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10-14-2019, 02:08 AM | #1 |
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87 GMC Sierra R3500 7.4L TBI vacuum diagram
Hello
I need your help I’m looking for the full TBI vacuum diagram for a 1987 GMC Sierra R3500 with 7.4L (454) engine & auto trans. The workshop miss up some vacuum hoses, and I need to put them back correctly Thanks
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1972 GMC Sierra C2500, V8-350 1986 GMC Sierra C2500, V8-454 1986 GMC Sierra C2500, V8-LS1 1986 GMC Sierra K2500, V8-350 1987 GMC Sierra R3500, V8-454 1997 GMC Sierra K2500, V8-454 |
10-14-2019, 06:47 PM | #2 |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
There aren't many. I'll try to get a picture of the label on mine.
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87 R30 CC Dually, TBI 454, NV4500, zero rust barn find 87 Jeep Grand Wagoneer, 6.5 turbodiesel, 700R4 |
10-15-2019, 04:51 AM | #3 | |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
Quote:
If you like, I can take pictures and post it so you can get better understanding
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1972 GMC Sierra C2500, V8-350 1986 GMC Sierra C2500, V8-454 1986 GMC Sierra C2500, V8-LS1 1986 GMC Sierra K2500, V8-350 1987 GMC Sierra R3500, V8-454 1997 GMC Sierra K2500, V8-454 |
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10-15-2019, 05:32 AM | #4 |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
See image
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10-15-2019, 07:07 AM | #5 |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
Excellent, thank you very much
The AIR system is removed, there is a 2ed PCV on the second valve cover do you know where the hose go to? Additionally there is a valve behind the TBI (F port) from the manifold sticking out with its port capped, do you know where if it should be capped or what
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1972 GMC Sierra C2500, V8-350 1986 GMC Sierra C2500, V8-454 1986 GMC Sierra C2500, V8-LS1 1986 GMC Sierra K2500, V8-350 1987 GMC Sierra R3500, V8-454 1997 GMC Sierra K2500, V8-454 |
10-15-2019, 09:30 AM | #6 |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
Here are some pictures
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1972 GMC Sierra C2500, V8-350 1986 GMC Sierra C2500, V8-454 1986 GMC Sierra C2500, V8-LS1 1986 GMC Sierra K2500, V8-350 1987 GMC Sierra R3500, V8-454 1997 GMC Sierra K2500, V8-454 |
10-15-2019, 01:05 PM | #7 | |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
Quote:
Fitting sticking up out of the manifold behind TBI provides vacuum to A/C controls and modulator on automatic transmission.
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87 R30 CC Dually, TBI 454, NV4500, zero rust barn find 87 Jeep Grand Wagoneer, 6.5 turbodiesel, 700R4 |
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10-15-2019, 02:22 PM | #8 | |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
Quote:
On regards to the fitting that supplies vacuum to the A/C controls and modulator on automatic transmission, should it be capped or where does go to? Thanks
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1972 GMC Sierra C2500, V8-350 1986 GMC Sierra C2500, V8-454 1986 GMC Sierra C2500, V8-LS1 1986 GMC Sierra K2500, V8-350 1987 GMC Sierra R3500, V8-454 1997 GMC Sierra K2500, V8-454 |
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10-15-2019, 10:06 PM | #9 |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
It supplies vacuum to the modulator on the trans and the A/C controls. One port would be capped if you have a manual trans and the other would be capped if you have no AC/Heater controls.
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87 R30 CC Dually, TBI 454, NV4500, zero rust barn find 87 Jeep Grand Wagoneer, 6.5 turbodiesel, 700R4 |
10-15-2019, 11:45 PM | #10 | |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
Quote:
the AC port is capped, so where does it go or connect? Thanks
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1972 GMC Sierra C2500, V8-350 1986 GMC Sierra C2500, V8-454 1986 GMC Sierra C2500, V8-LS1 1986 GMC Sierra K2500, V8-350 1987 GMC Sierra R3500, V8-454 1997 GMC Sierra K2500, V8-454 |
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10-16-2019, 08:08 AM | #11 |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
Do I cap the J port if the AIR Injection control valve is removed? Or leave it open?
