by "Urambo Tauro" (urambotauro)
Published 11/20/2017 at 12:00
by "Urambo Tauro" (urambotauro)
Published 11/20/2017 at 12:00
Tags: Saab 900
; Mustang
; project
; wrenching
STARS: 1
Is there an echo echo in here in here?
Over the past few months, my Mustang has intermittently had some extended crank times (sometimes up to 10-15 seconds), but only intermittently so. It’s been annoying but tolerable, since it would finally fire and drive normally. But it’s gotten worse recently, to the point that it just wasn’t starting, period.
!!! UNKNOWN CONTENT TYPE !!!
Meanwhile, my brother encountered a sudden failure of the 900 that we had JUST gotten
running again
after fixing the fuel system. After that initial run of about 25 minutes, it too developed a crank/no-start condition the next time we tried to fire it up.
We found the coil out-of-spec, prompting a replacement, but apparently not out-of-spec enough to be the source of the problem. The cap/rotor looked somewhat worn, so we replaced that too, if only out of an abundance of caution. But it turns out that we needed to dig deeper to find the true source of the problem...
!!! UNKNOWN CONTENT TYPE !!!
It took some digging to figure out my Mustang’s issue, too. Unlike the Saab, the problem was intermittent, which meant that I had to catch it in the act, or find excessive resistance or voltage drop somewhere. Despite having the shop manual, I was still missing the “Powertrain Control/Emissions Diagnosis” volume and its handy pinpoint test checklist.
Between Mustang forum posts and a bit of Google-fu, I finally found an issue of Wells CounterPoint investigating this very problem. Long story short, it contained specs that superseded the shop manual, confirming what others on the forum suspected: the stator/hall-sensor/PIP/pickup coil inside the distributor was indeed failing. It produced some voltage, but apparently the PCM wants more than it was putting out.
!!! UNKNOWN CONTENT TYPE !!!
On the Saab however, the hall sensor (which I’d prefer to call a crankshaft position sensor) is not inside the dizzy, but located behind the crank pulley. Which, on these cars, is up against the firewall thanks to the backwards orientation of the engine. This also means that we don’t have much room to get a wrench on the crank so that we could turn the engine over by hand (for testing the sensor).
So we located the 3-wire connector for the CKP next to the oil dipstick and used that to conduct our testing. The EZK (ignition control) module is supposed to send battery voltage to it, and receive a signal that alternates between <0.4V and >3.0V as the crank turns. So we unplugged the connector, and found the EZK unit sending only 11.7V to the sensor, about one volt less than the battery had to offer.
As for the sensor itself, I used a battery jump-box to send a full 12V directly to it. But we still needed to turn the engine over by hand, as the starter would rotate it too quickly to observe the expected voltage fluctuation. So we opted to put the transmission in gear and turn the front wheels by hand (spark plugs out to relieve compression).
The signal coming back from the sensor did fluctuate back and forth, reacting to engine rotation, but only slightly, not nearly enough high-end signal. It was always less than 0.2 volts. So I guess we’re gonna have to get in there after all.
At least the distributor on my car will be easy to access...
"jimz" (jimz)
11/20/2017 at 12:15, STARS: 2
On the Saab however, the hall sensor (which I’d prefer to call a crankshaft position sensor) is not inside the dizzy, b ut located behind the crank pulley. Which, on these cars, is up against the firewall thanks to the backwards orientation of the engine.
y saab
y u do dis
"Akio Ohtori - RIP Oppo" (akioohtori)
11/20/2017 at 12:21, STARS: 0
Good detective work! You’re making me feel bad for thinking “ehh... the part is cheap enough I’ll just throw one in...”
Fun fact: If you do start having hot start problems, it might end up being the starter. I’m 100% unfamiliar with NA 16-valves, but on the 8-Valve Turbo the starter is exceptionally close to the exhaust manifold. Apparently a common problem with Bosch starters (not just on Saabs) is as they get older and then hot the ignition switch is no longer able to provide enough voltage to activate the solenoid. The solution is to add a hot start relay, which can be done for less than $10 if you know what you’re doing.
"Urambo Tauro" (urambotauro)
11/20/2017 at 12:28, STARS: 0
To make the clutch easier to change? Who knows. Must’ve been developed during the dark months of the year.
"Urambo Tauro" (urambotauro)
11/20/2017 at 12:30, STARS: 0
Interesting. I don’t expect any hot start issues on this one. The starter’s on the opposite side here, close to the dipstick and alternator.
"Akio Ohtori - RIP Oppo" (akioohtori)
11/20/2017 at 12:42, STARS: 0
Oh excellent. (Lucky jerk)
"Urambo Tauro" (urambotauro)
11/20/2017 at 12:49, STARS: 0
Haha, wanna trade? I bet my brother would love having to deal with a dizzy-mounted hall sensor right now...
"shop-teacher" (shop-teacher)
11/20/2017 at 13:25, STARS: 0
I blame the lingonberries.
"shop-teacher" (shop-teacher)
11/20/2017 at 13:25, STARS: 1
Sounds like you’ve got some fun ahead of you!