engine wont start

[Supra]

hello everyone

This zaid from the american university of sharjah i am working on the FSAE project we are using the motec m4 on a honda cbr RR the setup that we have is:
IJPU=15
IJCU=0
IJbc=4
IJOP=0
EFF=1
LOAD=1
LDS=100
CYLS=4
rFSn=2
SYSn=2
rEF=14
crT=12
crip=480
ign=1
coil=2
dell=3
dly=50
we are using an igniter for the coils, coil for cylinder 1 and 4 fire spark at the same time 2 and 3 at the same time, injectors are connected in this order 1-2-4-3 but the problem is that we keep gettin backfires from the intake manifold and whenever i remove the feul relay or switch it of the engine start to backfire from the intake and exhaust and starts for 5 sec i went to the fuel trim and set it to -60 sice it was too rich and still same problem the inj pulse width was 8ms using the -60 overall trim. i keep getting sync error

please help since its our first time to work on this project.

[Mikey Antonakakis]

Any engine will start given a decent amount (not too much, not too little) of fuel, and a spark at approximately the right time. Set your advance to about 10 degrees. Verify that it is correct with a timing light, and fix any offsets. If you are using stock injectors, at least on an F4i, between 2 and 3 ms open time should make the thing fire... it's up to you to find the correct value, but it should fall somewhere in that range. If you get the engine to fire, and your advance and AFR are where they should be at idle (it's up to you to choose, but somewhere around 10 degrees and stoich should be a good starting point), and it dies after a few seconds, it's time to start checking any warmup or after-start enrichments you have enabled (not sure how all of that works on the motec).

If you are getting backfires into your intake, in my experience this is usually because you are running too lean, or you have too much advance, or both. Again, if you have a reasonable idle advance (around 10 degrees), check your timing. If that works, add some fuel and see what happens. Our overall pulse width (after any corrections) at idle is around 2ms, using stock F4i injectors. I'd assume the F4i injectors and the RR injectors have a similar flow, although I could be wrong. If they do, 8ms is far too long of a pulse width.

[Luniz]

First of all, please watch your spelling. For me as a non-native speaker it is extremely hard to figure out what your problem is like this.

The first thought that ran through my mind when reading your comment was: Are you sure that your camshafts are in the right position?

[BrettHutchens]

Ain't got no gas in it!

[Mikey Antonakakis]

Originally posted by BrettHutchens:
Ain't got no gas in it!
Yep, this is also a common cause of intake backfires (for us, at least). I'll be tuning, everything is going well, then I start to run lean. So I richen, then it gets leaner. Eventually I figure out that we've ran out of gas, so the first thing you should do is make sure you have a full tank http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Supra]

guys thanks for the help, the feul tank is full and the coils and injectors are connected in the correct order. i think it has something to do with the injectors since sometimes it backfires from the intake and exhaust. the engine seems fluded.

[355HZ]

Hey mate the cbr600rr's have 3 teeth on the cam ref you need to get rid of two then re-claibrate for one tooth at TDC. solves sync errors.

[VFR750R]

Front and back fires are common on FSAE engines (I think this was brought up recently on this site). With two sparkplugs firing at the same time, if you have a air/fuel mix in the runner on a cylinder during overlap, there is going to be a spark at say 10BTDC and it will ignite that mix back up into the plenum igniting everything.

That said, when running sequential, make sure the injector is firing during the intake stroke and not significantly before, or it will be potentially spraying during the spark event during overlap and can go boom every time.

Could be related to 355HZ's post on cam timing. Maybe you aren't firing injectors....or spark, when you think you are.

[UNSWTIM]

If you think the problem is your fuel, go and buy a can of aerostart (glorified hair spray), disconnect the injectors and see if you can get the engine to tick over on aerostart only. If it ticks over for even a few seconds you know that perhaps the problem is in your fuelling.

Make sure that when spraying aerostart into the intake, spray it slightly across the duct, not straight in, and dont spray too much. You want it to atomise and not form liquid everywhere.

Finally, wear a leather glove because if your backfiring, it is likely to shoot flames out the intake onto your hand.

[355HZ]

Originally posted by UNSWTIM:
Finally, wear a leather glove because if your backfiring, it is likely to shoot flames out the intake onto your hand.

not the best idea you've ever had. great way to burn yourself even with a glove on. i highly doubt it will be a fuel related issue. if it is backfiring then there has to be spark with the inlet valve open which will relate to a timing issue not an injector issue.

