Joined: Apr 2012

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So I picked up a project 951. No start. I checked the speed and reference sensors at the connection in the engine bay and they ohm out okay. So I checked them at the DME connector. They ohm out okay there as well. I saw a video on ECU Doctors website about checking voltages while cranking. I tried that but don’t see any voltage on the pins mentioned in the video. Gotta be honest I’m not sure what the no voltage from the sensors means when cranking. Sensors are toast (even though they ohm out okay?) or that they’re not at the correct depth? Just trying to understand why I would see voltage from a sensor. I don’t see how it’s getting voltage anywhere, just a magnet essentially that’s breaking polarity at a certain spot on the flywheel every time it makes a revolution.

What am I missing or not understanding correctly?

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From: Northern California, '86 951

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Yup checked all that and checked out ffine. Ran a few weeks ago when I went to look at it before purchasing it. I towed it home because the clutch master/slave was out.

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From: Atlanta, Ga

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No, I haven’t changed those parts out yet. I have the brake master, clutch master and clutch slave, just haven’t changed them.

i just purchased the car a few weeks ago. When I checked it out the car started and ran fine. Turned it off and restarted it several times. Came back a few days later to pick the car up with a tow truck (because the clutch pedal was going to the floor) and it wouldn’t start. Battery was low and I attributed the no start to battery dead, old gas (car has sat for at least 3 years).

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From: Atlanta, Ga

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From: Toronto, Ontario, Canada

Did the seller remove something between you looking and picking up?? Crazy.

If it started and ran then 2 weeks of sitting won't start. I assume you changed the battery and cranking at proper speed? Too slow may not give from sensors--min. is 200rpm I believe.

IF you are cranking properly, I doubt the sensors just died like that. You just might be checking the wrong pins; easy to do on that unmarked connector. I would suggest plugging in a 12v LED instead and see if it blinks. While you have it (super cheap at any electronics supply), use it to check for blinking at any fuel injector plug + the coil.

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No tach bounce. Haven’t checked compression. I’ll do that in the morning. I am making the assumption that no tach bounce means something wrong with the DME.

Just thinking out loud here, but even if compression was zero on all cylinders the flywheel would still be spinning...and the pins would be passing the sensors...and the sensors would be sending that signal to the DME...and the DME would then cause the tach...which would bounce the needle.

Brand new battery.

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From: Toronto, Ontario, Canada

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From: Honolulu,HI

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Well, did a little more work here. Was at a swap meet this morning and a guy had an N/A DME. Tried that but still no tach bounce.

I checked compression in cylinders 2 and 3, just because those are easy to get to. Almost 140 psi in each. Seems a little high but I’ll attribute that to gauge error. I haven’t looked it up so I’m not certain but I don’t believe both cylinders 2&3 would have both their intake and exhaust valves closed at the same time. So if the timing belt was broken one of the four valves and in those two cylinders would be open...and I wouldn’t get 140 psi.

I also checked to see if I got 12v at the coil when the key was in position 2 (just before turning over the starter). I didn’t get any voltage there.

i checked a ground on the back of the bellhousing. Looking it up now it looks like there may be two grounds back there. I’ll check to see if that’s the case and if so I’ll ensure it’s making good contact.

On Monday I’m going to pick up a DME relay (that way I’ve got an extra for the glove box). I checked the DME relay previously and it tested okay. When I jumped the relay I can hear the fuel pump running. I’m also going to pick up two sensors and change them just to be sure. Even though I’m getting ohm readings within range when I test the sensors I don’t have an oscilloscope to test their wavelength. I’m also not getting and voltages at the DME connector when cranking (but am getting ohms).

Joined: Apr 2012

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Just to wrap this up it was the speed and reference sensors. While they ohmed out okay, they weren’t providing signal to the DME. Replaced them in 10 minutes and the car started up. Rough idle at first. Realized 3 and 4 ignition wires were in the wrong position. Swapped them to correct location and it ran better. Gas was old so I put in about 10 gallons of premium. After about two minutes it smoothed out. Bought new cap/rotor and plugs but have yet to install. I’m sure that will help.

Now I have to determine why the alternator doesn’t seem to be charging. Battery is new so I’ll check belt and connections to alternator. Will post a new thread if I need help with that.

Thanks all for contributing to this thread, definitely helpful.

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From: Toronto, Ontario, Canada

Interesting! I guess the time before the sensors stoo working, the are working lol

Curious how both just died like that, at the exact same 2 week rest period. That, and at 10mins, you're a ref sensor switchout pro