95 K2500 7.4L TBI issue

[PlayingWithTBI]

I got the original OEM number and am going to verify the replacements I got are compatible.

Does that part number match one in the chart on post #2? I'm curious so I can update my list too.

 

[grampadirt]

Maybe I can help..My Burb is a '95 with a big block and sounds like it's the same setup as yours.This year big block needs fuel pressure to be 26-31 psi.The cold idle as Shurkey says is controlled by a diaphragm attached to the side of the tbi unit and that is controlled by the idle solenoid which is controlled by the pcm.There is a vacuum line going from the base of the tbi unit to that idle control solenoid and then on to the vacuum diaphragm on the side of the tbi.there should also be a wire connector attached to the the idle control solenoid so the pcm can turn it on and off.When the engine reaches a pre designated temp the pcm will activate that icm solenoid and cut the vacuum therefore releasing the idle vacuum diaphragm and dropping the idle to what the pcm wants.Hope I explained this correctly

Added note:I have an old laptop(using Vista OS)that I monitor my engine with and also use Tuner Pro RT...very helpful.

 

[MtnMan]

Thanks for the info. I will be doing more research on PSI requirements for replacement injectors. I just find it odd I have a factory GM service manual and it says 10-13psi but I can't find the specs for the OEM part number (17113080) or a replacement for that number to compare what I have to use as a replacement. I really don't want to change the fuel pump in the tank. It's been running great for years with the low pressure pump.

 

[Schurkey]

Thanks for the info. I will be doing more research on PSI requirements for replacement injectors. I just find it odd I have a factory GM service manual and it says 10-13psi but I can't find the specs for the OEM part number (17113080) or a replacement for that number to compare what I have to use as a replacement. I really don't want to change the fuel pump in the tank. It's been running great for years with the low pressure pump.

I downloaded two different 1995 manuals--the regular '95 service manual, and the '95 Driveability and Emissions manual.
www.mediafire.com/download/g4u6ekld8i0n62n/GMT95_CK-2_1995_GM_CK_TRUCK_DRIVABILITY_EMISSIONS_AND_WIRING_DIAGRAMS.pdf

GMT95_CK-2_1995_GM_CK_TRUCK_DRIVABILITY_EMISSIONS_AND_WIRING_DIAGRAMS

MediaFire is a simple to use free service that lets you put all your photos, documents, music, and video in a single place so you can access them anywhere and share them everywhere.

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I found NO mention of fuel pressure specs in the regular service manual by searching for the phrase "fuel pressure". That's why I downloaded the Driveability and Emissions manual.

Page 4A-14 of the Driveability and Emissions manual gives specs for fuel pressure:

Start engine and observe fuel pressure reading. It
should be 62-90 kPa (9-13 psi) on 4.3L, 5.0L and 5.7L
engines. On 7.4L engines the fuel pressure should be
179 to 220 kPa (26 to 32 psi).

This assumes you have an L19, VIN N 7.4L. I'm sure you do...that's the only one listed for '95 C/K trucks.

What are your fuel trim numbers? Towards the rich-command I bet.

You need a higher-pressure fuel pump for certain. You may need a higher-pressure spring in the pressure regulator. MAYBE you have the correct spring, but the existing pump can't provide more than 13 psi. (That seems unlikely, I thought even the low-pressure pump could squeeze to 15--16 psi, perhaps a pound or two higher.)

And I have no idea at all about the injectors themselves.

"Won't stay running when cold" could just as easily be an issue with the vacuum-powered throttle kicker system as the fuel pressure. The whole point of the throttle kicker is to knock the throttle open a little bit more when cold. The throttle kicker, IAC, and minimum-idle setting all work together to produce a proper idle speed cold, warm, or hot.

And then there's all the usual issues not specific to 7.4L engines--faulty coolant temp reported to the computer, faulty MAP or TPS signals reported to the computer, incorrect spark advance including the electronic advance, EGR issues, etc.