EGR system

TAL SHAHAR

MEMBER
1994 GMC SIERRA
5.7L
V8
4WD
AUTOMATIC
200,000 MILES

Just bought this truck (k2500, gas) few days ago and something looks weird in my EGR system.

The EGR Valve is disconnected and I am missing the solenoid as well. But looking at the TBI am missing the vacuum pipe and the harness that I have does not fit any of the solenoid I found.
Adding some pictures here maybe someone can shed some light here.

On the other hand the wiring diagram that I have specifying a EGR regulator that am missing on my block as well.

Thanks in advance.

Tal

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7 Replies

KASEKENNY

MECHANIC
18,907 POSTS

More than likely they were having an issue with it and they just removed it.

Does the truck run okay?

I attached the info below on the system that gives a little more detail.

What I would do is just go through and replace these parts and as for those connectors they don't appear to be for the EGR. They look more like sensor connectors.

Can you get pictures of the wiring colors and we can try to match them up?

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Wednesday, April 21st, 2021 AT 3:02 PM

TAL SHAHAR

MEMBER
7 POSTS

Thanks for your reply. The truck runs fine but I have a fuel smell from the exhaust and am suspecting it related to the missing EGR system. Am missing the solenoid and the relevant connectors. Please find attached picture for the 2 floating connectors.
Also my TBI is missing the J vacuum pipe which associated with the EGR. Am guessing it was replaced with some older model.

I would have bought the solenoid but am missing the other parts to connect to. If you will be able to shed some light here it will be great. In addition I can not find any correlation between the colors of my connectors to the wiring diagram available on the web.

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Sunday, April 25th, 2021 AT 12:03 AM

KASEKENNY

MECHANIC
18,907 POSTS

The three wire connector is for the EGR regulator. The two wire connector appears to be for the EGR valve itself.

I attached the wiring diagram below and the info about these items.

Hopefully this helps. Let us know what other questions you have on this.

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Monday, April 26th, 2021 AT 7:17 PM

TAL SHAHAR

MEMBER
7 POSTS

Thanks a lot, that really helps.

In the wiring diagram we have a regulator and solenoid - I thought they are the same module.

I am missing both of them and found one (pic #2). So am not sure where is the regulator should be located though?

My TBI as you saw in my first post has a house connected to its S port. May I use this port as the vacuum one to the solenoid? As I don't have any other port on the TBI:
1. For the PCV Valve
2. For the Clean Air Vapore
3. Is the one with the house - guessing is the Air intake one

Thanks,
Tal

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Monday, April 26th, 2021 AT 9:21 PM

KASEKENNY

MECHANIC
18,907 POSTS

Take a look at the diagram below. This mounts to the valve cover and does use the vacuum line coming from the TBI. They call is port J but anything under the throttle body will work because it just needs manifold vacuum and the manifold vacuum is the same south of the throttle body and north of the heads is manifold vacuum. You can literally run a drill into the manifold and tap your own source if you want to. Clearly this is not needed and I would not do it but the idea is you just need to tap into manifold vacuum so if you want to use a different source, it doesn't matter. Think of it like the multiple ladders getting out of a pool. Multiple ways out but all from the same pool.

If this is the only port on the TBI then it is the correct one.

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