Need a starting point on diagnosing wiring issues (DPFi Mpfi)
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Honda-Tech Member
Joined: Jul 2019
Posts: 299
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From: West MI
Need a starting point on diagnosing wiring issues (DPFi Mpfi)
Long story, complicated issue, hoping for some insight.
Buddy of mine has a 90 HF CRX. It has a zc swap that had some pretty bad wiring for the dpfi to mpfi conversion. So we bought this harness DPFI to MPFI to hopefully clean up the wiring. The harness fits and works and we followed the simple pinning instructions. But at the same time we installed an OBD2a Dizzy off of a crv and used and OBD0 - OBD1 conversion harness to run a chipped p28. The ecu works and is tested in my car. I did the dizzy wiring perfect and I have full confidence in that.
The car does not start. No fuel, no spark, fuel pump does not prime.
Tomorrow I'm going to try to work backwards on the documented steps of doing a dpfi to mpfi conversion as the harness we bought should cover most of that.
What are things I could test and look into for diagnosing this problem?
Buddy of mine has a 90 HF CRX. It has a zc swap that had some pretty bad wiring for the dpfi to mpfi conversion. So we bought this harness DPFI to MPFI to hopefully clean up the wiring. The harness fits and works and we followed the simple pinning instructions. But at the same time we installed an OBD2a Dizzy off of a crv and used and OBD0 - OBD1 conversion harness to run a chipped p28. The ecu works and is tested in my car. I did the dizzy wiring perfect and I have full confidence in that.
The car does not start. No fuel, no spark, fuel pump does not prime.
Tomorrow I'm going to try to work backwards on the documented steps of doing a dpfi to mpfi conversion as the harness we bought should cover most of that.
What are things I could test and look into for diagnosing this problem?
Honda-Tech Member
Joined: Sep 2002
Posts: 5,647
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From: colorado springs, co, usa
Re: Need a starting point on diagnosing wiring issues (DPFi Mpfi)
don't understand - CRX HF was not DPFI - it was MPFI - are you sure the car was HF? - sounds like not? - HF engine harness is not the same as Si engine harness, although they are both MPFI - the harnesses are not interchangeable
Thread Starter
Honda-Tech Member
Joined: Jul 2019
Posts: 299
Likes: 20
From: West MI
Re: Need a starting point on diagnosing wiring issues (DPFi Mpfi)
It's an HF (maybe not), car was clearly converted to mpfi, pretty poorly at that. And then we bought the mpfi conversion harness to do it properly and now it's giving us issues. I know the whole thing is complicated.
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Joined: Apr 2017
Posts: 98
Likes: 18
Re: Need a starting point on diagnosing wiring issues (DPFi Mpfi)
The starting system is independent from the ECU so the engine will turn over even if the ECU isn't in the car. The fuel pump, ECU and injectors are powered by the main relay. A12 and A14 ECU pins provide a ground to the fuel pump side of the relay and A2 and A4 provide the ground signal for the injector relay and ECU. Power comes into the ECU from the main relay on A13 and A15.
Based on your description, I doubt the problem is under the hood. I would test the main relay along with the wires between it, the ECU and power coming from the ignition switch. Get the CRX workshop manual and look at the diagram on page 6-13. Also check all the grounds.
Based on your description, I doubt the problem is under the hood. I would test the main relay along with the wires between it, the ECU and power coming from the ignition switch. Get the CRX workshop manual and look at the diagram on page 6-13. Also check all the grounds.
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