Bump starting causing starting issues
 

Bump starting causes my car to have some rather serious problems.

First few times I do it it's nearly seamless. But then it starts having problems. Hard to explain, it doesn't want to start-- kinda lags... then it threatens to stall. have to drop to a lower gear and try to bump start again after it starts momentarily and then stalls. Second time usually has it bump started successfully. But after more bump starts, it would just stall. I'd start it again and then it would stall again. At one point, key starting it, I was afraid the car wasn't going to start at all after it kept stalling. Eventually it did with some turning over. I think someone at some point was having a similar problem without bump starting. Will see if I can dig up the thread. In the meantime, anyone have any ideas? Bad alternator? Ugh.

Could be something as easy as a loose ground. Check your grounds in the engine bay to make sure they are free of corrosion, and are nice and tight. But since the VX takes so long to go into lean-burn after the o2 sensor gets cold, you might just want to avoid turning the motor off. But really, I don't know why it wouldn't want to restart with a bump start.

i'm a few decades behind in engine technology, (carbed engine), but when i bump start by just releasing the clutch it really is a "bump" start, however, when i prep the automatich choke, by depressing the gas pedal all the way with the engine off, everything goes smooth, eventhough when i key start (buttonstart catually) when the engine's hot, prepping the choke has an adverse effect.

i'm not entirely sure what the injection eqivalent is a choke is but perhaps you might look in that direction... the engine "thinking" something else is going on, and therefor not adjusting the ammount of fuel to what the engine needs to restart...

Interesting. Thanks. I am getting an ECU today which might fix the problem. Mechanic said my ECU might be funky because it wasn't reading the RPM when he hooked it up to his $7000 computer.

In a carb engine the pressing of the gas to the floor is not needed unless it is really cold outside. That pressing pumps in gas to the intake with the accelerator pump - when used hot it floods the engine so don't pump it when warm. When a little Cold only press it 1/2 to 1/4 the way down so you set the choke up and the throttle stop to fast idle but you don't inject too much fuel to prime the engine. If it keeps stalling it is usually because you fouled a plug or two with too much gas from pumping it all the way to the floor.

Does the fuel pump cycle correctly when you eoc. Try double cycling the fuel pump. Key off and then back on, let it build up to fuel pressure and see if this helps.

Sometimes if I muddle the first bump or key start by not giving the engine enough revolutions it goes into what I call "grumpy lean" mode and requires a long key start.

I don't think I give it any gas when I bump start it. If I do i give it about 1/8th or 1/16th pedal. Just ever so slightly. It seems to only happen on the third and subsequent bump starts on a trip. Like by the third bump start it's out of starting power, so it's gonna give me a hard time. As far as cycling the water pump, I didn't know I had any control of the water pump. Nor would I know how to cycle it. When I bump start, I turn the engine off, then wait about a second or two, turn the key to on. I leave it on for the entire glide (usually about one minute or two) then put it in gear and let out the clutch. Granted some of the EOC I've been doing has been at night and almost always the radio is on. But it was doing this with radio and lights off (the ingition has always been on)

I don't know if I buy this. How much can the o2 sensor cool down by in such little time? And how long can it take to warm up again? Seems like this would be very negligible. It's not like I'm gliding for 10 minutes at a time. And if I was, seems the cooling down of the o2 sensor in that time would probably be offsetted by the gas saved with the engine off. My idle is high, so I'm probably using twice as much gas in neutral than a healthy VX in neutral.

I feel pretty confident that it not starting has to do with low battery.

You could eliminate the battery by testing your voltage with a DVM while your eoc'ing. It does sound a little suspect to me. I always found it real easy to kill the civic battery just because its so small. I can tell that my battery is not the healthiest when eoc'ing at night too.

I wasn't talking about cycling the water pump. I was saying to cycle the fuel pump. Just key off and then back on right before you bump start. This will cycle the fuel pump.

aww, okay. Maybe I test that tomorrow. (not the DVM, but the cycling of the fuel pump.

