I think a perfect battery would drop somewhat less than that. However, 12.3 V ought to be plenty to run everything correctly. The voltage requirement would certainly not be above 12 V, or at idle, with accessories on, everyone would have problems.

Therefore, something else has to be the cause.

 

Ah, I found it - the battery must be 12.4v or higher.

Page G-10

 

If I'm reading this correctly, it says the voltage has to be above specification (9.6 V or higher in the box to the right) under load, so I still think 12.3 is OK. It just says to recharge the battery if it's below 12.4 before or after the test.

 

Thanks for checking it out.

The box in the middle of the flowchart says that those numbers apply to a test of 150-165A for 15s, and that after 15s the voltage should be above the numbers in that chart. So that's really a simulated cranking test.

For normal open-circuit voltage, the pass/fail is 12.4v. I'll keep looking if there is a system that actually checks for 12.4 volts.

Any guesses as to the humming noise? I'm thinking injector, OMP, off the top of my head. Can't think of much else that would make noise that is powered electrically.

Dave

 

The pass/fail 12.4 V criterion is immediately after charging, not after some use...

Solenoids often hum, but that's usually only the case when using alternating current, so I don't know the answer to that. However, a DC solenoid / motor can hum if a voltage-reducer is powering it.

 

Doh! Of course the solenoids - when bench testing, some of them hummed from time to time.

Oh well, I'll get the battery charged and see if the TPS adjustment makes the difference. I find it odd that the TPS was out of spec - the car ran well before I did all this work, and I didn't adjust anything on the TB. Oh well, s**t happens.

Dave

 

Were you using a battery, or a DC power supply to bench test? A DC power supply is rectified AC, so that will cause a hum. I didn't think a battery (as long as it was not being charged at the time) would make a solenoid hum.

 

Hmm, well, yeah I was using a cheap 12v DC charger for the bench testing. So I'm sure as far as rectifiers go it probably wasn't a very good one either.

Yesterday it was strictly running from the battery.

Dave

 

Well, today was big progress. After pulling the UIM to verify I didn't have the primary injector leads crossed, and after testing dozens of electrical signals and connections, I put it all back together and cleared the ECU yet another time. TPS, MAP, CkPS's, Igniter, etc all checked out ok. Fuel rail still develops and holds pressure no problem. Applying a 9v battery across each injector circuit confirmed they clicked when voltage was applied (looking back 9v is probably too much). Basically I found nothing wrong. Knowing that my 9v injector test just shot plenty of fuel into the chambers, I did a thorough unflood procedure using 3x15s dry cranks, a little ATF, another 15s dry crank, and closed it all up with clean plugs.

I did do something slightly different: instead of cranking without throttle, or holding it wide open, I tried about half throttle and varying it as I cranked. Putt-putt, pop! I got some combustion. Tried it again, and it started up, but I needed to give it throttle to keep it going around 3-4k. Smoking like crazy (no doubt due to the MMO and ATF in the chambers), but running. Tried to let it idle, and it stalled.

I proceeded again, and the car started a little more readily, and I held it at 3-4k for a couple minutes. I also idled, although very low and shaky. I took it around the block, then around a few local streets. It was bucking and sputtering at times, but both rotors were firing cleanly. At one point I pulled out into the main road and it almost refused to accelerate - bucking and popping sounds galore, and 10psi of boost, but it got going again. So I changed the plugs - the front plugs were a little wet, and all were rather black.

This time it started fairly well, and held idle without issue. After another 10 min of idling in the driveway, and another drive around the block, things are coming back closer to normal.

I suspect that the coils, coil harness, and plug wires ought to be changed. I suspect much of the trouble was the solvent in the injectors, which I believe was WD-40. The injector test may have flushed all the solvent out so that the engine was finally cranking on pure gasoline.

I'm headed out now to give it another test drive, and hopefully close this chapter.

Trying to remain optimistic, at least now I can pull my UIM/TB assy in 20 minutes. Skillz.

Dave

 

Wooooo Hooooo!.
I couldn't help with any advice in all this mess, but I was following the thread, and for whatever it was worth, you had my moral support.

 

Thanks. This thread turned out to be a blog more than anything else. (The advice given was very helpful - the 'blog' was due to how much I rambled).

I just got back from the extra test drive, and although startup is a little shaky and the idle is high (needs readjusted following the TPS adjustment), it runs silky smooth in vacuum. But it sounds like there is a vacuum leak at the UIM and every time I pass 0 psi into boost, it bucks and stumbles. I'll have to do some searching and FSM reading, but I suspect it's FPR or something like that. I'll worry about that tomorrow - for now I'm happy to have a car that starts and moves, so I can move it into the garage.

Dave

 

I forgot something else important when I got it to start - the FSM (in one of the 3 'won't start' troubleshooting lists) said to jumper the f/p to ground in the diagnosis box and try to start it with the jumper in place. That, combined with playing with the level of throttle, is when I got the first sputter of life. Then I pulled the jumper and continued as normal.

Dave

 

Update:

I think I found the problem with the stalling - the hose to the FPR had a small tear down near the FPR nipple, facing the firewall. After fixing that, the startups and idle are back to normal. Readjusted the TPS to within spec and put in new plugs (the old ones were a little fouled). I've tested all the fuel and ignition components per the FSM as well as I can with my multimeter.

I am having trouble with bucking above 0psi. Sometimes it's at 2psi, sometimes it's at 8, always is enough to create a noticeable buck and drop in boost. At one point between bucks I saw the boost gauge read a 14psi spike!. Up to the point where it bucks, the car appears to be operating completely normally. I can drive it at low speed, but it's not safe or driveable on the highway or outside my neighborhood.

Forum searches suggest this is ignition breakup. But is it?
(My only experience with ignition problems was on a 2001 Eclipse 4cyl w/auto tranny, and it felt like the tranny was slipping. I assume on a manual tranny the breakup leading to a bucking rather than slip since the clutch is engaged.)

I already have on the way a set of RC-cleaned low mileage injectors that I will probably install next. Then if that doesn't fix it, I'll go yell at Zach Keller for blaming the injectors and start swapping a known-good leading coil and plug wires. (My coils have 62k, and my plug wires have 10k). Other possibilities include the ignitor and ignition coil harness (which should be the updated version since I have a 94). I also borrowed a timing gun - would timing issues only affect high load/rpm?

Please, any suggestions to narrow this down and avoid me throwing $$ and parts at the problem. I would prefer to stick with my existing injectors and use that money elsewhere.

Dave

 

Dave,

I found this thread while searching around for some tips as to what my problem could be (car starts and idles like a sewing machine, just won't accelerate smoothly under load, backfires if you try to give it much throttle, etc.).
What ultimately turned out to be your problem?

Thanks!

 

Injectors. It started in this thread when the car was having trouble running. After getting it running and idling ok, that's when I found it would stumble under load, and I started this thread:
https://www.rx7club.com/showthread.p...=bucking+boost

I suspected injectors all along (zkeller said it first) and I chose to exhaust all other options first, in the hope that would be easier in the long run. It wasn't - an injector cleaning by RC Engineering solved it.

Dave