Avenir SR20DET wiring - weak spark

[ddog]

Hi folks, I recently installed an Avenir style SR20DET into my B14 and now having some issues getting it to start. The particular version of the engine is from the Nissan liberty.

I am getting a very weak spark out of the distributor, too weak to start the engine. Initially I though it may have been a weak coil or bad igniter but replacing the distributor did not make a difference.

What did help a little was adding more grounds from engine to chassis. After this the spark got a little brighter when using an inline tester. When grounding a spark plug to the valve cover I can now barely see a spark jump the gap but still too weak to start the engine. If I crank over for more than 5 seconds the engine sometimes sounds like it just barely catches in an attempt to start.

I have also cleaned cap and rotor but the spark is weak even when using a test light straight from the distributor cap. The test light has to be very close to the distributor cap for it to jump the gap. The spark is orange and as thin as a hair.

I double checked all power and ground connections:
Switched 12V on pin 36,38 & 47.
Constant 12V on pin 46
12V on crank on pin34.

All grounds on the ECU plug check out with 0.4 to 0.5 ohms continuity to chassis:
Pins 6,13,21,39,48,108 & 116.

I can post my under dash connections if required.

To note, at the moment I do not have the O2 sensor, power steering switch and factory boost controller connected to the ECU as these were not integrated into the factory harness so I will have to run these separately and connect via the under dash harness. I don't believe that this would prevent the engine from starting but still wanted to mention it.

I also wired the consult port and scanned with ECU talk. All sensor live readings are reflected on ECU talk and even displays base ignition timing when cranking. It does flag a code 21 fault every time I crank which i believe reflects an "ignition signal missing" fault. What's confusing is that it does spark but just very very weak.

Anyone ever encountered this or has any ideas what might be causing this?

[Dave]

If the cap and rotor is worn and high resistance built up in the wires these will all cause a weal spark. A failing coil will also. I am sure you swapped back all used parts over 20yrs old.

[ddog]

I did try 3 distributors in all, but as you said all used. While possible I would find it strange that they would all have the same problem and unfortunately I had no other vehicle to test them on. There are new plugs and relatively new plug wires from my GA16 engine that was known working.

I did try a quick and dirty test of using a GA15 ECU on the SR engine to at least to hear it start as they both have the same pin out and ended up with the same problem. Quite possible to still having failing coil or ignition module.

I have searched online but only find the 2 plug style distributors that came with the US SER Sentra. Ultimately I can rewire to work once I can get the plugs but need to rule out if the issue really is coil or ignition module.

[ddog]

Quick thought just popped up, are the GA and SR internal coil and ignition module the same?

[ddog]

Anyone knows if the Avenir and VVL distributors are the same? I see they are both 8pin.

[ddog]

For anyone curious, the problem was the 12V feed to the coil positive. On the liberty harness the 12V feed for the coil comes from the ECCS relay. I have the switched 12V feed to the distributor and around 10V on crank which is normal. As the voltage checks out OK I assume it seems to be an amperage problem, probably due to bad or loose connection on the harness somewhere.

I came across this when I decided to test an external coil with direct 12V feed from the battery and coil negative connected internally on the distributor. I got a bright spark from the external coil then realized that I used a direct feed from the battery. Used the direct feed to the distributor coil instead and engine fired right up.

[Dave]

Nice man, glad u got it sorted.