Oh yeah the fuel pump would stop running if there is no ignition pulsing after a few seconds or it could be running all the time and flooding the engine when the car is moving and bouncing the carb float in the bowl. Either way you are not really saving a lot of gas if you only turn off the engine for a short amount of time and have it running rough after it starts again. Bump starting should be a quick clutch out and in again then let the engine run a few seconds and then get it up to speed all without giving it any gas then step on the gas to match rpm to speed and let the clutch out again normally. However if the engine is not running smoothly then you probably have some fuel leaking from the carb fouling the cylinders and will end up with gas in the oil and loss of lubrication in some cylinders that get flooded which will eventually cause ring and cylinder wear. The Cat runs at about 700 degrees and it will cool off pretty quick when you consider that you are moving at speed with no additional combustion heat being supplied to it. Not sure if it makes much difference if you just took your foot of the gas and kept it in gear though.

I don't RPM match. Usually my idle isn't that much lower than my RPM when I am reengaging. Not sure I understand all that you are saying. I have fuel leaking while the engine is off? Or all the time? (That sure would explain a thing or two....) It only struggles after the first two flawless bump starts. The third and subsequent times is when it starts to have trouble.

had that fuel pump issue with my 91 CRX, fixing it made all the difference. Try just sitting in your driveway and just turning the key to the "ON" position repeatedly, just make sure that you can hear the fuel pump humming behind you for a few seconds each time that you do so. If you don't hear the humming , or it varies each time, then it's time to pull out your DMM and test the wiring and the fuel pump to make sure they're all still in good working order.

I bump start all the time, and have no problems at all. I use as high as gear as possible, at least 3rd

Sometimes when you first turn the ignition to the on position the engine will squirt some gas into the intake to prime the engine - usually only for cold starting. Injectors can leak slowly and if the engine is off for a long enough time the fuel evaporates but if only off for a few minutes it may be enough to flood a cylinder or two. Carb engines have a float in the carb bowl that holds back the gas from the fuel pump - if the float bowl is bouncing around it can allow some of the fuel in the lines still under pressure to overfill the bowl and overflow into the intake. Plus with the key still on the fuel pump may still be pumping and maintaining pressure.

I had a very similar problem in my now retired '92 Civic Si. First few bumps were always fine. Intermittently I would have difficulty bump starting after that. I never figured out why but it seemed to happen more frequently on hot days. After trying a couple times I usually wound up at the side of the road with the flashers on. After a couple of cranks it would start. The other manifestation was with engine off coasting to a stop. Then when the light changed I would crank but it wouldn't fire. After a couple more tries and a little embarrassment it would start.

Yeah, sounds pretty similar. Sometimes I think it has more difficulty at slower speeds. Second gear and sometimes third often lurches the whole car before starting. It hasn't been so bad of late because I haven't been doing it quite as often. If I could fix my idle I'd be much less inclined to bump start altogether, but seeing as I have a high idle I feel that it has some savings.

Maybe I should start coasting with the key in the off position, and only put it to the on position right before I bump start to see if that makes any difference.

Maybe let the engine spin a little more in gear after you turn the key off to pump some of the fuel and air out then push in the clutch and then when the engine stopped turning - turn the key on again. This way if the injectors are leaking a little after shutting off they have a change to clear the cylinders. I used to rev the engine in my Geo and then turn off the key to flush and hold the gas pedal down out the moisture from the exhaust in cold weather as I turned off the engine.

Find our whats wrong with the car. :)

Bump or key start it should fire right up.... I bet when you find the problem your mpg will get better. :)

When I bump start, I let the clutch out in order for the engine to come back on. I don't put the clutch back in again immediately after I bump start to let it warm up as you say, I just start driving. I only put the clutch in again immediately after bump starting if it starts doing the laggy business. But I have just been bump starting a max of 3 times per trip in order to prevent the problem since it seems to occur from excessive bump starting.

Is there a reason you put the clutch back in again after bump starting? Engine runs fine immediately after bump starting the first few times I do it.

When I turn the car off, I put the clutch in and turn it off at the same time. I want the gear to be disengaged when I turn it off so that I don't have any engine braking robbing me of precious momentum. My car doesn't roll very well, so I hate the idea of losing any momentum.

Psyshack, you really think it's an indication of something wrong with the car? I mean, cars aren't really supposed to be bump started on a regular basis, right? Although I guess many of you do do it on a regular basis with no ill effects.

