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EF-37 Circuit Test


n2deep

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Thanks Blue. I have read that and many many other tech tips from you. The issue is I get a NG on test 1. No continuity from pins 2 and 18. I have an extra TPS with the cover off. Cleaned the contacts, watched the connections open and close as it rotated, installed that on the car and still failed test 1. So I was just trying to follow the FSM and circuit check the solid lines on EF-37. The TPS I pulled off is relatively new and still sealed.

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I'm reading the 77 Datsun 280z FSM. There is a series of tests on page 103 or EF-21. The next page describes the tests. Test 1 /throttle valve switch. If you get a NG result then check circuit highlighted on page EF-37.

Are you thinking if the TPS is not set properly as you describe, it will fail the test?

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The Test 1 is for measuring continuity at idle. The contacts are numbered 2 & 18. The accelerator pedal should be at idle to measure continuity (low resistance near 0 ohms). The referenced drawing for Test 1 is figure:EF-35 on page EF-25.

If you get continuity at the TVS but not at the ECU connector pins (with the TVS re-connected and the pedal at idle) then the harness connector probably has corrosion at the TVS).

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The Test 1 is for measuring continuity at idle. The contacts are numbered 2 & 18. The accelerator pedal should be at idle to measure continuity (low resistance near 0 ohms). The referenced drawing for Test 1 is figure:EF-35 on page EF-25.

If you get continuity at the TVS but not at the ECU connector pins (with the TVS re-connected and the pedal at idle) then the harness connector probably has corrosion at the TVS).

Yes I understand how to do test 1 at idle position. There was no continuity between 2 and 18 as I stated in post #4. I did get continuity between 3 and 18 (WOT) position. The FSM said to check the circuit highlighted on EF-37 if you got no continuity between 2 and 18. How do you do that?

Also how are you checking continuity at the TVS?

77 280z

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At the TVS, just pull off the harness connector and plastic cover. You should be able to see the centre vane (18) bend from the idle contact (2) and to the wide open contact (3) as you open the throttle by hand. Just measure the corresponding points with the ohm meter touching the connector terminals on the TVS. When the centre vane touches the idle (18-2 continuity) , you should have continuity between these two contacts, when the centre vane is not touching either you will have no continuity. When the centre vane touches the WOT contact (18-3 continuity), you should have continuity between these two contacts.

The FSM is well written for mechanics to quickly troubleshoot at convenient locations however the fundamental method of trouble shooting source-sink systems like this is to measure (collect data) at the source (TVS), then continue outward along transmission line (wire harness) that carries the data (continuity changes)............ so you collect data at the TVS (visual observation of contacts making braking and corresponding continuity changes at the terminals on the connector) then follow these same signals along the cable to the sink (ECU connector)

post-7641-14150827112147_thumb.jpg

Edited by Blue
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Thanks. That is what I thought it meant. To check continuity from point to point. (source to sink) EF-37 highlights pin 17 to negative ground at the battery. It apparently goes to a common ground junction. I will start at the TVS and see if I can track back to pin 2.

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Yeah if you just follow the instructions it will work out but if you go the step further to understand the path and what is being sent along it then you will intuitively know. The toughest part of electrical testing is translating a nice pretty and compact schematic to a dirty complicated snarl of wires.

The one good advantage you have is knowing that most electrical problems with a Z are at the connectors. If you simply disconnect the battery then do a search and destroy mission of finding every connector, inspecting, cleaning/burnishing (remove corrosion), applying a contact cleaner, applying dielectric grease (water proofing) then reassembling; you will fix a lot of problems and many waiting to happen.

The connectors in the steering column (remove plastic) and the many down around the passenger foot well (even under the carpet) are important to clean too.

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Thanks. As you probably suspected in the beginning, the TVS was set in a position preventing idle contact. I have eyeballed now enough to get continuity and will reconnect everything to set it more accurately at 1400 rpm.

I don't know why the FSM did not suggest checking that first as you did.

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I think it is in there somewhere in the print...could be in the EFI bible or in a graph.

Page EF-56 in the 77FSM says to adjust so that the idle contact opens after 7 degrees of throttle plate rotation.

I'm happy to help.... once you dig in a bit more you will be an expert. I remember doing what you are now doing :)

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