PushStart a 4+3? Need quick HELP!
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From: Decatur Al
PushStart a 4+3? Need quick HELP!
I need a really quick answer from anyone who happens to be online this morning. I have an 87 with a 4+3 transmission. Can I push start this car? Or does the overdrive unit prevent this?
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From: Decatur Al
I was thinking more along the lines of the fact that this O/D unit is really a two-speed automatic transmission. If the O/D is not engaged, is there a mechanical connection between the driveshaft and the manual transmission such that the engine will turn over when the clutch is released with the rear wheels rotating?
Burning Brakes
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From: Dunstable MA
St. Jude Donor '05
It'll work so long as there is enough juice left in the battery to power the ECM and all that. I did it once with my 87 4+3, or rather I pushed and my wife did it. She told me she had never done anything like this before: 
,but it worked out fine.
,but it worked out fine.
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From: Decatur Al
Ahh!! The voice of experience! That's what I needed. Thanks!
Background: Switch to run, everything is ok. Intermittently lately when I've moved the switch to start, nothing happens at the starter. Most times it will work after several tries. Following the diagnostic steps, I checked voltage at the Start Enable relay and the problem is not VATS or Ignition Switch. Next step is to check the Starter Solenoid, but I can't for the life of me figure out how to get my hand up into that area, let alone put a multimeter probe on it. Anyway, car has had the no-start problem for two days, then I was showing a neighbor how to turn the key and the car started right up! So it's starting ok for now. I have to go on a trip this weekend and I needed to make sure that it will push start if the problem recurs.
Thanks again for the responses, Rich and Mike!
Background: Switch to run, everything is ok. Intermittently lately when I've moved the switch to start, nothing happens at the starter. Most times it will work after several tries. Following the diagnostic steps, I checked voltage at the Start Enable relay and the problem is not VATS or Ignition Switch. Next step is to check the Starter Solenoid, but I can't for the life of me figure out how to get my hand up into that area, let alone put a multimeter probe on it. Anyway, car has had the no-start problem for two days, then I was showing a neighbor how to turn the key and the car started right up! So it's starting ok for now. I have to go on a trip this weekend and I needed to make sure that it will push start if the problem recurs.
Thanks again for the responses, Rich and Mike!
Team Owner
Joined: Mar 2001
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From: Cincinnati, Oh USA
I recommend that you do not push start your C4 4+3. Last year I started rolling my 87 out my driveway in reverse and popped the clutch to start it. It damaged my OD and I had to have it rebuilt. Starter motor only for me. Apparently a thrust bearing in the OD cannot take push starting.
Team Owner
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From: Sussex,Wi
2023 Corvette of the Year Finalist - Unmodified
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Originally Posted by jfb
I recommend that you do not push start your C4 4+3. Last year I started rolling my 87 out my driveway in reverse and popped the clutch to start it. It damaged my OD and I had to have it rebuilt. Starter motor only for me. Apparently a thrust bearing in the OD cannot take push starting.
Not a pretty site.
Never seen it happen while going forward.
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From: Decatur Al
I appreciate all of the info. I'm back from my trip and fortunately the car started for me, so I didn't need a push. Maybe I can get this thing fixed this week. JFB, sorry to hear of your misfortune. I will definitely not try a push unless an absolute emergency!
Team Owner
Joined: Mar 2000
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From: Boston, MA
Originally Posted by touringmike
OD only works in 2nd thru 4th.
Believe it or not this is incorrect. There are a couple situations where OD is active in 1st gear. Check out this chart...
http://www.5speeds.com/43table.htm
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From: Decatur Al
Chris, thanks for the input. The resistor in the ignition key is definitely a place to look for the type of problem that I'm having. However, I've already checked power all the way through the start-enable relay. Start-enable relay is where the VATS combines with ignition switch to send start voltage on through the clutch switch and then to the starter solenoid. Since the VATS side of the start-enable relay is OK, the resistor in the ignition key should be fine.
I'm going to start a new thread in the Tech section to ask for advice about how I can get my voltmeter probe onto the starter solenoid to check the voltage there.
I'm going to start a new thread in the Tech section to ask for advice about how I can get my voltmeter probe onto the starter solenoid to check the voltage there.
Burning Brakes
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From: Springdale AR
Originally Posted by BamaVette87
Since the VATS side of the start-enable relay is OK, the resistor in the ignition key should be fine.
On mine when ever it wouldn't read the resistor properly I had to wait approx 5 mins berfore I could try again, if you don't it resets the timer everytime.
Also, FYI, if you wait an extreme long time before you go get a new key made, the dealership may not be able to read the resistor either, if that happens I'm not for sure what they do?
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From: Decatur Al
Thanks for the followup, Chris. My understanding is that if you are getting a "go" signal from VATS to the start-enable relay, then the relay will allow voltage to go to the starter solenoid. I verified that by unplugging the sensor wire going to the key switch and then turning it to start. That's like using a key without the resistor pellet. I lost the start-enable signal from VATS for almost 3 minutes when I did that. Plugging the sensor wire back in and waiting for VATS to timeout restored the signal to its proper value at the start-enable relay. All of this was proof to me that the ignition circuit and the VATS circuit are operating correctly.
(FYI -- Start-enable signal from VATS is 12v to disable and goes low to enable the start-enable relay)
(FYI -- Start-enable signal from VATS is 12v to disable and goes low to enable the start-enable relay)
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From: Sussex,Wi
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Originally Posted by joezr2
So I should assume from above that a bump start in reverse is different than a bump start in 1st? Why? Why would the engine move foreward when the rotational force isn't in that direction? 
Now, with the car going backwards, the fan blade still turning the same direction, the clutch on the fan dis-engages and pushes into the radiator.
Now I don't know if this is correct, but I have seen it happen to my Brother's car.
That's my story, and I'm sticking to it.
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From: Decatur Al
The only time I've ever seen a straight-shift car get its drive-train damaged when being pushed off in reverse was many years ago when we were push-starting an old Rambler American. A close relative of mine was the driver. He popped the clutch after we got him up to about 10 miles per hour going backward down a slight hill. Awful noise ... something obviously broke inside! ... he had left the tranny in first gear! Ouch!
But, I shall head the warnings from this thread and be "extra special careful" if I have to push start this thing!
But, I shall head the warnings from this thread and be "extra special careful" if I have to push start this thing!