[Supra]

guys i have chopped two of the cam teeth, and i keep getting sync error, should i remove the cams and align the tooth with its sensor when the piston is a top dead center would this solve the problem.

[Nishant Jain]

What would you guys say if the backfiring occurred in an F4i running a stock ecu? We had the same problem recently.

We've got it on a Power Commander. It refuses to start, since we took it apart once to examine the cam-shaft.

I'm quite certain it was put back together properly. But now it refuses to start. Even if it does spark, it doesnt sustain itself and stops running in about 3-4 seconds.

I myself assumed it was a sparking problem. But how can that occur in a stock ECU which cannot be tampered with? The Power Commander hasn't been touched since the last tuning either.

[Drew Price]

I distinctly remember CMU having almost this exact problem at FSAE West two years ago - the fuel pickup in their fuel tank worked it's way into a corner, and starved the pump, so it'd sound like it was trying to start, then die right away.

Pull your injectors and crank the engine and make sure you're getting a good spray pattern (point them into something, no smoking nearby, all that stuff), to add to your list of troubleshooting.

It took them 2 days to find the problem.

Erring that, isn't their indexing marks on the cams and the crank to double check you got the chain and sprockets back on exactly right? Hopefully popping the cam cover is easy enough to just check that too.

Best,
Drew

[Nishant Jain]

We've already done both. We've triple checked the cam indexing and crank shaft timing and its fine.

We have also checked our injectors. Since it was our first time, we found them to be working fine once they'd sprayed a good amount of fuel all over our clothes. And then we set some stuff on fire by accident. So yeah, they work.

I really dont think the fuel tank is the problem in our case, although I'll check now that I hear its a possibility.

Honda's OBD shows a dysfunctional TPS and MAP sensor. For no valid reason I can think of. Is it possible to pass a direct voltage of 5V into the ECU from another source to substitute the TPS and MAP for a few seconds and see if the engine runs ok?

[ZAMR]

Well you're not going to want to substitute 5V exactly since 5V usually signifies WOT (or higher!). As long as your TPS is calibrated correctly (say for example .8V for closed throttle and 4.2V for WOT) then you shouldn't be encountering an error like this.

As far as your wasted spark goes, I'd make sure you're not spraying the walls of your intake too much. Like VFR750R said The hot gasses (or the spark itself) might ignite extra unwanted fuel during overlap. 8ms open time is rather high in my experience.

Although if you're still getting sync error I'd take an oscilloscope reading off your crank/cam position to make sure your signal doesn't look out of the ordinary.

Zach Moorhead
Sooner Racing
Engine & Body

[Nishant Jain]

I'm only thinking of substituting the MAP and TPS for a few seconds, so as to see if the engine starts ok and can sustain itself.

I have tried pretty much all of the above suggestions already, so I'm pretty clueless at this point. Except for passing direct voltages, since the MIL light on the dashboard shows the MAP sensor malfunctioning, is there anything else I can try?

As for fuel pulse width, we have a Power Commander installed already which took care of business before.

This is what we tried with the crank/cam position sensors a week back --> we got the engine to run for a few seconds and measured crank sensor (i.e ignition pulse generator) output which was found to be 0.7V as it should be according to the manual. This in turn, is supposed to give 0.7V at the cam position sensor (i.e. cam pulse generator) as well. This is the weirdly spaced 3-teeth cam shaft by the way.

The cam pulse output, however, wasn't 0.7V. It stayed somewhere around 0.2V. Figuring we might have a faulty Cam Sensor, I switched it with another Cam Sensor off an RR engine. Same output.

[Discretely elite]

Originally posted by Supra:
guys i have chopped two of the cam teeth, and i keep getting sync error, should i remove the cams and align the tooth with its sensor when the piston is a top dead center would this solve the problem.

What is your injector timing? Is motec defining the off angle of the injection event?

I'm not sure about wasted spar mode (which you say you are running), but as 355HZ said, motec only wants one trigger tooth on the cam. Make sure the type (magnetic?) and polarity (rise or fall) is right on this sensor.

Take a ref/sync capture to examine the peaks produced by the crank wheel teeth and cam tooth. Look at the polarity and for any irregularities. Take note of the voltage at the peak and play with the sync trigger voltage.

Def check your timing with a timing light.