Unfortunately I lack the time, resources and know how to find this problem. :( I mean, this is a resource, but I have a hard time translating text instructions into application to my car!

Bump starting is no longer causing any issues with my car. Dunno why. Maybe I am letting my foot off the accelerator for a very small fraction of a second before killing the engine, but I don't really feel like I've changed my EOC habits too much. But it sure is great to be EOCing again. :D

Although now that it's cold, 35 degrees on my ride home today, the CEL comes on if I EOC too much cause the engine is getting a chance to cool down. The CEL is almost an FE aid for me at this point, because it lets me know when the o2 sensor is not hot enough. :)

1993CivicVX -

The CEL is your friend, especially when you have a manual fan radiator switch that is not tied to the ignition. 30 Amp draw can soak your battery real quick. I almost want to modify my CEL image to show a little fan, :D .

CarloSW2

Well, I think letting the foot off the throttle before shutting engine off really makes a difference! Been doing much more EOC without any ill effects.

Although one strange thing is it does not like to bump in 2nd gear. It really lurches (slows way down) before engaging, and when it engages it's pretty rough--sound not so good. 3rd gear bump starting is really smooth tho.So even if I'm only going 17mph, I'll bump into third, suffer a momentary lug, and put the clutch in and go into 2nd. Maybe I'm just going too fast when I bump start into 2nd--maybe I'll try it at 10mph.

Use higher gears and just pop the clutch out an dthen in again - you really should only have to turn the engine over a compression stroke or two for it to start running and using a higher gear will put less strain on the clutch, gears, engine mounts, and you will loose less momentum. The idea of popping it out and then in again in a higher gear is that you want to turn the engine over to get it started in as high a gear as possible but that gear would be too high for driving as the RPM would be too low but it will be high enough an RPM to start the motor. You should be able to bump start in 2nd at about 3-5 mph. The best way to figure out which gear to use is to idle the engine in each gear and see what speed the car moves at when at idle. In my xB at 17mph I am in 5th at low idle - 1000 rpm is about 20mph.

hah, bump starting this car at 3-5mph would make the most awful sound and would be terrible for the car. One thing I don't like about this car's tranny is that the first and second gear should be closer with begger distances between the last three gears. 10mph is prolly good. Maybe 8, but even that could be harsh on the car.

5th gear is about 29mph at 1000rpm

That's why you just pop the clutch out and in as fast as your foot can move then let the engine start up and then pick the right gear to accelerate with i.e. a lower gear. My xB will idle in first gear at 2mph with the clutch out.

Bump starting should be transparent to the average passenger. The saturn can be bump started at any forward speed. The process involves rapidly releasing the clutch and then back in again. You only looking to spin the engine 1-2 revolutions. In the saturn it only the clutch only needs to travel 3/4 the way out. This allows the engine to start and attain its idle smoothly. Usually passengers don't realize I EOC. They'll look over, see the oil light on and say "you should check your oil".

That can depend upon the compression ratio of the engine as well as the displacement, flywheel weight and transmission gear ratios as to how much you feel. It should be pretty smooth if done right just like you say.

Haha, yeah I noticed that about the dummy lights. I agree that bump starting shouldn't be a jolt at all. It's very smooth as long as you push the clutch in quickly after releasing it.

One thing I noticed recently is we get so used to doing things and in that process we inadvertently rush through the procedure. This apparently made a difference on my truck, you think your problem was bad, mine somedays wouldn't start for 15-20 minutes as I'd sit stuck at some intersection :p

Yes sir, all it took was 1-2 of those experiences and I just about gave up on shutting down the engine for a glide. Odd, why it never gave me this problem in the mornings?

What I learned to do is when doing a glide to keep the ignition off for 3-4 seconds, then turn it back on but keep it on for 3-4 seconds before starting.

So whether a cold start or a glide / EOC / F-AS, always:
Keep ignitions off for at least 3-4 seconds.
And when turning on, let them sit for a bit before starting ICE.

That helped, before starting switch to ignition ON and just wait a sec.

I think this helps the computerized parts get all their bits and processes in order.

Well, i've been taking my foot off the gas right before turning the engine off and it has been bump starting very well now. Also I do agree that you can bump start at 2-5mph in 2nd gear and that any faster is not ideal. So thanks everyone for the good advice!