Thanks
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1972 GMC Sierra C2500, V8-350 1986 GMC Sierra C2500, V8-454 1986 GMC Sierra C2500, V8-LS1 1986 GMC Sierra K2500, V8-350 1987 GMC Sierra R3500, V8-454 1997 GMC Sierra K2500, V8-454 |
10-16-2019, 02:34 PM | #12 |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
There should be a vacuum line coming out of the firewall, just to the passenger side of the distributor. The line comes off the fitting on the manifold to a T and one side of the T connects to the line coming through the firewall, and the other connects to the vacuum reservoir (should be tucked over by the main electrical connector on the firewall).
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87 R30 CC Dually, TBI 454, NV4500, zero rust barn find 87 Jeep Grand Wagoneer, 6.5 turbodiesel, 700R4 |
10-16-2019, 02:35 PM | #13 |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
Cap it.
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87 R30 CC Dually, TBI 454, NV4500, zero rust barn find 87 Jeep Grand Wagoneer, 6.5 turbodiesel, 700R4 |
10-17-2019, 05:02 AM | #14 |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
Done, I also connected the AC line as you mentioned (),
I’ve replaced all vacuum hoses with new silicone hoses, old ones are brittles, Thanks to you If the truck runs rich, how do I tune the TBI? This a video that I made on YouTube on how this truck, https://youtu.be/WHcGnic6_Yo
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1972 GMC Sierra C2500, V8-350 1986 GMC Sierra C2500, V8-454 1986 GMC Sierra C2500, V8-LS1 1986 GMC Sierra K2500, V8-350 1987 GMC Sierra R3500, V8-454 1997 GMC Sierra K2500, V8-454 Last edited by Captain J; 10-17-2019 at 05:03 AM. Reason: Add more texts |
10-17-2019, 05:06 AM | #15 | |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
Quote:
Thanks
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1972 GMC Sierra C2500, V8-350 1986 GMC Sierra C2500, V8-454 1986 GMC Sierra C2500, V8-LS1 1986 GMC Sierra K2500, V8-350 1987 GMC Sierra R3500, V8-454 1997 GMC Sierra K2500, V8-454 |
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10-17-2019, 11:16 AM | #16 | |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
Quote:
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87 R30 CC Dually, TBI 454, NV4500, zero rust barn find 87 Jeep Grand Wagoneer, 6.5 turbodiesel, 700R4 |
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10-17-2019, 11:43 AM | #17 |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
Watched your video. Find out what is causing the CEL. Put a jumper between the A & B pins on the OBD connector (I use a bent paper clip) and turn the key to the Run position (do not start). Light will flash code 12 - one flash, short delay, then 2 flashes. It will do that 3x, then it will start giving codes in that same format - series of flashes, short delay, series of flashes, then a longer delay. We need to find out what is causing that immediate light to come on.
