How to smoothly bump start / clutch start an engine

[cfg83]

dcb -

Originally Posted by dcb

Cfg, does sg1 have an open loop indicator?

Yes, it does have an open/closed loop indicator.

Another interesting difference is that when I am in DFCO, it stays in closed-loop. Others have reported that open-loop and DFCO go together, but I am not seeing this in my 1999 Saturn. I am thinking, however, if I was on a super long downhill, it would eventually go open-loop if my exhaust-heated narrow-band oxygen sensor cooled off to the point where it was no longer accurate.

CarloSW2

[PaleMelanesian]

Both my Hondas hold DFCO down to 1200 rpm. You can feel a "surge" as the fuel is turned back on at that point.

[Mustang Dave]

My SG II indicates Open Loop when my Mustang goes into DFCO. And I can feel it in the change in deceleration.

You can feel a "surge" as the fuel is turned back on at that point.

I feel that same "surge" in my Mustang when it stops DFCO-ing.

[RobertSmalls]

I can hold my engine kill switch to force DFCO, and it gives me the option of wide-open-throttle DFCO. I only ever use these options when the motor oil is very cold, when restarting the engine would be bad.

It's interesting to listen to an engine at WOT, DFCO. It sounds much throatier than with the throttle closed.

[justjohn]

I have a question about this. No matter how slowly I let the clutch out the engine always seems to jump right to the full rpm for what gear I'm in if I have the key on. (I feel like just letting it touch and then backing off doesn't start it. I can definitely feel some slowdown and not have the engine kick in.)

So I tried a couple times with the key off and it's a lot smoother, and no jumps or anything when I key back on with the engine already spinning. However, everyone on here seems to say keep the key on.

1. Why is it better to bump start with the key on?

2. Any further suggestions about technique or anything for key on bump starts?

[Daox]

Originally Posted by MetroMPG

• 2) let the clutch out part way, smoothly & relatively quickly, only as far as needed to spin up the motor

• 3) immediately depress the clutch as soon as the engine spins up

The key is to let the clutch pedal out for a very short time and then press it back in.

You have to bump start with the key on so the engine starts up!

[justjohn]

Well first, if I do that the engine doesn't start

Second, perhaps I wasn't clear, I let the clutch out slowly and after the engine is spinning I keyed on. This was smoother than key on before starting to let the clutch out, so I would like to know if/why I shouldn't do it that way.

[Kodak]

Originally Posted by PaleMelanesian

Both my Hondas hold DFCO down to 1200 rpm. You can feel a "surge" as the fuel is turned back on at that point.

Originally Posted by Mustang Dave

I feel that same "surge" in my Mustang when it stops DFCO-ing.

How strong is the surge? Is it really noticeable, or just a slight 'bump'?

[Daox]

Originally Posted by justjohn

Well first, if I do that the engine doesn't start

Second, perhaps I wasn't clear, I let the clutch out slowly and after the engine is spinning I keyed on. This was smoother than key on before starting to let the clutch out, so I would like to know if/why I shouldn't do it that way.

So, your problem is you're key starting the engine. Then you go to engage the clutch and you get the jerk? If thats the case, just blip the throttle to match the rpms closer together before engaging the clutch.

[justjohn]

Hahah, no. I'm not sure how I'm being so incomprehensible. Let me try once more. I've tried two entirely separate ways of clutch starting.

1. Normal way. EOC, then key on, then let the clutch out. This is the method where letting it out a little and then putting the clutch back in doesn't seem to start the engine.

2. Other way. EOC, the slowly let out the clutch, after engine is already spinning THEN key on.