RCrosby

Greetings,
My first time asking for assistance. Thank you to all for everything I have already learned here. Situation: 12/95 LS400 so 1996. Car parked running OK, Check engine light was on before parking but running OK. Next morning no start. Went through the basics, Has spark. Fires with starting fluid. Open circuit relay is clicking rapidly. (negative feed is pulsing battery voltage which I believe is fed from ECU ( searched online and could not find anyone who mentioned this pulsing open circuit relay) . Hooked up scanner - no communication to ECU. Opened ECU and found leaking Capacitors. Replaced all 6 capacitors. did find one area that was pretty dirty. Several had green spots at solder joint. Cleaned well, did not appear to have an open trace but trace was exposed. After reinstalling ECU no change, still no start, still no communication with scanner (tried 2 known working scanners) still has clicking open circuit relay and will fire with starting fluid. Jumped open circuit relay, pins 3 and 5 if I remember correctly. When jumped fuel pump runs all the time with key on and getting good flow and pressure .Without jumping fuel pump turns on and off rapidly. Injectors not clicking. I don't have noid light (yet)
So the question - Does this still sound like ECU with either poorly soldered capacitors, bad trace in circuit or something else wrong with ECU and I should acquire replacement. If so any recommendations for vendor?
Thanks for reading this and I will appreciate any advice.
Best Regards,
Russ

LeX2K

Sounds to me like the ECU still has issues I would seek out a replacement.

Gerf

Will the car run normally if you jump FP-B+ in the diagnosis connector in the engine bay?

RCrosby

The FP+ hole in the diagnostic connector for this 12/95 LS400 is empty. No electrical connector there. Does not appear to have been altered.

LeX2K

You misunderstand that will bypass the circuit opening relay aka fuel pump relay and force the pump to run. Wait there is nothing there at all? I thought your year had that diagnostic feature.

Gerf

OK, the reason I asked you that was when relays are clicking rapidly it can be a voltage issue. did you check the circuit opening relay off the vehicle for normal operation before you did the capacitors?

Gerf

If you are referring to me, there was no misunderstanding.

LeX2K

No the OP maybe didn't understand but looks like I'm the one since apparently the pins to jumper are not there.

Yamae

Sorry for your trouble. Without investigating your car myself, I can't say much but what I can assume from your statements above are as follows. The ECU has still some issues such as the internal layer is damaged or the leaked QAS damaged some components as well as traces. Another issue I worry about is that your car is in inhibiting mode.

Was your engine running a few to several seconds right after you installed the ECU and started the engine? If so, the possibility of the inhibiting mode is high. This can be confirmed by bypassing the circuit opening relay short-circuiting Pin #3 and #5 of it.

RCrosby

Thank all for your responses,
I referred to the circuit open relay as clicking, a better description would be that it is stuttering. The negative pin that closes the relay is receiving negative current on and off very rapidly making the relay open and close rapidly. ( prior to the voltage feed test I substituted a known good relay.). This is in the key on position. (my understanding is that the fuel pump should not run in the key on position) In the key on position it is pulsing on and off in concert with the relay opening and closing. When I jump pins 3 and 5 the fuel pump runs constantly with good volume and pressure but no start.
Was your engine running a few to several seconds right after you installed the ECU and started the engine? No it did not .
.Also scanners are reporting no communication link.
I believe there is interment it negative coming out of the ECU making the open circuit relay turn on and off rapidly and also affecting negative feed to injectors ( i need to confirm injector pulse, but I can hear no click of injector with stethoscope. Or I'm missing something vey simple. I've checked every ground I can get a hold of.
Thanks for reading this and I appreciate your opinion and kind response.
Russ

Yamae

Judging from your words, the ECU is not functioning well enough. Especially the symptom, "scanners are reporting no communication link" is telling so. It seems to me that the ECU still has some problem. As LeX2K suggested at the post #2, to seek out a replacement ECU may be the way to go, I think.

RCrosby

Greetings - Wanted to report my results in case anyone has the same symptoms. I ordered a reman ECU from Digital Auto Technology (DAT) in Riverside, CA.
Great success, Car runs great now. 1996 LS400 with 87K. In summary a pulsing negative to the Open circuit relay led me down the ECU path. Also no Communication with scanner. I tried replacing the capacitors but circuit board was in rough shape from leaking caps, also could have been a solder error which forced me to purchase a replacement. Great service and price at DAT. Thanks to all who responded. I appreciate your help,
Russ

Yamae

Thanks for reporting us the result. I'm glad that you succeeded to fix.

The leaked liquid is the condensed QAS (Quaternary Ammonium Salt) which is the very strong alkali and eats copper traces and through holes quickly. Many old ECUs were damaged by that. I used to recommend people to replace those QAS capacitors before the leak starts.