MSefi.com read only forum (Jan.15,2018)

I've got a VW 2 liter motor that I'm having issues getting to start up. Have a MS v3.0.

Verified these things:
--starter sw/motor turns over
--fuel pump is working
--have power at the coil
--plugs get spark
--fuel injectors are getting pulse
--I can get the motor to fire up and run for a few seconds by spraying carb cleaner in the intake.

Strange thing is that both the positive and negative side on the coil are hot. I bought a new one, and it does the same thing. Wondering if this type of coil is just like that and/or maybe I have the wrong type of coil, or is it hot because where the ignition system is sitting.

Any help would be greatly appreciated.

I can get the motor to fire up and run for a few seconds by spraying carb cleaner in the intake.

Therein lies an important clue. If it starts on carb spray, it would indicate that you are not getting any/enough fuel.

fuel injectors are getting pulse

Can you confirm that the injectors are actually spraying though?

Strange thing is that both the positive and negative side on the coil are hot.

Hot meaning voltage measured at the coil connections or temperature? If the latter, how hot are we talking?

Under any circumstances it is clear that the coil/ignition is working. (since the engine starts at all)

Ken

Hi Ken,

I haven't confirmed that the injectors are in fact spraying, I guess that's my next test. pulling the injector tube off and cranking it? It's got one injector on each cyl.

As for the coil being hot on the negative side, I meant in testing it using a voltmeter it shows 12 volts when the key is in the run & start positions.

thanks for the reply,
Pete

That's how the coil should be - there's no current flowing, so the full Vbatt should appear on both sides of the primary. When the coil driver(s) turn on to charge the coil(s), the voltage at the -ve side should drop to pretty close to the Vf of whatever driver is installed; this only happens for a few msec at a time, so you basically need an oscilloscope to see it.

X2....

Don is absolutely correct.

pulling the injector tube off and cranking it?

That will work, but I would disconnect the coil before trying it. Not a good thing, catching your car on fire!

Ken

Ok, so 2 of the injectors aren't spraying. Also, I'm not convinced the fuel return (through the regulator) is working.. going to check the vacuum line to that and replace the injectors then on to the next thing, seems like this is the issue.

I appreciate the help, will update on the status after these things.

Ok, so the injectors are $125 bucks each so I'm soaking them overnight and seeing if that helps. Next I guess head over to Dr. Injector and see if they can clean them before I make the 500 plunge.

To be continued....

Next I guess head over to Dr. Injector and see if they can clean them before I make the 500 plunge.

Yikes!!
At that price, it sounds like cleaning is in order!

Ken

EDIT: Just an afterthought......

Assuming that you are running 2 injectors per bank.....

You need to make certain that the 2 injectors, that are not firing, are getting the correct signal from the MS?

pistolpete wrote:Ok, so 2 of the injectors aren't spraying. Also, I'm not convinced the fuel return (through the regulator) is working.. going to check the vacuum line to that and replace the injectors then on to the next thing, seems like this is the issue.

I appreciate the help, will update on the status after these things.

It's a good idea to check the actual fuel pressure using a gauge. You can adapt a tyre one for this with a bit of ingenuity.
IMHO, it's unlikely two injectors have failed, so I'd check they are indeed being driven - especially if they're on the same output.

A useful tool for checking injector drive is a dwell meter. These were common for setting points ignition - they measure the mark/space ratio. Ie, the ratio of the points being closed to open. So will also do the same with injectors. Cheaper than a 'scope and can often be bought secondhand for very little. And can also check the dwell on most coils. A DVM for car use should have that facility too, as well as RPM etc.

Or you could make up an LED with a 1k series resistor and wire that across the injector - at low revs (or cranking) it will flash, same as on a stim. At higher revs it will appear lit continuously.

I made a little tester using an LED light, checked each of them and the light flashes for each.

Am running over to Dr. Injector tomorrow, since they weren't open Saturday. Will have them cleaned or replaced if need be. Found that I can get them for $65 each.

pistolpete wrote:I made a little tester using an LED light, checked each of them and the light flashes for each.

Am running over to Dr. Injector tomorrow, since they weren't open Saturday. Will have them cleaned or replaced if need be. Found that I can get them for $65 each.

Did you wire the LED across the injector terminals with the injector still connected? If you just unplugged the injector and substituted the LED, virtually no current is being drawn which could give a false result. MS has sophisticated injector drivers which need to be set correctly in the software. Injectors failing totally is quite rare IMHO. Two at once even rarer.

Have you checked the resistance of the injectors? A burnt out one would be very different from the others.

Well, I think you are right.. the injectors tested to be fine, so the megasquirt computer needs to be programmed.