Engine speed way too high

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gshoger
MegaSquirt Newbie
Posts: 5
Joined: Thu Sep 10, 2009 11:51 am

Engine speed way too high

Post by gshoger »

I have MSII controlling a Honda GX35 engine. I have not yet gotten the engine to run using this, but i have got it to inject while using the pull start. When I pull the pull start the engine speed that appears on the control panel on the labtop is way too high. Is there any common reason why this may be happening?
grippo
Site Admin
Posts: 286
Joined: Mon Feb 16, 2004 6:55 pm

Re: Engine speed way too high

Post by grippo »

The higher speed can be due to 2 things: a misconfiguration in your inputs, which generally shows up as an rpm that is double what you would expect. Noise in the ignition Input channel that can cause a noise pulse to come between 2 real pulses and therefore the ECU thinks the engine is turning faster than it really is. The latter is generally random with ridiculous rpms like 5000 when cranking. This usually shows up as the rpm frequently jumping to 0 then back to a high number, etc.
gshoger
MegaSquirt Newbie
Posts: 5
Joined: Thu Sep 10, 2009 11:51 am

Re: Engine speed way too high

Post by gshoger »

I think the problem is probably the signal noise. Should I just try and insulate the wire better? Also would that have any affect on actually running the engine. I try to run the engine and I know the fuel injector is squirting but I dont think there is ever a spark. Can you offer any advice on this?

thanks,
G
grippo
Site Admin
Posts: 286
Joined: Mon Feb 16, 2004 6:55 pm

Re: Engine speed way too high

Post by grippo »

If you get fuel you should get spark, but we need to see your msq and a short datalog of the startup to see what is going on.
gshoger
MegaSquirt Newbie
Posts: 5
Joined: Thu Sep 10, 2009 11:51 am

Re: Engine speed way too high

Post by gshoger »

ive got the engine running now but the RPMs are still way too high. i think that it is because of noise in the ignition input channel. do you have any advice on how to fix this?

G
grippo
Site Admin
Posts: 286
Joined: Mon Feb 16, 2004 6:55 pm

Re: Engine speed way too high

Post by grippo »

gshoger wrote:ive got the engine running now but the RPMs are still way too high. i think that it is because of noise in the ignition input channel. do you have any advice on how to fix this?

G
If rpms are too high, are they double the actual rpms ? If that is the case then it's likely a configuration problem (too few skip teeth or something like that). If there were ignition noise the car would run terribly and you would see the rpm go all over the place and also drop to 0 instantly every time it lost synch. You would see the rpm gauge needle dip to 0 for an instant every so often.

There are a lot of fixes for input noise starting with making sure the inputs don't cross plug wires. But first make sure it is noise.
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