Meanwhile, change fuel filter. I found out mine was very sensitive to any restriction at all. That seems to have cleared up with upgrading to the EP381 pumps. 1 - change fuel filter 2 - get codes 3 - fix codes 4 - set timing and minimum idle speed
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87 R30 CC Dually, TBI 454, NV4500, zero rust barn find 87 Jeep Grand Wagoneer, 6.5 turbodiesel, 700R4 |
10-19-2019, 10:30 AM | #18 | |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
Quote:
I did the light (LED flash light) and I captured it, On YouTube https://youtu.be/b3Uxt8WR5YM
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1972 GMC Sierra C2500, V8-350 1986 GMC Sierra C2500, V8-454 1986 GMC Sierra C2500, V8-LS1 1986 GMC Sierra K2500, V8-350 1987 GMC Sierra R3500, V8-454 1997 GMC Sierra K2500, V8-454 |
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10-19-2019, 10:35 AM | #19 | |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
Quote:
I did that and made a video (on you tube) https://youtu.be/gwxRZxo7S5A 6 months ago I changed the fuel filter, intank fuel pumps and sending units (Spectra), and I installed fuel tanks (in excellent conditions)
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1972 GMC Sierra C2500, V8-350 1986 GMC Sierra C2500, V8-454 1986 GMC Sierra C2500, V8-LS1 1986 GMC Sierra K2500, V8-350 1987 GMC Sierra R3500, V8-454 1997 GMC Sierra K2500, V8-454 |
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10-22-2019, 12:04 PM | #20 |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
Code 24 is speed sensor malfunction. The sensor is built into the speedometer. You should be able to see (or feel) the wires coming off the back of the speedometer and make sure it is plugged in. If sensor is bad, then you have to replace the speedo.
Code 44 is lean. I chased lean codes for a while on mine. I had bad wiring to the O2 sensor, bad fuel pumps, plugged filter. Watched the video with your injectors and they should not be going on and off like that - you want a continual steady spray. I'd probably start with replacing the electrical connectors on the tops because those look bad. There are also small filters on the injectors themselves. Get a rebuild kit and pull the injectors out of the pods and replace those screens. I can't tell if the injector just isn't firing or if you are getting air in your fuel. Use a stethoscope to listen to the injectors and listen for consistent clicking - if it still clicks when you have no fuel spraying then problem is with supply. If it stops clicking intermittently then you have an injector or wiring issue.
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87 R30 CC Dually, TBI 454, NV4500, zero rust barn find 87 Jeep Grand Wagoneer, 6.5 turbodiesel, 700R4 |
10-22-2019, 12:27 PM | #21 | |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
Quote:
I got mine from TBI Chips aka harristuning.com. My combo is mild so it has worked. I do have surging @ idle but it's not enough of an issue that I have done anything about it.
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10-23-2019, 08:28 AM | #22 | |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
Quote:
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1972 GMC Sierra C2500, V8-350 1986 GMC Sierra C2500, V8-454 1986 GMC Sierra C2500, V8-LS1 1986 GMC Sierra K2500, V8-350 1987 GMC Sierra R3500, V8-454 1997 GMC Sierra K2500, V8-454 |
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10-23-2019, 08:40 AM | #23 | |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
Quote:
For the speedo sensor is it behind the cluster? Do you’ve a picture? So what I should do to fix Code 44? I did order the electrical connectors, and I’ve a rebuilt kit, and I’ll work on it. I’ll check the clicking to verify your diagnostic. When you say ”if it still clicks when you have no fuel spraying then problem is with supply” what you mean? Thanks
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1972 GMC Sierra C2500, V8-350 1986 GMC Sierra C2500, V8-454 1986 GMC Sierra C2500, V8-LS1 1986 GMC Sierra K2500, V8-350 1987 GMC Sierra R3500, V8-454 1997 GMC Sierra K2500, V8-454 |
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10-23-2019, 08:50 AM | #24 | |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
Quote:
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1972 GMC Sierra C2500, V8-350 1986 GMC Sierra C2500, V8-454 1986 GMC Sierra C2500, V8-LS1 1986 GMC Sierra K2500, V8-350 1987 GMC Sierra R3500, V8-454 1997 GMC Sierra K2500, V8-454 |
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10-23-2019, 01:52 PM | #25 |
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Re: 87 GMC Sierra R3500 7.4L TBI vacuum diagram
That looks like the plug. The sensor itself is built into the speedometer. That harness plug in next to the speedometer cable.
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87 R30 CC Dually, TBI 454, NV4500, zero rust barn find 87 Jeep Grand Wagoneer, 6.5 turbodiesel, 700R4 |
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