Injector Balance Test. A couple of times on the forum I have seen it brought up, but I can't seem to find any instructions on how to do it.
Sunlit, I saw you mention the test before. Do you have the information on how to do it?
Thank you,
Kyle

 

[SunlitComet]

you need a fuel pressure gauge and the proper injector electronic tester or a proper high end scanner.

---------- Post added at 03:39 AM ---------- Previous post was at 03:38 AM ----------

if you dont have both head to a shop for what should be a one hour job.

 

[99 2dr]

Sunlit, Thank you.
Since my post yesterday, I have worked on it a little more. Using a Snap On fuel pressure gauge, I found that I am only getting 45psi of fuel pressure with the engine running. As soon as I shut the truck off, the fuel pressure goes to 0. If I cycle the key without starting the engine, the pressure builds to 55psi with the pump running. As soon as the pump shuts off, the pressure instantly falls to zero.

At first I thought that the pump wasn't making enough fuel pressure with the engine running, but my two other Tahoes only build to 55psi upon cycling the key and keep a constant 47-50 psi with the engine running. The difference is that when you shut the key off in them the fuel pressure holds 55psi for a good 15-20 mins before it even begins to bleed down.

Here is my next idea.
Today I am going to get 2 line clamps at the parts house. Then I will jump the fuel pump relay to make it build pressure and install the line clamps on the soft portions of the fuel lines near the transmission. I should then be able to turn off the fuel pump and have it isolated from the engine. If I loose fuel pressure on the engine side then I will know that the spider or fuel pressure regulator is bad. If i don't loose fuel pressure then I will know that the check valve in the tank is bad.

I updated the spider 80,000 mi ago and the fuel pump is only a year and a half old. Fuel filter was changed when I swapped to the manual trans a couple months ago. Both were dealership purchased parts. so perhaps the fuel pressure regulator is the cause? It's the only thing I haven't changed.

I'm thinking that whatever is causing the pinging/detonation/cylinders5,7 lean; has something to do with my fueling issue. The truck actually runs fine until I start to pull a grade or a heavy trailer. Maybe the fuel pump isn't making enough pressure to supply the engine under load.

Any other ideas?

 

[SunlitComet]

first, the hoes holding there pressure at engine running but 47-50 psi are F***ed.

second the first hoe that is running 45 psi is F***ed.

third, to reiterate, your hoes are F***ed.

now the the fuel reg is on the right side closest to the cyl 4&6 so if it was leaking they are likely to be rich more then others. the pressures you are getting will lean out cylinders. but if the lines you plan on choking on the LEFT SIDE OF TRANNY are metal or plastic DO NOT DO IT.

i will see about getting the proper testing procedure for fuel pressure up shorty.

In the name of the holy Sun follow the service manual.

---------- Post added at 04:59 AM ---------- Previous post was at 04:34 AM ----------

Here. be one with the service manual. before you start, read it. read it again. then read it again. read it again before pinching hoses unless it tells you too.

http://www.sunlitcomet.com/pdf/auto...96-chevy-tahoe-fuel-pump-pressure-testing.pdf

 

[99 2dr]

Sunlit,

The fourth box down in your manual says to "Block fuel pressure line by pinching the flexible hose." I'm Just following the manual............

The second box on your manual says that with the engine off and the key on the fuel pressure should be 56-62 psi. My other two tahoe's make 55 psi..... seeing that they are both within one lb of specified pressure, It could just be the gauge.

The fifth box says to start the engine and open the throttle quickly. Pressure should be 56-62 psi. I attached my fuel pressure gauge to the windshield and drove all three tahoe's. Under hard acceleration they make 61 and 64 psi between the two of them. They are both operating correctly.

Anyhow, I wasn't able to pinch the lines tight enough to stop all fuel flow; and I didn't want to pinch them any harder than absolutely necessary as they do have 290,000 mi on them.
I ended up disconnecting the engine feed line from the fuel pump line last night and connecting the gauge directly to it. It Held 60 psi with the pump off, and leaked down 1lb every 4 mins. So I am now sure that the fuel pump/ check valve are in proper working order and they are not the cause of my problem.

I am going to pick up a new injection spider unit/ fuel pressure regulator this afternoon and install it over the weekend.

 

[SunlitComet]

sounds good get the delphi FJ10566 from amazon if you can wait. anywhere is pricier.

 

[99 2dr]

Well I just talked to my engine shop where I got the first spider. He worked a little magic and got it warrantied out. New spider and Fuel pressure regulator @ no charge. I just have to pick up a gasket kit and we will be back on the road.

 

[SunlitComet]

so it was the issue?

 

[99 2dr]

Last night was new tire night. Toyo At's We are racing tonight, Injection spider tomorrow morning.