need help with part ID 1988 turbo ECU

[Dave WM]

I replaced with reg diodes when pump would not shut off after 5 seconds with key in ON position.

found these two to be dead shorted (out of circuit). it all works but I am guessing they maybe special (maybe avalanche) I am pretty sure they are not Zener, the pcb has "D" printed on it. That and I dont think a reg diode would work in place of a Zener but not sure about that. 

anyway pump works and ECU works but I don't want to use it incase they are some kind of clamping high speed diode to protect the rest of the circuit. 

anyway if anyone has any ideas about these please let me know. its the two round ones one blk and one red for the cathode.

 

 

Edited September 17 by Dave WM

[Dave WM]

I bought a cheap 86/87 200sx computer on the outside chance the parts will be on there. Hopefully the only real diff is the number of cylinders and not any thing to do with the pump driver parts...

Edited September 18 by Dave WM

[Patcon]

@Captain Obvious

[Captain Obvious]

Hmmm... Really not much to go on. Those old parts can be really difficult to identify.

Dave, I can see why you potentially ID'ed it as an avalanche diode. Everything I found (quick internet search) in the old SOD case was avalanche style, designed for circuit protection.

So how are they connected in circuit? Are the two of them connected together at the middle? If so, it's a check in the column for circuit protection.

PS - I give that pic the "crappy tiny picture award" for the year. The year isn't over yet, but you're running strong to win the award!!  Congrats.   

[SteveJ]

8 hours ago, Captain Obvious said:

Hmmm... Really not much to go on. Those old parts can be really difficult to identify.

Dave, I can see why you potentially ID'ed it as an avalanche diode. Everything I found (quick internet search) in the old SOD case was avalanche style, designed for circuit protection.

So how are they connected in circuit? Are the two of them connected together at the middle? If so, it's a check in the column for circuit protection.

PS - I give that pic the "crappy tiny picture award" for the year. The year isn't over yet, but you're running strong to win the award!!  Congrats.   

It looked fine to me.

[Dave WM]

that was a capt kirk copy (kirk in what are little girls made of?), will get a better picture later. Hopefully the sx200 ecu on the way will have a similar circuit I can steal from. 

[Captain Obvious]

Haha!!!

Thinking about it a little more, if both diodes were dead shorts, they couldn't be camping right to the two rails or the ECU would have sucked a whole bunch of current. There has to be more to it than that.

[Dave WM]

only symptom was a fuel pump that would not shut off. Its supposed to run 5 seconds with intial ign on, then shut off until start.

I was checking some of the resistance readings from pin 108 (the ground on circuit for the pump relay). It had 10 ohms with no power attached. Apparently enough to ground the pump relay. working ecu had like 50k IIRC. At 1st I was thinking a shorted C-E driver transistor, but traced back to in and seemed ok.

more tracing I "think" i found a trace from that same area to around those diode. Not sure anymore. 

anyway one of them looked brown so tested, found it shorted, then same for one next to it. Clipped out of circuit, checked again dead short.

10 ohm go away to much higher K ohms iirc, so must have been in the circuit some how.

 

 

 

 

 

Edited September 19 by Dave WM

[Dave WM]

looking forward to getting that donor ecu (200sx) to see what it has inside..

[Dave WM]

maybe IIRC a damper diode?

[Dave WM]

anyway the plan is to get the 200sx, look it over, see if I can figure out A if the has the same type of diodes, B clip them out, C see if I can trace back to the pump control ciruit to see how they are connected. Dont really want to mess with the current working ecu until i know more about it. I have a unmolested ECU that I can also reference. 

[Zed Head]

Just an observation, but I'd guess that any 80's era ECU of any brand would have those types of parts inside.  If you have a local wrecking yard and get tired of waiting.  I don't think that electronics were as varied back then, they probably came from the same supplier.  You probably know that.  Looks like a fun project.